Many users buy the Valveking and are not satisfied with the tone straight out of the box. These users (myself included) modify the amp so that a much better tone can be gained out of it. It really is quite extraordinary how much of an improvement can be made with a few simple mods. Here is an overview of the more technical Electronics mods. Please read the disclaimer below, we don't want any electrified guitarists on our hands :).

Please be sure to read the Warnings page before doing any mods to your amp.
"...Pulling the chassis and poking around inside the amp however is dangerous deadly dangerous...."


The standby switch does not turn off the voltage to the o/p valves anodes (plate) You can safely drain the capacitors by leaving the standby ON and turning OFF the power. The o/p valves will continue to draw current as the heaters cool down and drain the caps to a safe level.Remember to turn the standby switch OFF before you power up again to prevent cathode stripping the valves, Always remove the power connector before working on the internals. (recklessrog)

The capacitors inside the Valveking Chassis are NOT self-draining. Be sure to let them drain efficiently. Be careful!

One method I use (cap47) is to pull a power tube with amp unplugged. Use a meter to check the voltages of each pin to ground. If voltages are present use a test lead with alligator clips clipped to chassis on one end. In the remaining end clip a resistor by one end and wrap the resistor with insulating tape exposing the remaining end as a probe to probe the socket. Probe each hole for each pin for approximately ten seconds to drain the charges. Recheck with a meter before proceeding with your work. If charge remains then repeat and recheck until the voltage is very low or gone. Recheck voltage occasionally for safety. The use of the resistor eliminates sparking when the charge drains.

VK112 owners please read this first before modifying your amp.

Please note there are now two versions of the VK112 those made before Jan-June of 2011 (we can't place it exactly but it's in that range of dates somewhere) and those made after that that have now been dubbed Version 2's. We now have PDF schematics for both versions here on this page Warnings

The difference is in the circuit just after V2 gain stage 2 and before the lead channels tone stack where Resistor 173 is now changed to 100k and placed in series with a new Capacitor at C105 a 50volt 2.2nf Capacitor. Like this Signal from C100-->C105-->R173-->AGND1. C149 is changed from 50Volt 1nf to a 50Volt 820pf. C100-->C149-->AGND1
This supposedly brightens the amp slightly (needs verification) ala the clip out C149 mod in a version 1 amp.
This change may have ramifications to some of the amp modifications posted below. If your not sure by all means ask either here or at the VK thread at Ultimate Guitars "Guitar gear and Accessories" forum.ValveKing Thread MKII
The second change made...
The circuit board trace from the send/return loops return side to the power amp circuit board has been replaced with a plug and a shielded cable running from a plug near the return jack to the power amp board. This change was made to eliminate a slightly louder hum some users where experiencing in the VK112. The VK212 and VK100 already have this cable from the factory.

Of course Peavey does not officially acknowledge that there are now two versions of the VK112 amp. Lucky us ::eyeroll::
The only way to tell for 100% certain is ask peavey when your VK112 was made or drop out the chassis and check for a fat cable that goes from near the return jack from a plug to the power amp board. Or look at R173 to see if it is a 100k resistor. Version 1 boards will have a 3.9 megaohm resistor in this spot.

Anyone with information on whether or not the VK212 and VK100 have had the above factory circuit mod near the tone stack done to them please let us know.

I wondered why there had been a tail off of posts on the VK thread about the amps sounding dark and muddy.

R100 mod

The r100 mod is said to improve the gain boost control and make it less trebly, cutting and overall harsh when used.
(Credit stratoJim)
The r100 mod is easy with minimal soldering experience. Just get a resistor (any will do) and use the solder lead to go from lead to lead on resistor 100 (which is labeled) thereby bridging the resistor. The r100 mod made the gain boost feature usable and great for a classic rock tone with the gain less than noon.

(Credit ilya-v)
About the R100 mod:

Remove the resistor and slam a 1M pot there.
What do you think the Noise Gate on the Peavey JSX is? external image wink.gif

R171 clean boost mod

(Credit 65 SG, submitted to wiki by Sadistic Sponge)
This mod allows the gain function to work on the clean channel. The end result is a volume/treble boost for the clean channel that helps give it a bit extra punch. To do this mod simply locate R171 and cut it. That is all!

