Output Cap Question

[WntrMute2]

Simple question here I believe. How does changing the value of the output cap in a "simple" preamp circuit change the sound? I have both 3.3uf and 4.7uf.

Thanks in advance.

 

[Alllensoncanon]

From a simple bandwidth point of view, if a 1K load is assumed, the cutoff (-3db) freq for 3.3uf is about 50Hz and 4.7uf is about 33Hz. But if one use a more real world loading of 50K, the cut off for 3.3uf is already about 1Hz.

 

[Klimon]

It all depends on the input impedance of your power amp:

Coupling Capacitor Calculator by V-Cap

Simon

 

[WntrMute2]

220K

 

[Klimon]

The calculator is your friend 😉

 

[rayma]

220K

The most you need is 0.5uF, which also allows you to use a better capacitor.

 

[WntrMute2]

What I have available is 3.3 and 4.7uf. What happens if I exceed the 0.5uf?

 

[rayma]

Maybe nothing. Larger than necessary coupling capacitors can sound poorer than smaller ones.
Lower than needed LF bandwidth may cause instability if in a nfb loop or through
power supply interaction. The amplifier and speakers could see unnecessary LF disturbances,
especially from phono sources.

 

[egellings]

Too large a cap could cause a large turn -on thump. After that transient passes, it would be fine.

 

[rayma]

The preamp might be fine, but maybe not the amplifier and speakers.

 

[WntrMute2]

Thanks folks. So going from the specified 3.3uf to 4.7uf will not cause any additional problems. Whether or not the 3.3uf is in itself too large is another matter. I appreciate the information.