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#1
I got my version three (V3) Valve Jr. head way back in late October. Since then I have been playing with it and modding it off and on. I originally wanted to voice it to be like a Fender. After building and finishing my Vibro Champ though I decided I want to give it more balls and gain. So I kept what I had done to the amp prior and started doing more Marshalley mods.

Even when I voiced it to be a Fender it never really worked. With no tone stack and that EL84 the VJ doesn’t stay clean for long. So yeah I did some Fender mods but then I decided I wanted it to sound a bit more Marshalley so now my VJ has a bit of both worlds in it. It has that clear sharp Fender tone but it also has a lot of gain and grit.

(All resistors 1/2W carbon film unless otherwise noted)
R1 – 1M
R2 – 22K
R4 – 100K carbon comp. Why I used carbon comp… http://www.geofex.com/Article_Folders/carbon_comp/carboncomp.htm
R5 – 220K resistor. Wires go to either side of resistor. Then they go to lugs 1 and 3 of an Alpha 500K pot. Run a wire from lug 2 to the side of R15 closer to the input. Now you got a master volume control. Haha very technical.

R6 – This resistor is my gain switch. I use a DPDT (On-On) switch to select between a 320K and 1.2M resistor. This gives me a gainey sound with balls and lots of boost. The other side is much cleaner and more compressed it seems. I call this my Fender/Marshall switch. I experimented a lot with the values these are the best imo.

R7 – 39K resistor with Alpha 100K parallel. This is an effective gain pot.
R8 – 1.2K
R9 – 1K
R10 – 1K 3W
R14 – 244ohms 1W
R15 - 6.9K I played with this a lot. It can really affect the Marshall/Fender voicing of the amp.

C1 – 0.0068mF Orange Drop. Makes the tone less harsh. Orange Drops keep things clear and sharp, I used them for the coupling caps (C1 + C2)
C2 – 0.022mF Orange Drop
C3 – 2.2mF (I used these vintage Australian caps here, I really like em) The stock cathode bypass caps (C3 + C4) are 22mF, 2.2mF tightens up the bass nicely.
C4 - 2.2mF (I used these vintage Australian caps here, I really like em)
C5 – 100mF 25V (vintage Sprague)
C6 – C9 – 47mF 450V. This stiffens up the filtering, reduces hum and makes the bass more solid.

I also replaced the stock volume pot which is a preamp volume with a new Alpha 1M pot. I added a tone “tweed” style tone control while at it using a 500pF Silver Mica and a 4700pf vintage mustard cap. I used an Alpha 1M pot.

I retubed, I don’t like Sovtek tubes (like most people). I used JJs, I have always liked them and they sound great. I hate EHX tubes…..microphonics bah

I also have drilled a pentode/triode switch so the amp has an output of 5W or 2.5W. After considering it for a while I decided it would be stupid to install the switch. The amp is 5W and I can crank it and it doesn’t hurt my ears and no one complains. I think I will use the switch to install a bright switch. Should clean thing up a bit more.

What I have now is a VJ that does not break up as quick as a Marshall voiced VJ. It has solid tight bass when clean or when dirty. This was an issue that took a while to fix and deal with. I always like tight bass and the VJ provides. With no tone-stack it is full of mids. And it also has nice sharp highs, the perfect frequency curve. I get a sharp clear tones when clean or dirty but yet I great a great distortion tone. The distortion is thick and full. It is also dead quiet with better quality components in the signal path and new great quality filter caps. It is very versatile with more controls. Anyways very fun amp with lots of fun controls to play with now. Not bad for a noisy amp that only had a volume control. Great tube amp that probably only cost $200 with all the mods. Just thought Id share my experiences.

Pics...
Controls (left to right) Fender Marshall switch, unused switch, Pre-amp volume, Master Volume, Tone and Gain


You can see how big the filter caps are here.


I didn't put a whole lot of effort into making the off-board pretty like I usually do.


This is a good comparison shot of the the stock vs modded filter caps.
Last edited by kurtlives91 at Mar 27, 2008,
#2
Can you post an mp3 of this?

After my guitar build, i'm thinking of delving a little into the fine art of amp modding.
I don't remember where I was,
When I realized life was a game.
The more seriously I took things,
The harder the rules became.
#4
Thanks, i've been looking at buying a VJ to mod for awhile now.

Any good reference sites you could link me to?
I've done electronics before, but I don't know how different amps are to Radios that I was doing.
I don't remember where I was,
When I realized life was a game.
The more seriously I took things,
The harder the rules became.
#6
Oh yeah, sorry I totally forgot about SYK's resource thread.
Thanks.
This amp should sound wonderful, can't wait until you post a mp3.
I don't remember where I was,
When I realized life was a game.
The more seriously I took things,
The harder the rules became.
#8
Ok SYK you said...

you probably can make the runs much shorter if you relocate R6 to the volume control.