Original thread:

Sadistic_Sponge notes: I have the mesa mod engaged here, meaning R122 is removed, meaning that the gain boost is always engaged. This does NOT impact this mod's functioning as far as I know. It sounds great and adds a little functionality- I can imagine it being super useful and it's easy as all hell.

Anyone doing This Mod may be interested in also adding a BALANCE pot to equalise the bias to each O/P valve. Even matched sets can draw differrent amounts of current and as they age this can become quite pronounced. If anyone is Interested I will post details of how to do it. (recklessrog)

Bias Pot Mod

The bias pot mod allows the amp user to adjust the bias of the valves using a dial that is modded into the back of the amp. This allows the user to dial out some of the sterility in the tone and generally "warm up" the amp.
(Credit stratoJim)
The bias mod really warmed up the amp and took out a lot of the grittiness and increased responsiveness. It was very noticable in the clean channel but affected the whole tone.

Peavey VK112 Bias Mod (credit cap47)

By Charles Peck 06/06/2009
In this package I will discuss the steps I took to mod my VK112 so that it can be biased manually. Besides the parts that are shown you will need tools for the job. Below is a list.
1.Good quality soldering iron.
2.Cutting pliers (small)
3.17/64 drill bit
4.Countersink for deburring
7.Bias Rite or similar
8.Small diameter electrical solder (rosin core)
9.A shoe horn or paint can opener to remove knobs
10.Cut yourself some wood blocks to prop board on, long enough to reach across chassis and not too thick
11.Wrenches to remove jack and pot nuts and Standby Switch
12.Small Phillips screwdriver and medium size. Small flat blade.
This picture shows the parts for the bias pot mod. You need one each.
If the Weber bias pot is not availible try Mojotone 25KL or 50KL pot. Also 50K Trimmer Pot #
9010105. Just about any 25KL or 50KL would work, they are not locking though. 6/01/12 cap47
Also Weber WP253-slot-lock is a 25K bias pot.
To start, I inserted my bias probes and took readings on each tube before proceeding and recorded those readings. I also took readings across the 15k resistor touched at left
terminal and probed center terminal. I then preset the resistance for pot with 15k resistor to 33k. Same as the resistor you will be removing. Using alligator leads on the terminals and your multimeter leads so you can adjust setting.
Now you are ready to disassemble the amp. Make sure amp is unplugged leaving standby on..Drains Caps!

Remove all tubes, power and preamp.
Unplug speaker and reverb. The reverb has white plug at the chassis so you don't need to unplug at the tank. Just pull gently. Take out the two screws under back ledge. Remove the Peavey logo at front and the metal plate at front just under chassis. Now remove the 4 long bolts at the top of the amp and support the chassis. You then slide the chassis out and put on your work bench.
Now it is time to gently pry the knobs off each pot on the front of chassis using the shoe horn as shown.
Use appropriate wrench to remove nuts from Standby switch, pots and front jacks. Check standby switch with mm for voltage before proceeding. Always check voltages for safety. The capacitors are not accessible until board has been removed and flipped. VK is NOT self draining See Disclaimer above. I assume no responsibility if you undertake this mod. If you don't have the experience, don't do it. The reason the standby switch is removed is to give you room to flip the main board. You will find a plastic wire tie that holds the wires near the switches. Clip and remove it. Power switch stays in, do not remove.
Now you will find small black screws holding the board in. Approximately 7 or so. Remove them with the appropriate size Phillips screw driver. With the standby switch loose you can gently lift and slide the board out of front pot and jack mounts.
Locate resistor R205 on the board. This is the baby you will remove, mark it's position on the opposite side when board is gently flipped. With board turned slide the wood blocks under the board for support. Now you can check voltage at Capacitors. Shouldn't be any. Beware tho. If all is good voltage levels you can proceed to unsolder the 33k resistor at R205. Note this process can be followed for the 39k resistor for the VK212 and VK100 head. Only difference is preset the pot and resistor in series to 39k. Use a probe to pull it down on each pin until it comes out. Clean out the 2 holes. Take the new resistor and cut one lead about 1/4” on one end only. Insert that end thru far enough to get it soldered to the board at the left hole shown in picture. Before going too far tho you should test place the bias pot to determine where to drill the 17/64 hole for mounting to chassis. See picture.


