Coupling Cap Size for Quickie

[coca]

The size of the coupling cap for the Quickie is 2.2uf: Is there a range in size above that, that can be used in the quickie circuit?

Bernie.

 

[Paul Birkeland]

It depends a bit on the input impedance(s) of what you're driving.  1uF-10uF is fairly common.

 

[Paul Joppa]

Larger values are OK; the plate is at a positive voltage less than 36v, so electrolytics will work as well. If you have a couple 100,000uF 60v caps lying around, give them a try! (Give it a day or two for the startup transient to die out, though  :^)

Here is a table of approximate minimum values, based on -1dB at 20Hz, as a function of the load impedance (input impedance of amplifier which is driven by the preamp):

Load  uF
10K    1.5
15K    1.0
25K    0.6
50K    0.3
100K  0.15

However, one possible source of hum is minimized by using values greater than 1.0uF in Quickie, or 0.5uF for Quickie with PJCCS, Reduction, or Eros.

 

[coca]

Thanks guys. That information is very helpful.

Bernie.