Passive RIAA and cap variation

[Klimon]

Hi,

Regarding component choice for a passive RIAA compensation circuit consisting of three resistors and two caps (amp in question is Thorsten's simple phono pre http://www.diyaudio.com/forums/attachment.php?s=&postid=335624&stamp=1077837811); how should I visualise what is happening in the capacitors? Does each 'handle' a certain frequency range (1n and 10n in the given schematic)? Reason why I'm asking is that for both caps I'll be using silver mica's of a different breed and it wouldn't seem desirable to me if each would give their (differing) sonic signature to a part of the frequency response.

Thanks!

Simon

 

[robmil]

Hi Klimon

I would not use Silvered Mica caps in this application. The preferred type is a 1% or better film type. Polypropylene is an excellent choice here. RIAA filters, or any other really need low noise close tolerance film.

I hope that helps.

regards

Rob

 

[Klimon]

Hi Rob,

I've read quite the contrary, silver mica's being the preferred choice even when used as coupling caps if thou can find high enough value. As in many cases personal preference might be a factor though. Regarding tolerance the silver mica's I have are 5% for the 1n (but hand matched by the vendor, I'll recheck) and 0,3% for the 10n!!

Simon

 

[analog_sa]

Hi Rob,

I've read quite the contrary

You will have to try for yourself. People have strong reactions to silver mica caps: it's either love them or hate them. Maybe some types are absolutely great but i've never had a chance to try those.

Don't assume that the different caps deal with different frequency bands as they significantly overlap.

 

[Klimon]

Don't assume that the different caps deal with different frequency bands as they significantly overlap.

Good thing

I think I know what type of sound to expect from the silver mica's; if I don't like it I can always go polypropylene. All power supply caps and the output caps are paper and PP in oil so a little silver mica might blend in nicely for some more bite.

Cheers, Simon

 

[Geek]

You will have to try for yourself. People have strong reactions to silver mica caps: it's either love them or hate them.

Agreed.

When playing with passive phono stages, I tried several types of caps and all were different sounding, though the RIAA curve measured the same.

I wouldn't say any was better, just different sounding.

Cheers!

 

[robmil]

Hi Klimon

only one of the 10n caps is used for coupling, the other 2 for part of the RIAA filter network. I must try sm caps to see what they sound like.

 

[Klimon]

only one of the 10n caps is used for coupling, the other 2 for part of the RIAA filter network. I must try sm caps to see what they sound like.

Yes.

Thanks for the input all.

Simon