Jeff,
Low DCR PS is all I could pick from your builds, rest is not convincing to me, so far.
I would like to experiment with low DCR line up in B + and would actually build two exactly same amps but one with lowest possible DCR chokes, keeping the B + same on both of them.
Are there any options to choose from other than Hammond 159ZA power supply chokes ?
I did come across a chap who owns a vintage tube amp (not sure if it was RCA) with total 10 ohms of the DCR from transformer to B+ lineup and he said it has excellent dynamics. (Though amp alone does not bring out excellent dynamics)
EE or EEE or Physicists or Scientists, don't generalize them. Education does not make them narrow minded, rather it does the opposite.
I am a Physicist by education, a Scientist from experience (two US Patents, and still a practitioner, unlimited lab hours confinement in high vacuum and plasma) and am quite known to be non-stop experimenter (call me crazy) in sound reproduction. Passion for music makes us dare attempt things which we could not imagine to do otherwise.
Your above post absolutely totally and fully delights me !!
At last, after some time posting on HFV, I have a good DIYer willing to TRY out a new idea, and listen to it !!!! Bravo , Yogibear, Bravo !!!
First of all, I will reprint the late Dr. Chales E. Halijak's letter to me from 1989, " Figure of Merit of a Power Supply ". I suggest we all can use this as an overall general guide to Power Supplies for tube amps. You and others may recall, Dr. Halijak was an audiophile, friends to Dennis Fraker ( my audio Mentor ) and myself. He was also the Dean of the College of Electrical Engineering at the University of South Carolina.
Allow me to repost his letter below, and we will discuss specifics afterwards. here we go :
http://db.audioasylum.com/cgi/m.mpl...+figure+of+merit+of+a+power+supply&r=&session=
1989
Dear Jeffrey,
This letter is concerned with the power supply and the use of chokes.
A choke must have some internal resistance and its non-standard figure of merit is the ratio R over L. The best choke is the one with the smallest figure of merit and the best power supply has the least series resistance. It is not too difficult to obtain R over L = 10 but one can easily obtain R over L = 30 or more. The latter should be avoided but the ongoing shows that in a way it is unavoidable.
The choke input filter controls the diode by timing and not by ohmic losses. ( jm: current vs: voltage waveforms) The best place for a choke is at the input and the worst place is at the other end of a power supply filter chain because resistances tend to be higher there.
Suppose we start with your case and R over L = 10. When diode ( 5U4GB ) and transformer resistances are taken into account we have :
15 ( choke ) + 70 ( rectifier ) + 70 ( power transformer resistances )
------------------------------------------------------------------- = 103
1.5 ( HY )
( the 70 ohm power transformer resistance is a guess )
If four 5U4GB are placed in parallel one has :
15 + (0.25 ) ( 70 ) + 70
__________________ = 68
1.5
Both figures of merit are way above the original 10 but your listening experiment told you that 68 was alright; this actual figure of merit is the best you can do because the largest power transformer was used and the smallest resistance available choke was used. You can see that stock power supplies are not anywhere near being the best cases.
*. Most tube and transistor electronic engineers are unconscious about power supplies, but good.
* Also the best cases need not have zero internal resistance - a utopian goal. One strives for minimal non-zero resistance !!
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On the subjective side, below is what Audio Consulting of Switzerland said about their four and a half ohm DCR @ 10 HY choke, from their literature, please do note
everyone, their wording "one optimum" and "only way to make real progress":
"Get micro and macro dynamics out of your amplifier's power supply. Get the power into the music!
First we would like to explain our general philosophy :
There always is one optimum for a given problem.
It costs tremendous amounts of time to find it, but this is the only way to make real progress.
Jeff writes 10-2019 :
Dr. Halijak would have Stancor custom make chokes for him, rated 1 Hy at 8 Ohms, in the 1980s.
This that follows is advertising of Low DCR Ls from a High End Supplier in Europe, maybe Scandanavia or that area North ( 2022 : I
think it was Audio Consulting of Switzerland ) :
“
Low DCR plays a key role in getting life-like dynamics out of an amplifier.
We have noticed that the lower the DCR gets, whether in a SE OPT or in a power supply choke, the more micro-information the system is able to provide.
We have gone as low as 4.5 Ohms for a 10 Hy choke that provides incredible sonic results when used in tube amplifiers.
The 16 Hy / 16 Ohms model is also very good, and maybe more reasonable when it comes to weight and size than the previous one.
More classical chokes of 30 to 50 Hy and 105 Ohms DCR may also be offered."
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * **
By the way, Charlie's letter was in response to me experimentally paralleling up to four 5U4GBs to a common DYNACO ST-35 amp in 1989.
Let us let the above sink in. Suggest everyone read it more than one time, and revisit it. Rather than dilute Dean Halijak's above letter, allow me to do a follow-up separate HFV Post on specifics. Thanks !!
Jeff