Creating High Voltage for Tube Power Supply: Serial/Shunt Regulator and Passive RC Filter Chain with Choke/Inductor; Pros and Cons

[tiefbassuebertr]

Some developers of tube amps claim, that for HV power supplies (for anode voltage) only passive filtering (maybe with zeners for slightly shunt regulation) are ensures the best possible sound quality resp best sonic performance. I. e. only one or two inductors and a chain consist of several RC filters. From my experience this is right, as long only top quality elcaps are in use and in the last RC filter additional a MKP version with 50-100uF.
An example are several pre-amp devices from Klimo.

Schematics of first five attached images show such passive versions - i. e. without serial or parallel voltage regulation (except one version in inage 2 with the zeners).
The later attachments show schematics of serial regulators in several variations.

At first glance the benefit of serial and parallel regulators are a very stable voltage, that is additional adjustable in a wide range.
But is it in real live really a fact, that a stable anode voltage provide a better audio than a passive filtered voltage ?
In general I don't think so.

Thank you for comments.

P.S.: some URL's:

HV Serial Regulator
https://tubecad.com/2021/10/blog0546.htm
https://pearl-hifi.com/06_Lit_Archive/14_Books_Tech_Papers/Broskie_John/HV_Regulator_OP27_IRF820.pdf
https://www.bartola.co.uk/valves/2015/01/10/popping-the-shunt-voltage-regulators-clogs/
https://www.bartola.co.uk/valves/2012/07/15/new-ht-bench-power-supply-600v/
https://www.bartola.co.uk/valves/page/2/
https://www.tubecad.com/2021/10/blog0547.htm
https://www.tubecad.com/2020/02/blog0493.htm
https://www.tubecad.com/2021/09/blog0545.htm
A commodity-based HV regulator: FlexHV
High Voltage Jung Regulator

HV Parallel (Shunt-) Regulator
https://www.tubecad.com/2006/11/blog0087.htm
https://www.tubecad.com/2021/11/blog0548.htm
https://www.tubecad.com/2021/01/blog0527.htm
https://www.tubecad.com/2007/06/blog0109.htm
Very low parts count shunt regulator

Passive Filter (RC/LRC)
https://www.jogis-roehrenbude.de/Leserbriefe/Carsten-RIAA/Carsten-RIAA.htm
https://www.audionist.de/2015/11/27/netzteil-fuer-einen-roehrenverstaerker-2/
https://www.turneraudio.com.au/audiofilterchokes.html
https://www.turneraudio.com.au/audiofilterchokes-page2.html
Choke ratings and resistor values in choke input supply?

TUBE AMP POWER SUPPLIES (basics to all supply variants)
https://www.turneraudio.com.au/powersupplies.html

croft series 7 HV regulator
https://www.tubecad.com/2021/10/blog0547.htm

 

[tiefbassuebertr]

Image 1-3 show some serial regulator schematics like used in the Croft tube pre- and power amps series 7 (image 4 is the topology from the croft series 7 itself.
Are there a colloquial naming for this kind of serial regulation ?
Thank you for an advice.

 

[ron68]

Hi!

HV power supply only provides you the GND and +V.
Ideally, +V should be a constant fixed value and should not interfer with sound quality.

Some questions just to provocate the discussion before discussing the technology.

1) What is the influence of +V variations (slow related to regulation and fast such as ripple and/or noise) in the output amp signal?

2) Real world is not ideal, so what should be the minimum specs of +V (regulation, ripple, noise etc)?

3) If the power supply is in a "black box", how do you detect how the +V was generated? Would it matter? I could make some tests to see if I "like" the +V or not and would infer more or less about the circuit inside the box..

With these questions well answered, then we can move to the discussion about the technology to produce the +V to get the adequate and best sonic +V.

 

[jpk73]

Maida style regulator...?

 

[20to20]

Some developers of tube amps claim, that for HV power supplies (for anode voltage) only passive filtering (maybe with zeners for slightly shunt regulation) are ensures the best possible sound quality resp best sonic performance. I. e. only one or two inductors and a chain consist of several RC filters.

What is ...YOUR... definition of ''best possible sound quality'' ? Does any of the examples create that? How do you know?

 

[Miniwatt]

I used to be in the regulator camp, I used Maida regulators for anything critical.
When I was prototyping my latest preamp (I was very happy about the sound) I got curious how an unregulated C-L-C would compare.
I prefered it! The regulated supply sounded restricted. Unregulated was more dynamic, lively, sharper stereo image.
Just my $0.02

 

[tiefbassuebertr]

Maida style regulator...?

yes, good advice (AN007335, National Semiconductor Linear Brief 47, Michael Maida, March 1980)
An interesting approach to use low voltage integrated regulators for regulated high voltage power supplies.
https://www.ti.com/lit/an/snva583/snva583.pdf
https://www.ti.com/lit/an/snoa648/snoa648.pdf
additional URLs to Maida style HV regulator
http://www.pmillett.com/HV_reg.html
https://attackllama.com/pages/hardware/high-voltage-filter
LM317/TL431 High Voltage Floating Regulator
21st Century Maida Regulator
High Voltage Regulators (Maida or zener)
Maida regulator
21st Century Maida regulator doesn't regulate heavy load
Maybe it is possible to make things better in the version used in croft series 7.

 

[tiefbassuebertr]

I used to be in the regulator camp, I used Maida regulators for anything critical.
When I was prototyping my latest preamp (I was very happy about the sound) I got curious how an unregulated C-L-C would compare.
I prefered it! The regulated supply sounded restricted. Unregulated was more dynamic, lively, sharper stereo image.
Just my $0.02

exact this observations I had note in general when I compare unregulated against regulated power supplies wich I had make several times while repair services (BTW - both in tube and solid state versions). Because the main electrolytic capacity in most cases is located in front of the regulator instead after the regulator one will get the unwanted effect, that the regulator is partly in the signal pad (slow voltage variations, which occurs when only LRC parts for filtering are in use, seems to be no disadvantages regarded the sonic performance).
I remember long time ago (80s) Klimo explained during a demonstration of his tube amp devices (with outdoor power supplies) at a trade fair (High End, Gravenbruch Kempinski/Ffm), that only with a passive filtering the very good sound results, which were clearly comprehensible on this day, could be achieved.

P.S.: (reply post #5) ''best possible sound quality'' means for me, a maximum authenticity, i.e. the presentation of the recording on a listening test session gives the illusion that it is taking place "LIVE"

 

[analog_sa]

But is it in real live really a fact, that a stable anode voltage provide a better audio than a passive filtered voltage ?
In general I don't think so.

Over the years i have changed my opinion on this a few times. In the 80-ies i couldn't stand regulation in tube circuits; it was either batteries (MC step ups) or multi stage RC filtering. The chokes i could get at the time were really horrible and not an alternative.

Later on there were choke inputs + shunt regs. The choke input being pretty much non negotiable with mercury rectifiers.

Today i have no rules at all about power delivery, both in SS and in tube circuits.

Some circuits in some systems sound better with minimal or no regulation, others are just fine with 317/337 regulators and in some cases a shunt regulator is a must. There is no universally best sounding solution.

Looks like i may be getting away from chokes as these have the tendency to slow things down. Used to love them 10yrs ago. Perhaps hearing and taste change a lot over a lifetime. Most of my PSs are half wave rectified so that may also be a consideration when choosing the type of regulation.