Most Musical 6NS7 tube for a Preamp?

atma- Sorry. How much is the MP 1's retail? (That is the 2 chasis, 6NS7
model correct)?

@chorusYes, but the MP-1 is balanced. We make three preamps- in your case the UV-1 is probably the preamp to look at since your Pass Labs amp only accepts single-ended inputs. 

Sheesh- we don't get in the mix?
I can vouch for Andy Bouwman of Vintage Tube Services. We have many consistently positive comments from our customers going back 25 years.  

Yeah @atmasphere, for pre-amp applications, Roger had a hard-on for the 6DJ8 (used in his RM-5 and the Audible Illusions Modulus 2 & 3). He was a man of "firm" opinions. ;-)

@bdp24 We used the 6DJ8 in some our early stuff, since the tube is very linear (which is probably why Roger liked it) and you could get good bandwidth as it supported high currents.

But finding one that wasn't microphonic was really challenging! I often found examples you could yell at and hear yourself in the speaker- and that was in an amplifier!


The 6DJ8 was not intended for audio- it was more for instrumentation (look in a Tektronix 'scope sometime- the tube ones are full of them) and television work. OTOH the 6SN7 *was* designed for audio, and like many products there were hiccups along the way but they did get the design right.  When we started using it the only source of current production was Russia and they were dreadful. But then the Chinese got in the game and their 6SN7s were pretty good! Since then there has been no turning back and we use the 6SN7 in  all of our products.

When we came out with the UV-1, instead of using the 12AU7 (which is based on the 6SN7) as we were doing in our modifications of the Dynaco PAS-3, since we had the room and the current in the power transformer, we opted for the 6SN7 as the centerpiece of that preamp.


What's nice about the 6SN7 is that if a line stage design is at all competent, it will easily keep up with line stages costing a lot more. It does not have to be a complex circuit- in our UV-1 there's only one tube per channel and 4 resistors!


Audio Research makes respected preamps, but I would expect many of the 6SN7-based preamps on this thread to keep up with any of them. This is not an attack on ARC, its simply a statement of how well 6SN7s work in line stages!

@bdp24  Roger and I disagreed about his assessment of the 6SN7. For some reason he only used the early Tung-Sol documentation to support his views of the tube as you can see in the YT video. The issue was corrected by Tung Sol in later versions and by different manufacturers.


I agree with his assessment of some of the 'boutique' fuses. If they have a Teflon tube inside, the fuse will not blow correctly and so can damage the equipment its meant to protect!

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!!