91A derivative - question to Paul Joppa

RE: 91A derivative - question to Paul Joppa, posted on January 7, 2015 at 12:05:08
Paul Joppa Industry Professional Posts: 7296 Location: Seattle, WA Joined: April 23, 2001	It seems likely a grid choke would work. I don't know the sensitivity but it's probably high due to the pentode driver. Remember this is WE's design with just some minor variations by Joe Roberts and myself, to accommodate different parts. I never did a full engineering design analysis.

Thanks (nt), posted on January 7, 2015 at 17:21:35
xcortes Audiophile Posts: 1221 Joined: July 23, 2003	Nt

RE: 91A derivative - question to Paul Joppa, posted on January 7, 2015 at 17:23:12
Tre' Industry Professional Posts: 17305 Location: So. Cal. Joined: February 9, 2002	The output impedance of the pentode stage is going to be high. Be sure to get a grid choke with low winding capacitance otherwise the HF may suffer. Tre' Have Fun and Enjoy the Music "Still Working the Problem"

RE: 91A derivative - question to Paul Joppa, posted on January 7, 2015 at 18:06:15
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	Gain is going to be pretty high, my lazy, end of day estimate would be a bit under 30dB. (Call it 27dB)

RE: 91A derivative - question to Paul Joppa, posted on January 7, 2015 at 19:34:28
Paul Joppa Industry Professional Posts: 7296 Location: Seattle, WA Joined: April 23, 2001	I get the same (27dB), with my own completely independent lazy, end of day estimate. Coincidence? Intelligence?? We may never know ... :^)

RE: 91A derivative - question to Paul Joppa, posted on January 7, 2015 at 21:03:45
xcortes Audiophile Posts: 1221 Joined: July 23, 2003	And not out of laziness but out of ignorance. How does that translate to the voltage required to get the full power? Thanks Pauls

RE: 91A derivative - question to Paul Joppa, posted on January 8, 2015 at 06:11:58

awsjr
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hi Xavier, Tre, Paul B & Paul J... I have grid chokes in there...
BCP-16 GC HN... Mike's specs are as follows - Inductance (H) "Holy @#&%!! and the DCR "On the Money"... the amps sound great, deep bass and the highs are crisp... mid range is superb... the gain is high compared to some other amps I have but at the minimun volume level it is low level background music... I may put a 270K AB resistor in sometime to see how it may change things... thanks once again to Paul J for the design

RE: 91A derivative - parts list , posted on January 8, 2015 at 06:59:13

awsjr
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Posts: 235
Location: Austin, Tejas
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if there's any interest my parts are below...
R1 50K 25w ohmite
R4 1K 50w ohmite
Rstop 220r riken
R5 220K AB or 100K PEC pot
R6 1.2K caddock mk132
R7 30K 5w mills
R8 75K 5w mills
R9 91K 2w audio note
R10 250K 2w AB or Magnequest grid choke
R11 27K 1w audio note
C1,C2,C8 Obligatto film & oil 22uF 630v
C4 ASC 45uF can
C5 Mundorf 15uF 350v mundorf aluminum silver & oil
C6 Jantzen 8.2uF 800v superior Z
C7 Relcap tft 0.1uF 630v
Cpf Mundorf 10uF Supreme silver w/ oil
D1-4 schottkey diode
L1 Triad C-7X
L2 Magnequest EXO-003 plate choke
L3,4 Hammond 155B
T1 Magnequest PGP 8.1 PS
T2 Magnequest TFA-2004 cobalt OPT
hum pot PEC 100ohm 2w carbon pot
sockets gold teflon
RCA and binding posts Cardas
IEC Furutech FI-10
1/8" brass top plate, .06 Al bottom plate

RE: 91A derivative - parts list , posted on January 8, 2015 at 14:31:24
xcortes Audiophile Posts: 1221 Joined: July 23, 2003	Thanks for the comments ans parts list. Looks like a great amp. And comgrats on your build!

RE: 91A derivative - question to Paul Joppa, posted on January 8, 2015 at 18:10:11
Paul Joppa Industry Professional Posts: 7296 Location: Seattle, WA Joined: April 23, 2001	If full power is 8 watts into 8 ohms, that would be 8 volts RMS output. 26dB is a factor of 20, so 8/20=0.4vRMS. 27dB is 1dB less, or about 0.36 volt.

Thanks Again! nt, posted on January 8, 2015 at 18:36:24
xcortes Audiophile Posts: 1221 Joined: July 23, 2003	Nt

RE: 91A derivative - parts list , posted on January 8, 2015 at 20:56:23

drlowmu
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The part I like the most in your new amp is L1, the Triad C-7X. Wow.

10 HYs at 270 Ohms.

That will give it unusual performance capabilities, ripple will be sooo low !!!

'Way to go buddy.

Jeff Medwin

ALT. 1., posted on January 8, 2015 at 22:25:47

drlowmu
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ALT 1.

Not perfect, but ALT. 1. does this :

(1) This totally eliminates a nasty C-input filter.

(2) It reduces series resistances to the 300B Finals Filter, from 270 Ohms to 19 Ohms, a 14-fold reduction.

(3) It reduces B+ ripple from 457 mVAC to 437 mVAC.

(4) It offers a much SMOOTHER non-ringing step response.

(5) In my A-B testing since 1982, L1/C1/L2/C2 always sounds "more refined" than any single L/C filter.

- - - - - - - - - - - - - - - - - - - - -

Question : Which amplifier B+ filter do YOU think would sound best? Why ?

Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 05:16:09
cpotl Audiophile Posts: 1002 Location: Texas Joined: December 6, 2009	Jeff, could you explain why you apparently attach great significance to the response of the power supply to a stepped load? The power demands from an SE amplifier are not remotely like that. Chris

RE: ALT. 1., posted on January 9, 2015 at 06:11:07

cpotl
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"It reduces series resistances to the 300B Finals Filter, from 270 Ohms to 19 Ohms, a 14-fold reduction."

What do you mean by "resistance to the 300B Finals Filter"? I can see that what you have done to get your two numbers (270 ohms vs 19 ohms) is to add up the DC resistances of a subset of the components in the power supply circuit (i.e. just the chokes). But the resistance of the power transformer secondary is just as much in the circuit as the chokes are. As is the rectifier.

If you really mean the output impedance of the power supply, in the zero frequency limt (i.e. DC), then you can read that off from your simulations, by calculating (Delta V)/(Delta I), where Delta V is the change in output voltage, once steady state is reached, resulting from the change in current Delta I when the stepped load is turned on.

This output resistance of the power supply can be seen to be about 570 ohms for the first simulation, with the 10 H choke, and about 650 ohms for the second simulation, with the 1 H and 1.1 H chokes.

