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In Reply to: Re: Jeff's low initial C PS ideas may not be entirely novel ... posted by Perseo on April 20, 2007 at 06:04:18:
Hi Steve,I don't know what mikeyb is talking about as it doesn't apply to me. He is again grasping for straws a second time I'm afraid, to try to discredit me in any silly way possible. Thats OK, .... people read him.
Correct. I eliminated the 30 uF cap input filter on the stock HF-81 by installing a 37 mHY choke input filter. ( A Panasonic V-850 high current low DCR series, rated 22 mHY, measures 37 mHY. at well under 1 ohm DCR. )
So, it is thus: 2 EZ-81s, 37 mHY, 30 uF, off to output stage B+, 350 ohm R, 30 uF off to G2, and the rest of the integrated amplifier as R/C/R/C/R/C to various stages.
Whenever possible, I now AVOID any C input, even a teeinsy weeinsey one like a microfarad or so. Regards.
Jeff Medwin
Follow Ups:
Jeff, could you please supply us with more information on that Panasonic 22 mH choke? Perhaps a picture of the choke, or better still, a picture of the underside of your modified Eico HF-81?Thanks.
Sure, sorry to not have answered quicker, my car's transmission failed yesterday and so, I've been busy !!I just looked it up for you. Mikeyb, its a Panasonic AC Line Filter. V series, 850 Type, good for 1.8 A rms. Digikey P/N PLK 1018-ND. It is simply a compromise choice, as it FITS under the Eico HF-81 chassis and sounded better than none at all ( C input ) to me. Regards.
Jeff Medwin
Common mode!?!? Hmmmm, I have a pile of them around here somewhere...
Thermionically addicted.
Jeff -I can't find a 'V-850' choke listed in any Panasonic literature. Can you verify the number? Is it axial leaded?
My thought is that most mH type chokes are designed for RF, not 120 Hz. That '22 mH' choke may have an inductance of 22 mH at 10 KHz, but not at 120 Hz.
Since when did inductance depend on frequency? If it did, why would both terms appear in the formula for reactance?
All ferrous core chokes exhibit varying inductance over frequency, so much so that specifying one without the other is almost meaningless. The formula for XL is obviously based on the actual inductance at the frequency of operation.
Correct me if I'm wrong here, but all the references I found state inductance is linearly proportional to permeability and effective complex permeability decreases with increased frequency for a number of reasons. That 22 mH device should have more inductance at lower frequencies, not less. It's interwinding capacitances should be small enough that it remains an inductor well past the operational limit of near any OPT, save maybe a Plitron.
Thermionically addicted.
Thank you for putting me right. I see I need to revisit RDH4.
For backing me up on this important point.
Well, I agree that the impedance is frequency dependent.I do think it is reasonable to want filtering at frequencies considerably above 120/100 Hz. What I wanted to show is that it might (probably will) require another choke in addition to the usual smoothing choke. The extra choke does little to smooth low frequency ripple, but who cares? That's not why it's there.
-- Dave
So if we add a "RF" choke to the 120hz choke all is well? I mean we can have them both, good 120hz filtering and good RF filtering? Can we just add the RF choke between the rectifiers and the 120Hz choke? ( In a choke input PS)Thanks, Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
First of all, I want to make clear that I'm not necessarily thinking of an all-out RF choke. Really, I'm just thinking that something that reaches out to a few tens of kHz might be an improvement over the couple of kHz that an ordinary smoothing choke might be good for. It might be that Jeff's low L chokes do that. I don't know, it's just a thought.But, yeah, I suppose that intuitively it makes sense to put the choke as far upstream as possible, i.e. right after the rectifier. I have expressed concern here before that, depending on the following capacitor, such a choke might see fierce current spikes which might result in core saturation. Again, I don't know, I really can't predict what will happen when one plunks an inductor intended for an entirely different application into their power supply.
