MK V90 vs MKVII Master Controls

[Guitarfreak]

So...was reading a comparison on another site about how the MKVII and the JP do not use the final master and solo level controls. Can't you just turn the output master on 9 or 10 on the amps that do and use each channel master for your volume and get the same effect? Only problem I find with most pots is they have no friction and if you slip and accidentially jack it up by mistake that it could really hurt somebody.

 

[mace]

Sure, I think what you are asking is possible on the TC and Mark V, for example. But, the extra circuitry of the OUTPUT is still in the signal path. So, from a purist point of view, this isn’t *exactly* the same as just eliminating the OUTPUT circuit altogether. On the Mark V one can hard bypass the final OUTPUT control, however.

And yeah, on the VII it’s a good idea to remember to turn all MASTERs to zero when finished…it can be an unpleasant surprise to switch channels and forget that the MASTER is turned up!

 

[domct203]

I prefer the global output control as I use all the channels on my amp. Once the channels are balanced and set to unity gain with the FX Loop effects it’s nice to have just one volume control on the FX Loop return.

I’m bummed that the newer amps do not have the global output control.

 

[endofall]

Never really understood the need for a global master volume. Why not just set your primary channel to your desired volume then set the rest of the channels to match the actual volume of that channel. Also as far as a solo boost a TC electronics spark mini in the loop is perfect and totally solves that function.

 

[domct203]

Never really understood the need for a global master volume. Why not just set your primary channel to your desired volume then set the rest of the channels to match the actual volume of that channel. Also as far as a solo boost a TC electronics spark mini in the loop is perfect and totally solves that function.

That’s fine until the FOH tells you to adjust your volume and you have to either guess on the other 2 or 3 channels or piss off the sound man while you fiddle with all your volumes. It’s much easier to just turn one knob and still have balanced output from all channels.

 

[mace]

That’s fine until the FOH tells you to adjust your volume and you have to either guess on the other 2 or 3 channels or piss off the sound man while you fiddle with all your volumes. It’s much easier to just turn one knob and still have balanced output from all channels.

Just turn around and act like you turned it down then ask if that’s Ok. They’ll invariably give a thumbs up. I thought that is what everyone did? LOL

 

[domct203]

Just turn around and act like you turned it down then ask if that’s Ok. They’ll invariably give a thumbs up. I thought that is what everyone did? LOL

Right after that thumbs up you get your channel fader turned down LOL. At least that’s what I did when hosting a show and dealing with a ‘rock star’.

 

[endofall]

Right after that thumbs up you get your channel fader turned down LOL. At least that’s what I did when hosting a show and dealing with a ‘rock star’.

Sounds like a bad sound guy? Most of them can deal with an amp at a reasonable volume. The only times that I found a sound guy that could not was when they honestly didn't know what they where doing.
I'm editing this post to say, I believe this is probably genre dependent. Most hard rock/metal etc type of shows are/should be use to loud amps and that's not much of an issue which which is the majority of my live experience. Regardless maybe using the 10/45 watt selections at a scenario like this would help bridge that gap?

 

[domct203]

My point was about the simplicity of turning one knob when needing to turn down (or up) vs having to rebalance multiple channels. Adjusting stage volume is not an uncommon senario at a gig, especially when room size changes from show to show even when you’re not mic’ed.

 

[Eevil]

That’s fine until the FOH tells you to adjust your volume and you have to either guess on the other 2 or 3 channels or piss off the sound man while you fiddle with all your volumes. It’s much easier to just turn one knob and still have balanced output from all channels.

This is why i prefer also the global master.. When I had ED and had “the talk” with FOH guy it was a pain to balance clean and drives correctly within half a minute..

And when show starts guitar is completely washed away then same process in reverse while playing - and the volumes were really touchy in certain volume range

 

[bandit2013]

The Mark VII has both pre FX loop volume and post FX loop volume. No way to set them separately since the volume pots are ganged on the shaft. That explains the two pots and double set of wires. I saw this when I took a gut shot of the Mark VII and zoomed in on the volume pot. All three channels are wired this way.

As for the JP2C, that amp also has the volume control after the FX loop. I was comparing the Mark VII and JP2C and decided to slave each amp into the other. If the JP2C was true to the real deal, I would not be able to adjust the volume on the output when slaving into the JP2C. In other words, you have three volume controls in place of one global master. The Badlander is much the same way. The Mark VII is the only one that has to volume controls. Slaving into the Mark VII from the JP2C, I had to adjust the channel master of the channel that was turned on to adjust the output on the Mark VII.