I don't think these zero-frequency figures are particularly important, in fact, since as I said the nature of the time dependence of the power requirements of an SE amplifier is very different from that of a stepped load. But if you do want to talk about "DC resistance," then it seems your prefered power supply has a larger value than the other one.

Chris

RE: ALT. 1., posted on January 9, 2015 at 07:30:08

drlowmu
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Chris,

I was already fully aware of all that you wrote. Thanks. Now answer this :

Question : Which amplifier B+ filter do YOU think would sound best? Why ?

RE: ALT. 1., posted on January 9, 2015 at 08:09:17

cpotl
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"I was already fully aware of all that you wrote...."

So you agree that the DC resistance of your preferred power supply is greater than that of the one you are comparing it with?

But you didn't address my main points:

1) What do you mean by "resistance to the 300B Finals Filter"? The figures you presented are just the sum of the DC resistances of the chokes. But why would that figure, of itself, be significant? The transformer secondary and the rectifier are also in that circuit.

2) A stepped load is not representative of the power demand from an SE amplifier. The current draw by the amplifier is, on average, constant, with the timescale of the fluctuations being the timescale of the frequencies in the audio signal. So what really matters as far as the amplifier is concerned is the output impedance of the power supply at audio frequencies, and how that impedance varies as a function of the audio frequency.

Chris

RE: ALT. 1., posted on January 9, 2015 at 08:29:58

drlowmu
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Please don't try to hijack my thread. Just honestly answer the key, germane question I posed, IF you seek to participate . We should think in terms of instantaneous pulsed power delivery, rather than constant sinusoidal.

Question : Which amplifier B+ filter do YOU think would sound best? Why ?

RE: ALT. 1., posted on January 9, 2015 at 08:36:49

cpotl
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"Don't hijack my thread. Just answer the question I posed, IF you seek to participate ."

First of all, it's not your thread. The OP was xcortes. And all I am doing is asking you to explain some points relating to the posts that you made on this thread.

As I said before, "what really matters as far as the amplifier is concerned is the output impedance of the power supply at audio frequencies, and how that impedance varies as a function of the audio frequency." Without knowing that information for the two power supplies, I don't know how to answer your question about which would sound better.

Chris

RE: ALT. 1., posted on January 9, 2015 at 08:50:16
rage Audiophile Posts: 793 Joined: December 17, 2010	Chris, There was a time Jeff was tuning with the assistance of the math you provided. He and JLH called it "Dynamic impedance". He also tuned to minimize the recovery time. (<50ms as I recall) Jeff has since moved on to other variables and dismissed his former critiea.

RE: ALT. 1., posted on January 9, 2015 at 08:53:35

drlowmu
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The amp is held constant, ALL we are discussing is the B+ Filter to the Finals, three or four parts choices, and what will perform best, on the basis of instantaneous pulsed power delivery.

I am amazed that you don't know, but that is all you really need to say.

Lets see if others will answer and tell us why.

How "deep" does this SET AA Forum go ?? Who responds, and what they say as to "why" will be telling.

Paul Joppa has always been interested in us respectfully commenting on designs he has posted, as a way of possibly improving a circuit's audio performance.

Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 09:00:45
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Lets not get sidetracked and get off course. Rage, which B+ filter do YOU think would sound best, and why ?? Chris says he doesn't know.

RE: ALT. 1., posted on January 9, 2015 at 09:11:59

rage
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I don't necessarily believe I'm side tracking here as I find it interesting that some math that was brought up was previously used by yourself. If anything it validates my own belief that the previous ideas were releveant and you jumped ship a bit early on a well thought out power supply.

anyhow, I'd lean closer to your variation given that there are two chokes being used and I think two small chokes, particularly in the 1H+ range will filter better than a single 10H. on top of that, your variation uses more capacitance which will also help things.

I suspect your supply could compete with the other supply, in terms of "dynamic impedance" (or using chris' math), by the simple addition of a small input cap... you'd call it a cLCLC. varying that first cap, from .1uf to .68uf will change the "dyanmaic impedance" and give some further flexiblity in tuning the two stage power supply.

I'd actually like to see a simulation done without a current step, which would tell us which supply would be lower in ripple. My money says your variation would have less ripple. (more capacitance, two stages)

Also I'd not get so hung up on that 30uf first cap, I suspect that is specific to DFs exact implimentation.. (and it was 35uf in his amps)

RE: 91A derivative - question to Paul Joppa, posted on January 9, 2015 at 09:22:54

Ivan303
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.

First they came for the dumb-asses
And I did not speak out
Because I was not a dumb-ass

RE: ALT. 1., posted on January 9, 2015 at 09:24:25

cpotl
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Location: Texas
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"The amp is held constant, ALL we are discussing is the B+ Filter to the Finals, three or four parts choices, and what will perform best, on the basis of instantaneous pulsed power delivery."

I'm not sure what you are driving at when you say "The amp is held constant."

As I have tried to point out several times, the nature of the power demands of the amplifier, as it plays the music, governs the criteria that one needs to consider when designing the power supply. For a class AB amplifier, the net current draw by the amplifier can grow a lot larger during the course of a loud, and maybe and prolonged, crescendo in the music. By contrast, in a single-ended amplifier, which is class A, the net current draw, averaged over the timescale of the audio frequencies it is reproducing, is essentially constant and independent of whether the music is loud or quiet.

Thus, the design criteria for the power supply can be very different in the two cases. For a class AB amplifier, your criterion of looking at how the power supply responds to a stepped load would be quite relevant. For a class A amplifier like an SET, on the other hand, the power supply will not encounter any such prolonged increases in the loading. The important thing for a power supply for an SE amplifier is that it should allow the audio signal to pass through it with minimal let or hindrance. Thus, the important point is that the output impedance of the power supply in the audio frequency range should be small in comparison to to the impedances associated with the output stage of the amplifier itself, so that there is no significant frequency roll-off.

One can fairly easily make some estimates of the impedance at the output of the power supply, but one would probably want to use SPICE in order to do a better job.

Armed with such information, one would be in a better position to say which of the two power supplies you presented would be better. Neither of them looked very good to me.

Chris

RE: ALT. 1., posted on January 9, 2015 at 09:37:56

tube wrangler
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HINT: The current draw in a Class A amplifier is NEVER, EVER "constant" when the amplifier is reproducing musical dynamics.

The THEORY that current draw is constant in ANY kind of amplifier is an old-wive's tale that needs to be put to rest.

Constant current draw DOES NOT EXIST in any circuit that is processing musical dynamics.

