Up for air finally after spending days reading and watching Youtube videos on the use of capacitors in audio circuits.
What an amazing adventure!
I thought I knew all I needed to know having had a recording studio and worked in radio for years, but there's so much more that I didn't know!
There are some fabulous technical videos on Youtube... some of them have previously been linked here... just search key words like "capacitors audio", "resistors", "RF ground", "antennas", "batteries", be sure to eat, drink, sleep and say hello to your wife, but those videos can hang you up for days.
And be sure to check out Mr. Carlson's lab.
Years ago I designed and built a magnetic phono cartridge preamplifier taking care to get a low noise op amp. All went well until I tested this, it sounded great but there was some rumbling in the background. On the scope I observed a low frequency random signal. Lots of effort to locate the source revealed that the multi layer ceramic capacitors used to couple the signal were the source of the rumbling.
Yes, the choice of capacitors in audio ciruits matters. I highly recommend polypropylene capacitors for audio applications. They are not expensive.
I just recapped a vintage tube amp with these and am very happy with the outcome. The distortion is not measurable (below 0.5 % THD at full power output) and there is no rumble.
Neil