Peavey VT 120

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Peavey VT 120

Postby coman61 » Tue May 13, 2008 11:31 am

I don't know much about this amp but a friend of mine has one and asked if there is a way to tame it down so it doesn't break up so fast... this is comming for a guitar player :o
Anyway I understand its a hybreed. He has tried messing with all the gains and what nots with no luck. I told him if wanted clean tone buy a fender. Yellow_Light_Colorz_PDT_01
O.K. time for my question. How can I keep the tubes from saturation at lower levels. Should I play with B+ voltages or bias currents or both. Would it be better to do this on the 12ax7s or at the 6L6's. Anyone know anything about this amp. Yellow_Light_Colorz_PDT_20
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Postby dhuebert » Tue May 13, 2008 12:54 pm

I need the schematic. It is possible to sub a 12AT7 for AX7. Does the gain stage have cathode bypass caps? Try removing these caps. A resistor divider can reduce interstage signal levels. Lots you can do but without a schematic it's all guesswork.

It's extremely unlikely to be the output stage if it is breaking up early.

Don
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Postby Newbietube » Tue May 13, 2008 1:21 pm

Hi, I could be wrong but you may find that the "VT" prefix means valve transistor. I have such an amp waiting for service called the Peavey Deuce which has transistor preamps and valve (4x6L6's) output stage. I believe these were popular with country and pedal steel players. It should sound loud and clean. If you go to the peavey website you should find the original manual in the archive section.
Hope this is of some help.
Cheers Just
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Postby coman61 » Tue May 13, 2008 9:30 pm

I made a mistake in the model number, Its a VTM 120. It does have a tube front end. I found a site that has some mods that I might try. I'm still searching for the schematic.
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Postby Gingertube » Fri May 16, 2008 12:40 am

Schematic is here:
http://www.schematicheaven.com/newamps/ ... tm_120.pdf

These amps have a high gain input and a low gain input. The high gain input puts an extra gain stage in the sound path.
He should be using the Low Gain Input, is he? The inputs should be clearly marked but the low gain input is the right hand one.

An owners manual can be downloaded from Peavy web site. click the support tab and then the manuals line. Change the "dot" in a circle to search archived manuals rather than current manuals or it won't find it.

If he doesn't have the manual I strongly suggest that he down load it. The amp has a set of 8 DIP Switches called "Response Modification". The switch labelled Gain #1 adds in an extra gain stage to give breakup at lower volumes, the switch labelled Gain #2 sets that extra gain stage to run at its limit for modern preamp overdrive "Metal" sounds. If either of those DIP Switches are On then he will struggle to get any clean sound. For "Classic British" sound and Gain ALL 8 of those switches should be OFF.
BEST to get the Owners Manual so you know what those switches do.
Cheers,
Ian
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Postby coman61 » Fri May 16, 2008 2:14 pm

Thanks for the schematic gingertube. I do think he does have the manual but if not we will download it. One of the big problems is that this amp sat in a dirty garage for a good while, it was broke and we repaired a broken wire on one of the ribbon cables. That was good enough to get it working. The dip switchs might still be very dirty, we might have to replace those.
Here is the mod from the other form. Do you think it will work?
http://music-electronics-forum.com/show ... php?t=2495
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Postby Gingertube » Sun May 18, 2008 5:38 pm

I couldn't see his prposed schematics but the description of what he intended to do makes sense.

Tip - always get you're amp up to 100% before embarking on any mods - you may change your mind about the necessity for the mods.

Cheers,
Ian
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