Koop wrote:
Thanks, that's what I thought, I just don't recall seeing a single gain stage like that before.
It's actually the standard Marshall 18W preamp. Although not common in most Marshalls, it is fairly typical for amps of the late 50s-early 60s Vox era.
Koop wrote:
The normal channel seems to have plenty of gain and breaks up nicely, the TMB needs to be pushed more for the break up (has more headroom).
In the sIII TMB variant, they have deliberately put in some measures to further throttle back the naturally available gain in the TMB channel. The regular 18W TMB, which the sIII derives from doesn't have those mods, and produces IMO a better level of gain. The actually clean headroom of the amp stays roughly the same, since that's more factor of how much clean power the power stage can push out before it starts to breakup.