---Dennis---

RE: ALT. 1., posted on January 9, 2015 at 09:50:48

cpotl
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"The current draw in a Class A amplifier is NEVER, EVER "constant" when the amplifier is reproducing musical dynamics..."

Indeed, of course it isn't. As has been said many times, for an SE amplifier the current draw fluctuates in step with the audio signal. But the average current draw, averaged over the timescales of the audio frequencies in the signal, is approximately constant. (The current oscillates up and down around the quiescent current. Assuming there is no gross distortion, the fluctuations above and below the quiescent level, on the positive and negative halves of the audio cycles, are essentially equal in magnitude, and hence the average current is essentially constant.)

Chris

RE: ALT. 1., posted on January 9, 2015 at 10:01:10

drlowmu
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Thanks for responding. There is hardly any meaningful difference in dynamic impedances and ripple between the two supplies, Chris gave the impedance figures, ( 570 Ohms stock, 650 Ohms ALT.1, a 17% increase ) and I have originally posted, ALT 1. is 437 mVAC. versus 457 mVAC ripple with the original 10 HY choke, ( about a 5% decrease with ALT.1 ).

However, there IS a 14 times reduction in B+ filter series resistances with ALT.1 to the Finals tube. Which B+ filter would sound better ? Why?

Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 10:01:49

Garg0yle
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Yes it was explained in that other thread. I myself self learned something from that thread.

It was interesting when I modeled a typical PSU compared to the low-everything (Farkwin), the low everything was worse in regards to how long it could hold the original desired voltage.

Drlomu's PSU drops voltage like a stone in comparison, specifically in the region where transient response is important.

This reenforces my experiences that "stiffer" power supplies deliver better transients.

While I agree that PSUD cannot replicate the amplifier load accurately, it does however give an idea as to how the PSU will respond to a dynamic request.

Since the desired response is a flat line, then you want a PSU that holds a flatter line, if only for a short time.
Music is transient and random. Liveliness IMO comes from the attack.

If you look at my model below from at the start (4.1 seconds), to say 4.12 seconds you will see that Drlomu's PSU has already dropped more then twice the voltage of my more typical design.

Even though tubes sag more over time then SS diodes, I find that the initial slope is comparable between the two. Therefor one doesn't have to be overly concerned on the choice of rectification from this particular transient viewpoint.

I used a similar concept but with SS diodes in my little RH84 with wimpy OPTs and 604 duplex, it has dynamics that will make you blink.

△This message will self destruct in 10 seconds△

RE: ALT. 1., posted on January 9, 2015 at 10:05:29

Tre'
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"Constant current draw DOES NOT EXIST in any circuit that is processing musical dynamics."

Assuming perfectly linear tubes, a push pull Class A output stage will draw constant current on a moment by moment basis.

Assuming reasonably linear tubes, the current draw of a push pull Class A output stage will not change by very much at all.

So while you statement is in fact true, it's misleading.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

RE: ALT. 1., posted on January 9, 2015 at 10:17:10

rage
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the difference is 80 ohms. that's hardley a difference?

we used to shoot for ~ 200 ohms...we're talking 570 vs 650 ohms now. (when I say "we" I mean those of us that attempt to follow you on power supply design)

if you do believe in using the step response then surely the math that is used to evaluate it is relevenat?

or are we just looking at DCR and using step response to show the smoothness of the waveform?

all you're doing is comparing "under dampened, over dampened and ringing power supplies". (from the JLH documents you sent me)

also, do these 1H 9.5 ohm chokes really exist, or are you manipulating the inductance to get the results you are looking for? since you are now locked in at 30uf and 50uf, all you can vary is the chokes?

Good post. You have the proper understand of the issues invloved. (nt), posted on January 9, 2015 at 10:27:00
Tre' Industry Professional Posts: 17305 Location: So. Cal. Joined: February 9, 2002	. Have Fun and Enjoy the Music "Still Working the Problem"

what spice sez, posted on January 9, 2015 at 10:38:19
dave slagle Manufacturer Posts: 5430 Location: NYC Joined: April 27, 2001	and increasing the values of the caps in the CLC version

RE: ALT. 1., posted on January 9, 2015 at 10:59:09

drlowmu
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Rage,

You write : "the difference is 80 ohms. that's hardley a difference?"

Correct about 17%.

Correct, for all intensive purposes, the supplies are similar in Z and ripple. Chris was just posting the "usual" up here, anything to confuse and obfuscate my question of : which sounds better, one with 270 Ohms series resistances or 19 Ohms, a 14 fold difference !!!

We have another cat below that is talking about P-P amps, and this 91 amp is a SE er, and the question doesn't get answered by him either. Confuse, obfuscate, never answer which sounds better and why.

Rage, since early 2014, we do 2.0 HY at 9.5 Ohm chokes, under two pounds. It would not be any problem what so ever to do 1 HY, small in mass - under two pounds, at the same 9.5 Ohm DCR, or likely even less in DCR.

Jeff Medwin

RE: what spice sez, posted on January 9, 2015 at 11:03:19

drlowmu
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Thanks Dave,

Not too many of us amateurs are comfortable with Spice. Could you please tell us ( me ) what that means?

Also, could I ask you what "you" think might sounds better between the two filters, and why ?

Thanks, you are a benefit to us all.

Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 11:07:58

cpotl
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"which sounds better, one with 270 Ohms series resistances or 19 Ohms, a 14 fold difference"

But you are presenting an incomplete picture here, by only including the DC resistances of the chokes. If you want to add up the DC resistances in that circuit, then you certainly need to add in the DC resistance of the secondary winding of the power transformer. And the rectifier is in the circuit too.

In your preferred PS, for example, any current that flows through L1 must necessarily also flow through the power transformer secondary and also through the rectifier. So just adding together the DC resistances of the two chokes is simply wrong.

Chris

RE: ALT. 1., posted on January 9, 2015 at 11:14:51
dave slagle Manufacturer Posts: 5430 Location: NYC Joined: April 27, 2001	Assuming reasonably linear tubes, the current draw of a push pull Class A output stage will not change by very much at all. This comment always bothered me. Chris covered it when he included the "over a period of time" but when we look at the actual current through the output the picture is quite different. this is a few watts out of a 2A3 with a DC bias of about 58.5ma dave

RE: ALT. 1., posted on January 9, 2015 at 11:22:26

cpotl
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" "Assuming reasonably linear tubes, the current draw of a push pull Class A output stage will not change by very much at all."

This comment always bothered me. Chris covered it when he included the "over a period of time" but when we look at the actual current through the output the picture is quite different."

That statement you quoted was for a push-pull class A amplifier. I think the plot that you displayed is for single-ended, right? The current as a function of time looks just right for single ended; fluctuating roughly equally up and down around the quiescent level.

