Updates....
These are juuuuuuuuuuust about ready to make music... the delays have been numerous... most of it had to do with Sol being stupid busy with work and not having time to work on these at all evenings and weekends.... or just being too wiped out and wanting to do anything else *but* work on amps after a long day at the office... But a good chunk of the delays have also been attributed to things not quite working as expected once you start putting theory into practice... The circuits have been redesigned a few times... but we're finally at a point where Sol feels it's close to being done and shouldn't change anymore...
I'm excited to report that other than some final tweaking on the negative bias supply, these are pretty much ready to have their first listen....
The latest features and specs:
- This is a fully balanced circuit from input to output if you feed it balanced to its XLR inputs... there is switched inputs, either RCA or XLR....
- push-pull output with a pair of 6C33C output tubes. Power output is measured on the scope at least 72 watts from below 20Hz out past 20KHz with only some very minor 3rd order harmonic distortion. The proof will be in the listening, but it appears the amorphous core Lundahl output transformers are going to be up to the task...
- driver circuit is a 6922 DC coupled to a 6SN7. There is only one coupling cap in the entire circuit between 6SN7 and the 6C33C tubes. It's about the only area of the amp that can be tweaked beyond the good parts used elsewhere... copper in oil, duelands, etc... I'm going to experiment on this one....
- The power supplies for everything, including B+, is fully regulated... it doesn't matter what kind of crappy power is fed to it, it is beautiful, rock solid power being fed to the tubes.
- The amplifier has got the coolest auto bias I've ever seen. Unlike almost every other 6C33C based amp I've seen, this is spectacularly good at holding bias rock solid automatically. I've seen how much 6C33Cs can drift with another amp I have here... no worries with this amplifier.... The only drawback, if you can call it that, is that the auto bias needs the tubes to come up to temperature a little bit on first power up. So ideally, you shouldn't listen to the amp for the first couple to 5 minutes after firing it up... there is a mute circuit built into the amp so you don't need to power cycle it to swap interconnects, preamps/sources, etc..
- lots of cool safety features to shutdown the B+ and amp if tubes run away or otherwise don't stay in ideal operating parameters... if a tube goes in the amp, it's not going to take a speaker with it... or even parts within the amp with it....
again, the proof will be in the listening... but Sol's enthusiasm wore off on me today when we talked... I have a feeling this is going to be a nice sounding amplifier.... I can't wait to hear it now...
