eBay

Hi and welcome to my listing for this "Marshall" mod kit for a V.3 (version 3) Epiphone Valve Junior 5W Class A Combo or Head amp (black circuit board and 14 digit serial numbers).

This mod kit is specifically for the V.3 Epiphone Valve Junior Combo or Head ONLY.

It is NOT suitable for V.1 or V.2 Epiphone Valve Juniors, nor the Harley Benton GA5. I supply other kits for these amps, (see my other listings).

The V.3 is improved over the V.2 and V.1 amps. It has corrected input impedance (1megohm), 12AX7 preamp tube biased to Fender spec, output transformer with a 5K2 primary winding, and 3 output jacks (4R, 8R and 16R loads) for both head AND combo amps.

As a result, it is much better sounding straight out of the box.

However, the B+ (HT) voltage is still way too high, resulting in a too high anode dissipation for the EL84 output valve. There's still no Standby Switch, nor HT fuse. And the circuit still needs tweaking in a number of areas to bring out the potential of these amps.

Mods available:

1. Drop HT voltage to a safer level so increasing valve/tube life.

2. Fit extra HT filtering to further reduce hum.

3. Fit HT fuseholder and fuse to protect mains transformer should a fault occur on the HT rail.

4. Re-bias pre-amp tube to give a Marshall "crunch" sound.

5. Change interstage resistive network to further clean up sound.

6. Fit Standby switch (increases valve/tube life).

7. Fit Pentode/Triode switch (Pentode = normal, Triode = low power)

8. Fit Line-out jack with built in ground lift

9. Fit Mallory 150M coupling capacitors to give a smoother sound.

Instructions and pictures are kept in a folder. The folder is stored on a download site (dropbox). You will receive a download link via email which will be sent to you at the same time as you receive confirmation from eBay that the kit has been shipped. I will use your PayPal registered email address unless you inform me of an alternative preferred email address.

Important! Dropbox has recently changed and now requires you to open an account with them before you can access the files.

You will need a pdf reader to access the instructions. You will need a picture viewer to view the pictures.

Your amp can feature some or all of my latest prototyped and fully tested mods Some of them in more detail:

HT voltage: the stock amp still has a much too high HT voltage. This results in the EL84 output valve being worked too hard. Designed working voltage (anode to cathode) is 250V. Maximum voltage is 300V. I measured 316V anode to cathode. My mod reduces this to around 300V. What's more, the absolute maximum anode (plate) dissipation for an EL84 is 12 watts. I measured and calculated 12.6 watts. Clearly too high. This can result in a burnt out valve, or shortened valve life at the very least. My mod reduces anode dissipation to around 11 watts. You can now use your NOS Mullard safe in the knowledge that you won't destroy it!
Standby Switch - absolutely essential in my opinion. All valve amps (especially those with silicon rectifiers) should have a standby switch. It allows the valves to become fully warmed up before applying the HT (high tension) (high voltage) to the valves. Eliminates cathode stripping and other damage. With proper use of the Standby Switch (wait at least 30 seconds before switching on, and switch to standby before switching off the mains power switch) your valves should last at least twice as long! NOTE: anode to chassis voltage surged to 389VDC on switch-on, before dropping back to 326V as the valve warmed up and started to conduct, yikes!
HT Fuse: let's take a look at the protection for the Valve Junior. The mains lead itself is protected by a 5amp fuse. The mains input to the amp (mains transformer primary winding) is protected by a T1AL 250V time delay (slo blo) fuse. The heater (filament) supply is protected by a T4AL 250V fuse. That leaves the HT winding (with no protection)! Imagine if the output valve is damaged by vibration and shorts out. Or, what if a power supply capacitor blows or shorts - voila! there goes your expensive mains transformer! For the sake of a few quid it ain't worth the risk!
Pentode/Triode Mode selector switch. A rather elegant way of reducing the output power from 5watts (pentode) to 2watts (triode). Triode mode also produces a mellower tone with a different distortion character.
Line-Out Jack with built-in ground lift. Rather than take the line-out signal from the pre-amp output, I decided to take the signal after the output transformer, thus giving it the true output valve distortion sound. Now there is no need to mic up at a gig, simply run a lead from the line-out jack to the mixer desk, or into a more powerful amp, with no more worries over microphone feedback.