For push-pull class A, the total current should be very nearly constant, since it should be like the sum of the plot you showed plus an inverted version of that plot.

Chris

RE: what spice sez, posted on January 9, 2015 at 11:29:52

cpotl
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Here is my attempt to simulate the drlowmu power supply, using the same set-up as I think you have in your SPICE simulation. I took the two chokes, 1 H and 1.1 H, to have DC resistance 9.5 ohms each, and I copied your 100 ohms as a model for the power transformer plus rectifier. (I'm really not sure how good a model that is, which is why I've been a bit hesitant about making strong claims about how the PS would perform.) Anyway, with 30 uF and 50 uF for the two capacitors, my calculation in Mathematica then gives this result for the impedance as a function of frequency.

Chris
(This is a corrected plot. Had a typo before.)

RE: ALT. 1., posted on January 9, 2015 at 11:36:49
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	You are dancing around again, we are using the same EXACT power transformer and rectifier tube, so there is nothing else to take into account. We are just looking at two different B+ supply filter topologies, in the same amp. Now, answer my question Chris. Which B+ supply filter will sound best? And WHY ?? Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 11:43:05
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	And furthermore Dave, isn't this discussion about a B+ filter to a SINGLE ENDED A1 amp, and not a PUSH PULL A1 output stage ?? I am certainly no electronics whiz, but might that be significant ? If so, why would one anyone inject P-P examples in a SE amp design discussion ? Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 11:49:38

cpotl
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" We are just looking at two different B+ supply filter topologies, in the same amp...
Now, answer my question Chris. Which B+ supply filter will sound best? And WHY ??"

Well, if Dave Slagle's approximation for the power supply is a reasonable one, then your preferred filter set-up gives that impedance resonance peak around 45Hz, in the audible range, which I showed in my previous post. The other filter set-up, disfavoured by you, gives this result instead.

Based on the appearance of the two plots, I would probably expect the one you don't like to give a better rendition of the audio signal. I don't think either of them is anything to write home about. But then, if it were me, I'd just use solid-state rectifiers, big capacitors and a small resistor, and avoid most of the LC resonance problems altogether.

Of course, an entirely different question is which one would give the sound that you personally prefer. That is really a psycho-acoustical and psychological question, which I would not attempt to answer.

Chris
(This is a corrected plot. Had a typo in the Mathematica routine before.)

RE: what spice sez, posted on January 9, 2015 at 12:07:23
dave slagle Manufacturer Posts: 5430 Location: NYC Joined: April 27, 2001	Well, we do have the resonances in the same spots :-) what concerns me in your sim is that it drops below the series resistance values at low frequencies and mine levels out at the series resistance numbers. dave

Great Post !!!!, posted on January 9, 2015 at 12:10:59

drlowmu
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You have taught yourself how to download and input data into PSUD2. Good job.

Now, you need to learn how to properly interpret what it shows AND how it applies to audio design in power supplies. You are not doing that at all, you have several things backwards.

Swenson, a graduate EE, has measured music and he tells us essentially, that the first 50 mS are "free". He tries to get "his" supply to settle within 50 mS. ... but I don't do that any more, I have other design priorities.

Opposite of what you wrote and thought, it is beneficial for the supply to " fall like a rock " and settle quickly ( but smoothly ) in the first 50 mS. After the 50 mS. time, the quicker it settles "overall", the more able it will be - to play back the very next large transient, inherent in the music.

With all that UNusual storage ( 30 HYs and 150 uF ) the supply you simulated has a better dynamic Z than ALT.1, but, ALT.1 settles fully, and smoothly with no overshoot, in 250 mS, ( 4.35 mS. ) whereas yours is still recovering in up to 400 mS. of time ( 4.5 mS. ). When music's next transient comes along, your supply is still dropping, and ALT.1 has possibly fully recovered, and is ready to please.

The worse thing of all is, the human ear / brain will instantly pick up on large slow B+ filter parts to the Finals ( high L and high C ) as being slow and out of time with the music. So it sounds out-of-time, slow, like an audio amp - like 99% of the amps out there, and not like real music.

Where do we find a 30 HY choke at 220 Ohms ? Would 19 Ohms of series resistances in a B+ filter to the FINALS sound better than 270 Ohms ?

Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 12:14:36

drlowmu
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Thanks for contributing Chris.

What about from 100 HZ to 20 KHZ, does that matter any ??

Jeff Medwin

RE: what spice sez, posted on January 9, 2015 at 12:22:01

cpotl
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"what concerns me in your sim is that it drops below the series resistance values at low frequencies and mine levels out at the series resistance numbers."

Sorry! You are quite right. I had a stupid and inexcusable typo in my Mathematica routines. I've corrected the two plots now.

Chris

RE: what spice sez, posted on January 9, 2015 at 12:22:06

rage
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I'm going to watch the results of these sims be hashed out amongst the group here... and enjoy Dave and Chris' bringing simulations to the table...

I'd just like to point out that it'd be next to impossible to speck a choke at 1.1 henry, vs 1 henry... that has to be an error on jeff's part in the sim.. I can't imagine that .1 henry difference making a significant difference, just know that the chokes will measure differently under different current levels and that he couldn't speck two difference chokes, one at 1h and one at 1.1h.

Jeff we've had debate over different chokes meausuring differenctly...using a LCR or a real bridge, etc.

that is the main probelm with tuning in PSUD2 to these extremes...its difficult to get an accurate indutance on the chokes, it is all guess work.

on another note, I'd still stick with the two 1h chokes and believe Dave's simulation shows lower impedance across the board, albeit with the resonance around 50-60hz... which might help dynamics :)

RE: ALT. 1., posted on January 9, 2015 at 12:27:30
cpotl Audiophile Posts: 1002 Location: Texas Joined: December 6, 2009	"What about from 100 HZ to 20 KHZ, does that matter any ??" Nothing particular of interest, in the higher frequencies. Just the expected fall-off because of the final capacitor. All the "drama" is in the lower frequency part of the spectrum. Chris

RE: ALT. 1., posted on January 9, 2015 at 13:32:55

91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014

Hi Jeff,

You are much more experienced at this than I am, but is the way you have your x-axis configured fails to show something that might be relevant?

Your model does not show the irregularly undulating waveform.

In closer detail:

This is not something that is unique to your modelled PS; I have noticed it with most LCLC supplies. Is it caused by the interaction between to the two LC filters (resonances or some such)? Do you think this could this be an issue in practice?

Regards,
91

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: Great Post !!!!, posted on January 9, 2015 at 13:53:44

Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014

My PT is not 65 Ohms to center tap as your simulation shows, there is no hump and not that the hump is even relevant.

