SP14 Output Capacitor Values

Hi there,

I'm curious to know if anyone has experimented with 0.22 uF vs 0.33 uF capacitors in the C3/C3a position of an SP14 preamp.  The reason I ask is that my parts list calls for 0.22 uF, but all photos I see on the internet show 0.33 uF caps there.   My understanding (I'm slowly learning circuits) is that this capacitor, among other things, affects the LF rolloff point.

Cheers,
Martin

0.33µF will give a slightly lower bass roll-off point.  The difference should not be significant.

The exact frequencies depend on the impedance of the load.  Into a 100KΩ load, often seen in
tube equipment, the -3dB rolloff point of 0.22µF is approximately 7 Hz; of 0.33µF, approximately
5 Hz.

SOME amp stages limit output bandwidth to keep them from getting into trouble at low bass
frequencies.  A well-designed one will not have to rely on the difference between 0.22µF
and 0.33µF!

perfect reply, thanks GP49

Wonderful, thanks for the reply.

All makes sense.

Following this, I looked up the math. 100k is the right value for impedence, and I don't much care if the rolloff is 5Hz or 7Hz. Turns out a friend has some Mudorf Silver/Gold Oil caps he can lend me. Also found some 0.22 uF Russian Teflon caps. Should be interesting.

Cheers,
Martin