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I have no idea what I am thinking lately about using chokes with 100 or so ohms and say 10H or so as compared to using lower DCR(under 20 ohms) with much less inductance values. Some say larger inductance with 100-300 ohms is great to use and others say much lower inductance with low DCR is the best way to go. Can someone steer me in the right direction or is this just hypothetical and someones belief? What does this all mean?
Thanks!
Paul
Follow Ups:
Here's my experience:
For front end (signal) tubes that draw low current. High H chokes and the DCR should also be rather high. How high.... you don't want to starve the front end tubes. Been there/done that. My front end tubes pull 18mA. I've tried 5H, 12H and 30H, all varying amounts of DCR. By far the 30H sounded best and swept the best, but 600ohm DCR is too much and did starve the tubes. As you go up in H, the DCR follows. Maybe there's a reason for this?
As for OPtubes, high current needs low H and very low DCR. "typically" 2-5H and very low DCR. As you go down in H so goes the DCR. maybe there's a reason for this?
Have a stash of varying sized chokes on hand, listen and sweep the amp.
Check out some vintage amps schematics.
Hi Paul,
If there is one thing I learned in amplifier building, then it's that more than one road lead to Rome. You just need to find the one you like best. The only way to find your road is by trying it out yourself.
Some of my friends and myself hosted an audio event last weekend in Munich. I built an SE801A amp for that. It was about 1.5W and used power supply chokes with 680 Ohms (!) and tens of Henries . This together with a final cap of 1uF (!!!). As you can see I tend to like very high inductance chokes and very low value caps lately.
We had about 30 people listening to that amp and there was not a single complaint about it. Quite the contrary. The amp got a lot of compliments for it's extreme resulution and life like sound, especially for the energy it revealed in piano recordings. People were surprised about it's low wattage rating. It was able to effortlessly fill the (not so small) room with sound. Speakers were in the 100dB range.
So I'd say go and give various approaches a try. Stick with what you like best. Trust your own jusgement.
Thomas
Hi Thomas!One great thing about what you did is that 1uf cap. You have most of the energy storage in the iron, and the small cap can be chosen among the worlds best caps. You wouldn't use that small a cap unless you had the large inductance.
Why can't this work? It CAN! Congratulations. You're thinking out of the box.
This isn't low-DCR, BUT the iron chokes store power-- lots of it. You are not suffering from too much time delay either, because the cap is so small. I think this is brilliant. If you now choose a low-loss path in the amp circuitry AFTER the last choke and small cap, you're there!
I argue against storing too much power-- in any capacitor that I can't buy in world-class quality, and I argue against placing a lot of resistance in the way of power paths..
In this case, if the sizing of the power transformer and associated chokes is optimum, you have largely negated the effects of high-DCR in the chokes. Since the cap is so small, energy can be delivered into circuit demand instead of unnecessary capacitor charging.
Tell me more about the Munich show. Munich is a great town. I'd like to know your experiences in Munich.
Are you able to attend Denvers RMAF 2008? I'll be there in Room 2020. This is in Denvers Marriott Tech Center Oct. 10, 11, and 12.
I would really like to meet you.
---Dennis---
Edits: 10/06/08 10/06/08
Hi Dennis,
> This isn't low-DCR, BUT the iron chokes store power-- lots of it. You
> are not suffering from too much time delay either, because the cap is
> so small. I think this is brilliant. If you now choose a low-loss path
> in the amp circuitry AFTER the last choke and small cap, you're there!
Thanks for the kind words. Could you elaborate, what you mean by the low-loss path after the last choke ? I use what I call a filament bias arrangement. The bias is provided by the filament current, which is drawn through a (low value) cathode resistor. See attached schematic.
> Tell me more about the Munich show. Munich is a great town. I'd like to
> know what it's like.
It was more like a semi-public event or private party. We call it "Schall & Rauch" ("Sound & Smoke"). It was the second installment of such an event in Munich. The main purpuse is to give people the chance to listen to some of the systems of the "Munich Triode Mafia" at their homes. So we organized small groups of 4-5 people who visited the Munich guys. In addition we had a central location called the "Vinyl Mafia Central" or VMC, where we set up a system and where we did turntable comparisons. We had 13 or 14 different turntables, vintage classics like various Garrads, studio EMTs and modern legends like the Scheu or Morsiani. All turntables where listened to using the same (externally mounted) arm and the same cartridge. I'm sure some reports will appear on the web soon, with photos.