I have 30H 220 ohm chokes on the bench right now, shouldn't be hard to find.

As it has been explained to you, the part of the Sim that is relevant is the is the beginning.

The rest of the Sim shows a steady state draw on the PSU, which isn't whats happening with an audio signal.

Try again.

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RE: ALT. 1., posted on January 9, 2015 at 14:49:24
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	I THINK it MAY be a difference between my earlier downloaded PSUD2, and more recent downloaded copies, which is different. I will do 1,000 sec and look ! I did not recall seeing what you are showing me. Jeff

RE: ALT. 1., posted on January 9, 2015 at 14:52:50

Tre'
Industry Professional

Posts: 17305
Location: So. Cal.
Joined: February 9, 2002

That looks like the current draw for one tube playing music.

Add to that another tube with an input signal out of phase but otherwise identical and the total current draw change on the power supply should go down.

If both tubes were 100% linear and if the drive signals were 100% out of phase with each other but otherwise 100% identical then the current draw change would be zero.

There's no such thing as a 100% linear tube so Dennis' statement "Constant current draw DOES NOT EXIST in any circuit that is processing musical dynamics." is true but in the context that he made it, IMO, it is misleading.

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

RE: ALT. 1., posted on January 9, 2015 at 15:05:21

tube wrangler
Manufacturer

Posts: 2484
Location: USA
Joined: January 29, 2007

Just for BS sake, that first cap (after the L) is two G.E. "80uf" units in series with a bleeder resistor across each one.

I have measured hundreds of these, as I match each pair very closely. They nearly always measure 69uf-- variations are not much at all.

In any case, the seriesed pair calculates at about 34uf.

There is more to this story however-- as two in series do not do the same thing that one of that value would do. Seriesed caps with bleeders behave differently, also the bleeders are figured into this circuit electronically. I have good reasons why I like that setup as the first capacitor.

---Dennis---

RE: Great Post !!!!, posted on January 9, 2015 at 15:07:21

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

GG,

Ohh my goodness, I now do see you are using 165 Ohms, and I "saw" the "one" in one sixty five as a "parenthesis" on my small monitor. My visual error. Are you suggesting 1/2 your HV secondary is 165 Ohms?

As for this " As it has been explained to you, the part of the Sim that is relevant is the is the beginning."

That is incorrect, you have the "beginning" bass ackwards, the drop in the first 50 mS. is GOOD to be sharp and get "most" of the settling done smoothly and quickly as possible.

I will re-PSUD2 with 165 Ohms. BTW, That 165 Ohms PT DCR is a LOT worse than 65 Ohms. It WILL however, damp the waveform, and make EVERYTHING go in slow, out-of-time motion. Now, I'll go back to PSUD2 with 165 Ohms DCR, yikes !!

Jeff Medwin

Corrected the Simulation , posted on January 9, 2015 at 15:41:51

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

GG,

We "match" more now, wondered why we differed !! Now I know, GIGO.

You still have this LONG fully-settle time - 400 mS. It stays the same.

Now however, this cheap-wimpy-soggy 165 Ohm Power Transformer has increased the Z of your supply, to where its worse than ALT.1. Your B+ filter drops 8.83 VDC peak to trough settled, and ALT.1 drops about 7.83 VDC peak to trough. On a similar change of 12.25 mA. ( the current step ) your B+ Filter NOW has a calculated Z of 720 Ohms, and ALT.1 has a Z of 631 Ohms.

Amps with 165 Ohm Power Transformers and 270 Ohms chokes sound like you are listening to the music on your 604s, with a big woolen blanket thrown over the coaxial driver. What I may need to do is bring one of my DC amps up to Chicago area, next time I visit there, and let you hear it for yourself.

Jeff Medwin

RE: ALT. 1., posted on January 9, 2015 at 15:46:44
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	Thanks Jeff. BTW, I am using version 2.0.3 Regards, 91 "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: what spice sez, posted on January 9, 2015 at 15:47:00

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

Dave, since you are doing those simulations in SPICE, I wonder if it is fairly straightforward to include the transformer and rectifier in the sim also? One could then look at the behaviour when the power supply is loaded with a constant quiescent current and a superimposed sinewave current (so I = I0 + I1 Sin(w t), simulating a typical load of an SE amplifier reproducing an audio frequency f=w/(2 \pi)). It would be interesting to see how the magnitude of the audio "ripple" on the power supply output voltage behaved for various frequencies f in the vicinity of the resonance in the low audio spectrum in the drlowmu supply.

The reason I am wondering about this is that the approximation of putting that 100 ohm resistor to "represent" the power transformer and rectifier is a bit of a rough and ready one. The behaviour of the impedance curves changes significantly if one alters that 100 ohm value. I think the qualitative feature of the resonance is always going to be there, however.

I'm not familiar with using SPICE, and although I can handle LCR networks fairly easily (when I'm not making stupid typos!) using Mathematica, it's a rather tougher proposition to try to deal with rectifiers without the aid of a dedicated program like SPICE.

So it might be interesting to see what SPICE would reveal, along the lines I was suggesting. Oscillatory loads are much more relevant than stepped loads for probing the relevant features of a power supply for an SE amplifier.

Chris

RE: ALT. 1., posted on January 9, 2015 at 15:56:07
dave slagle Manufacturer Posts: 5430 Location: NYC Joined: April 27, 2001	What is all this PP talk in a SE forum.... what next those ideal transistors? dave

RE: ALT. 1., posted on January 9, 2015 at 15:58:04

91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014

Hi Chris,

I am rather new to this (surprise!), but I am wondering: what are the technical and sonic implications of the impedance peak in the "audible" range. How does it affect what is produced at the speaker drivers?

Does the increased impedance affect the ability to deliver current or affect the voltage at a given frequency? How does this translate sonically?

Just trying to learn.

Regards,
91

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: ALT. 1., posted on January 9, 2015 at 16:04:41
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	.

More Lowmu Baloney , posted on January 9, 2015 at 16:07:39

Triode_Kingdom
Audiophile

Posts: 10049
Location: Central Texas
Joined: September 24, 2006

"Swenson, a graduate EE, has measured music and he tells us essentially, that the first 50 mS are "free"."

What event precedes the "free" 50mS that you're referring to? Surely not the onset of a musical demand by the amplifier?

" the human ear / brain will instantly pick up on large slow B+ filter parts to the Finals"

The amplifier can only be properly powered when the supply maintains constant voltage against changing current demands. The opposite of this is a sloppy, quickly moving supply that sags and resonates. That seems to be the sort of thing that you equate with high quality reproduction.

