groove tubes gt12ax7m vs sovtek 12ax7lps

rs16iandy · Mar 16, 2011

Hi im after some advice please.
I've be checking the 4 pre amp tubes in my f50

I found
V1: GT12AX7M (ECC83/7025) groove tubes

V2: GT12AX7M (ECC83/7025) groove tubes

V3 12AX7LPS sovtek

V4 12AX7LPS sovtek

Im after a fat bluesy sound but i find i cant get much tube over drive with the channel 1 gain at full .
and i would quit like to be able to go from distortion on channel 2.
I find full gain on channel 1 is about the same as the gain at 9 o'clock on the channel 2 with out the warmth

would i be better to swap V1 and V3?
or do i just need to re tube it or just leave it as it is?

I have mesa boogie STR 425 5881 power tubes
but do own a pair of gt 6L6-GE tubes but they have a distortion ratio of 10 which i fear is to high for a fix bias amp and will run to cold or is it the othe way and they will run hot and brake up very early.

I have changed the black shadow mc90 to a celestion gold and it is a massive improvement and has brought the f50 alive
cheers andy

MrMarkIII · Mar 16, 2011

If those Groove Tubes are rated at "10", they will be super clean with a lot of head room.
The STR-425 will break up much sooner. They will have a bit less output as well.

Here's what each pre-amp tube does, according to the manual:

V1 A= Input Stage both Channels
V1 B= Clean Channel

V2 A= 2nd Input Stage both Channels
V2 B= Channels 2 & 3 Boost Stage

V3 A= Channels FX Send
V3 B= FX Return

V4 A / V4 B= Phase Splitter

You could start by just switching one of the Groove Tubes with one of the Sovteks.

rs16iandy · Mar 16, 2011

Am I right by thinking the sovtek tubes are higher gain than the grove tubes I have so to get a fater clean do I want a sovtek in v1 or v2

MrMarkIII · Mar 17, 2011

The only way to tell is change them around and find which combination sounds the best to you.
I personally have not found much difference in gain between different brands of 12AX7s. There are more differences in tone, as in the quality of the high end, midrange, bass, etc.