Eq between V1a And V1b vs. After V1b

[richon]

Hi,

I was wandering what difference would be having the Eq between V1a and V1b versus having it after V1b (between V1a and V1b it would be only a "gain/Clean" pot)

[ayan]

Hi,

I was wandering what difference would be having the Eq between V1a and V1b versus having it after V1b (between V1a and V1b it would be only a "gain/Clean" pot)

The whole architecture of the amp would be compromised...the tone stack introduces a significant loss and V1B is there to restore the signal level before you hit the PI (at least in clean mode). If you have two stages back to back and you want your clean sound to be clean, you would want to set what you refer to as "gain/Clean" control low, otherwise you would get some overdrive. Then, you'd introduce the tone stack loss but without being able to jack the signal up again which could mean you wouldn't have enough volume out of your clean channel. An analogous argument can be made in regards to how you might never have enough overdrive from the gain channel if you want the clean tone to be clean.

Gil

[ChrisM]

Hi,

I was wandering what difference would be having the Eq between V1a and V1b versus having it after V1b (between V1a and V1b it would be only a "gain/Clean" pot)

Then you'd have a Marshall more or less (no CF).

The TS can drive the PI, look at Marshalls for example.

[Smitty]

I agree. You must really look at a Marshall, though. And when you do you will see that the tone stack is driven by a low impedance device. The direct coupled cathode follower. Because the DCCF is low impedance it can drive the tone stack more efficiently. You end up with more voltage on the other side of the tone stack...enough to drive a 12AX7 long tail phase inverter. Perhaps not enough to drive a 12AT7 and certainly not enough to drive a 12AU7 LTPI.

I don't think you'll see an undistorted 4 volts after a F/M tonestack driven by a common cathode gain stage. So you will likely have some difficulty driving the phase inverter in clean mode. I know you can drive another common cathode gain stage (V2A) into clipping, though. Just not as hard as a gain stage not loaded by a tone stack can.

The suggested architecture could work. It would, as Gil points out, likely sound very different than what builders on this forum are used to hearing.

[talbany]

I messed around with this years ago on an amp 2 gain stages (vol in between) TS off the top of the treble into the PI and worked OK..I think I used a kind of 2nd gen TS with that amp.. Pretty much a clean sounding amp until you lifted the stack or really cranked the input.. In a Dumble Style (Od added) I don't know how it would sound?..A TS before the OD imparts a different load (impedance) on the 1st OD stage (also the tone of your OD would change more drastically given that your clean TS is directly coupled to your OD input??)..Perhaps if you put your input (vol) control between the 1st and 2nd stage you might have better gain control and perhaps need to tweak the OD trigger

If you have 2 gain stages preceding the TS obviously there is enough signal to drive it and the PI or an added OD section the question is how would it sound and function and balance?..

The CF IMO won't buy you any increase in perceived gain just changes how the TS functions and is voiced which is generally brighter due to the impedance shift..Oh and also helps with the loading on the master (if it has one) and the PI as well,which is why master vol's (on Marshall's) seem to function better..IMO

Cool Marshall (2204)mod is if you break the Treble and PI connection and add in a passive loop you don't need a buffer to dive the effect and use the gain stage before the CF as a return amp..Built in loop..

Tony