RE: RH84 ..., posted on January 9, 2015 at 16:11:42
deathtube 667	"I used a similar concept but with SS diodes in my little RH84 with wimpy OPTs and 604 duplex, it has dynamics that will make you blink." How ironic. I have recently set up a variation of the SE RH EL84. Exactly what PS are you using and what is the B+ off the rectifier? Did you get any distortion or bandwidth measurements? I posted some measurements on Tube DIY of my circuit performance.

RE: Great Post !!!!, posted on January 9, 2015 at 16:18:32

91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014

Hi again Jeff,

>>> the drop in the first 50 mS. is GOOD to be sharp and get "most" of the settling done smoothly and quickly as possible. <<<

I dunno, isn't the speed of the drop that only part of what matters? I would have thought the *magnitude* of the drop against time would also be an important aspect (wanting to keep the voltage up as transients hit), as would the time to recover and (lack of) overshoot and ringing.

Non-technical conceptualisation:

When a big transient hits, the PS voltage should fall fast enough to support sufficiently quick recovery, but should not fall far so as to maintain voltage for the transient. Recovery should be smooth and fast enough that voltage has recovered and the PS stabilised before the next big transient hits.

The caveat for me is, does the 15% stepped current in PSUD2 reflect anything like real-world conditions and can we really extrapolate audible effects from it?

Of course, this ignores PS impedance and maximum accepted ripple etc.

Regards,
91

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: ALT. 1., posted on January 9, 2015 at 16:26:07
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	Hmmm, I think it may be related to screen size/ resolution. I am using a relatively longer x-axis. I can see some evidence of what could be similar ringing/variation in your image, but it is hard to draw any conclusions. Interesting. Thanks. Regards, 91 "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: Great Post !!!!, posted on January 9, 2015 at 16:29:56

Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014

"That is incorrect, you have the "beginning" bass ackwards, the drop in the first 50 mS. is GOOD to be sharp and get "most" of the settling done smoothly and quickly as possible."

I disagree with this, you want to hold as much voltage in the beginning as possible.

The sharper the drop, the more voltage you have lost, as in your case.

A shallow drop on the other hand delivers a stronger leading edge to transients because it holds a higher voltage for a longer period of time.

Remember transients are gone as quickly (aside from residual decay) as they arrive, so I fail to see why you are so concerned with what is happening a half second later on a simulated resistor.

A step drop off means you have less power when you most need it.
A fast charge time is nice, but doesn't mean much if you don't have the immediate capacity when needed.

It's the area under the curve that is important.

Have a look below, you tell me which one sounds better.

Your approach:

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RE: Great Post !!!!, posted on January 9, 2015 at 16:30:31
Garg0yle Audiophile Posts: 859 Joined: December 1, 2014	Or mine: △This message will self destruct in 10 seconds△

RE: Great Post !!!!, posted on January 9, 2015 at 16:30:40
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	I think you have it nicely said on a conceptual basis. But I am not a EE Guru PSUD2 expert. The 15% step was something EEs Swenson and Hasquin used. I just copied their examples Raymond. Jeff

RE: what spice sez, posted on January 9, 2015 at 16:40:50
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Guys, ALL I did was change the Finals filter in Paul Joppa's schematic. This is hardly a supply I would use, as an overall supply. Nor is it an amp I would build. I was only changing out the high HY high DCR choke, and asking everyone, "which will sound better and why? " !!! Have fun, hardly anyone has answered my question above. Jeff Medwin

RE: Great Post !!!!, posted on January 9, 2015 at 16:55:34

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

GG,

This is really sort of funny !! You have it very wrong. Please send me your private email address, and I will email you, as attachments, all the SWENSON and HASQUIN posts, in chronological order, for you to read and digest some.

If you don't want me to contact you directly, no problem, find a Forum Member we both know, and It could be forwarded, them first, to you second.

I understand your line of thought, its just that it is not correct. The first 50 mS. are "free" according to SWENSON's measurements of music.

Your call on proceeding, I have the posts in Word Files. I am just being fair and open with you, certainly you recognize that.

Jeff Medwin

RE: RH84 ..., posted on January 9, 2015 at 18:08:33

Garg0yle
Audiophile

Posts: 859
Joined: December 1, 2014

"Did you get any distortion or bandwidth measurements?"
No

Here are the details of the RH PSU in the sim below.

Also for comparison with the two examples I submitted earlier, I applied the stepped load and the same 2V - .125 second scale to the chart.

As you can see this RH PSU is a little stiffer again then my earlier example. It's got some snap to it.

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RE: More Lowmu Baloney , posted on January 9, 2015 at 22:53:47
Ray Moth Audiophile Posts: 2784 Location: Jakarta, Indonesia Joined: November 10, 2003	"The amplifier can only be properly powered when the supply maintains constant voltage against changing current demands. The opposite of this is a sloppy, quickly moving supply that sags and resonates." Absolutely! The one thing we DON'T need is a B+ that squirms about.

RE: 91A derivative - question to Paul Joppa, posted on January 10, 2015 at 00:35:12
Todd Krieger Audiophile Posts: 37333 Location: SW United States Joined: November 2, 2000	You posted an image that comes up as broken.........

it was a simple question, posted on January 10, 2015 at 04:59:04

awsjr
Audiophile

Posts: 235
Location: Austin, Tejas
Joined: November 30, 2006

about using grid chokes.... then it gets hijacked into theoretical PS opinions.... first of all, this design originated back in 1993 by Joe Roberts and Paul Joppa was kind enough to rework it into a parafeed design.... could the amp be improved ?.... what amp can't ?....

these discussions constantly seem to end up revolving around a serious amp design that is so full of the latest and greatest stuff, but no schematic, test results or updated pictures are ever provided.... so far only one person has popped up with one of those amps and he got dissed as the design techniques have improved so much lately he has an out dated amp.... LOL.... its past time to say put up or stfu....

plus there is constant criticism about what people actually hear with other amps that do not follow these "modern" design rules.... music is "too slow" or "out of time" or other nonsense....

no doubt the amp is a huge piece of the sound puzzle.... my source is a Core Mac Mini to a Schiit Gungnir to speaker system with Onken 360L GPA 515-8LF bass, Oris 200 with AER MD3 mid and Fostex 900T highs.... not to mention all the cables and the XO construction that's there.... until you can match that don't even attempt to tell me what I hear....

please don't get me wrong.... I could care less what the "opinions" are of what I build, listen to or am perceived to hear.... my thought is some people could improve what that hear just by getting the wax out of their ear canals.... so what... the point is until we start to see the entire picture of whats being compared to what in reality then its all subjective.... and that's pretty much all it will ever be as there are too many different parameters that each of us have....

this is a great forum.... I learn a lot and am grateful to people for sharing their knowledge.... but the "my way is the only right way" is counter-productive....

