Epi Valve Jr Head Mods...so far, so good...

[oldguy]

After replacing the tubes in my V.Jr head in November, I kept getting the itch to do something else to it. So I ordered a Hammond 125DSE output transformer. The Hammond is larger than the stock OT, plus it's wired for 5K impedance, which is much closer to what the EL84 tube likes than the stock 7.5K transformer that comes with it. $32.00. I pulled the chassis out of the amp, wired in the Hammond, did a little wire tie cleanup, and put it back together. It helped the sound quite a bit. I think I'll change a few resistors out and see if it "opens up" the sound as much as the "mod squad" guys say.

[M29]

Hello oldguy,

Do you mind telling where you got he Hammond OT? I think I am going to go this way and maybe put a VJ in layaway for a while.

Oh also did you get any more speaker taps? 4/8/16?

Thanks oldguy

M29

[oldguy]

M29,
I bought the Hammond from STF electronics.com. Pat Bunn will answer your e-mails quick and professionally, and the service I got was great.
Speaker taps, no, you still end up with one each of 4,8, and 16 ohm.
You do have to solder the new leads to the speaker out PCB inside, and add two spade connectors for terminal T3 and T4 on the trace board, took me about an hour, but I'm always trying not to tear something up, so I work kinda slow.

[M29]

Thanks oldguy, I was not aware that the VJ had 4/8/ and 16 to begin with. That is good.

Take care
M29

[oldguy]

M29,
The 3 outputs for speaker are only on the head version. If you buy the combo you can add outputs, but it is a little more involved. That's why I got the head version. I've changed some resistors and lifted one leg on the C3 cap and the amp's really starting to open up and sing. I still need to balance the bias on the tubes, and reduce the heater voltages some, which are usually a bit hot as far I can tell. It seems the Valve Jr., while built on a budget from the factory, can be made into a good little screamer for around another $50 if one wants to do some mods and spend the time tweaking it. I'm still learning, but I'll keep you posted as I go if you're interested. HB's are still a little boomy, but single coils are sounding pretty nice at this point.
BTW, DuhVoodooMan's ZYS now makes this thing scream if you're into high gain or boost sounds.
IMHO, all pedals are sounding better w/ it now.

[M29]

Hello oldguy,

Yes please keep me up on this. I have been looking at building a Champ from scratch but considering a VJ instead so any info will be helpful. I know there is going to be additional money going into the VJ but a little at a time is not bad to have a nice tube screamer. I have two 16 ohm Tonkers in separate cabs which I would be able to use individually or both in parallel with these speaker taps which gives me some versatility.

Thanks again oldguy.

M29

[oldguy]

Check your PM's when you get a chance, M...
There's more to this little amp than meets the eye...

[duhvoodooman***]

Glenn, do you have some specific web links to some of the mod info you've been using? Some of what you mention are things I didn't come across when I was modding my VJr combo (v.1), mostly to get rid of the hum that the original configuration had. I'd be interested to see what else the mod community has come up with since, and if these mods can be done on the original combo version.

[F_BSurfer]

sounds nice one of these days I am going to mod my combo just have to take the time to do it already have all the parts for DVM's mods would be interested in learning more on the mods you are doing

[oldguy]

DVM,
The mods I'm using are a combination of those found on 18W.com and S2amps.com.
There are some very good suggestions on both websites. The 18W website even has spreadsheets to suggest what mods are recommended for different results. The S2 site explains what to do to "fix" the amps shortcomings as it comes from the factory, and what each stage does. Very interesting and FUN! Some resistor and cap swaps do alot for this amp, but personally, the first thing I would do is invest in a Hammond output transformer and some good tubes. The 125DSE tranny and good tubes should run around $50.
After that, one of the best mods I've found is to replace R1 w/ a 1M and R2 w/ a 10K resistor. Seems the stock amp is wired to shunt 50% of the input signal to ground, resulting in a drop in signal/noise ratio that is like a low input jack signal.
Also, changing R6/R7 to100K helps open the amps gain up.
You can also lift one leg of C3 to add some negative feedback, which helps balance the clean to crunch, and if you don't like it, just solder it back.
There are ways to quiet the heater noise if you haven't already done that, and you can also wire the amp for more speaker outs (combo version).
I am still trying to voice the amp to my guitars, and I'm getting closer w/ each mod. Another thing I'd suggest is to check heater voltages, as well as screen grid. The amp is biased a little warm from the factory. Adjusting R10 to 1K 3 Watt, and R14 to 240-270 1 Watt will help reduce the B+ voltage to around 300-310 volts at the EL 84 plate pin 7, and reduce the EL84's diispation, the stock is over the limit of 12 Watts. I'm still waiting on parts to do this, but I think reducing these to a "browner" sound will be one of the last links in the chain, running on the edge of A/ AB.
I've only done 1 or 2 mods at a time, and it's slow, but I don't want to do a dozen mods and not like the sound, and have to go back and trace what didn't work! So far, every mod has helped, IMHO. If you'd like a little screamer, (ala Marshall), I'd go for the "gold" mods on 18W.com. Zaphod Phil helped every step of the way, and he knows his stuff.
Be forewarned... if you want to read it all, it's over 300 pages of information... that's where I've been when I wasn't at work.
It was worth it.
This amp circuit is similar to a Champ and a Bad Cat Mini, with a few variations, and the PCB, which is perfect for a new modder like myself.
Check it out, and let me know what you think.

