Warming up the Mark II clean channel

[Mike67]

I want a more vintage sound from my MK II. I've had success with other amps by switching the preamp tubes with NOS, and tubes with different gains. I have several NOS 5751, 12ay7s, and 12at7s.

I am only conerned with warming up the clean channel, but I don't know which of the four preamp tubes effect it. Any suggestions for a dum@$$?

Thanks,

Mike

 

[hans-jürgen]

I am only conerned with warming up the clean channel, but I don't know which of the four preamp tubes effect it.

The first one from the right (close to the speaker output transformer) if you look at it from the back. Depending on your Mark II model it might even be a MOS-FET, not a tube, that's why there is an extra switch for the the correct voltage on the amp chassis just beside the socket. In case you didn't take off the tube covers and find that MOS-FET, you might want to change it with a tube which will sound warmer, but also with less gain.

 

[RussB]

Without reverting to a schematic, I will say that many of the pre-amp tubes in the MKII's are shared between functions...

That is, that 1/2 of a tube will be 2nd gain stage for the clean channel, while the other 1/2 will be the FX return (this is just an example, like I said, I didn't check the schematic)

 

[TigerStrat]

V1 is your input, 1st clean gain tube, and affects the clean as well as the overall sound of the amp. It is the socket nearest to the input. Stick that 5751 in there! That's what I have in mine and it shimmers. Try one in V2 also if you have another, although an old GE 12ax7 is my current V2 pick. Put a good 12at7 in V4 to smooth out the reverb...any of the ones you mentioned would probably improve the reverb

 

[TigerStrat]

V1 is your input, 1st clean gain tube, and affects the clean as well as the overall sound of the amp. It is the socket nearest to the input. Stick that 5751 in there! That's what I have in mine and it shimmers. Try one in V2 also if you have another, although an old GE 12ax7 is my current V2 pick. Put a good 12at7 in V4 to smooth out the reverb...any of the ones you mentioned would probably improve the reverb

 

[TigerStrat]

V1 is your input, 1st clean gain tube, and affects the clean as well as the overall sound of the amp. It is the socket nearest to the input. Stick that 5751 in there! That's what I have in mine and it shimmers. Try one in V2 also if you have another, although an old GE 12ax7 is my current V2 pick. Put a good 12at7 in V4 to smooth out the reverb...any of the ones you mentioned would probably improve the reverb.

 

[TigerStrat]

V1 is your input, 1st clean gain tube, and affects the clean as well as the overall sound of the amp. It is the socket nearest to the input. Stick that 5751 in there! That's what I have in mine and it shimmers. Try one in V2 also if you have another, although an old GE 12ax7 is my current V2 pick. Put a good 12at7 in V4 to smooth out the reverb...any of the ones you mentioned would probably improve the reverb.

 

[JazzRules]

V1 is your input, 1st clean gain tube, and affects the clean as well as the overall sound of the amp. It is the socket nearest to the input. Stick that 5751 in there! That's what I have in mine and it shimmers. Try one in V2 also if you have another, although an old GE 12ax7 is my current V2 pick. Put a good 12at7 in V4 to smooth out the reverb...any of the ones you mentioned would probably improve the reverb.

Yes indeed, the V1 and/or V2 sockets are where he should try first. 5751's 12AY7s and 4025s would be a good thing to try for that old Fender charm.

One thing though, and it might not be so apparent to some, the V1 is encased in a metal EMI/RFI sleeve. It's a half turn bayonnette mount if I recall, simple half twist and it comes off.

Another thing that might be nice is a 12AT7 with matched triodes for Phase Inverter duty.