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Gus

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http://www.linear-tech.com/search/searchResults.do?did=2


Look for AN13 pages 25 and 26 have some good stuff.

The whole app note is good to read some of the stuff applys to audio gain stages in preamps etc.
 
I think this might be related to what my ears don't like with bypassed electros.
 
upon reading this it doesn't say that bypassing a coupling cap will *always* lead to ringing or worse responce, it's saying that you have to pick components carefully. it does not state if the popular polyester/polypro bypassing 'lytics would be bad in any any certainty. testing is needed, however in our applications we are not trying to supress any ripple, we are meerly trying to pass it along. this brings up point number two..

Of course their "bypassing" is power supply bypassing to ground in order to smooth power lines, our bypassing is not trying to do the same thing at all. I think they are two different animals that we are talking about here. too many terms meaning different things as I see it.

:thumb:
 
[quote author="Svart"]in our applications we are not trying to supress any ripple, we are meerly trying to pass it along.[/quote]

[quote author="Svart"]Of course their "bypassing" is power supply bypassing to ground in order to smooth power lines, our bypassing is not trying to do the same thing at all. I think they are two different animals that we are talking about here. too many terms meaning different things as I see it.[/quote]

Actually, lots of audio circuits have bypass caps near IC's or at the power connector, etc. Not to mention cathode bypass caps in tube and transistor circuits, passive LPF's, etc. I think you may be confusing "coupling" and "bypassing".

I understand and generally agree with your comment, though. It would be nice to do some experiments AC-coupling a low-distortion oscillator to a scope using different caps and taking pictures, measuring distortion, etc.

Now there's an idea!

Peace,
Al.
 
well maybe all of our definitions are confusing :green: ..

i consider *decoupling* and *bypassing* the same thing, where we place capacitors between gnd and pwr pins to smooth a rail or short an AC component to ground like in noise filters for motors.

*coupling* of course in this use of the word is joining two stages through a capacitor, using the capacitor to block a DC component.

so i think maybe decoupling and coupling are kind of confusing since they have the same root word but mean two different things.

:thumb:

Cheers!
 
I like the simple test circuit. It might be a good thing to build to test caps. Something like a 555 pulsing a transistor. We should not see anything that extreme in a well designed audio circuit except if switching relays etc using the same power supply.

I think we hear better than we can see on a scope sometimes. The circuit will be an extreme test but I think it can help see things we hear because of the extreme nature of this for audio circuits.

Alot of the ANs there are good to read.
 
yes please, if someone can do some of the obvious favorites like Fc's bypassed with polyester/polypro and so on, we would be extremely grateful!

:guinness:
 
the concept of scientificly testing caps at audio frequencies for distortion is a worthly one. Fortunately for us it has been done! Cyril Bateman wrote a series of articles for Electronics World in 2002 that put all types of caps to the test. The articles start off with his development of a test oscillator and analyser that could measure down to 0.00003% at 1kHz. This series of articles is indispensible for anyone interested in engaging in the capacitor sound debate. Electrolytics, Bipolars, Tantalums, metalised polypropylene, dielectric absorption, bypassing electos with polys, "black gates" even resistors, pots and trimpots...it's all in there! Take note of which opamps he uses to get 0.00003% distortion! enjoy!
 

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