Best regards
Thomas
Hi Thomas. Sounds like fun. I remember one system at a fellows home in L.A. He had an attic, each side of which was a part of an "A"-frame double-slope.
Inside, he had made concrete tunnel-ports (ala JBL Paragon!), but these were tall enough to stand up in, and wide enough to walk through. Each roof slope formed a side of each tunnel.
At the APEX-- on the floor- where sloped wall and the other side of his tunnel joined the floor-- that formed a corner. In each corner was a JBL 18" SVG type woofer.
Next, was a JBL 15" SVG woofer, enclosed in a transmission-line box. This box was placed IN the tunnel, on the floor. It was moved around to get "best sound".
Then, he used a 2" JBL midrange driver (similar to 375, etc.), with his own horn-load attached. This was a simple Fiberglas flare-horn. (not truly Tractrix or Exponential). Next was the tweeter, which was a small "bullet" placed in the room where he had deemed it to sound good. (Time-aligned).
A 300B amp drove both the tweeter and mid unit thru a passive crossover that was "simple"- oil cap and inductor.
The 15" woofer was driven by a Conrad-Johnson tube amp, and the 18" had a 200Watt Solid State unit.
Now, one might expect that all of this would not sound coherent. But, the guy was a pro baseball player and had no knowledge of electronics.
Therefore, he just did it right-- he had no preconceived notions or methods that he copied. He just set it up until it sounded right.
It is the 2nd best system I have ever heard, period.
I like your ideas. Low-loss path means that you use power supply energy in creative ways in the amp circuitry so as to avoid voltage and current losses (heating of signal-carrying components and leads). Layout and wiring perfection aids you in this process.
Where you need a low-DCR source from a dropping resistor to power a driver stage, etc.,, you can waste power here-- but NOT in the active circuitry-- with shunt regulation, and make the load "see" a low-DCR power source.
For sonic and reliability reasons, I use only resistors for shunt-regulators, the output of which receives additional low-DCR, and low-capacitance filtering..
This additional step does add the final control for the main power supply as well, finally bringing it into correct inductance and capacitance balance-- as an operating whole.
In earlier posts I had claimed that the ENTIRE amplifier was all power supply components-- this step is part of that. I don't think people "got it".
The LSES idea is still being judged by the MAIN p.s.-- as if it was the only thing operating there-- by itself-- containing two chokes and two caps. That system is a VERY SMALL PART of one of my power supplies.
---Dennis---
Proper power supply design requires some DCR and enough inductance to keep the first cap's charging current constant.
Other power supply designs will work but not as well.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Tre,
Define the terms "some DCR" and "enough inductance." 20 ohms? 100 ohms? 200 ohms? 10H? 5H? 15H? A friend showed me the formula to find out how much inductance to use on a circuit in a particular part of the crcuit or the whole circuit.
Thanks!
Paul
The formula for critical inductance is for the input (first part after the diodes) choke. Lc = ((voltage / current) + DCR of choke))/1000
So if your B+ will be 400 and the current draw is 80ma. with a choke that has 60 ohms DCR you need a 5.06Hy choke.
boris' math works out to be almost the same. He's right about using a choke larger than the formula just to make sure.
The DCR of the choke has to do with the value of the caps and the DCR of the power transformer. I don't have a formula for that but the Duncan PSUDII is very helpful.
Too little DCR and the supply will ring (the voltage will not only drop when more current is drawn, it will also "bounce").
Tre'
PS Low DCR is a good thing as long as the ringing can be controlled and other, more important things have not been compromised.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
For a 60hz input, critical inductance is Lc > RL/1130 (From RDH4), where RL is the load resistance. You can usually approximate it by RL = VL/IL where VL = 0.9*(VAC-Vdrop), IL is load current, where VAC is the AC input voltage to the filter (per leg) and Vdrop is the diode drop voltage (you can approximate here). You can do all the math here, or a few button clicks in PSUDII :).
Whatever value you find, it's best to use 25%+ minimum inductance to ensure it won't drop into DCM and deregulate (B+ will increase). Just make sure your inductor resistance isn't too high that winding dissipation will risk an open-coil. Usually < 5 watts on an average sized choke is the maximum you'd want (hard to say what 'average' is, but I'm looking at a 2.5" x 3" x 1" lamination stack choke here that has 75 ohms and is rated for 300mA -> 6.75 watts @ max DC current). Having some resistance helps with damping and ringing with a changing load. Hope this helps!