Here's a few comments received from previous customers, (for my modded amps):

Nigel,

I have to say I'm very impressed with the amp - it's a really good match for my Jazzmaster. Whatever you're doing, you're doing it right! I never thought you could get those wonderful, open, valvey sounds at this kind of volume. It makes you wonder why Epiphone make them like this in the first place!

Best Regards,

Mark (refering to a basic modded V.2 combo)

Hi Nigel

I have been trying out the EVJ out against a £1000 + TopHat Club Royale - 20w boutique valve amp, and this was just with the EVJ at about ten to max, and a health warning to my neighbour...

I couldn't figure it out, they were so close at those volumes, but to cut hours down to minutes, the outcome was this: when I put the EVJ 8 ohm out into the TopHat speaker I got the best (subjective of course) result. Whereas the TopHat benefited over the EVJ with the 12" speaker, I actually preferred the clarity and openness of the EVJ, which was revealed even more with it being released from the "constraints" of the 8" speaker, playing through the TopHat's 12". Somehow with the EVJ the notes "meant more" with "more space around them".

So, to sum it up, the amp for me is your "H" modded EVJ into a 12" speaker cab - of course it was a fraction "edgier" than the TopHat, but definitely with more "life" - and a lot cheaper! Obviously the extra 15w is going to tell at volume, but for reasonable to loud; it's a pretty damn good outcome!

Class A all the way!

H (refering to a modded V.2 combo fitted with Hammond 125DSE for a deeper, cleaner Fender sound)

Hi Nigel
thanks very much for the amp. What a great sound!
At low volume with a tube screamer in front (with keely type mods) it sounds fantastic and doesn't annoy my wife (much!)Wound up it's lovely and dynamic with a really full and controlable sound.
The 8ohm output allows me to run it through an extention cab which is even better. What do you think about upgrading the speaker? A 10 inch doesn't look like it will fit.
Thanks again.
Mike (refering to a fully loaded V.2 combo)

Hi Nigel - finally today the parcel arrived and to cut the long story short - all I do since 5 pm is play guitar through Briggs Valve Jr and my various amps boxes etc ...

It sounds fabulous - BLUESY & SWEET - with volume between
10 am - 2pm but the speaker has it's limits above that.

I'm sure that even the brilliance and overall body will improve with fine new valves yet this is already fabulous by any standards.

When I plug it into Fender Deluxe Reverb - it is Paradise for sure, and if I add some reverb and tremelo it's like a drug for women in an old fashioned dancing hall :-)

The baby adores my Keeley moded Blues Drive for those screaming bluesy overdrives, yet I can play most of the stuff just by playing volume; I also like it with my tube compressor (if needed) and it loves also my very transparent ZenDrive : sounds like a $10'000 Dumble ...

In short, this baby is BETTER than my Cornford Harlequin, and with even finer valves and maybe new speaker will be as boutque as it gets, so I am definitely selling most of my amps and various pedals: THD Univalve, Gibson GA-15Rv, Fender Cyber Champ, Fame class A 6L6 hand made in Russia and most pedals ... all on sale :-)

Finally, as you knew anyway, after few hours of playing the amp sounds even better so the question is now:

When will I sleep :-)

In summary - great job - thanks - I can strongly recommend your work to anybody as the mdifications make this a boutique league amp for 1/10th of the price.

Cheers !

Davor :- )

(from Switzerland) (refering to a fully loaded V.1 combo fitted with Hammond 125CSE for a more VOX type saturated tone)

All my mods are thoroughly researched and developed and tested before making available.

Please be aware that any work that is undertaken without the manufacturer’s permission will invalidate their warranty.