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Old 3rd April 2011, 09:17 AM   #1
M Gregg is offline M Gregg  United Kingdom
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Default Choke power supplies and bypassing.

Just for interest,

I have a few Ideas however, I would like to know if others have any experience with this!

I thought I would post a few things I have found "empirical research" I suppose you could call it whilst trying a few things with my project single ended.

Findings are that the value of choke seems (I say seems because some will argue, this is not slight its chalk and cheese) to effect the presentation of the music. The hum levels remained the same "Very low".

10H choke gives a warm almost sickly 2nd harmonic presentation!
2H choke complete change much less warm with details muffled and bass in your face! This would seem to say that the choke stifles the music?

Bypass choke with 47 Nano farad 630V cap vast improvement in bass, and detail.

This was followed by first PSU cap bypassed with polypropylene 0.1.
Cap after choke across 2nd PSU cap 2.2 polypropylene.

If I put a 22pF cap across the audio input detail increases again.

I just wondered if someone can put some light on this without having to try and measure the "invisible again"!

Regards
M. Gregg

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Old 3rd April 2011, 09:52 AM   #2
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Hi!

It is always the whole PSU which interacts and not just the choke.
The choke forms a resonant circuit with the cap. If you change the value of the choke you shift the frequency of the resonance which of course can have a big impact. Discussing the choke in isolation makes no sense.
If you are bypassing the caps, you can have multiple resonant circuits in your PSU.

Do you know PSUD? This will show some of the differences. However it cannot simulate when you add caps parallel to the choke. Such things can be simulated with LTSPICE

Best regards

Thomas
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Old 3rd April 2011, 09:56 AM   #3
almarcy is offline almarcy  United States
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Default Schema?

I am an olde tube geek (64, she still feeds me). Prose is OK, but, if I could see the schematic, it might improve my comprehension of your comments.

Happy Ears!

Al
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Old 3rd April 2011, 10:38 AM   #4
M Gregg is offline M Gregg  United Kingdom
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Quote:
Originally Posted by Vinylsavor View Post
Hi!

It is always the whole PSU which interacts and not just the choke.
The choke forms a resonant circuit with the cap. If you change the value of the choke you shift the frequency of the resonance which of course can have a big impact. Discussing the choke in isolation makes no sense.
If you are bypassing the caps, you can have multiple resonant circuits in your PSU.

Do you know PSUD? This will show some of the differences. However it cannot simulate when you add caps parallel to the choke. Such things can be simulated with LTSPICE

Best regards

Thomas
I know PSUD. This was an observation from practical experiments.

Just for interest

Resonant-choke Power Supply

I am just looking at the choke Vs non choke PSU and effect on sound quality perhaps I should say "type". Because it seems to me the two are not the same sonically.

Regards
M. Gregg
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Old 3rd April 2011, 11:33 AM   #5
M Gregg is offline M Gregg  United Kingdom
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Thomas,

Thank's for your reply, this raises other issues. Is there any research on PSU resonant frequeny and sonic performance of amplifiers?

Has any one done a check on Ongaku PSU resonant frequency and compared with others? I.E. what is optimal for sonic performance, because the DC voltages are very similar. So once the level of ripple is reduced to minimum we only have the AC pass frequency of the PSU.


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M. Gregg
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Old 3rd April 2011, 12:34 PM   #6
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Hi!

Each PSU will have different impact on different amplifier circuits. PP will act much different to PSU changes than SE. Also different output tubes will react differently. There is no easy answer like how PSU x will sound like in general.

Higher rp tubes are much more forgiving on the PSU, low rp tubes require a PSU with low Zout. I also found that output stages with an ultrapath cap react differently to PSU topologies.

Anything you find out empirically will only be true for the context you tried it within.

As for the resonant PSU: This was a 'trick' to get better filtering from the same size parts. It requires the cap and choke to be tuned to your ripple frequency. If it is just a little off, the effect will be reduced dramatically. I would not recommend such a scheme since it might drift from the optimum setting even if carefully tuned.

Best regards

Thomas
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Old 3rd April 2011, 12:40 PM   #7
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Quote:
Originally Posted by M Gregg View Post
Just for interest

Resonant-choke Power Supply
Fantastic article. I'll bookmark that one, and go back to read it over again a few times. I think I want to experiment a bit with those resonant supplies.
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Old 3rd April 2011, 01:18 PM   #8
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Quote:
Originally Posted by M Gregg View Post
10H choke gives a warm almost sickly 2nd harmonic presentation

I don't belive any of the common considerations can explain much about the sound of chokes. Yet, same as capacitors they do seem to have some inherent "sound". I have a box full of chokes i just cannot use for any quality audio. Nothing wrong with their basic parameteres but irrespective of PS topologies or application they just don't sound any good. Even in preamps, being followed by high performance regulators.

Luckily i started using Lundahl chokes and they are a lot more predictable sonically than the random makes in the cursed box.

Are the different chokes you are comparing similar in construction? What you hear may have very little to do with inductance...
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Old 3rd April 2011, 01:44 PM   #9
bigwill is offline bigwill  United Kingdom
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Quote:
Originally Posted by analog_sa View Post
I don't belive any of the common considerations can explain much about the sound of chokes. Yet, same as capacitors they do seem to have some inherent "sound". I have a box full of chokes i just cannot use for any quality audio. Nothing wrong with their basic parameteres but irrespective of PS topologies or application they just don't sound any good. Even in preamps, being followed by high performance regulators.

Oh come ON
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Old 3rd April 2011, 02:25 PM   #10
DF96 is offline DF96  England
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The effect of a subsonic resonance in the PSU will depend, among other things, on the frequency and damping of the resonance. The frequency may interact with other relevant frequencies such as record warps, arm-cartridge resonance, mains supply voltage variations etc. Because of this, what works for one person might not work for someone else. When someone says "this choke is superior to that choke", all they may be saying is that this choke moves the PSU resonance away from my typical mains variation frequency, or it may modify the PSU damping provided by my particular amplifier DC load.
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