Presence mod

Have any of ya'll tried putting a presence control mod on a 2275-65 with PI? I would like to be able to have it go from no negative feedback to some value of negative feedback that would be well suited for this model. It can't be that friggin' complicated. I have seen a few for Fender BF that did not take much. It could be one or both channels.
What is the deal with jumping channels with a shorty chord. Is the phase correct for this.

I don't know about a Presence mod, but the channel-link technique is very cool on two channel MM amps.
The second input jack is different in that it is coupled to the circuit using a larger resistor. This is done for a couple of reasons.
The #2 jack can be used by itself for high-output "active" guitars or "hot" pedals. It can also be used as a "channel coupler". If you plug your instrument into Jack #1 you can use the #2 jack of the same channel as a link to Jack #1 on the OTHER channel.
This puts both channels of your amp in parallel and offers a variety of intersting tonal capabilities not possible with a single channel alone.
Putting both channels in parallel is essentially the same method that people used for wiring multiple older Marshall amps together on-stage for that "wall-of-sound".
The interesting thing about using both channels of a two-channel amp rather than two completely different amps is that the signals mix and cancel electronically inside the amp which cause all sorts of interesting tonal possibilities that are completely controllable and independent of room acoustics!
Using the amp this way is like having your tone control section on steroids! Try it, you'll like it! ALL of the controls make a difference and are interactive... a real tone candy-factory!
Steve

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I once tested with a sort of presence control. I put a 250k potentiometer in series with R47. I also tried with a switch that lifted the connection completely. The sound becomes a little "flabby" (hard to describe). A matter of taste.
Greetings from Sweden.

A presence control can be added. I just finished a 2100-65 12ax7 phase inverted Bass head. I modded it for guitar, I did not put a pot for the presence though, I tried it and it works well, but the owner wanted it preset at an overall good setting so I hardwired it to work, and it is right where he wanted it, just a tad more presence than stock. A 100k linear pot would work pretty good, since at the lowest setting would be pretty much bypassed. Basically the first 1/2 of the 12ax7 driver stage, there is a 1.5k cathode resistor, you add a electrlytic cap, about 1uf and put the pot between it and ground. Works like a champ!