Fixed now?, posted on January 10, 2015 at 08:10:01

Ivan303
Audiophile

Posts: 48887
Location: Cadiere d'azur FRANCE - Santa Fe, NM
Joined: February 26, 2001

One of those where I can see it but others can't?

Must be my Porn Blocker is disabled? =:-0

First they came for the dumb-asses
And I did not speak out
Because I was not a dumb-ass

RE: Great Post !!!!, posted on January 10, 2015 at 08:50:43
GEO Audiophile Posts: 4749 Joined: April 7, 2000 Contributor Since: September 9, 2000

RE: Great Post !!!!, posted on January 10, 2015 at 08:51:20
GEO Audiophile Posts: 4749 Joined: April 7, 2000 Contributor Since: September 9, 2000

RE: Great Post !!!!, posted on January 10, 2015 at 09:27:05
Garg0yle Audiophile Posts: 859 Joined: December 1, 2014	I can't see GEO's last two posts. △This message will self destruct in 10 seconds△

+1...., posted on January 10, 2015 at 12:12:00
Ivan303 Audiophile Posts: 48887 Location: Cadiere d'azur FRANCE - Santa Fe, NM Joined: February 26, 2001	Hard to thing of any topic that will not eventually evolve into a low resistance PS discussion, or so it seems. First they came for the dumb-asses And I did not speak out Because I was not a dumb-ass

RE: 91A derivative - parts list , posted on January 10, 2015 at 12:36:07
Caucasian Blackplate Industry Professional Posts: 8313 Location: Seattle Joined: June 18, 2004	Why are you simulating for a class B amplifier?

Sponsoring a sub forum would be a start, posted on January 10, 2015 at 15:18:14
GEO Audiophile Posts: 4749 Joined: April 7, 2000 Contributor Since: September 9, 2000	That would clean up a lot of the crap. People interested in pursuing "modern power supply design" will know where to find the pertinent info. BTW, AER drivers are nice. I looked at Lamhorns a long time ago that used those drivers. Reps are also nice drivers.

+1, with caveats., posted on January 10, 2015 at 16:02:33

91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014

I agree in general principle.

In this case, the off-topic posts/threads started with when you posted a response that was a parts list prefaced with "if there's any interest my parts are below...". Unintentionally, your post opened the door for off-tpoic responses without addressing xcortes' question. When I read Jeff's response to your post I considered calling-out Jeff on his off-topic, but I realised that it could be stretched that he was on topic in relation to your post.

With that said, I believe I did not help by asking questions in relation to power supplies and their modeling; my bad and I will try to always keep the *original* poster's question and intention in mind, rather than continuing subsequent off-topic posts. I agree that far too many threads evolve into debates about PS topologies and build methods that are at best extremely remotely related to the original post. It would make for a more productive forum if the instigators could stop (start a new topic!) and moderators make some attempt to keep discussions on topic.

I think we need to alert moderators to off-topic posts. If enough of us can do that, perhaps we could start to see more constructive discussions.

Regards,
91
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

Response to OP

DIYaudio has a power supply forum, posted on January 10, 2015 at 19:31:37
kyle Audiophile Posts: 1839 Location: London Ontario Joined: September 29, 1999	Maybe they could go there.

RE: ALT. 1., posted on January 10, 2015 at 20:55:49

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

"I am rather new to this (surprise!), but I am wondering: what are the technical and sonic implications of the impedance peak in the "audible" range. How does it affect what is produced at the speaker drivers?

Does the increased impedance affect the ability to deliver current or affect the voltage at a given frequency? How does this translate sonically?"

A very good question. I've spent some time today learning some of the basics of how to use SPICE, and I think I've succeeded in modelling a reasonably realistic power supply, with an applied load corresponding to the kind of thing that would arise with a class A single ended amplifier. It seems to confirm more or less the same qualitative features discussed already, in the case of a drlowmu style power supply with small values for the chokes. Namely, some sort of a resonance in the low audible spectrum, resulting in quite a strong modulation of the power supply voltage. Whether it is enough to be audible, I really don't know. But since he says he hears a difference with his power supplies, and since this modulation of the supply voltage seems to be a fairly robust feature of the models, perhaps these two things are indeed correlated.

Chris

RE: ALT. 1., posted on January 10, 2015 at 21:03:19
Garg0yle Audiophile Posts: 859 Joined: December 1, 2014	"Does the increased impedance affect the ability to deliver current or affect the voltage at a given frequency? How does this translate sonically?" Weak bass. △This message will self destruct in 10 seconds△

RE: I apologize, posted on January 11, 2015 at 03:36:26

awsjr
Audiophile

Posts: 235
Location: Austin, Tejas
Joined: November 30, 2006

you're right to a certain extent.... I did post a parts list although my PS cap are 22uF not the 15uF use in the sims (not that the results would change that much)....

but more important, my thought is people are sincere in their efforts to share knowledge.... a lot of people have forgotten more stuff about electronics then I know.... Jeff M is a good example.... always willing to jump in and offer some thoughts.... however there is a difference between teaching, coaching, correcting AND feeling like you are having something shoved up your arse.... perhaps remembering what it was like to be mentored would give some perspective on how things sometimes come across when trying to mentor.... anyway Jeff, thank you for your suggestions.... now Dennis is another story.... ha.... dude, until you open up your kimono with a schematic, pictures, test results etc you are on thin ice.... remember your post about mounting capacitors and not to cut their leads but winding them like shock absorbers ?.... classic.... like making little RF antennas....

inevitably we migrate towards people who we feel offer knowledge and advice we relate to or are comfortable with.... its all good... in the end we build designs that interest us and live with the result.... or tear it apart and redo as we see an approach that could be an improvement.... so again sorry to all and thanks to all for the wealth of information shared.... best -Al

RE: +1, with caveats., posted on January 11, 2015 at 05:23:29

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

"In this case, the off-topic posts/threads started with when you posted a response that was a parts list prefaced with "if there's any interest my parts are below...". Unintentionally, your post opened the door for off-tpoic responses without addressing xcortes' question. When I read Jeff's response to your post I considered calling-out Jeff on his off-topic, but I realised that it could be stretched that he was on topic in relation to your post."

Ironically, however, Jeff then accused me of hijacking HIS thread!

Chris

http://www.audioasylum.com/forums/set/messages/7/edit/782072

RE: DIYaudio has a power supply forum, posted on January 11, 2015 at 07:20:57
GEO Audiophile Posts: 4749 Joined: April 7, 2000 Contributor Since: September 9, 2000	I have no idea why Dennis and Jeff are so opposed to this concept. I believe they must like the bickering. It seems like they would do more to advance their "research" in a dedicated sub forum. Call me crazy.

