The 6SN7 is in my opinion the best tube for a line section in a preamp.
Back when we started using them the tube was considered obsolete and no-one used them at all. Obviously that’s changed in the last 30 years!
The Pass Labs XA25 only has single-ended inputs so the 6SN7-based preamp can be quite simple. Just make sure that the preamp is not going to have a problem with the input impedance of the amp, but the XA25 is 47K so should not be challenging for most preamps.
IMO/IME a simpler circuit is better- less to go wrong.
The best sounding 6SN7s of current production are coming out of China. We’ve seen fairly short lives out of the Sophia tubes, but otherwise the Chinese boutique 6SN7s seem to hold up well. I would stay away from the Russian fare unless you are able to find 1960s-era Soviet 6SN7s which are excellent.
The best of the Americans are the Ken-Rad, Metal base Sylvania Chrome Dome (WW2 vintage), the RCA red base, probably in that order, and assuming the individual example you find is actually good. But almost any American made 6SN7 is a decent tube- even the RCA coin-base tube.
The Chinese Shuguong tube is a copy of the Phillips JAN (Joint Army-Navy) 6SN7 and sounds very much like it. We’ve had good luck with this tube- they seem to hold up for years.
Of course its a simple fact that with high performance tube equipment, the tubes **must** be handpicked for low noise and low microphonics.
Have fun!!
Back when we started using them the tube was considered obsolete and no-one used them at all. Obviously that’s changed in the last 30 years!
The Pass Labs XA25 only has single-ended inputs so the 6SN7-based preamp can be quite simple. Just make sure that the preamp is not going to have a problem with the input impedance of the amp, but the XA25 is 47K so should not be challenging for most preamps.
IMO/IME a simpler circuit is better- less to go wrong.
The best sounding 6SN7s of current production are coming out of China. We’ve seen fairly short lives out of the Sophia tubes, but otherwise the Chinese boutique 6SN7s seem to hold up well. I would stay away from the Russian fare unless you are able to find 1960s-era Soviet 6SN7s which are excellent.
The best of the Americans are the Ken-Rad, Metal base Sylvania Chrome Dome (WW2 vintage), the RCA red base, probably in that order, and assuming the individual example you find is actually good. But almost any American made 6SN7 is a decent tube- even the RCA coin-base tube.
The Chinese Shuguong tube is a copy of the Phillips JAN (Joint Army-Navy) 6SN7 and sounds very much like it. We’ve had good luck with this tube- they seem to hold up for years.
Of course its a simple fact that with high performance tube equipment, the tubes **must** be handpicked for low noise and low microphonics.
Have fun!!