The board is shown here where it mounts but is not yet screwed back in. Once you have ample clearance to get pot connections soldered drill and deburr the hole in chassis. Clean all chips out of the chassis and board areas using a small vacuum or blow it out good with a can of air. Don't want any chips shorting things so check good. Mount the bias pot as shown and gently tighten. Now insert the jumper into the other board hole and solder at the circuit side. Flip the board back to its final assembly spot and gently bend the resistor with small pliers until it meets the pot terminal shown. Put a shim under the terminal so the lead does not short to chassis and solder it to the terminal. Repeat with the jumper and solder. My jumper is actually two resistor leads soldered together. Be sure you made good solder joints, very important. Damage can be done if it is not a good connection. Notice which terminals were used. In this picture the far right is not used. By using the left one and the middle it gives you an increase in milliamps going clockwise.
If the other end terminal were used instead of the one shown the increase in milliamps would have been CCW. Check all your work and make sure it is clean. Put the screws in the board snug. Put the standby back in. Put the plastic nuts on all the jacks and only finger tight. The nuts will split if over tightened. Put the metal nuts on the pots and snug them, don't over tighten. Push the knobs back on and reassemble the amp in reverse of taking it apart.
Remember we preset the ohm rating of the pot with the 15k resistor. Now you have to use the Bias Rite or similar to set the bias. It is best to use an old set of tubes to start with. The pot should be close enough to get it fine tuned. Once you are confident every thing works right you can put in the good tubes and tune it in.

Now the good part. Play the damn thing!

Bias Test Jacks

Done by Jason43 on his 212-head conversion VK.
>Allows each individual power tube bias to be tested with ease.Test jacks:
external image VK007.jpg
For this, you need to install a 1 ohm, 1 watt resistor across pin 8 of each power tube and ground. There is a jumper on each socket that connects pin 8 to a ground trace on the pcb. Remove each jumper and replace with the resistor. Once you mount the test jacks in the chassis, run a wire from pin 8 of each power tube socket to each of the red test jacks. The black jack connects to ground. The jacks are sold through Weber speakers.

PLEASE NOTE!!! the resistors should really be 3 Watt wire wound. This is because if the valve should develop a short circuit and a 1watt metal film or carbon resistor is used, it will burn out and go open circuit leaving the test point at a possibly HIGH VOLTAGE!!! Apart from the obvious shock hazzard, it could damage your test meter if you have it set on a low range. Ideally the main power fuse should blow BEFORE the resistor!!!! (recklessrog)

Alternative Bias Pot & Test Jack Positions

Credit: Nik Player (sizzlingbadger) 5th Feb 2011

This allows the bias to be measured and adjusted via the rear panel of the amp.


Tips on bias

Credit GioBos

Measuring the voltage of the plate, on my ValveKing, the result was of 470V. It should be the same on other versions.
Suggest the formula for the bias, based on the plate voltage of the ValveKing:

mA = [(0.6 * 30) / 470] * 1000

0.7 = 70% of the power (suggested calculation from 50% to 70%)

30 = Maximum wattage dissipation of 6L6

470 = plate voltage

Recommended bias:

Cold bias: approximately 31ma (50% power at idle, suggested for metal tone, tube long life, high headroom)

Average bias: approximately 38ma (60% power at idle, suggested for all, tube normal life, mid headroom)

Warm Bias: approximately 45ma (70% power at idle, suggested for Warm tone, tube short life, low headroom)

These data based on a calculation of the correct bias of the 6l6 tubes on valveking.
I would recommend going by ear and taste, from 30 to 45.

Stock bias in my ValveKing was 21, just too cold!! and main reason for the stock crossover distortion.

