Been thinking myself about that, too. I had a First Sound preamp which I really liked, however my ideal preamp to mate with a pair of Spectron M3 SEP will have to have:
- 6SN7 tubes, as I like this family more than the 6922 family. In ultimate terms, on average (there are exceptions, of course), 6sn7 is placed on the thicker, fleshier side of neutral, while the 6922 tubes are on the thinner, brighter side of neutral.
- TVC as opposed to resistors
- remote control
- separate, tube based power supply, and I personally like the 5Z3 tubes.
- preamp out should be true balanced XLR via transformer.
- tube amplification stage should be single ended triode transformer coupled (thus no capacitors) to output transformer. I chose single ended tube as opposed to balanced tube because I want the tube stage to be as simple as possible and I want to be able to roll rare NOS tube pairs without worrying about finding matched quartets.
- 2 XLR outs in order to use the Spectron in monobock config. Also 1 SE out for compatibility.
- low gain, low output impedance (around 50)
- both SE and XLR ins. The XLR input is trully balanced, signal goes to TVC, TVC out is unbalanced to triode stage, then the output transformer balances back the signal to amp. Keeping the signal fully balanced throughout would require 4 matched 6SN7 tubes which, aside from the inconvenience caused by having to find rare NOS tubes to match, I feel doesn't sound as good (less magic) as a SET stage. But this will have a penalty when it comes to measured (not audible) noise.
I'm having this preamp custom made by Promitheus audio as I type this, so I guess we'll see how good it is when I receive it. I expect it to be perfect, and then some...
- 6SN7 tubes, as I like this family more than the 6922 family. In ultimate terms, on average (there are exceptions, of course), 6sn7 is placed on the thicker, fleshier side of neutral, while the 6922 tubes are on the thinner, brighter side of neutral.
- TVC as opposed to resistors
- remote control
- separate, tube based power supply, and I personally like the 5Z3 tubes.
- preamp out should be true balanced XLR via transformer.
- tube amplification stage should be single ended triode transformer coupled (thus no capacitors) to output transformer. I chose single ended tube as opposed to balanced tube because I want the tube stage to be as simple as possible and I want to be able to roll rare NOS tube pairs without worrying about finding matched quartets.
- 2 XLR outs in order to use the Spectron in monobock config. Also 1 SE out for compatibility.
- low gain, low output impedance (around 50)
- both SE and XLR ins. The XLR input is trully balanced, signal goes to TVC, TVC out is unbalanced to triode stage, then the output transformer balances back the signal to amp. Keeping the signal fully balanced throughout would require 4 matched 6SN7 tubes which, aside from the inconvenience caused by having to find rare NOS tubes to match, I feel doesn't sound as good (less magic) as a SET stage. But this will have a penalty when it comes to measured (not audible) noise.
I'm having this preamp custom made by Promitheus audio as I type this, so I guess we'll see how good it is when I receive it. I expect it to be perfect, and then some...