If you want a straight answer, leave this forum immediately and go to diyaudio.com.There is a group here that views any DCR to be evil, rather than as a parameter which should be optimized to produce a well-behaved power supply. Think of DCR as the struts in your car's suspension - it provides the damping between the interaction of springs and vehicle mass (inductance and capacitance) as it responds to varying forces (currents). Too low of DCR, and the power supply rings at too high of a quality factor, and can add excessive color to the sound under dynamic load conditions (i.e., in a single-ended amplifier). Just like a car bobbing up and down with leaky struts, responding poorly. A low-DCR power supply for low-current applications might sound "full of life", but it's not necessarily the music you will be listening to. This can, and should, all be optimized via simulation - PSUDII is a good starting point. Too much DCR is a bad thing, but an optimized DCR can be of benefit.
For more information about filter theory for classical mechanical and electrical systems, check out Olson's Dynamic Analogies - one of the best references on this topic, and one of the most brilliant engineering texts I've encountered.
I'm surprised this debate has survived for so long!
BTW - the low-inductance in the LSES supply is something that I cannot take seriously, and is far more controversial than the simple low-DCR fad - it is not reasonable to expect input chokes below critical inductance to properly supply stable B+. A low-DCR power supply with sufficient L will perform well. The LSES as I've seen it described looks more like a bad cap-input supply with added resonances than it does a proper LCLC filter. I would not be willing to invest in building one.
Edits: 10/05/08
DanL
Indeed. It's all very well for people to say that a couple of 320 mH 10 ohm chokes don't cost much, but it isn't just the layout in materials. It's also the investment in time to procure the materials and to make the change and conduct the tests. There's also the nuisance factor due to the intrusion of making the change to an existing amp.
Hi Ray,
Be truthful, you ALL have spent FAR more time over almost two years, writing about this on various Forums, I would estimate 200 to 1, versus the time to breadboard the L/C/L/C supply filter into existing gear and listening!!
Jeff Medwin
I don't respond to emails requesting assistance transferring funds from someplace far away either, and they're reasoning is waaaaay better than Dennis' on why LIES works.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Your prejudices and ego is showing, and it doesn't relate at all to what myself and other people hear !!
Jeff
It isn't supposed to be in any way related to what you claim to hear.
Are you going to claim there is a single consistent description of this LIES design? ( just to save you the time, that was a rhetorical question, but you should go ahead and show your character by answering it anyway ).
So far you've presented nothing that deserves any attention. 'I hear something', would usually be quite enough, but the piles of manure delivered to requests for more information are about enough to obscure that reasoning. If it were real, it would also be consistent. First it was low DCR( and there was a high inductance, low-mu special designed ), then it was the Flywheel...and as soon as some insight and investigation was brought to bear on that, the design changed again. Not going to go off with some inconsistent design when it is just as troublesome to implement a consistent one.
Get your story straight, maybe it will be worth listening to then.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Just buy some of the low DCR parts and conduct your own evaluations.
Then you can decide the outcome.
maldar
Don't let people confuse you. It's ohms law. You just can't get high current pulses through any appreciable amount of resistance with ordinary plate voltages.. Period.
Low-DCR throughout a B+ system is a design REQUIREMENT-- it's not subject to opinion-- it is subject to supplying a definite need.
There is no contest. Amplifiers built with high resistance chokes and power transformers sound lifeless compared to the alternative.
This can be a matter of taste. If you want clean, smooth easy listening with no excitement-- no big dynamics, then you can have a really clean, good behaving high-DCR power supply and like it.
I suspect, however, that once you hear really clean, powerful dynamics across the whole audio bandwidth being done right-- just like it was recorded, you won't be looking back. You'll be smiling-- a lot.
You're always going to get arguments against this. It just never stops, and it often takes the form of very good illustrations and proofs to prove its various points-- and then sometimes, it is just observation.
YOU have to decide what you want. If you want to have tube equipment out-perform the best solid-state at what solid state does best, and then have also what tubes do best-- in one amplifier-- well, that has been done. It is LSES and it is low-DCR.
---Dennis---
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