Adding a mid control to a old Fender amp without drilling any additional holes.

[Slobrain]

Hey ampagers,

I wanted to ask if anyone has a mod to add a mid control to a fender amp like a pull pot that can be used for the bass control in normal position, then pull the knob out and it becomes a mid control?

Sort of a stacked pot that has a 250k pot for the bass and a stacked 10k pot on the back of the 250k pot? Has anyone ever seen something like that other than on old car stereos?

my only other option is to add a tweakable mid control pot behind the low input jack that can be adjusted by a tweakable plastic screwdriver thru the low input jack. No one sees the pot but adjust the mid to your taste.

Just an idea

Thanks

[Tage]

I have yet to see a concentric pot with different values, short of making one by swapping tracks, much less a pot that switches between them. You could figure a couple spots were you like your mids focused and use a push pull pot to select between those two settings. I like the idea of the conceled pot in the low jack and think that would be a classy solution.

[olddawg]

Why can't you just use a floor pedal equalizer? It will work better and not butcher your amp.

[jmaf]

I needed a stacked pot with two different values for a similar purpose and wasn't able to find one.

I thought of modding a double Alpha pot, taking out the original track from the back one and adding in one with the value I wanted off a normal Alpha pot. But I had to stop that project and never got to try it.

[Slobrain]

Thanks for the replies guys,

I think I'm going to make a metal bracket that will bolt behind the low input jack and then extend out to the front and maybe use and old pot that was a 15k pot that was used to adjust the bios in a old fender amp. Then I'll need to make a plastic screwdriver that can insert into the low input jack and adjust from there. or a plastic shaft with a screw tip and a small knob onthe other end? even better....

Leo's designs were great but adding that mid pot sure would have been better... No wonder guys like the twin reverb.

I wonder how hard it would be to get a manufacturer to build a concentric pot for this purpose? I wonder if it would sell??? especialy in this economy? I even wonder would very many people want to have a pull out bass pot to do this? seems the guys that like vintage gear would have a heart attack...

I wonder....hhhmmmmmmm

[olddawg]

Most people would and do just use an EQ pedal or a boost pedal with a 3 band EQ like a Bad Monkey. It is usually not advisable or necessary to modify vintage amps for something like this. Just IMHO of course, but think about it or at least try it before you start chopping on a nice old amp.

[Enzo]

Do you use both input jacks on the channel? The old trick was to remove one of the input jacks and mount a new control in the vacant hole. Wire up the remaining jack as needed. A small knob on the new control won;t interfere with the other jack. No new holes, no really convoluted mechanical setup, and whenever you want to pass along the amp, just remove this mod and mount the old jack back where it was. AMp won;t know it ever was different.

[Slobrain]

Hey Enzo,

Thats a good idea. I might go that route. I was just trying to see what all folks have done in different ways and ideas to get the mid pot added. I also have an old Bandmaster Reverb that I only use the 2nd channel due to it has the mid pot added already from the factory.

This bandmaster head I have now actually sounds darn good. Its got alot of mids that sort of gives it a Marshall vibe.

[Bruce / Mission Amps]

Drop the extra input jack.
That is basically what I do to a Champ chassis.... use just one input jack with a 1M grid load resistor and use the other jack hole to install a 1M audio pot with a small diameter knob. Put tone caps on the pot (as a tone control). No reason you couldn't remove the grounded 6k8 resistor off the bass pot, use a 10K-25K pot in that part of the circuit and have yourself a mid control plus a little boost if you use a +25K pot.

[Slobrain]

Hey Bruce,

Thanks for that info, glad to see you here. I hope all is well for you.

Man, since I've been back posting lately I notice that the Electronics forum just doesn't get the folks here like back in the old days at Ampage.

Sure would be nice if T-boy went back to the old Ampage forum format....

I sure miss the old Ampage.... I can remember when Amapage had the live chat going and bunches of folks would be on posting about all kinds of amps, mods and other cool amp stuff. What happened???

[Gtr_tech]

Concentric pots with differing values for each element used to be very common. I have several, and they're still out there.

4K/25K Dual Pot-The Electronic Goldmine

Of course you can always "roll yer own" if you use a std CTS type and swap the carbon elements.

[JoeM]

Are you just trying to add more midrange? If you dont use the bright switch, you can use the switch to add some additional resistance to the stock 6.8k mid resistor. (Added in series)

[Slobrain]

Hey fellas,

That dual concentric pot looks like what I need. yes, I have swapped out carbon strips on the CTS many time to get what I needed and using the CTS works well. Actually I was thinking about a pull on/off switch/pot to replace the bass pot and putting 2- 6.8k resistors in parallel with the on/off switch to have stock 6.8k then pull the switch to parallel the 2 resitors to 3.4k for a scooped mid sound. right now I have a 2.7k on the bass pot on the tremolo channel to drop the mids back alot. I figure one channel stock, the other channel mid scoop modded a bit for some different sounds. Fenders are so darn easy to mod, I'm just trying to make them look stock while adding in those cool mods. I still like the idea of a dual concentric pot in the bass position that when you pull it, then you can adjust the mids too. no one would ever know you could do that except the owner of the amp.

Cheers

[jrfrond]

In the old days, there were "mod pots" and you could stack whatever you wanted. If I recall correctly, they were by Centralab.

You could take a 250KA dual concentric meant for guitar use and use a parallel 11K resistor across the hot lugs to achieve the proper value (in this case, it's about 10.5K).The taper may not be exactly what you want, but that just determines the set point of the control, which, because you will need to use unlabeled guitar knobs that fit the pot, you will be doing it by ear anyway.

[deci belle]

Since I don't use the Vibrato effect in my bf amp, I have the mid-range pot where the Vibrato jack was.