Footswitch Delay Fix (C124 mod) (only applicable to older models)

The footswitch mod is designed to fix the slight delay when changing channels on the footswitch (this only happens on older models so users who have not experienced this problem need not carry this mod out). Below is a copy of the e-mail correspondence between a VK user and Peavey Technical Support:
(credit Mathamology)
Originally Posted by me!
Hi there,

I assume this is the correct address to send this message to! I own a Peavey Valveking 112 (serial number K0238806), I believe it is one of the older models. As I'm sure you are aware, there is a delay when switching between the two channels. After a bit of research, I found something that suggested the removal of the C124 capacitor in the curcuit would solve this issue. Could you please clarify if:

A. This is true
B. If it is true, do I need to replace the capacitor with anything?
C. I know it's not really associated with the power section, but does this capacitor have the potential to shock?

I hope to hear from you soon, and many thanks in advance,
Here is their response:
Originally Posted by Peavey
Hello Matt,

Thank you for your question.

Yes this does improve switching. The change is removal and will not need substituted.

You have to be very careful with all valve amps as they can store extremely high voltages even when the unit is not powered up.

Fixing the switch delay, as advised by Peavey
The removal of the C124 capacitor in the Valveking should improve switch response. The capacitor does not have to be replaced, so complete removal should do the job. A small pair of clippers will be suffucient to remove the capacitor.

(Credit ilya-v for finding, Peavey Forums for source)
Here's what I've done to reduce channel switching delay in my VK100 head.

First of all, you need to understand why there is a delay. If you have the schematic, notice Q101, this FET is used as a switch that temporarily mutes the audio signal while the relays switch channels. This was added in order to remove the short pop that is created when switching from clean to lead. Therefore, the temporary muting is necessary, but it doesn't have to be so long as it currently is. What I mean is that you can remove some muting, but shouldn't remove all of it.

So let's get to business; the way this circuit works is as follows. When either the front panel switch, or a footswitch, is used to change channels the voltage at R142 changes from ground to +14V. C131 only lets the change in voltage reach the Triac and pulls down the gate of Q101 very fast. This results in Q101 muting the audio signal for some time. The gate of Q101 will remain at ground until it is pulled back up to +14V by R138. The exact amount of time it takes for R138 to do this is dictated by 2 factors: The RC time constant formed by R138 & C130, and by the Vgsoff of Q101. If you look at the datasheet of Q101 (J174), you'll find that Vgsoff can be anywhere from 5V to 10V. So let's use the median value of 7.5V for simplicity's sake. This means that the muting will be complete and the audio will return when R138 has pulled the gate of Q101 up to roughly 7.5V, which is about 53% of the total voltage. If you understand time constants, you'll know that R138*C130 = time it takes to reach 63% of the total voltage. So take out your calculator and multiply 2.2M by 22n and you get 48.4ms (the actual time is a bit less due to 63% > 53%), this muting time is definately long enough for anyone to hear.

So how can you make this faster, well you can reduce the size of C130 or R138, but reducing C130 will affect both the turn ON and turn OFF times of the muting circuit, so I recommend reducing the value of R138. I've changed R138 to 1M in my VK100 and found that channel switching from clean to lead was much faster and not noticeable anymore. Of course, due to the huge range of Vgsoff in Q101 (5V to 10V), you might not get the same effect by using 1M in R138. So experiment with smaller values, 470k is probably the lowest you should go, but remember that if you make R138 too small, some channel popping might start showing up at the speaker since you're inhibiting the muting circuit.

(credit ilya-v)
"SAG Resistor" Mod w/bypass
No sound difference in low volumes, But when playing loud (Power tubes need more current)
The resistor acts like a Tube Rectifier.
Beautiful. external image smile.gif
external image sag.jpg

The resistor lowers the Plate Voltage by 25v (Bias un-changed) like a 5V4-GA.
Also lowers the bias from 40ma (460v, -45v) to 25ma (435v, -45v).
But when I rebias to 40ma the voltage drop is 50v like a 5R4GYB.
Oh well... Got me a Tube Rectifier Emulation Sag Switch. external image biggrin.gif

(credit ilya-v)
*Also made the Distortion channel tighter by changings the C103 from 2.2n to 1n.
made the bass roll off at 700hz (300hz old).

