Tubes with different gain for Moscode 401HR


I am vertically bi-amping 2 Moscode 401 HR amps and would like tubes with lower gain for the HF than those used in the LF. Any Moscode users'/pundits' experience/advice would be most welcome.
springbok10
6922 have higher gain than 12AU7.

If I recall correctly, the 401HR manual or the Moscode website has specific info about tube gain.

Not sure if mixing the two types will result in a satisfactory sound since they create different presentations in the 401HR.
I am currently using 6922s (6DJ8 - Amperex orange logo) for LFs and stock 6GUYs (+ 12AU7s next to them, so insides are 12s and outsides 6)for HFs and the sound is better than matching the 6922s for HF & LF.

You are not bi-amping, are you, Tvad?
The outside position has a more obvious affect on gain. If you swap the 12AU7 to the outer position in the HF amp, you will notice a difference, IMO.

12AU7 tubes produce a wider, yet shallower image than 6922. It's also a touch softer in the top end and upper mids. This was a more musical sound, IMO, and it would explain why you find the sound better in the HF amp using 12AU7.

I am not bi-amping, and I no longer own a 401HR.
The solution may well be a Differential pre-amp, such as the Supratek Cabernet Dual, with different outputs and tubes to LF and HF. Yet more $$.........

Problem with the 12AU7 on the outside means you cant use the higher gain 6DJ8 tube with it, so there is no way of getting differential gain.

May I ask what amp you are now using, Tvad?
11-15-07: Springbok10
The solution may well be a Differential pre-amp, such as the Supratek Cabernet Dual, with different outputs and tubes to LF and HF. Yet more $$.........

Problem with the 12AU7 on the outside means you cant use the higher gain 6DJ8 tube with it, so there is no way of getting differential gain.

I don't know what that means. Are you talking about not being able to use the 12AU7 and the 6922 in the same amp, but in different positions? This can be done. If you're talking about not being able to use 12AU7 and 6922 in different amps because the gain will be inherently different, then this is true. I thought that was your goal?

Why not use a tubed crossover like a Marchand unit? I believe the gain can be infinitely adjusted this way.

I'm using a VAC Musicblock 160 monoblocks with an Atma-Sphere MP-1. I have Atma-Sphere M-60 amps on the way for comparison.
What I mean is that you cant use a 6 series with a 12 series in line - so if a 12AU7 is on the (LF) outside, another 12 series tube must be used on the HF (outside), (according to George) defeating the purpose of using the higher gain tube.

I too have an Atma-Sphere MP-1 and MA-2 in my main rig. The kings, undisputed. But in this system with Mark-Daniel speakers, (4 ohm, down to 2.8, 85 db sensitivity) LF must be driven by ss/mosfets, unless I drove them with the big Atma-Spheres, which I'm not about to do.
11-15-07: Springbok10
What I mean is that you cant use a 6 series with a 12 series in line - so if a 12AU7 is on the (LF) outside, another 12 series tube must be used on the HF (outside), (according to George) defeating the purpose of using the higher gain tube.
I see.

If it were me, I'd try it anyway despite what George says.

Otherwise, I'd investigate the Marchand tubed crossover.
I will try horizontally bi-amping with one amp tubed with NOS 6DJ8s (quad) and the other with NOS 12Au7s. Former for LFs, latter for HFs.
Sounds like a good experiment.