Peavey VTM 60/120 'Dual Channel' MOD

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Peavey VTM 60/120 'Dual Channel' MOD

Want to make your VTM 60/120 a 'two channel' amp?


I bought a Peavey VTM 60 and was fairly happy with the sound of it.

You can dial in the 'Pre' and 'Post' pots for a fairly clean sound or you can dial them in for a real 'dirty' or 'grungy' sound.

Problem is, you can't do both. Until now that is.

Peavey used 1 meg ohm pots for the 'Pre-gain' and the 'Post gain'. So I thought "Wouldn't it be nice to be able to switch between the 'clean' and 'dirty' sounds without resetting the pots?"
I just knew if I looked long and hard at the circuit there would be a simple fix, so this is what I'm doing to cure the problem.

I'm replacing both the 'pre' and 'post' pots with 'stacked' 1 meg ones and a relay to switch between the two 'channels' using a foot switch.

You will need two 1meg stacked mini pots. A 6 pole relay. A diode and cap and a 1/4 inch jack(for the foot switch). (power is drawn off the 6.3volt heater tap for the relay)

First, I'll need to replace the single pots with the stacked ones which I'm going to mount on the front panel and run wire to make the connections.
Next I will need to wire the pots to the exact locations as the old pots, but without the 'center tap' connection. Those will be wired to the relay.
The relay will be powered by the 6.3v heater winding using a 1 amp diode and cap to rectify the voltage to DC.
I'll wire the relay 'hot' and run the 'ground' side through the foot switch jack on the back of the amp. If you run without a foot switch, the relay will be grounded and the amp will always be on 'channel 1'.

Of course you will need to drill a new hole in the back of the amp for the jack, but there is plenty of room and besides, for the price of the amp this would just be an improvement.

What's nice about this set up is that you can 'dial-in' the clean sound you want with the first part of the pots (outer or inner) and the 'dirty' sound using the other half of the pots, and just switch back and forth using the foot switch.

Remember though, you are sharing the 'EQ' section between channel 1 and channel 2. To be really versatile, adding a second 'EQ' section would be better. But hey, the cost is cheap.

Here is what I have drawn up so far. I haven't included the hook ups for the relay power or foot switch yet, but this should be enough to get you started.
I also don't show the brightness cap 'C2 .001' because I removed it from my amp already. If you still want it, you will have to install one on each half of the Pre-gain 'stacked' pot by simply soldering them directly between the 'input' terminal and the 'center' one. No biggy. You could also wire a switch to cut it in and out of the circuit as well.



I should also add that there are other simple mods to this amp to make it even more versatile. One of the things Peavey did was make the 'mods' section simple to implement.

To 'boost' the gain all they did was 'ground' the circuit when the switch is in the up position. The same applies to the 'compression' switch. So... If you want gain and compression on for a solo, just wire another relay (and footswitch) to kick them in and out of the circuit. I have a 3 switch pedal I'm going to be using on mine. Actually, since the 'boost' and 'compression' circuits are just tied to a resistor, you could probably just add another jack without the relay. Just make sure the jack is 'non shorting' or the boost and compression will always be on.

Since I bought this amp a month ago, I haven't had it in it's case because I've been playing around so much with it. I might even rewire the power sockets for EL34's. I'll be able to switch back and forth between them and the 6L6's.

If anyone has anything to add or can point out anything I missed feel free to comment on it.

I don't claim to be an expert. These are just modifications I'm doing to my amp to improve it's usefulness.
__________________
I play guitar because it was too hard to learn the violin.

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I've updated the circuit to show the relay power and footswitch.

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I've updated the schematic to show an alternative connection for the relay.

There has been a problem with the relay 'latching' in the original circuit, so I added D2 across the relay windings and modified the connections to the heater voltage supply.

The foot switch jack should be isolated from the chassis unless you are using the alternate circuit.


(Note) J5 on the input side is from the 'low gain' input jack.

J5 on the voltage side is from the preamp board.

Pins 1 and 2 are the lower pins looking from the front (foil side)on the right side of the preamp board.

[claudeflame]

I am interested in performing this mod on my VTM, but I am having trouble in locating relays. Could you direct me to a location where you obtained yours? This would be very helpful as I am not sure if I am searching for the right subject. I attempted 6 pole relay but come up with very little to go on. Thanks

Nathaniel

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Originally Posted by claudeflame

I am interested in performing this mod on my VTM, but I am having trouble in locating relays. Could you direct me to a location where you obtained yours? This would be very helpful as I am not sure if I am searching for the right subject. I attempted 6 pole relay but come up with very little to go on. Thanks

Nathaniel

I got mine from an old Marshall amp chassis I had but they can be had at most electronics stores.

You can also use This one I found on eBay.

Even though it's a 5 volt relay, the coil is rated from 3-48 volts/DC so there shouldn't be a problem using it.