A/AB Pot removal

*Removed the A/AB class Pot. (Made the amp alot louder) no shit in the signal.
Here is what ilya-v said he did: Remove A/B pot and it's wires {leave ground wire per his edit)(clip/unsolder them) Change C144 to 47N (to be = toC135) or you can use the existing C144 in series with unsoldered C1 from the A/AB board. Caps in series behave like resistors in parallel. Ex. Cap47 in series with Cap47 is Cap23.5. Now solder a small jumper from pin 8 to the C144 leg near it. Edit by ilya-v:There is a ground wire in the 4 wires of the A/AB pot, leave it connected clip the 3 others.

*Modded the PI to this scheme :

*Removed the FX loop mod I did earlier.

*Added a Marshall Switch which leaves the Distortion channel with only
2 gain stages (instead of 4) and EQ. (like Marshall Plexi).

(credit ilya-v)
JCM800 mod
I've got to post it guys... My (old) JCM 800/Marshall mod.

What it does:
It bypasses one gain stage. The one with the diodes (which I removed anyway).
And leaves you with 3 gain stages & the EQ on the gain channel, (just like JCM800).
*VK has 4 gain stages on the distortion channel, thats why its too saturated & not
articulate enough.
The JCM 800 has 3 then EQ & Plexi has 2 then EQ.

Also I bypassed the C149, it was cutting the high end other amps have.
*(this is essential to the Marshall sound), (on the photo).
*Not shown on the photo, but was added later on the DPDT switch,
to return the VK to its original sound.

Sounds BEAUTIFUL !!!!!!!
I've got amazing CLEAN sound with gain till 5, Yes CLEAN sound.
Very Plexi like drive with gain on 10.
With the Gain boost On. its HEAVEN.
No boosting Pedals needed just articulate beautiful ROARING distortion.

Now I can actualy control the Amps drive with my guitar volume.

Here it is:
Click my Avatar for Sound Samples.
or here:
*Everything was recorded ONLY on the Lead Channel of the VK (on the JCM 800 mod).
*The first few riffs Gain on 3, 5, 7, 10 (no boost).
*One SM57 1 inch aways from grill, on the edge of the cap.
*I actually like the Cleans on the lead channel better now. external image smile.gif
*Played with the Neck & Bridge PU in no order (EMG 85 & 81).
(mind the playing, It was only for the demo).
external image JCM800.jpg

How does it work:
Use DPDT ON-ON Switch.
1. Take the signal from the C106 & R106 junction to one of the swithes legs.
2. Unsolder R107's left leg (on photo) solder it to the other leg.
3. The Center leg goes to where you unsoldered the R107 (left hole).

*if you want the C149 back:
Solder C149 to the VK side on the switch, & to the bottom leg of where it was.
Solder the Center to ground, upper leg of where it was (on the photo)

Thats it.
All it does is selects if 2 (JCM) or 3 (VK) stages going into the last stage then EQ.

The master volume is pointless now, as I can have anything from clean to Crunch to
Full on Metal just by playing with the Gain & Mod Switch.
I wanted to install the ppi master volume to make the clean channel cruch,
Don't need to anymore.

There is a new JCM mod from the Peavey Forums. Credit 65 SG!
Use this link
Added by cap47.
Read all for info and comment!

Testimonial by Sadistic_Sponge: I modded my VK112 with both the MESA mod (see below) and the JCM800 mod. The JCM channel feels a tad thicker with more balls to it but less gain, while the mesa mode is a bit tighter. Both sound MUCH better than the stock VK distortion and they have MUCH more definition and the fizziness of the distortion is now gone!

Testimonial by LivingExperiment: I modded my VK112 and ALSO my VK212 with ilya-v's JCM800 mod. Clean channel stayed the same and was completely unaffected which I really liked. When you complete this mod all your favorite EQ settings will have to change for the distortion channel. If you can live with that, do this mod. Both of my VK's sound amazing now, and I wish I had done this sooner. Everything at 12 o clock on the gain channel makes a nice Bush-Machinehead tone, but crank the distortion and tweak the EQ and you can now do metal. VK212 had to be cranked (just like any Marshall) to get the same tone that the VK112 has at lower volumes. I have also done the MESA mod. While both mods are, no joke, 10x times better than stock VK distortion, I prefer JCM800 to the MESA mod since my band Living Experiment does "danceable rock" cover band stuff and some metal. If we did primarily metal stuff I'd go with the MESA mod.
Added by LivingExperiment

