Tubes Asylum

"I have the 6SN7 adapter on hand"

75.138.96.180

1973shovel

A

In Reply to: RE: "I've kept the original 12AT7 board" posted by Mick Wolfe on November 14, 2023 at 08:59:34

With but a few resistor changes to the voltage amplifier (center) tube, you could easily convert that to use a 6SN7 via your adapter. for a couple of bucks and a little bit of soldering, it should give you a good idea of the changes the full 6SN7 board might bring.

I'm thinking of converting my phase inverter tubes from 12AU7 to your 12AT7, since I already have some NOS JAN 12AT7s in stock.

I appreciate your feedback on your friend's preference for the 6SN7 board. As I noted elsewhere in this thread, Roy Mottram said 90% of his customers preferred the 6SN7 board over the 12AU7 version. It's hard to argue with 90%

Follow Ups:

Phase Inverter - Triode_Kingdom 16:02:33 11/16/23 (1)
"I'm thinking of converting my phase inverter tubes from 12AU7 to your 12AT7, since I already have some NOS JAN 12AT7s in stock."

I will be very surprised if this produces any audible or measurable improvement regarding distortion. The LTP is inherently "linearized" due to internal feedback, just like a cathode follower. My last amp used a 6J6 LTP and managed < .035% THD at 5W output. Curves for the 6J6 clearly don't support this level of performance.
- Thank you, TK - 1973shovel 17:39:53 11/16/23 (0)
  That's one less thing to 'obsess' over!
RE: "I have the 6SN7 adapter on hand" - Mick Wolfe 09:17:06 11/16/23 (1)
Thx. Although I could easily live with the 12AT7 board, I will most likely proceed with the entire 6SN7 board. My tech is only 2 miles away and he has that board on hand. He used to be Bob Latino's builder for the amps shipped west of the Mississippi. And the board swap is reversible if for some reason the 6SN7 experiment didn't pan out. I'll let you know how it all shakes in the next month or so.
- You mentioned being on a budget - 1973shovel 11:00:58 11/16/23 (0)
  ...and since you already have the adapter, changing out only six resistors to use one 6SN7 (which is also reversible) would save you money. That's why I suggested it.
  
  And despite what I just read on the VTA forum by someone there who should know better, a 6SN7 is decidedly not just an octal 12AU7. The noval version of the 6SN7 is the 6CG7, not the 12AU7. The 6CG7 (and the octal 6SN7) is a far more linear tube than the 12AU7 on paper (see link below), and in many people's opinions, including mine, it sounds far better.
  
  Note that a 6CG7 is NOT a direct plug in replacement for a 12AU7, as their pin-out is different, which is accomplished in the 6SN7 adapter.
  
  Good luck with it, and I look forward to hearing your take on the 6SN7 board.
  - 12AU7 vs 6CG7 (Open in New Window)

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