(BTW, your ZYS makes this thing scream now... )

[Tone2TheBone]

Man...I sure wish I had one of those ZYS pedals!



Glenn why don't you post a clip or two of your new mods using the infamous Yellow Zonkin'.

[oldguy]

Which guitar should I use, Tone? (Assuming I can find time?)

[Tone2TheBone]

Which guitar should I use, Tone? (Assuming I can find time?)

Your Tele...on the neck pup. Zonkin' set for nice OD. If you please.

[oldguy]

Your Tele...on the neck pup. Zonkin' set for nice OD. If you please.

Surprise, surprise!
The voicing on the VJ is still a bit dark, is it cheating if I dial up the treble a bit to compensate for that? Or would a bridge HB'er on another axe suffice?

[Tone2TheBone]

Surprise, surprise!
The voicing on the VJ is still a bit dark, is it cheating if I dial up the treble a bit to compensate for that? Or would a bridge HB'er on another axe suffice?

No no...turn up the tone knob on the pedal for more treble. I live on single coil neck pups! I wanna hear the new mods in this manner with the ZYS....if you don't mind.

[oldguy]

Well, this isn't exactly what Tone asked for, but here's a clip of the mods so far, first the amp dry, then w/ the ZYS, then with a bit of delay and the ZYS, then clean w/ delay at the very end.
Tone the Tele has a weird "tink" sound on the high E for some reason, and it's driving me nuts to play, so I'll get a clip w/ it for you when I get it sorted out. This clip is the bridge HB on the Switch (EMG select).
The amp volume was at 10:00, and it's loud. With the amp at 2:00 and the Zonker it starts to scream. It's still voiced a bit dark for my taste, but I'll see whether I want to keep tinkering w/ it or just stick an EQ pedal in front of it.
It's more touch responsive now than ever, which is good if you play really clean. I'm getting finger and string noise, and can see I need to practice playing much cleaner. I also notice the resonance and chime of the strings has improved, full chords ring much nicer than before. It also sustains great, listen to the very end of the clip where I let the chord ring.
Lots of fun doing it, and worth the $50, to me at least.

http://www.box.net/shared/4lqravgoxh

[Justaguyin_nc]

After replacing the tubes in my V.Jr head in November, I kept getting the itch to do something else to it. So I ordered a Hammond 125DSE output transformer. The Hammond is larger than the stock OT, plus it's wired for 5K impedance, which is much closer to what the EL84 tube likes than the stock 7.5K transformer that comes with it. $32.00. I pulled the chassis out of the amp, wired in the Hammond, did a little wire tie cleanup, and put it back together. It helped the sound quite a bit. I think I'll change a few resistors out and see if it "opens up" the sound as much as the "mod squad" guys say.

The Price on the Hammonds are going up.. cheapest I can find and get is about 37.99 - 49.99 shipped... ANGELA INSTRUMENTS on ebay... just a heads up.. I assume now this would make this amp rated at 10 watts or is more needed to achive the 10 watt rating? now to get the other parts...

http://search.ebay.com/search/search...&fsop=1&fsoo=1

[F_BSurfer]

For a lower cost output transformer you can try this one I used it in my combo

http://www.musicalpowersupplies.com/2.html