Just a note:
I did 65SG's 'new' JCM mod to a tee, except the resistor across the switch contacts to even the volume between the two lead channel 'modes', as I didn't have a 750k resistor handy, and didn't want to run any in series (extra solder joints, potential for worse sound junk in signal, etc). Anywho, I put it all back together, tried it out, and for some reason my two modes (while they sound like they should, which is AWESOME now, thanks to 65SG's tutorial) don't have a difference in volume, just the difference in gain/tone. I am running a peavey valveking 212 (one of the newer revisions). PRS_Tim

(credit ilya-v)
MESA mod
It makes the gain channel million times better (exaggerating).
Mesa and Bogner like (Not exaggerating).

Remove R122 (no jumper needed).
Leave R124 in place (Don't touch it).
R116 to 10k (Wattage don't matter here).(10K has more gain, 22K has less... tightness of tone depends on EQ and setup)

The tone stack cap & resistor are crutial to Mesa sound;
C2 to 470pF
R4 to 47k

If it's too dark remove C149 (cut one leg of it).

The clean is unaffected.
You'll lose the low gain option (always high gain now, with less gain [10k]).
*But still can be very low or Very high gain.
The structure and articulation of the gain now is fenomenal .
The gain button now controlls C115 (470n) on/off, Soldano(off), Mesa/Bogner(on[tighter])
*If you liked the gain channel with a boost pedal, you'll "Die" from happiness on this mod. (it has plenty of gain now on the normal gain, and plenty & tighter gain on the

The Mesa mod removes the low gain mode completely.
And it lowers the high gain mode a bit and makes the sound much, much cleaner and defined but still with plenty of gain.

The gain switch now acts like a fat button.
What was the low gain (off) now has plenty of gain.
And what was with the gain boost on, now is a lot more
defined and clear.

(credit Stefan_L_01)
Just a note about the Mesa Mod: The higher the resistor value, the lower the gain. I tried once 39k and this almost disabled this stage, reducing it to the "normal" gain mode.
It´s logic, with a 100k or so you would have the cathodyan phase splitter with gain 1...

So if you want keep a noticable difference between the 3-stage gain and 4-stage gain, i´d use max. 10k. This already reduces gain a lot. You can compensate with a higher gain setting of the control, but again, the 2 gain channels get closer together.

If you need a low gain rock tone and a high gain mode ( cover band ), leave it the way it is, or increase it slowly and find the best setting for your style mix (2k, 4k, 10k, 20k).

Sadistic Sponge notes:
After doing both Mesa and JCM mods I had difficulty telling the two channels apart. Based on Stefan_L_01's observations changing R116 to 5k helps the issue immensely. I also changed R101 to 100k to make the mesa mode more distinct. Lastly, make sure that you use appropriate resistor values if you use 65SG's mesa mod. This varies depending on your tube setup, so you might need to trouble shoot. I have 470k and 220k and it works great.

I've also put a 20k pot in place of R116, which lets me take the channel lower gain than the JCM mode to ultra high saturation. Note, however, that you should put a 2k resistor attached to the pot or it will squeal like a stuck pig when you turn it all the way!

WARNING: You have to be very careful with all valve amps as they can store extremely high voltages, even when they are not powered up!
You have been warned!


VK 112 External Speaker Jack for internal/external speaker use:

As we already know, when using the "stock" ext. speaker jack it shuts off the internal speaker...bummer !!!

So I have added an external speaker jack of my own...

This is VERY easy and ...


You will need:
a mono 1/4" standard jack, a suitable jack plate, a 1-1.5' length of 16 ga. speaker wire,
a couple of female solder-less spade connects, a drill and 7/8" wood bore bit and screws to mount the jack plate...

Drill a hole in the bottom rear panel of your VK 112 with the 7/8" bit...

Attach the solder-less connects to one end of the speaker wire, makng note of plus and minus...
Then attach them to the corresponding terminals on the "stock" speaker...

Thread the speaker wire through the "guides" on the inside of the VK112 cab and
out through the hole in the lower panel that you drilled ...

Solder the the speaker wire to the jack, again making note of plus (tip) and minus (shield)...

Mount the jack to the plate...

Mount the plate assembly to the cab's lower panel...

