Has anyone tried to replace the OD Trim pot with a 'volume pedalish' pot so you can adjust the OD amount on the fly via a foot pedal?

the range of OD tones is great, and looking to see if that would be a way to take advantage of this range in a live setup.

I was envisioning something like an Ernie Ball volume pedal where you can set the min/max values to give you quick acces to at least 2 settings.

thanks,
sean

Old, good idea.

There are two ways of doing this:
1. Add third relay and third footswitch to bypass a trim pot, so you will have 3rd  powerful lead channel with loads of gain.
2. Add a stereo jack to back plate and reconnect trimmer’s filaments to it. Connect with a stereo lead to the potentiometer in your pedal (one can use old, empty WAH pedal) so you can gradually increase gain.
Cheers

Hi, and yes, I'm ready to be ducking rocks thrown at my head, but here it goes...

No amp mod is absolutely necessary if you get the right volume pedal!

Am not a big fan of any volume pedal that has a pot in it, I hear too much roll off of treble and harmonic content at lower volumes.  So I have an active pedal steel volume pedal that works very well and provides a bit of clean boost.  Has range control for minimum volume setting, and it exhibits tonal consistency between minimum and maximum settings, no treble rolloff, it uses optical components rather than a pot.  Here's what I have: 

http://www.hiltonelectronics.com/lowprofilepedal.html

It is wonderful to use with my el34 loaded 50w HRM with the LNFB switch.  Has one mono input, two mono outputs.  Also has a trimmer to adjust treble, full up it actually brightens the guitar tone somewhat, so I set mine for a slight amount of roll off until the guitar sounds the same treble-wise running through the pedal as straight into the amp. 

I enjoy using all four modes from the footswitch.  I set the OD trim and gain in OD mode for that prototypic smooth Carlton-ish gain/tone at my pedal's personally set minimum, and it can go right on up to an awesome sounding Marshall-y roar when the pedal is depressed, continuously variable between the two extremes.  I get a huge variety of volume as well as gain/tones that way, and nice to have the ability to easily control dynamics, swells, etc.  I can have great control over harmonic feedback and sustain too.  May not be for  everyone, but I'm VERY happy with this setup when playing out.   

Mavguy,
can you explain a bit more the process/changes you made on the amp side to use this pedal and get the four modes?  did you go the route of replacing the OD Trim pot on the amp with a stereo jack and virtually move the pot to this pedal, etc?

the idea of going from the smooth carlton type OD to the roaring marshall is exactly what I'd like to do.  I know that it only takes a move from 8 o'clock to 11 o'clock on the OD trim iteself.
thanks,
sean

PVB has it right. 

NO mods to the amp at all.  I start with clean gain at 6 on the dial, get a bit of fur/harmonic feedback on the edges with pedal full down, clean at minimum.  Then I go to OD no boost, match OD channel master volume same or slightly louder than clean + PAB with what OD trim , OD gain I like (trim 10:00-ish or slightly less, goose the OD gain knob on front to noon-ish.) 

Clean, louder with PAB, then OD no PAB as dirtier alternative to clean+PAB same ballpark-ish overall volume, finally OD+ PAB for max volume and gain. 

Can't emphasize the importance enough of using a very high quality volume pedal, not some cheapie with a pot in it.  That user-preference range of adjustment thang is critical, as is no treble rolloff coming from the volume pedal at lower volumes, you'd lose harmonics otherwise.

Higher OD trim settings yield more compression, I try to avoid lots of compression, but if you wanted to do that, by goosing up the OD trim you get enough compression for that volume pedal to act like a gain control with not very much increase in volume in OD modes.   It's possible to set the pedal range up to go from clean to scream with a single channel amp, or however you want the 4 modes in an OTS type amp to behave.  All four modes sound good, so I use 'em.  Hope this helps.  It sure helps me when playing out!

Yep, there's only a slight amount of clean boost coming from that pedal, though. 

Looking for any feedback or thoughts on my plan.
Usable OD trim resistance levels seem to be between 100K and 200K ohm. That is measured directly across the OD trim pot from 7 o'clock to around 1 o'clock.

I plan to replace the OD trim pot with a stereo 1/4" jack, connect ground and filaments as they are connected to the pot today. Use a housing (box or old pedal) and have 2 separate 100K ohm pots, both linear taper. One pot will be on the side of the pedal, the other will be controlled by the pedal itself. Wire the 2 pots in series to show anything from 0 to 200K ohm total resistance.

I would leave the side mounted pot set to 100K, to set a total minimum value (toe down) and would have a total maximum resistive level of 200K (heel down). I could adjust the side mounted pot to 0 ohm if I ever want to go massive OD. This is my first thought on how to get the maximum flexibility with this approach.

Have I missed anything?  Thanks to all who have posted so far with ideas.
Thanks
Sean