-- Dave
Right, and I'll spell it out a little more. Any inductor, even one with an ideal core will have winding capacitance(s) that shunt the coil. What this means is that above some frequency the device acts more like a capacitor than an inductor. It's called the self resonance frequency and we might be surprised how low it is with typical off the shelf power supply chokes. One or two kilohertz is not uncommon.The other factor is the core material. The silicon steel cores used in typical power supply chokes is simply not effective at higher frequencies. Once the core 'goes away' you are left with an air cored inductor which Obviously has much less inductance. It's surprising how soon silicon steel disappears. It's also surprising that going to a higher grade grain oriented silicon steel might actually make things worse.
Anyone can observe this on the bench: put a resistor in series with your inductor and drive the combination with a signal generator. Sweep the frequency while looking at the voltage across the choke. It will reach a peak at some frequency and fall off above that. Don't bother calculating XL=2*pi*f*L above that frequency, or even anywhere near it.
So, to the real questions: do we want our ps chokes to work at frequencies higher than 120Hz? How much higher? What kind of choke do we need for that?
-- Dave
> > So, to the real questions: do we want our ps chokes to work at frequencies higher than 120Hz? How much higher? What kind of choke do we need for that? < <Dave asks EXCELLENT questions. I think the answer lies in the particular service placement of a choke. An inductance that's stable up to 500 Hz. rates to be fine in choke I/P or pseudo-choke I/P service. The ripple waveform is or very nearly is a sine wave. Filtering out overtones of the ripple fundamental is not particularly necessary. OTOH, a voltage doubler using LARGE caps. in the stack exhibits a HIGHLY triangular waveform (SMALL conduction angle). The amount of ripple freq. overtones here is substantial and the choke following the doubler stack is the defense against the "hash". The inductance needs to be stable to fairly high freqencies.
Eli D.
what makes you think that 120hz is the frequency of interest wrt the sonic benefits people claim to hear from the use of the small L input filter?dave
My point exactly. I don't believe the choke that Jeff describes has any effect at 120 Hz, but if it is indeed a RF type choke it's only effect will be in the above 100 Khz region.
Calculate the roll-over frequency into a 30uf or 50uF cap, you'll be surprised. These are components typical of speaker crossovers after all.
Thermionically addicted.
See this to solve for - 3dB frequency easily .Jeff
That's fine, Jeff, but the point is that the formula ASSUMES a constant inductance with respect to frequency, which, as has been pointed out, is NOT a valid assumption for most real world inductors.Please, can you give us more details on the choke? What kind of core does it have (steel, ferrite, or air)? That is the critical question in determining what effect it has on the power supply.
As a general rule (assuming constant flux level), as frequency goes up, inductance goes down so i would expect more inductance at 120hz than at say 10Khz.dave
A bit off-topic, have you tried air-core inductors? Not cheap but you do report a correlation between reducing the amount of iron in the inductor and sound quality. Might as well try the limit.
Thermionically addicted.
> So, it is thus: 2 EZ-81s, 37 mHY, 30 uF, off to output stage B+, 350 ohm R, 30 uF off to G2, and the rest of the integrated amplifier as R/C/R/C/R/C to various stages.> Whenever possible, I now AVOID any C input, even a teeinsy weeinsey one like a microfarad or so.
The circuit you describe installs nearly the full 30uF of capacitance as the filter's input element. The 37mH choke is virtually nonexistent as a reactive element at the ripple frequency. You're only fooling yourself with this misconception. Your equipment isn't better for it.
Frankly, you couldn't be any more wrong. The sonic consequences are quite significant.
> The sonic consequences are quite significant.Compared to what, a Bose all-in-one? I just hope no one here takes this seriously enough to waste their time installing magic wire.
I'll bet that choke isn't invisible to the diode switching.dave
Dave,Seems like Messers. mikeyb and Triode Kingdom are not reading too well, in their rush to ctriticise me.
AND..... notice, we have STILL not gotten Triode Kingdom to post his audio credentials to critique me, up on this Forum.
Here is what I posted :
" The first thing I did.... I added a neat 37 mHY choke as a choke input filter so I have a ( not meeting critical inductance at 60 HZ ) L input filter in my HF-81 to strip RF and control the twin EZ81 tube diodes !! "
I think thats pretty clealy worded, don't you?
