tube ideas for center-volume 6g4 Super

[Luthierwnc]

Hi Guys, I'm designing the winter project and needed some ideas on preamp tubes. The tube chart on these was a mix of 12AX7's and 7025's. With modern glass I'd be happy to get the quality of either but does anybody have a good experience replicating brown or early black Fender tones with current manufacture preamp tubes?

Thanks, Skip

[martin manning]

7025 and 12AX7 have identical specs for Ia, ra, gm, and mu at the same 250V Va, -2V Vg operating point. 7025 is basically a low-noise 12AX7.

[Stevem]

The preamp response of a brown era is more about getting the preamp voltages right then the added gain and top of a 7025 over a ax7!

[martin manning]

The preamp response of a brown era is more about getting the preamp voltages right then the added gain and top of a 7025 over a ax7!

Added gain and top? How do you get that when these two tubes are essentially identical?

[Luthierwnc]

I was mostly fishing for what is on the market today that best approximates the original preamp tubes. My experience with ANOS has been a bit spotty. Cheers, sh

[Teleguy61]

The preamp response of a brown era is more about getting the preamp voltages right

This is the key I feel.
Built a 6G6B clone, and put a similar pre and PI in a DR and they sing in a way the BFs just don't.
I'm using ANOS and used RCAs and GEs for pre and PI tubes.
Good luck.

[Stevem]

From my experience with 7025's over ax7s is since they are a more highly tested tube there gm and current drive are much closer to the intended design spec, not the only mid 80s gm numbers that most other tubes are lucky to hit!

Having a tube that drives a tone stack that is blessed with its rated current drive makes for a big big difference over a a tube that is 20% down or more!

[Structo]

The preamp response of a brown era is more about getting the preamp voltages right

This is the key I feel.
Built a 6G6B clone, and put a similar pre and PI in a DR and they sing in a way the BFs just don't.
I'm using ANOS and used RCAs and GEs for pre and PI tubes.
Good luck.

Is the 6G6B a 1963 amp? Blond?

[Teleguy61]

The preamp response of a brown era is more about getting the preamp voltages right

This is the key I feel.
Built a 6G6B clone, and put a similar pre and PI in a DR and they sing in a way the BFs just don't.
I'm using ANOS and used RCAs and GEs for pre and PI tubes.
Good luck.

Is the 6G6B a 1963 amp? Blond?

Wish it was!
Nope, it's a clone I built with txs I got from Gomez Amps when he closed up shop.
They are Mag Comps he had wound to 6G6B specs and they sound great.
Wish I had bought all he had!
I have it in a combo cab with a WGS ET-90.
Still have a white Showman OT I got from him at the same time, one of these days.

[martin manning]

From my experience with 7025's over ax7s is since they are a more highly tested tube there gm and current drive are much closer to the intended design spec, not the only mid 80s gm numbers that most other tubes are lucky to hit!

Having a tube that drives a tone stack that is blessed with its rated current drive makes for a big big difference over a a tube that is 20% down or more!

I don't find this to be true. 12AX7's and 7025's (new and old) don't seem to have any shift in average gm. The 7025's raison d'tera and advantage in practical use is low noise. Using selected 12AX7's will achieve the same result.

[Structo]

Didn't some of the 7025's have spiral filament for better hum reduction?


Many designations for 12ax7 or ECC83

[Luthierwnc]

Any bites on current production 12AX7's? Thanks, sh

[martin manning]

For standard (i.e. not gold pin or otherwise premium pre-selected types) I've been liking EH. My sample size is small, though, and I would recommend listening tests to make your own selection of the best sounding and lowest noise examples in the circuit.

[davesi]

I think David Allen ships his amps with EH.

[Luthierwnc]

Thanks guys. This project is behind another amp and two guitars but you can never have enough spare parts