Ampeg master volume footswitch

[walkman]

Hi,

Has anyone a schematic of an Ampeg master volume footswitch. It is for the v4 v3 etc, and goes in the external speaker jack. Is it an attenuator ? if i wanted to make one what would i need .... ? could it be made easily switchable ?

would this work for say a twin reverb too, so that i could remove the inbuilt MV control.

cheers

[Rick Erickson]

It's just an attenuator - it uses a volume pot to turn down the preamp signal. It won't turn your Ampeg into a fire-breathing dragon. If it has a footswitch to remove it from the signal path then it can be used as a Rhythm/Lead volume boost. I would expect some high Freq. loss due to cable capacitance though. For every cure there is another problem lurking.

RE

[Rob Mercure]

Hey Rick,

Is this an aftermarket device of something that Ampeg distributed? The reason I ask is that I've got an original binder of Ampeg amplifier service manuals from the late 1970s with no description of these foot petals. Although the manuals are pretty complete there are some omissions - such as the several variants of V-4 bias supply - but generally complete. But if the foot petal was a factory item I want to at least include a hand drawn schematic, etc., in my binder.

Thanks

Rob

[methodofcontrol]

hey guys, i've owned a few of these things. here is a stock one inside and out:




it's a 25k audio pot. they're very sensitive. about 2/3 of the sweep is barely noticable, then if you go a hair beyond that the volume goes way too low. it does tame my V4 just a bit though. and it also makes it usable for bedroom levels. and like any master volume....you will find yourself turning the highs up the lower the volume goes. i have another of these pedals missing the bottom rubber and sheet metal mounting plate. i was going to make my own plate and drill it for a switch and the pot as a sort of "lead boost"/ "rhythm cut" sort of thing. as you can see it's as simple as "tip to wiper, ring to ground CCW".

[Rob Mercure]

MOC

Thanks - I'll diagram this out for my service manual. If you've got one of the units open would you provide the date code on the pot? I'm just curious of the manufacture year.

Thanks

Rob

[methodofcontrol]

sorry...i sold that pedal long ago. it's kind of rare, so i archived the pics just in case! if i zoom in on my original photo...it looks like the pot says "1377821".
i would guess "137" as in CTS, and "7821" as in "1978, 21st week". hope that helps.

[stokes]

Since it plugs into the ext spkr jack it looks like it is more of a presence control,since the only connection to the preamp thru this connection would be the feedback.

[tboy]

It is for the v4 v3 etc, and goes in the external speaker jack.

Since it plugs into the ext spkr jack...

I don't know how walkman got the idea that it plugs into the speaker jack; I believe it was meant to plug into the preamp-out jack.

[stokes]

If you look at the photo,it says on the sticker,"plug into extension amp jack only".I would guess they mean extension speaker jack,although the preamp out jack would seem to make more sense,if it is really a MV control.

[Rick Erickson]

If you look at the photo,it says on the sticker,"plug into extension amp jack only".I would guess they mean extension speaker jack

No - It goes in the Ext. Amplifier Jack. It shorts the tip to ground. If you plug this control into an Ext. speaker jack you will smoke the pot. Or do you smoke the pot first, then plug it in wrong - darn - I always forget this one...

RE

[stokes]

Okay,a look at the preamp schematic clears that up,was just going on what he said in the first post.So who was it that smoked the pot and tipped over on the ground?

[methodofcontrol]

there are two "ext. amp" jacks on all the V4's i've owned and seen. they are "pre-amp out" "power amp in" jacks. if for whatever reason you need to run more than one of these beasts to get your desired volume, you can slave them together through these jacks using the pre-amp of one amp to drive the power amp of however many slaves you decide to daisy chain. "ext. amp", NOT "ext. speaker".

[walkman]

Thanks for all the replies

.... into the ext amp - preamp out ... got that mixed up


and 25k Audio pot ....


suppose that could be change for another value / type for smoother

control?


How many amps / volts does the post need to be?


Ps. thats not 25k an ounce (sic)