Anyone have a schematic for a Peavey Valve King 2 Mini Head 20MH...

[Steve A.]

... before I call Peavey tomorrow? BTW does anyone have the phone # I should call?

I just picked up a used one for $175 at GC... a great little amp head that doesn't take up the entire back seat of my car for casual get-togethers, etc. (I have a Bugera V22H Infinium head for more serious endeavors... one of the best bargains for top-notch tube amps these days! The OD channel can get the sounds of a Zendrive for those Robben Ford affectionados out there...)

Steve A.

[Jazz P Bass]

Here you go Steve.

Valveking2_20mh.zip

Peavey Ph # is: (800) 752-7896

[The Dude]

Steve,

Let us know what you think of the Peavey. I'd be interested to know how it sounds.

[Kenco]

Valveking II pair

Steve,

Let us know what you think of the Peavey. I'd be interested to know how it sounds.

I love mine, the cleans are beautiful and the reverb is good, for a chip. The gain channel is a little too hot for my taste, jumping from just breaking up on the clean channel to almost metal on the gain channel at the lowest settings. I’m going to experiment with a 5751 in place of one of the 12AX7’s to see if that gives me more range. The gain channel has a boost switch which punches up the volume, perfect for leads and a gain switch that really gets it dirty. With the gain switch on and the mids scooped your in metal territory. I just want to be able o dial in some vintage rock tones.
Thx for the MH schematic. Does anyone have one for the Combo? I have one of each and I’m building a stereo rig.

[Enzo]

Call customer service at Peavey and ask for it.

[Steve A.]

More on the Peavey 20MH...

I tried swapping tubes for the OD channel (5751, 12AY7, even 12AU7 - still way too much gain!) and finally found one that worked perfectly but there's a long story: it came from a circa 1950's Barber Coleman HVAC temperature/zone control board up in the attic of a church I was working at. It had two Mullard 12AX7's so I rushed home to swap them out for two Sovtek pullouts. "Oh, boy, vintage Mullards!"

The church HVAC worked great with the new tubes but I was very underwhelmed by the Mullards which had hardly any gain at all. But they worked great in the Peavey 20MH. I guess if I could figure out the actual gain figure I could wire up a pair of split plate load resistors for the V2A 150k plate resistor. V2B already has split plate load resistors (100k & 10k) so that might be a better idea for V2A...

It's usually fairly easy to add split plate load resistors to a typical PCB: you remove the plate load and coupling cap and mount the two resistors, one leg in each pad and then connect the coupling cap to the junction of the two resistors. (You consider the B+ to be the AC signal ground and wire up the resistors accordingly, in the case here, the 100k resistor to the plate and the 10k to B+.)

Just wondering if anyone has tried replacing the 1N4148 clipping diodes in various amps with germanium...? I see that all of time in FX pedals but can they handle the higher voltages in a guitar amp?

Steve A.

[Zozobra]

If you mean D28 & D29, then they act as a ghetto noise gate and they're found in a few of peavey's high gainers.

[Enzo]

Agree^^^^

Those diodes are the opposite of clipping diodes. CLipping diodes are ACROSS the signal path, and clip off any peaks larger than the diode voltage. These diodes are in series with the signal, and they cut out the small section between zero volts and the diode voltage. COnsidering the large signal voltage at this stage, it is a small cut. It cores noise from the signal. That is why the relay shorts across them in the low gain channel.

Germaniums ought to work there, but I think all you would gain would be more noise.

[xtian]

Got one on the bench today with the complaint that the clean channel is bad. I find that the lead channel works fine, but the clean channel is dodgy; the gain jumps when you strum hard, and the tone is poor. I tried swapping a good 12AX7 and 12AY7 into V1 with no change.

I downloaded the schematic from just above, and am trying to guess how the lead channel, which also passes thru V1a, can sound good, while the clean channel does not. The Clean Volume pot sounds clean and smooth, so I don't think the pot is an issue. Suggest any avenues of attack?

[John G]

Hi,
You could remove C4 to lower gain of the drive ch.
Or reduce the value R106 by shunting an additional 1meg across it, or do both ??
You can always remove/reconnect if it doesn't work for you.
John

[xtian]

Thanks, John, but I'm dealing with a fault, not an issue of too much gain.

[John G]

Hi, My reply was to the posts above yours.
Yours could be dry joints in the clean signal path, also a bad relay contact S12 ??
The clean circuit could still be faulty, being masked by the huge amount gain when in distortion mode.
John

[Steve A.]

Hi,
You could remove C4 to lower gain of the drive ch.
Or reduce the value R106 by shunting an additional 1meg across it, or do both ??
You can always remove/reconnect if it doesn't work for you.
John

Thanks for the suggestions! I am looking for a massive reduction of gain but every little bit will help. As for R106 I guess I could go as low as 100k, right?, and removing C4 should reduce the bass in that channel which I also think is excessive.

Steve A.

[John G]

Steve,
Maybe a 1Meg trimmer soldered across R106, and adjust to taste.
I think this amp was designed for the HM or Shred player.
C4 will reduce all frequencies equally.
John

[John G]

Steve,
Had a look again at the schemo, and can also see a level reduction point can be had by shunting R14 in a similar manor to R106.
Additionally you could try reducing the feedback resistor R8 to say half its value to see if that helps.
The EQ may change due to the change in negative feedback ???
John