How do the filter caps affect tone and feel of a guitar amp and why? I'd definitely like to understand the "why".
From what I understand they're just flattening the rectified signal, so why would it make a difference if we go up or down in those values as long as we adequately remove the 120hz hum and get a DC voltage? Do different values change the sag of the power transformer or something?
Thanks!
Filter caps and the resistors (or inductors) between them also acts as R/C (or L/C) filters for the 'corner frequency' in the power supply rail. R/C filters are low-pass filters and the bigger you make C in relation to R, the lower the frequency roll-off point will be. Theoretically, the lower the roll-off point, the more the power supply rail will shunt any low frequencies from the HT supply, meaning that more bass frequencies will make it into the signal. However, this is pretty hypothetical*, because with most amp designs having filter caps being between 10uF and 100uF (and most of those being between about 20uF and 50uF), there isn't that much audible difference between low frequency roll-off points that are typically achieved.
*But there can be some audible some differences, esp between using (say) 4uF for the preamp and 8uF for the B+ and screen node supplies compared to using 47uF for all filter caps - depending on how the other components in your amp (i.e. speakers and iron and cathode bypass caps and coupling caps and everything) are set up to carry bass frequencies 'good' or 'bad'. Another thing you might want to tinker with is having higher filtering on the screen supply node, which can help boost bass frequencies in the output stage (because it decreases the amount of screen current feedback at low frequencies), but it depends on what else is going on in the pre-amp and PI etc. YMMV
Topic: Tell me all about filter caps (Read 1772 times)