It sounded better as L - input IMHO, slightly better, but not at all as effective like the heavy high quality wire for B+ distribution to under 1 mA tube stages.
One other mod I did Dave, the tubes in the stock unit are getting disturbed by being physically too close to the irons' fields, both the HF81 power transformer and the output transformers. I've made metal shields to go around the power trannie and outputs, so as to shield them from fields adversely acting upon the four EL84s and two EZ81s. I also shielded the amps front end tubes from the EZ81 twin rectifiers interference. That was cool and the improvement couldn't be gotten any other way on the stock chassis !!
All else, audio parts wise, was left stock, just to show how important the power supply changes I did elect to change was - to ANY piece's overall audio performance. Cheers Dave.
Jeff Medwin
Was the sheilding made from mu metal? T Willman
Nope. But ANY metal is better than letting the iron's field freely RADIATE into the tube while it is operationg too close to the iron Tom. Right ??!! Regards .Jeff
It was used extensively in the early days of electronic design. How ever Crutchfeilds sells mu metal foil at a resonable price. Mu metal does a great job of sheilding low frequency emf. If you look around at swap meets and in vintage surplus electronics you can also find the thicker far more effective variety. That is if you want the killer stuff! T Willman
than the low DCR crapola being continually regurgitated onto this forum. The possibility that a strong magnetic field from an OPT might influence a nearby tube seems entirely plausible. It is, however, the sort of thing that should be measurable. In the absence of discernible mutual conductance or other tangible evidence, this concept should similarly be shucked in the nearest rotary bin. Building shielding when no such anomaly has been adequately demonstrated is self-delusional.
that the out put or the power tranny can emit rf. There for I would think that low frequency emf might be a problem in the right situation and proximity. My experience with mumetal was to sheild my power transformer from my output transformer. This ultimatly was only needed to lower hum during turn on while there was no curent flowing through the output transformer. I consider it wasted money because it was not needed after warm up. T Willman
I clearly qualified my statement with the phrase at the ripple frequency, .
According to Henry, it is the tuned interaction between the small inductor and small cap that behaves differently in his Flywheel filter design. That was not lowmu's work. It's all here, just use the search function.
so you agree that the choke could have some benefit, and were simply pointing out that the benefits heard are not the result of reactivness of the inductor at ripple frequency?
> so you agree that the choke could have some benefit"Could" being the operative word, yes, but then so could a 5Hy or 10H. Most important, none of this requires oddball, low-R components. The dynamics of the amplifier aren't enabled by drawing power directly from the rectifier, but rather from having sufficient DC reserve. I don't care how many veterinarians say otherwise, low-R is no breakthrough.
do you have any guestimates on the shunt capacitance of a 5-10hy choke vs. something like 50mhy?dave
> do you have any guestimates on the shunt capacitance of a 5-10hy choke vs. something like 50mhy?The shunt capacitance of a large choke is probably something under 0.001 uF, but that's purely a guess. I suppose a small choke might be on the order of 100 pF or so. How does this relate to the discussion?
so the smaller valued choke may actually provide more impedance as frequency goes up.what does he frequency content of a cap input filter look like?
dave
> so the smaller valued choke may actually provide more impedance as frequency goes upNot unless you're concerned about components in the upper MHz region. If you are, I suggest that you also consider the extremely small reactance of even a 10 uF filter cap at those frequencies, and the rapidly diminshing (i.e. miniscule) energy contained in those upper harmonics. All in all, a larger choke, 10-20 Hy or so, will be much more effective than, say, a 22 mH at the frequencies where XL is needed.
My view has always been that low DCR becomes important when the amp draws variable current depending on the signal, i.e. PP class AB or B. That's when you need minimum sag. However, for class A I would agree with you. That's when a good reservoir cap should provide all the DC needs and it shouldn't really matter (within reason) what comes before it in the PS.
