Bypassing filter caps with Smaller caps

[directdriver]

It has an effect on the sound and high frequency. I usually don't like it so I remove them. To each his own.

[AndrewT]

Originally Posted by Shoog

............I am a trained scientist and know full well the limits of measurement techniques in deciding these questions. .........

Should you also be aware that measuring different characteristics may be capable of showing the effect of the modifications, rather than relying solely on the subjectivist view that only y/our ears can tell the difference?

[wicked1]

I think you just need to accept that our ears are better measurement instruments than any man made device, for certain things. We have millions of years of evolution behind the design of our sensors. It's a matter of life and death, at times.

[SY]

Originally Posted by Troncones

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??

It depends on how it's done. If the smaller cap is placed local to the signal circuit, it can prevent or reduce the likelihood of oscillation. This is particularly true with circuits using high gm RF tubes like ECC88. If the small cap simply goes across the large one several inches away, its effect is negligible-to-zero.

[Shoog]

Originally Posted by SY

It depends on how it's done. If the smaller cap is placed local to the signal circuit, it can prevent or reduce the likelihood of oscillation. This is particularly true with circuits using high gm RF tubes like ECC88. If the small cap simply goes across the large one several inches away, its effect is negligible-to-zero.

And yet people commonly observe it and so it is there, it cannot be so easily dissmissed - and I very much doubt that it is predominantly attributable to oscillations. I have heard it reported that the film cap may induce oscillation when used as a bypass due to inductive- capacitive interactions between the two caps - who am I to say without having seen the particular evidence.

Should you also be aware that measuring different characteristics may be capable of showing the effect of the modifications, rather than relying solely on the subjectivist view that only y/our ears can tell the difference?

They may show differences (or they may not) but often these are grouped variables which are not directly attributable to any one particular property of the circuit. What exactly are you reporting in these circumstances ? Have you gained any better understanding of what is really going on within the circuit ?

I would not advocate anyone taking my subjective opinion of this - I advocate them taking their own subjective opinion. As directdrive pointed out, he observed the difference, didn't like it and took them out - I can respect that position as much as my own. Its such a simple and quick thing to try that I cannot understand why anyone would lose any sleep over just sucking and seeing.

Shoog

[Shoog]

It actually supports my belief that 9 times out of 10 when given a choice people will opt for a bandwidth limited amp for long term listening pleasure.

Shoog

[Tony]

Originally Posted by wicked1

I think you just need to accept that our ears are better measurement instruments than any man made device, for certain things. We have millions of years of evolution behind the design of our sensors. It's a matter of life and death, at times.

the ear as a measurement instrument is a lousy tool.......

but as a means to listening pleasure, yes it is very reliable, and yes it matters.....

[trobbins]

Shoog -perhaps you use large main filter caps with poor ESL, or place your bypass cap in a much better position? Large caps typically start rising in Z above 100kHz, and a 1uF film bypass is only going to get down to low Z above 1 Mhz - do you use a smaller electrolytic for the bypass? A bypass on the main filter cap can serve two masters - do you place yours for smaller loop area of the power supply, or the output signal stage?

Ciao, Tim

[Shoog]

I have generally used large computer grade caps (220-1000uf) and then bypassed them with something small such as a film cap of 1uf. Every situation is necessarily different. I add the film cap on the last electro in the power supply.
I also tend to bypass my cathode bypass electros (generally effective values of 500uf) with 10uf film caps. on the bypass cap, but again this depends a great5 deal on what is at hand.

Shoog

[Tony]

me too use those kind of caps in my tube amps, a capacitor bank per channel, capacitors shown are 470ufd/450volt ecaps.......this is a 4D32 pp amp i am building...a work in progress.....