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152.163.100.210
Greetings-Since I first learned of these chokes, rather than speculate on their "sound", I've been wanting to give them a try in an existing circuit, and finally an ideal platform came my way in the form of a pair of Heathkit 807 PP poweramps.The other "addition" to the power supply which really seemed to make a difference was the addition of a 40K "bleeder" non-inductive resistor (to ground) after the last cap in the power supply. This really seemed to make a big difference to me, unless I was/am hearing something else. I had emailed Jeff with my listening impressions, and rather than try to transcibe the whole thing, I find it easier to just cut and paste. I hope that Jeff is not offended that I am posting this without his permission, but his damn emailbox is full AGAIN and I can't wait forever. Here goes:
Jeff-
Thanks for your patience, I am now back in the womb (music room) and
listening and hearing things that I wouldn't have believed possible for a
mere $20.00 upgrade ( two Stancor C-2708 chokes) Wow!.To be honest, in my first attempt, probably because it was rushed and not
optimised, I really couldn't hear a big difference. However, upon installing
(into the system) an old McIntosh MX110 tube preamp with mono and L+R speaker
reversal switches, the change is not subtle and very easy to distinguish.I have a handfull of "demo" albums that I play when trying to evaluate a new
component or tweak . These range from Miles Davis "Tribute to Jack
Johnson" all the way to Stravinsky "The Rite of Spring" with some good
mono stuff in between . I use the Miles album to listen to Bill Cobham's
drums which are recorded exceptionally well. The bass ( kick ) drum is tighter
and more refined/defined and the snare has a "snap" to it .......that wasn't
there before.The midbass in particular has a more precise sound to it now.
I also put on various "classical" pieces that contain very complicated
piano passages which will sound like shit on a poor system. This is where
the power supply really shines !I really noticed a big difference, there is more of a "blackness" between
individual notes and certain chords, played with and without the sustain, I can
actually hear precisely when the pedals are depressed.wpod / Paul
Hi Paul,GLAD you actually built and readily heard it !! I assume you went L/C/L/C on
one mono amp, C-2708s and 40 to 50 uF for Cs.As I pointed out to you previously, you have gone from the WORST possible
configuration, a C-input filter, to the BEST possible, a L/C/L/C filter that
has low storage time and speed, DYNAMICALLY precise / correct, and .... you
have also beneficially eliminated DCR from the amps stock high HY and high DCR
inductor.You now have, what Dennis and I like to call, a " direct access to the music "
power supply, ...........just like a 2A3 can be a " direct access to the music
" amplifying device. That descriptive verbage " direct access to the music "
is my mentor Robert Fulton's words to me, 1975.IMHO, I have NEVER heard a better sounding, more wider-band choke, than these
.32 HY, 10 ohm, 600 mA devices, in ALL my years of audio listening. These
C-2708s, and probably the Triad C-40Xs, ( as explained previously - on how to
employ them ), SMOKE all other Ls in existence on a pure audio / listening /
performance basis. Nothing I know of will touch them, or even approach them .The bleeder resistor is important, as it draws constant current through the
supply, and allows it to perform better vs: the modulations / pertebations of
the music load. I must warn you however, you ONLY want to use one ( or two ) MILLS MRA-12s as a B+ to Ground bleeder, no other R will do as well there, drawing
current. The Mills MRA-12 is absolutely wonderful in that application, the BEST
possible known to me, use it !!Do the other amp, listen in stereo for awhile, and get back to me / us all, and
I will see about additional things to try. Ohh.... do this : temporarily add
clip leads in parallel to the B+ and Ground runs, to see if more wire gauge is
needed. Slagle ( hes the very best ) it. Enjoy this supply in STEREO next.
Have fun listening. I come on-board 8-3-07 on the Forum.Jeff Medwin
Edits: 07/17/07Follow Ups:
Great, we will never hear the end of this from Jeff ...
What were the changes you made? Adding a .32 Hy inductor before the first C of a CLC filter and adding a 40K bleeder resistor? Is that right?
Greetings- The stock power supply, which is on it's own chassis was originally 20uf > 6-8H 160ohm choke > 40uf. I disconnected the stock choke and after the 5V4g rectifier installed a Stancor C-2708 choke > 40uf Panasonic TSHB > 2nd C-2708 choke > 40uf ASC poly cap > 40K 25watt noninductive resistor to ground. This change also lowered my B+ by 20 volts, originally 415vdc, now 395vdc which I also beleive to be a slightly better operating point for the PP 807s at 50 ma.The plate to cathode voltage is now 365 vdc. Mike, I must admit that I was skeptical going into this, I could understand the low DCR part but the low H thing really bugged me. So I just said "screw it" and built it and I'm very glad that I did. It is NOT a subtle difference between the "sound" of the stock supply and the upgraded one, very easy to hear the improvements. The above picture was taken before the Panasonic caps arrived , so I was still using the stock NOS can electrolytics as the first cap. The link will take you to a picture of the stock supply. Regards, wpod
I did a quick PSUD2 analysis of the 'before' and 'after' power supply, which confirms the drop in B+ voltage (somewhat surprising to me). The transient behavior was about the same (well damped response to a change in current draw of from 100 to 120 mA), but there was considerably more ripple in the low DCR low H configuration. Whatever is going on is not obvious from the simulation results.
However, your 'experiment' is not really valid because you changed so many variables - differnt caps, added bleeder resistor, differnt supply voltage, etc. Maybe the improved response is primarly due to the better transient characteristics of the ASC oil cap as compared to the orginal electrolytic. I know, who cares - if your happy with it, stay with it.
Hi mikeyb,I have received a few e-mails from Jeff Medwin regarding your simulations. Here are a few questions resulting from those emails.
"Are you measuring the correct thing ??
Will you simulate the dynamic response of these new and
old supplies please?? "....That will nullify ALL his year's worth of BS, and is a NICE post, needed in the mix:
Respectfully submitted
Norris Wilson
"Are you measuring the correct thing ??"
That is, indeed, a good question. What PSUD2 allows you to simulate is an essentially instantaneous change in current draw from x to y. Is this realistic? Probably not. What is does reveal, however, is the power supplies response to transient signal. What you want is a ‘smooth’ response, with no ‘ringing’. We are looking at the response in the ‘time domain’, that is, a plot of output voltage versus time. Both versions of the power supply behave well on that account.
That said, what would be more helpful would be to look at the supplies response to a typical audio waveform, which (I would guess) consists of both transient and sinusoidal changes in current. You should also look at the supplies frequency response. You can’t do that with the PSUD2 simulator, but you can with PSPICE. It takes time and effort, but it could be done.
I’ll get around to it eventually, to satisfy my own curiosity and to hopeful end this continuing fight (debate). Yea, right.
http://www.audioasylum.com/forums/tubediy/messages/12/128000.html
Thanks mikeyb,
I am looking forward to your PSPICE simulations.
I hope that it will offer conclusive evidence of the physics behind Jeff's power supply design, finally ending the negative part of the discussion.
Norris Wilson
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