Vacuum the inside of the cab to remove the sawdust...

That's it !!!
You can now plug in and run an external cab with the internal VK 112 speaker simultaneously !!!

WARNING!!! This wires the internal speaker and an external cab in parallel..

Be careful to ONLY use a 16 ohm external cab with this configuration !!!
Peavey recommends a MINIMUM 8 ohm load for the VK112...

external image file.php?id=5543

Enjoy !!!

May God Bless,


This link is a mod taken from a UTube mod and refined upon by cap47.

The link takes you to the original post detailing the mod.

Gain Stage #3 Enhancement

(by jdoorn01)
Through a malfunction, I got a lot of time in experimenting with my Valve King 212. Q103 somehow broke down and became fused, which seemed to affect the bias of gain stage #2.
While it was malfunctioning, the tone of the gain stage was great. When I fixed it, I felt it was lacking a bit. I found that GS3 was a great stage to fool around with to remedy this loss.

Here's what I've got:
Remove C149 (improves Gain Channel brightness)
Replace R101 (150k) with a 100k resistor, I went with 1/2 watt CF.

What this does is decrease the gain slightly of the third gain stage while increasing the proportion of even order harmonics (good distortion).
It softens the sound of the amp slightly. This gets it a little closer to JCM 800 territory. If you wanted to go the extra mile, it might be worth swapping the first two gain stages load resistors,
R103 and R104, with 100k resistors as well. I did not, as this would affect how glassy the clean channel is.

Note that if you have the JCM 800 mod from ilya-v, this won't affect anything in "JCM mode."

Sadistic Sponge notes: You can also get away with removing C117 to brighten the amp as well. I've actually removed both, though the sound might we a little too sharp for some people. In this case put a 470pF resistor in place of C149.

50/100W Switch (VK100/212 ONLY)


Here's an idea lifted from Mesa/Boogie Lonestars, very simple.

If you remove the Texture board, you can have something better, imo. Save the 100n cap (C1) and install it in series with the 100n cap (C144) on the power amp board. This closely matches
the other side of the splitter (C135 47nF). Alternatively you could replace the pair with a 50n cap. You must use this set of caps to bridge the gap left by removing the Texture circuit. Refer to the
VK100/212 schematic for details.

Once you've accomplished this, throw a DPDT switch in its place. Locate the cathode jumpers for either V7 & V6 OR V5 & V4, pin 8. Take a lead from the pin 8 side of the jumper from each of the
two tubes you've chosen and run each of those leads to their own contact on the switch. Take the ground side of the jumper, or just solder to that fat ground trace and bring that to the two common
contacts on your DPDT switch.

What this does is disconnect two of the power tubes, one from each side of the push/pull, and deactivates the cathode ground. This is how Mesa does it in the Lonestar 100W series.

*Be sure that you are deactivating one tube out of each pair that forms the push/pull. That would mean you would use V7 & V6 OR V5 &V4, not V7 & V5 or V4 & V6.

This allows you to do the same thing as in a Marshall, where you could pull either the inside or outside pairs of tubes to cut it from 100W to 50W. Since the VK uses series heaters, we can't just do that.
This gets around it and is slightly more convenient, IMO.

Buffer Mod (take out annoying treble)
(Credit Giordano Boschetti - giobos)
Please be sure to read the Warnings page before doing any mods to your amp.
This is a very simple mod.
Not everyone likes the effect of high-end buffer loop, including myself.
In fact, especially in higain, feels very annoying treble that make the sound often confused, and crossover distortion like.
Solution: Low pass filter!

Material: one or two .010uf 50v (103pf or 10nf) capacitor
Solder one leg of the capacitor to the right leg of r174, and the other leg of the capacitor to the right leg of r169 (the signal goes to ground here), DONE!
Sound unbuffered, buffered:
with a .010 uf capacitor on send, the sound is more oriented to the medium frequencies, the pot "treeble" now controls the mid / high frequencies,
cutting the crossover frequency,and giving cream. The difference in volume is slightly above the sound without the buffer.
with two .010 uf capacitors in series to the send (.005 uf), equalization and sound are very similar to the sound without a buffer, but more "open",
cutting a part of the crossoverfrequencies. The difference in volume is almost like the buffer stock.
I used a DPDT switch for this, positioned between the midrange and treble pot, one capacitor or two capacitors in series (bright), the result is two very different sounds.
it is also possible to solder a 5k pot to right leg of R173 with the capacitor .010uf that goes to right leg of r169, so as to allow an fine adjustment.
I use Tung-sol Reissue V1, China 12ax7B V2, Sovtek LPS V3

A/AB pot removal (pratical alternative)

(Credit Giordano Boschetti - giobos)

First, thanks to ilya-v & cap47 for the informations.