I tried the choke input filter set up going with as low a dcr as Lundal could provide and found that to me it was much better. This is in a single ended parallel 845 design running at 1250 volts. I was suprised. As for low dcr I set no controls for that other than what was mentioned. Power transformers wher from same manufacturer just different voltages. I was surprized.T Willman
> > I tried the choke input filter set up going with as low a dcr as Lundal could provide... which specific choke did you use, what other changes (if any) were made at the same time, and how did you determine the results to be better? Can you post a schematic?
I am sorry but I think the directions for posting picture and schematics are so simple that I can't figure it out. Could someone give dummy'd down but detailed never the less instructions please. T Willman
Yes I will show my shi#. I have two pairs of amps each very close in size shape and circuit. There are only two differences. Please be patient I will post them shortly; I have never done this I will try to have it tonight. T Willman
Tom,Tell us please, does your 845 amp run in Class A1, where Ray thinks it " makes no difference ", ( but I always find it to be otherwise! ).
Almost 80% of my low DCR experiments have been conducted in A1 amp stages, both P-P ( mostly ) and SE stages, but Ray seems to give 'ole LowMu NO SLACK or appropriate recognition of this work and Forum-posted result, as it opposes what he has read in some book....probably RDH4. He constantly likes to quote book-learned stuff without always experimentally finding out for himself. But he is basically a nice chap - none the less, unlike a couple of others up here who I don't have to name.
Jeff Medwin
Jeff, my response was not aimed at you. I meant what I said, which was that IMHO with a big enough reservoir cap and no great variation in current demand, voltage sag shouldn't be a problem. Now, that is not to say that a reservoir cap solves all problems for class A. I'm not saying there's no point in refining the PS to make it sound better. Nobody wants to listed to HF noise, mains-borne inductive spikes, SS diode hash, poor quality electrolytics or any other undesirable effects that can be caused by a PS that's not doing its job very well.Once you have current demand that can vary, then you need a stiffer PS to avoid the dreaded sag (which may be loved by some guitar players but not by HiFi enthusiasts). Obviously, you're not going to achieve this with a PS with high DCR unless you use active regulation, which most people would rather avoid.
The good veterinarian has fixated on Low DCR as a prerequisite cure-all. It's a preemptive strike against noise, poor dynamics, narrow soundstage, lifeless amps, etc. etc. With apparently no legitimate evidence whatsoever, not even valid testing, he is not only intent on converting the world to his view, but on taking credit for this nonexistent invention. You will have to be satisfied with warning others. I predict common sense will continue to elude this individual.
URL below.T_K gets VERY quiet when we ask for HIS credentials.
T_K reminds me somewhat of the anger of the late Mr. Cho.
T_K does not speak to us - of his credentials.
Properly introduce yourself. "Question Mark" all over again ??
Jeff
That post makes me ANGRY!"T_K gets VERY quiet when we ask for HIS credentials."
Are you using the royal 'we' or do you actually imagine that other people besides yourself feel the need to know? If you do, then I think you're seriously mistaken."T_K reminds me somewhat of the anger of the late Mr. Cho."
How DARE you compare someone on this forum to a mass muderer with a psychopathically antisocial personality, just because they hold different views to your own? This is rudeness in the extreme, and a sign of your own inadequacies.
credentials are earned, and given around here. Not kept by the people they're referencing.has anybody given Jeff any lately?
All my stuff is posted on Inmate Asylum, my systems, etc. And Ty, if you have hung around here for several years, I've very openly discussed my DIY audio projects and ideas.Prior amps of mine were pictured in 1984 (?) in Sound Practices magazine, a very nice P-P A1 Type 250 amp and a complex P-P A1 6B4G amp. A triode line stage schematic of mine, at 600 ohms, was also published by Joe Roberts.
The same has not yet been said for "whoever" Triode_Kingdom is. He is an unknown, except that he can spell, access the Forum, and post nasty thoughts up here.
So, if he wants to on-Forum attack Jeff's every post, its fair for ME to ask him to post his audio credentials. I have earned mine over 40 active years in the hi fidelity hobby Ty. He has not come forth with his..... and he won't.