The Mark V90 uses two separate volume pots, one global and solo after the fx loop, and the other channel masters are before the FX loop. This holds true to the other amps like the TC, Rectifier amps (excluding the Badlander).

If that is a problem, one could always add a volume control pedal or sorts in the FX loop if there is no separate volume control for each channel. Never tried that though.

 

[endofall]

The Mark VII has both pre FX loop volume and post FX loop volume. No way to set them separately since the volume pots are ganged on the shaft. That explains the two pots and double set of wires. I saw this when I took a gut shot of the Mark VII and zoomed in on the volume pot. All three channels are wired this way.

View attachment 3093

As for the JP2C, that amp also has the volume control after the FX loop. I was comparing the Mark VII and JP2C and decided to slave each amp into the other. If the JP2C was true to the real deal, I would not be able to adjust the volume on the output when slaving into the JP2C. In other words, you have three volume controls in place of one global master. The Badlander is much the same way. The Mark VII is the only one that has to volume controls. Slaving into the Mark VII from the JP2C, I had to adjust the channel master of the channel that was turned on to adjust the output on the Mark VII.

The Mark V90 uses two separate volume pots, one global and solo after the fx loop, and the other channel masters are before the FX loop. This holds true to the other amps like the TC, Rectifier amps (excluding the Badlander).

If that is a problem, one could always add a volume control pedal or sorts in the FX loop if there is no separate volume control for each channel. Never tried that though.

If the dual gang pot was split into two separate pots how do you feel this affect the amp? It seems like an odd design, but if it was worth splitting using a concentric pot like on the 5150 III 50 watt models would make this a possibility without drilling any holes etc

 

[mace]

What is the purpose of double ganging the MASTER controls like this? Or, why do other amps not do it? Any insights are appreciated.

 

[bandit2013]

Since I have yet to see any schematics of the amp, I can only make an assumption since there is volume control after the FX loop as I confirmed that doing the slave trick. The other is probably a send level to the FX loop (assumed). It makes it difficult to trace out circuits that are terminated by a relay contact. I really do not have any desires to remove the main PCB from the amp to see the traces on the other side. No thanks. I would rather tear down the Mark V90 and rebuild it than to attempt to mess with the Mark VII or JP2C.

Using a concentric pot, not sure if that would give you the Mark V90 thing. It may do that (assumed) but will it be as effective? If I make the assumption this is close to a Mark III circuit, it has a channel volume as part of the tone stack feeding in to V1B (same trick used on the Mark IIC+). The Master volume is after the FX loop and is isolated by two DC blocking capacitors as it is on the plate side of V2B which would place it in front of the GEQ circuit.

Looking at the Mark IV schematic, that pot used as the channel volume changes name to "gain". The gain control in the lead drive circuit changes its name to "lead drive." Then you have the three channel master volume controls in front of the FX loop. the Master volume (same as the global output volume) follows the FX loop and, again, in front of the GEQ circuit. I can assume the Mark VII is more like the Mark IV where the one pot is pre FX volume control and the other is for the output from the FX loop circuit in front of the GEQ.

The Mark V90 on the other hand is a mixed bag of stuff. The clean channel does have a volume control associated with the tone stack, however, it is labeled as CH1 gain (similar to the Mark IV design). CH2 and CH3 use a voltage divider network in place of the potentiometer. Just note that CH2 gain is used on the V2A triode that is in front of the tone stack. The "lead drive" pot as referenced on the IV, is called "gain" on the Mark V so we are back to the IIC and III description. CH1, CH2, and CH3 masters are at the end of the gain stages in front of the GEQ circuit. This design uses the output of the GEQ to create the FX send level. The global master and solo boost is on the plate side of the FX recovery tube V6B which is in front of the phase inverter. The "output" or global master volume and solo boost design was borrowed from the Dual Rectifier circuit which includes a full bypass of the FX circuit entirely.

I would assume a concentric pot for separate pre FX and post FX volume controls would work like the Mark IV so you would get a channel volume but with three master volume controls. Also, due to lack of any schematic available to the general public, I would assume that Mesa took advantage of the relays responsible for each mode to compensate for signal strength through the FX circuit. I assume that using the ganged dual pot design keeps the signal levels the same or matched. This is just an assumption and I could be way off on this subject.