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Original Message

Re: Bypassing Output Caps in Preamps

Posted by Sector-7G on September 28, 2002 at 13:50:48:

I did understand the amp in question is a phono pre. The input impedance of the linestage is the important thing. At 20 Hz it must be large compared to the 8 kOhm impedance of the 1 uF cap. 100 kOhm is probably enough, but, the linestage folks with 100-200k imput impedance amps still want around 3uF of output capacitor. Just try a 20:1 ratio,so your linestage will want about 150 k Ohm impedance, if not then increase the cap size and use a good one. SCR Tin and polyprop is a good palce to start and they come in 1.5 uF size. The internal circuit mods may be necessary if this( 20:1 linestage input impedance to cap impedance ratio at 20 Hz) does not help, as I would then say that it's not the cap causing poor bass response.

the small TFE will probably not help bass much as you mentioned but I'd try it anyway if they are relatively easy for you to get, the better performing the cap the better the sound.