by BibBigDog » 21 Aug 2015, 20:04
I completed it and it works!!
I have been listening to it all day. I can't hear any hum or hiss even with the volume knob cranked all the way. Thank you so much for creating something that is so satisfying to put together and sounds so good.
I am driving it with the line output from a Meridian Explorer headphone/DAC and listening via Sony MDR-7506 studio monitors (63 ohm impedance). The difference between the Meridian's built-in headphone amp and the Frigate was really surprising to me. Where one might expect the transistor amp to be cold and the tube amp to be rounded and warmed over, I found the opposite. The Frigate has a very precise, clean sound, and the Meridian sounds warmer and more weighty by comparison. The fact that I'm using the same DAC in both cases helps pinpoint the differences. I think maybe the Frigate's sound is actually more accurate than the Meridian's amp.
I am not sure if the bass response/warmth differences I'm hearing is due to an impedance mismatch between my headphones and the Frigate, or if I've just become accustomed to a more bloated sound. I am tempted to try adding a resistor to see how that affects the sound.
I know the Frigate is an OTL amp, and maybe this is heresy or just a terrible idea, but I'm also intrigued by the idea of using a transformer to better match the output. Sowter has some that appear to be designed for this sort of thing. I do not want to second guess your design which is clearly very, very good but I am curious.
Oh, and what kind of fuse should I be looking for?