Tube recommendations for RM4

Rob,
What preamp tubes do you like in RM4s?

To be honest Jace, I have never really spent that much time rolling tubes through any of my RM4's. I generally like the Ruby 12AX7AC5 or AC7 in V1 on most MTS amps. I never use the loop on them, so that tube is irrelevant to me and the V3 is typically a Ruby as well.

My understanding is that V1 is the first tube in the signal chain. Your signal goes through this tube before it ever gets to any of your four modules. Because of this, I think the choice of tube in the V1 position is critical.

Because I prefer low-gain tones, I've tried a JAN GE 5751 in this slot. For me, the lower gain of the 5751 gave me a greater range of acceptable "Gain" settings on all of my modules.

For high-gain modules, you'd certainly want a low-noise 12AX7 or ECC803 in this slot.

The RM4 manual doesn't show which tube is V1, V2 or V3.
Looking from the rear of the RM4 which is which?
Same question for RM50 combo. Which is the P.I.?

audiomidijace said:

The RM4 manual doesn't show which tube is V1, V2 or V3.
Looking from the rear of the RM4 which is which?
Same question for RM50 combo. Which is the P.I.?

Click to expand...

There should be a STICKY for all tube locations for each model.

Looking at the back of the RM4, the single lower tube is V1. The upper right tube is the output driver and the upper left tube is the loop buffer/mixer.

I spent the weekend rolling tubes in my RM4 and modules. I previously used an RM50H and figured they were different enough to revisit everything. V1 ended up being exactly what JF posted, a Ruby 12AX7AC5 HG, which is what it came with. I tried RCA, Mullard, Amperex, Telefunken, Tung-Sol RI, EH, JJ, Sovtek... nope, the Grail just didn't get there without that Shuguang in V1.

For fun, here's what ended up working in my stockish mods:

Clean - V1 RCA 12AX7, V2 Tung-Sol RI 12AX7
SL+ - V1 Ruby 12AX7AC5 HG, V2 Amperex (Hammond) 12AX7
Grail - V1 JJ ECC83S, V2 Amperex (Hammond) 12AX7

Thanks so much for the info. I'll put some time in to trying some different V1 tubes this weekend. As you had the RM50H do you know the tube layout for that one as well?

Looking at the RM50H from the back, the tube furthest forward and to the right is V1 (it's right under the input PCB.) The middle 12AX7 is the loop buffer/mixer and the one furthest to to the left (closest to the power tubes) is the PI. I use a 12AT7 there.