Wolfgang wrote: ↑
Mon Nov 11, 2019 3:11 pm
Do you consider the psu caps in series with the output cap regarding the audio signal?
In this case a cap multiplier with very little capacity caps like I use with the InvOTL or a HV reg psu like the Maida reg. for the output stage (keeping the TL738 as CCS) would improve the SQ.
How did you calculate the size of your output cap?
Yep I did consider that in a single-ended amplifier, the power supply is in series with the audio signal, and the 2200uF output stage PSU caps are also now bypassed.
The output cap wasn’t calculated, it was all I could find in a box after I’d blown up one of the the previous caps on the breadboard, when a bad 13E1 arced over. Using the DC resistance of the speaker load, in this case 7R, with the 6800uF I had, got me a corner frequency of about 3Hz. “That’ll do” I thought. I’m aware that speakers do not act like resistors, but you have to work from somewhere.
Unfortunately, my OTL is very much the “poor relation” to both yours and Ray’s builds. I simply don’t have the funds to buy, or build HT regulators or DC heater modules. The cost of heatsinks is a problem for me, but thanks for the suggestions.
My OTL is basically, made up of bits and pieces that I’ve picked up here and there. The triple power supply arrangement is about as far as I can go with this OTL. That it even works, and better yet, sounds as good as it does, never ceases to amaze me. I have to smile very time I turn it on.
“In the supermarket there is music while you work. It drives you crazy, sends you screaming for the door.
Work there for a year or two and you can get to like it; I don’t work in supermarkets anymore” (Joe Jackson)