Jeff Medwin
I think you missed it. Those credentials are those you claim. They are not what I defined as legit. I suggest you re-read how I defined them.If you have made some breakthrough, I am sure it would spread much faster if you didn't get in the way of people who are trying to discuss it. It doesn't matter much if they're speaking positively or negatively. If you have indeed discovered something, get out of the way, it will spread if it is real. It also helps if the effect can be quantified, adjusted and explained.
Judging the response to your descriptions, I don't think you're getting very far. You may even go backwards.
Ty,There ARE people who implemented the low HY, C, DCR supply idea of Dennis'.... which I made public on Forum in 2006, and have reported positive,....actually, very positive results on Forum.
As for "lately", I just posted this information on 10 gauge / 30 gauge internal bi-wiring last week.
Give it some time, and DIYers will no-doubt, implement it, some will. It certainly is very demonstratable as the basic technique exists - optimized in all the Serious Stereo components, and, at a lower level due to my budgeting constraints, in my modded Eico HF81. I have the piece available for others to compare it - to a stock unit.
Jeff Medwin
There's no 'but' that's going to work here. You've presented the idea, now get the hell out of the discussion unless somebody calls you back into it. Then get the hell back out of it afterwards.Or do you enjoy this counterproductive arguements that crop up everytime you share your most recent revelation?
Hi Jeff, I have two parallel singled ended amplifiers (pair) that are the same exept they have one difference. One has a choke input filter in the power supply. Lundahl iron in both. They sound very different. Of course one is much bigger than the other. T Willman
Why does an over speced power transformer usually sound better? Why do we hear differences in rectifier tubes? Why is the first cap/inductor in a multiple stage filter audible?Bottom line, we know we hear differences on levels that can't be defended with "science". Best we strive to keep an open mind and not censor too much which only adds to the number of posts.
Russ
"Best we strive to keep an open mind and not censor too much which only adds to the number of posts."Do you realize what you just said? :)
Anyway, I was only talking about voltage sag,nothing more.
You may not have noticed but I did include the qualifier "within reason". Obviously, if your power tranny is struggling to cope with the load, or your rectifiers are adding HF noise, or you use inadequate filtering, then you need to do something to improve things that a decent reservoir cap alone will not fix.
Well, I'd like to thing I do so let's assume I was misunderstood:)My intent was that given that we do hear things that can't be easily explained I see little point in large numbers of posts refuting what Jeff claims to hear. It is only wasted bandwith IMHO. One could make an informed guess, in an attempt to explain, but really it isn't possible to know why Jeff hears what he does. The larger gauge wiring may, or may not, have anything to do with matters.
To Jeff; I'd say you would do well to build two very simple identical amps. Nothing too fancy but using known decent stuff....say 6sn7 voltage amp DC coupled to split load invertor cap coupled to el84/6v6 triode strapped. Everything class a1 with no global feedback. Wire one amp with small gauge solid silver sleeved in cotton or teflon and the other in huge gauge PVC insulated copper. See what you think. IMHO that eico has too many things in the way to use it as a testbed to evaluate.
Any good leads for litz wire on the cheap?
Russ
...$0.15/ft: 20ft min. This is intended for RF/IF apps and is not of huge gauge. The radio grade stuff is avail elswhere too as a search using your favorite search engine will prove.
Hi Russ!!,Leads for Litz wire on the cheap??!..... Russ, I don't know what to tell you.
I was sent some old Monster / Brisson speaker wire, multi stranded, shallow angles, but it was slightly corroded internally and I did not care for it. The Monster wire was paralleled BTW, with 30 gauge CCC magnet wire. Next I tried expensive 12 gauge stranded pure silver wire - with the same 30 gauge continuous cast copper magnet wire in parallel. After break in, I liked the silver 12 gauge, until one day I paralleled some clip leads across it, went back and forth with and without the clip leads added, on the same cuts at the same volume level, and decided even more wire (than my particular silver 12 gauge) was needed to keep fully-intact the music's dynamic expressions.
