Mark IV Preamp Tube Roles

[sparklesmcgraw]

Could someone post a simple list of what preamp positions affect which channel and aspect of tone?

The manual isn't that thorough. Looking for a simple version.

 

[MrMarkIII]

Page 17 of the manual (Tube Tasking Chart) is not crystal clear?

 

[aaronlyon]

Manual does not explicitly show: OUTSIDE pair of power tubes are active in Class A mode, BOTH pairs of power tubes are active in Simul-Class mode.

 

[dodger916]

Manual does not explicitly show: OUTSIDE pair of power tubes are active in Class A mode, BOTH pairs of power tubes are active in Simul-Class mode.

That's right, but the question referred to preamp tubes, not power tubes.

 

[MrMarkIII]

Manual does not explicitly show: OUTSIDE pair of power tubes are active in Class A mode, BOTH pairs of power tubes are active in Simul-Class mode.

Mark IV manual, page 12.
I quote:

"... In the Class A position, only the two end power tubes are active..."
"In the Simul-Class position, the middle two 6L6's switch on in parallel with the end tubes..."

Seems eminently clear.

 

[sparklesmcgraw]

Yes it is not 100% clear to me because I am a simpleton.

Could someone simply list what tube affects what channel etc.....?

 

[MesaDCLP]

Bold text is from page 17 in the Mark IV b manual:

V1A= Input Stage
V1B= Tone Recovery Stage (post tone controls)
So V1 affects all channels

V2A=Third Gain Stage (Rhythm Modes) and Fifth Lead Gain Stage
V2B= FX Return Stage
So V2 affects all channels and the FX loop which is alway in the circuit even if it's not used.

V3A= First Lead High Gain Stage
V3B= Reverb Return
So V3 affects Lead and reverb. However, the way reverb is wired it is always in the circuit, so the tube affects all channels even with the reverb off.

V4A= Second Lead High Gain Stage
V4B= Reverb Send
So V4's effect is similar to V3 except with slightly different jobs.

V5= Phase Inverter
This affects all channels.

So the moral of the story is that: all of the preamp tubes affect all of the channels in a sense. Keep in mind the preamp tubes are actually like 2 tubes in one bottle. You have an A side and a B side. That's why the manual lists them that way!!

Hope this clears things up for you. 8)

 

[sparklesmcgraw]

Thanks for that.

Does indeed help

 

[CudBucket]

So V3 affects Lead and reverb. However, the way reverb is wired it is always in the circuit, so the tube affects all channels even with the reverb off.

And this sucks. Because if you're playing with a low master volume setting on the Lead channel and have the reverb cranked for the clean channel, it crushes the tone. I think it's more noticeable with hot pickups.