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Old 6th April 2012, 05:45 PM   #1
mbeards is offline mbeards  United States
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Default Bypassing filter caps with Smaller caps

Hi everyone,

I am wondering what results people have with bypassing large filter and other large bypass caps with a small bypass capacitor to provide a better path to ground for high frequencies.

I have heard of this a few times but I am wondering if it is a good thing to conceder? I usually see somewhere around .1 uf recommended.

Thanks
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Old 6th April 2012, 05:58 PM   #2
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Bypassing PS filter caps is quite common, and beneficial.

jeff
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Old 6th April 2012, 10:48 PM   #3
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You only need it on the final cap, and my experience is that it definately improves high frequency performance to a surprising degree. It also works on cathode bypass caps.

Shoog
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Old 6th April 2012, 10:54 PM   #4
AJT is offline AJT  Philippines
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never used any.....
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Old 7th April 2012, 12:02 AM   #5
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you need faster caps.....if your power supply are electrolytic's, you can use poly film, meta lfilm, etc. if your power supply caps are ply film, then you need metal film, etc
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Old 7th April 2012, 03:19 AM   #6
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never felt any need for it in my tube amps....i used some on my ss amps though...
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Old 7th April 2012, 08:07 AM   #7
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Quote:
Originally Posted by speakerfritz View Post
you need faster caps.....if your power supply are electrolytic's, you can use poly film, meta lfilm, etc. if your power supply caps are ply film, then you need metal film, etc
I was surprised at how much difference it made to electro power supply caps.

Shoog
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Old 7th April 2012, 12:14 PM   #8
AJT is offline AJT  Philippines
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what i do is build my transformers with as low dc resistance in the windings as i can....that makes my ecaps charge faster than otherwise with conventional transformers.....that is why i do not need those added caps....
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Old 7th April 2012, 02:02 PM   #9
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I have asked before and didn't get an answer so here we go again. I believe with the proper test you should be able to see what you hear. Where will you see the difference with the PS cap bypassed? Output at HF? Sine Wave shape? Square Wave shape? Or??
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Old 7th April 2012, 02:13 PM   #10
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Quote:
Originally Posted by Troncones View Post
I have asked before and didn't get an answer so here we go again. I believe with the proper test you should be able to see what you hear. Where will you see the difference with the PS cap bypassed? Output at HF? Sine Wave shape? Square Wave shape? Or??
You can be an objectivist and attempt to find an appropriate measure to show what you are looking for, or you can insert a high quality film cap onto the last stage of your power supply.

One is easy and you are the judge of any change, the other requires sophisticated high resolution test equipment and a rigorous protocol to judge your results by.

There are a few people on these boards who claim that if they cant measure differences in THD then there will be no differences in the final sound - experience has told me they are wrong. I know which approach I go for in these circumstance.

I am a trained scientist and know full well the limits of measurement techniques in deciding these questions. On this particular point about caps - I was extremely skeptical until I tried it. I was also extremely skeptical about using transformers for input phase splitting and interstage duties (knowing absolutely for a fact that they degrade THD figures) but now I have not built a valve amp without them for about five years.

You takes your choices and builds your own crosses.

Shoog
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