In my most recent attempt, I've used Fulton Brown speaker wire, which is about a 10 gauge, multi strand, plated copper with shallow angles and tight bundling, and the same 30 gauge CCC magnet wire in paralllel.
THAT particular 10 gauge / 30 gauge combo was way-cool, 'gave me uncompressed dynamic experession on musical peaks, such as struck piano notes, etc, along with other nice cues relating to my speaker's dynamic resolution ...on ALL sorts of musical material.
I was listening to an early JBL D123 on an open baffle, with NO crossover components between the amp's output and the speaker's voice coil, and so, at 98 dB efficiency, I was able to "hear it all" very easily. The D-123 EXCELLS in transient response BTW, especially if you have good equipment powering it that does likewise.
No Russ, I don't have two of the same amplifier units to go back and forth with. But with the clip leads, EASILY added or subtracted to the existing B+ distribution wire, it allowed me to go back and forth in a controlled manner and listen to the effect of additional wire in key places. I really do trust what I heard Russ. It wasn't ever close, one way versus the other.
It was surprising to me - how much of a difference was made on my Rk self-bias resistor on the 6BQ5 output stage, when I replaced the Rk's solid wire leads with three ( and then four ) strands of Kimber TCSS. Of course, much of the amp's other wiring points was already optimized, so I could easily find the remaining weak points in wiring execution.
"They" always say, "keep the Rk self-bias resistor wiring on the output stage's ground return short", and NOW, I say, ALSO use about three or four runs of TCSS, right off the R's body, to conduct the audio signal wide-band and without information loss to ground.
As previously mentioned, I may build a 2 stage Loftin-White style DC coupled P-P amp in my old ARC D-75 chassis, using all these newer techniques. A single 6SL7 DCed into P-P 2A3s, two 5U4GB rectifiers and four 10 ohm low HY power supply Ls. The Fulton Brown speaker wire is no longer available. Dennis Fraker routinely uses expensive Siltec Silver inside his S.E. amps and attenuators, and discusses wire gauge and type, on his new Serious Stereo web site, go see that Russ.
Regards.
Jeff Medwin
> ...It was surprising to me - how much of a difference was made on my Rk self-bias resistor on the 6BQ5 output stage, when I replaced the Rk's solid wire leads with three ( and then four ) strands of Kimber TCSS....
This post is unbelievably bogus . There is not one crumb of real analytical evidence to support the claims being made here for this treatment of amplifiers. This is just snobbish, elitist BS taken to the extreme.
To nastily criticise me? This is the fourth time I've asked - and you do not answer.Tell us all YOUR audio credentials, so we can make some sense of the "reviewer" of my every post.
What sorts of systems do you have and have had in the past? How many years have you spent heavily into hi fidelity, and notice I said high fidelity, NOT electrical engineering. What sort of music collection do you have at home? When was the last time you heard live unamplified music??
What is your adjenda, mine is to further the audio art.
"Scientific proof" is not a prerequisite for posting up here Bubbah.
Jeff Medwin
> "Scientific proof" is not a prerequisite for postingBut it certainly is a prerequisite to credibility, particularly when one makes these sorts of outlandish statements. Your time would be better spent demonstrating that someone besides you can hear these lightyear improvements. Until then, you can expect the community to continue to take you to task for this snobbery. And make no mistake, it IS snobbery.
regardless of the doctors 'bedside manor',i know for a fact , that he can, Hear.
take what he says, (what anyone says),
with a grain of salt.
(or A BUCKET of salt)
Ah, I just said above that I heard it. Go back and read that please.
Very nicely said Russ. I'm proud of your classy post !!Jeff Medwin
Every time someone posts something that fits your view. Its pathetic.
Frankly, I found this article (AXIOM) by accident and was citing it to give your ideas some credibility by backing it up with other sources ...I don't belive that adding a 37 mH inductor in front of the 30 uFd cap is going to do much in terms of DC performance. Might get rid of some rectifier hash though. Did the DC voltages change after you added the 37 mH inductor?
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