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Old 23rd September 2012, 11:35 AM   #71
sonnya is online now sonnya  Denmark
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Hi Mike.

I like the way you think. You do not accept all that we write, and you are very critic, but at the same time you are humble enough and willing to admit if something is better than you thought...

That i like a lot!
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Old 23rd September 2012, 02:12 PM   #72
mikelm is offline mikelm  England
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Thanks Sonny,

I do feel I learnt a some useful things from this project particularly how important different topologies can be to achieve different "sounds".

It turns out that even though I would not include electrolytics in the FB path in my ideal amp their impact on the sound is way less than some other factors.

Western scientific method only works well if all involved have open minds and are happy to say bye bye to old theories as soon as they evolve.

Personally I am a little perplexed way anyone ever used bypass caps on power lines without snubbers. I repeated my spice research again to show to Salas and it confirmed again that my ears tell me whenever I have tried omitting them.

I Will present it below.
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Old 23rd September 2012, 02:24 PM   #73
mikelm is offline mikelm  England
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Hi salas,

here is my test circuit for bypass cap resonance
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File Type: jpg test cct.jpg (33.2 KB, 170 views)
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Old 23rd September 2012, 02:31 PM   #74
mikelm is offline mikelm  England
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here are results:

the lower lines green & red show the voltage on the caps

the upper lines green & green ! show the current in the nominal 0.1R resistor

You can see how the snubber smooths out the resonanes in the voltage on the caps.

But more significantly the upper plots show how much the current in the rails is also disturbed when unsnubbed & clean when snubbed
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Old 23rd September 2012, 02:41 PM   #75
mikelm is offline mikelm  England
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Here are the results from the similar test when I modelled the FB cct with caps.

You can see that the voltages ( below ) are disturbed and cured just as before.

But perhaps significantly the current in this much higher impedance circuit is disturbed very little. Tiny little red blib around 1Mhz - honest it is there but has got lost in the upload

So I think the bypass cap here in the FB circuit will not have anything like kind of an impact on the sound when compared with the bypass power rails.

Technically it will still be a good idea to include a snubber cct ( 0.1R worked well with 4.7uF ) but it might be hard to hear any difference
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Last edited by mikelm; 23rd September 2012 at 02:44 PM.
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Old 23rd September 2012, 05:54 PM   #76
Salas is offline Salas  Greece
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Mikelm thanks for the analytical presentation. Now what happens on the rails decoupling if the power source (PSU) shows the output impedance of a capacitor multiplier that has been proposed as a positive add on? Any adapted recommendation in this case?
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File Type: png Cmult_Zo.png (12.7 KB, 151 views)
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Old 23rd September 2012, 06:18 PM   #77
Salas is offline Salas  Greece
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P.S. You may add any L parasitics and ESR you deem adequate for real components and layout.
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Old 23rd September 2012, 06:25 PM   #78
Salas is offline Salas  Greece
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*Toshiba power transistors like 2SC5200 2SA1943 can be used if they would offer something really useful for the upper band impedance, if the big electrolytics and wiring won't hinder that area already.
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Old 23rd September 2012, 06:47 PM   #79
mikelm is offline mikelm  England
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I just spent about 4 hours trying to find, calculate, estimate, guess real world values.

It's surprising how few capacitor impedance graphs there are out there.

my presented results were using "guestimates" Now after my excertions my conclusions remain pretty much the same but I think some of the cap inductances guesses were a bit on the optimistic side.
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Old 23rd September 2012, 07:04 PM   #80
mikelm is offline mikelm  England
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Quote:
Originally Posted by Salas View Post
Mikelm thanks for the analytical presentation. Now what happens on the rails decoupling if the power source (PSU) shows the output impedance of a capacitor multiplier that has been proposed as a positive add on? Any adapted recommendation in this case?
Well, if you use snubbers as suggested on by pass film caps your cap bank should be stable.

If your regulators are also stable - which hopefully should not be difficult with no FB and 10,000uF in parallel then I think it should be OK.

Sonny,

Do you think this circuit will substantially benefit from regulators ?

After thinking about how you have protected your i/p devices with the CFPs & Jfet cascodes on one side and high perfomance CCS's on the other I am begining to think that this cct might be reasonably imune to regular audio frequency / signal induced noise.

My choke regulators with fused outputs provide excellent regulation against mains / diode VHF RH garbage etc but the highish o/p Z means they probably sing along to the music more than many supplies - yet your amps sound very good with them.

What are your thoughts on this topic ?

Last edited by mikelm; 23rd September 2012 at 07:12 PM.
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