What do you mean? Also where would the sheild of the sheilded wire go for the bright switch?
#9
I just looked at your layout. The bright switch is too far away from the volume control to get any benefit from moving R6. I would have thought the switch would be closer to the volume control. Scratch that idea.

Use 2 pieces of shielded cable to make the runs from R6 to the switches. Ground them both at one end only. At the PB would be a better choice, if you can find a good place to do that. R7 should be nearby. The ground side of that resistor would be an ideal place.
Meadows
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Last edited by SomeoneYouKnew at Mar 28, 2008,
#11
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#12
Today I was taking inventory of my parts for some projects I'm planning. I found a couple .022mF Orange Drops and put them in C1 and C2. Good recommendation! The difference is subtle, but definitely a little more smooth. I'll probably try some of your other values once I order more parts.
#14
I am constantly tinkering with my VJ and have a couple of additional questions on which I'd love to get input from you all. In your experience, what is the best way to ground the input? I'm using a shielded jack and see my options as stock grounding through the PCB, or (as I've read a few places) running a shielded wire directly to the other side of the board where the PCB ground exits the PCB. Any advice?

Also, would shielding the inside of my enclosure (not the stock one) with copper tape help eliminate some hum? I already have extra caps in the power filtering section. For a long time I was having very little hum, now it's quite pronounced. It increases with increasing amp volume but is independent of guitar volume.
Last edited by cedricsmods at Aug 7, 2008,
#16
R7 is a 1M resistor in series with the pre-volume.

Making R7 variable makes it act kinda as a gain control. Controls how much signal gets to the volume. I had to tweak it so the signal never got totally cut out. Its kinda neat, very interactive with the pre volume.
#17
Thanks for your mod info!

One question is your master volume pot across R5 a linear or audio taper 500M?
#19
hi, u're wiring ur MV 500k pot parallel with the stock 220k resistor at R5 am i rite? i'm doing juz like that and i don't really notice any darkness!
#20
I wired it as so...
R5 – 220K resistor. Wires go to either side of resistor. Then they go to lugs 1 and 3 of an Alpha 500K pot. Run a wire from lug 2 to the side of R15 closer to the input. Now you got a master volume control.

No darkness, never mentioned darkness.
#21
This is great build info...I just had a couple questions...

For R6, did you put the cap in parallel to the 1.2M only or parallel to R6?

Do you have a schematic avail for the tone control?

Are these all audio pots or any linear?

Thanks for the help!
#23
Those are awesome mods, Kurtlives, I think if I ever get a Valve Junior, I'm'a go with your mods. This is truly inspired.
Fact: Bears eat beats. Bears beats Battlestar Galactica.
#24
tag
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
#26
I think he's posting in the thread so that he can find it again.
Member of the official GB&C "Who to Listen to" list
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#27
Quote by wiliscool
I think he's posting in the thread so that he can find it again.

this!
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
#28
can i get a diagram of your r6?
sorry if this sounds noobish.
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
#30
Quote by kurtlives91

Thanks alot man, i'll ask if i have any more problems.
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
#31
another quick question what voltage for the caps that you didn't specify?
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
#33
Quote by kurtlives91
Which caps are you talking about? I used 500V caps throughout but you could use less in some areas.

I'm talking about
C1
C2
C3
C4
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
#35
Hey kurt I couldnt find any mf caps at mouser, where did you buy them from (hopefully some where that has the rest of the parts.) and also can you link me to what pots you used?
Btw what type of wires did you use?
can they be used for other amp builds?
Thanks kurt
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
Last edited by edge11 at Mar 15, 2009,
#37
Quote by edge11
Hey kurt I couldnt find any mf caps at mouser, where did you buy them from (hopefully some where that has the rest of the parts.) and also can you link me to what pots you used?
Btw what type of wires did you use?
can they be used for other amp builds?
Thanks kurt

mF and µF can be used interchangeably. You could also convert to nF and search using it.

Forget the type of wire. 22 AWG will be fine. Most amps use 18, 20 and 22.
#38
Hey can i get the mouser parts numbers for the pots?
Im having a bit of a hard time finding some from their large selection, pc mount, panel mount lugs no lugs ect ect. thanks bro.
hey i also couldnt find c1,c2 and c3 @ 500v in stock at mouser (i tried looking for poly cap) what cap material do you use? some part numbers for the caps would rule.
Thanks for your help kurt, you rule.
Quote by envoykrawkwar7


edge11
that was an epic win
best thing ive read all day

[feel free to sig this statement]

Gear:
Esp Ltd Ninja 600
Esp Ltd F-50
les paul elite
5watt jcm800 clone
Roland jc-55
Crate V33
Jca20H
Ibanez tubescreamer ts9
Keeley ds-1
Last edited by edge11 at Apr 12, 2009,
#40
I dont order from Mouser much so I dont know part numbers.

The caps can be polypropylene film or polyester film. There are lots of little stores that will get the parts to you quickly and are cheap. Hoffman Amplifiers, Small Bear Electronics, Antique Electronics Supply.
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