RE: ALT. 1., posted on January 11, 2015 at 09:26:46

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

"I am rather new to this (surprise!), but I am wondering: what are the technical and sonic implications of the impedance peak in the "audible" range. How does it affect what is produced at the speaker drivers?"

Here is my attempt at modelling in LTSpice what happens. I've set it up so that the power supply is turned on at t=0, there is a quiescent load of 60 mA, and then at t=0.3 sec, after the supply has settled down, a burst of 36 Hz sinewave, with amplitude 60mA, is superimposed, for a duration of 15 complete cycles of the sinewave. This represents the SE amplifier operating at full volume for 15 cycles of the 36 Hz audio signal, and then going quiet again. The trace shows the output voltage of the power supply, with the resulting modulation by the audio signal shown. 36 Hz is near the resonance peak. It can be seen that the resonance continues, decaying away, for a few cycles after the burst of audio signal itself has finished.

Below is an exaggerated version of the same phenomenon, achieved by dropping the output capacitor C2 to 20 uF. This shifts the resonance to about 44 Hz. The trace again shows the voltage at the output of the power supply, this time with a 15 cycle burst of 44 Hz audio signal played at full volume. The resonance is now very prominent, and there are at least a dozen or so cycles of decaying oscillation visible after the burst of audio signal has stopped.

The second simulation is, of course, deliberately chosen with a very small value of C2 in order to exaggerate the effect so that it becomes very obvious what is happening. But the same phenomenon is occurring, in a somewhat less dramatic way, in the first more realistic simulation.

(Of course I'm just using "off the shelf" solid-state rectifiers in my simulations, because I haven't mastered more sophisticated aspects of LTSpice yet. And my transformer construction might leave a little to be desired! But I think these simulations capture the essence of what is going on.)

I'm not sure what audible effects one might expect from this, but it is evident that in addition to the resonant audio ripple on the power supply output voltage, there is also a "ringing" phenomenon after the audio burst signal has stopped, which might or might not have audible consequences.

Chris

RE: ALT. 1., posted on January 11, 2015 at 09:57:39
dave slagle Manufacturer Posts: 5430 Location: NYC Joined: April 27, 2001	Interesting.... try putting a 5K resistor across the current source. dave

RE: ALT. 1., posted on January 11, 2015 at 10:20:51

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

"Interesting.... try putting a 5K resistor across the current source."

I think maybe that damps the ringing down just a little. But it's a fairly marginal difference, I think. Another thing I've just tried is adding a 100 ohm resistor in series, immediately after the silicon rectifiers, as maybe a slightly closer approximation to a vacuum tube rectifier. The resonant frequency seems to shift up a tiny bit, and the amplitude of the modulation on the power supply increases somewhat, of course. Here's a simulation with the 100 ohm series resistor and the 5K shunting the current source also.

Chris

(I'm not sure why some of the wires in the schematic aren't showing up in this jpg file, but they really are there! I don't seem to be able to find a way of directly saving the LTSpice window as a jpg or whatever, so I've been resorting to taking a screenshot and then cropping it. There must be a better way?)

RE: ALT. 1., posted on January 11, 2015 at 11:47:54
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Myself, and Dennis, never use solid state rectifiers. Sub in a directly heated rectifier, either a 5V3, 5V3A, or a 5U4G, and see how that goes. Q.: Have YOU ever heard one of Dennis' amps at RMAF, an owner's home, etc ?? Jeff Medwin

RE: ALT. 1., posted on January 11, 2015 at 11:50:32
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	BTW, the values you are simming are strictly "mine" as it applies to the Joppa filter, and it is NOT what DF and JM use for themselves exactly !! Jeff Medwin

RE: ALT. 1., posted on January 11, 2015 at 11:55:54
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Correct, and that is certainly not the case in Dennis' amps or mine, so, the simulation is inaccurate, looking at the wrong thing, or both !!!! Jeff Medwin

RE: That's what my friend says when he built this supply, posted on January 11, 2015 at 12:02:50
deafbykhorns Audiophile Posts: 1067 Location: Florida Joined: October 17, 2003	Weak bass. This was a couple years ago so maybe there's some revisions since then? It was powering a 2A3 amp that had perfectly good bass response with the traditional supply.

RE: ALT. 1., posted on January 11, 2015 at 12:08:42

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

"...the simulation is inaccurate, looking at the wrong thing, or both..."

I think the simulation is looking at the right kind of thing, namely how the power supply responds to the kind of loading an SE amplifier might put on it. I'm not claiming that the simulation is completely accurate for the specific details of your rectifiers, etc. And the capacitor and inductor values may not be precisely those you would choose to use in your preferred supply. Those could easily be changed, of course.

But I think the broad features are going to remain qualitatively similar, even if some of those changes are made. If the supply has a resonance in the (low) audio spectrum, then it is going to exhibit some ringing also, in the low audio spectrum.

Chris

+1 without caveats., posted on January 11, 2015 at 12:11:00
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	Though I don't mind Dennis' postings, for the most part. Regards, 91 "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

Yeah, it can get a little weird in the asylum. nt., posted on January 11, 2015 at 12:14:03
91derlust Audiophile Posts: 1101 Joined: December 25, 2014	. "Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

RE: ALT. 1., posted on January 11, 2015 at 12:23:17
GEO Audiophile Posts: 4749 Joined: April 7, 2000 Contributor Since: September 9, 2000	I don't know why it's so hard for someone who likes that supply to just say they like the sound of a sloppy supply. It obviously sounds better to their ears.

RE: ALT. 1., posted on January 11, 2015 at 12:30:35

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

"I don't know why it's so hard for someone who likes that supply to just say they like the sound of a sloppy supply. It obviously sounds better to their ears."

Yes, I agree. Jeff says he likes the sound of it. Basic EE theory and simulations say that it indeed has some characteristic features that quite possibly could account for there being audible differences between it and a more conventional power supply. It should not be too much of a stretch to make the link between these two statements.

Chris

Two questions, easy to answer ...., posted on January 11, 2015 at 12:36:59

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

Chris,

You only theorize.

Have you ever actually gone to a show, etc. and heard a Dennis Fraker 2A3 DC amplifier? Yes or No ?

Any idea why it got " Best Sound at Show " 2005 RMAF by Mr. S. Harrell, writing for Six Moons ??

Jeff Medwin

http://www.6moons.com/industryfeatures/rmaf05stephaen/rmaf05

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SET Asylum

91A derivative - question to Paul Joppa

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