I found a convenient and fast way to do this.

- Unsolder pot texture, and c1

- Cut the central pin of the clip (the left pin is the resonance, the right pin is ground, the center pins are connected to the pot texture, ValveKing 112)

- Solder c1, between pin 8 and the left leg C144 (C144 & C1 connected in series, in effect a bypass of the pot)

The picture says it all much more simply.


If instead you want to change the capacitor, we must act as he said ilya-v, change R144, pin8 connected with a jumper at R144

Half-Power Mod (how to pull the outside tubes on VK212 and 100)

(Credit jmjlai)
One of the easiest tricks to reduce the power on a AB push-pull amp is to pull the two outside or inside power tubes. This can usually be done because the two left and two right tubes are in parallel. On the VK212&100, this cannot be done because the heater circuit is wired in series. Simply put, your amp won't work. Following is what I did to take out the outside power tubes without permanently altering/damaging your amp. I also sent my mod into a Peavey engineer who replied "Should be warranty, though."
This brings the full power to 50W and I would assume the class A power is 25W.
The key to this mod is that heaters have a running resistance when hot which must be matched to:
  1. not overload the transformer
  2. not over-heat the tube
  3. not under-heat the tube
A 6L6 tube is spec'd to run at 6.3V @ 900mA when running. Therefore the resistance per tube we are shooting for is 7 Ohms capable of dissipating at least 6W.
I used 3 22Ohm, 5W resistors in parallel per tube. I mounted these to perf board and wired the resistor banks to the heater plugs on the tube socket (DON'T MESS THAT UP!!!) Make sure you look at the pinout. As for tube pins, I found that 4-40 machine screws work great. I crimped the wires to spades and used locking washers to ensure a solid connection.
I also added a cpu heat sync to the resistor bank because the resistors were giving out enough heat to burn the perf board. I then screwd the perf board into the side of the amp and presto! I now have a 50W amp!
One thing you will have to remember. resistors are much more linear than heater filaments so your 2 power tube heater filaments will take 3-5 times longer to start glowing. make sure you leave your amp on about 5 minutes before you take it out of standby. have fun being able to turn your amp past 2!
When pulling 2 power tubes on a 4 tube amp the ohm setting of your speaker should be reduced by 1/2 (16 to 8, 8 to 4 ohm etc.). cap47

Killing Excess Hum

(Credit to 65 SG, Submitted by Sadistic_Sponge)

Some VKs have too much hum when idling, which is caused by grounding issues. This helps to eradicate this problem. I have linked the thread below- scroll down a bit, the solution you want has you using soldering wick to ground the potentiometers and inputs. Note that this thread also gives detailed information on how to test and drain the filter capacitors on the VK board without sticking things in your power tube pins (which is actually my preferred method).

Peavey VK112 Modifications Quick Guide

Texture Pot/R100 conversion

Remove wires 2 and 3 from the P303/313 jumper. Remove C1 and R3 from the output breakaway PCB. Fit a wire link in place of C1. Remove R100 and fit two lengths of insulated wire in its vacant holes. Fit the other end of these wires into the pins 2 and 3 position of P313. Remove C144 and replace it with a 47n 400v Polyester similar to the type fitted at position C135. Fit a jumper link between pin 8 of V3 and the terminal of the new C144 nearest to it. You now have controllable gain boost and removal of the noise inducing, power sapping Texture control.
Improve distortion character
Remove C149, remove C103, fit C149 into position C103 and leave C149 position empty. Remove R101 and replace with value 100k.
Decrease channel switching delay
Remove C124 and leave its position empty, remove R138 and replace with value 1M.