Epiphone-M. Magnetics mod?

[rfgordon]

There seems to be lots of buzz over the Mercury Magnetics mod of the little Ephipone 5 watt amp. Does anyone know what the rest of the circuit mods are? Seems to me you could take that knowledge and make your own 5 watt screamer.

[Noel Grassy]

I did see 3 or 4 sites dedicated to this but that was last month. I remeber that a big issue was with the gounding and heater noise. Heaters are DC & one would assume that'd make them less susceptable to noise issues but in their case this isn't true. I'll check my bookmarks and see if I saved the links to the sites. I recently lost all use of IE when I tried to upgrade to versh 7. *%#@* Micro$oft!

[smokin' tone]

The big daddy thread is over at http://www.18watt.com. I would not waist the money on the MM upgrade.

[sliberty]

From what I hear, the VJ can be improved significantly by replacing the OT with almost anything. Apparently the OT they used is really crappy. So instead of spending $400 on the MM kit, you could spend under $100 on a really nice OT from several sources, and get much of the benefit. The PT is probably not as important to change, and the choke can be replaced with an inexpensive Hammond if you feel it will be worth it.

And if you are building from scratch, maybe the thing to do is buy a decent champ kit and tweak it for an EL84 (or not).

[rfgordon]

I agree on the $$ for the MM not necessarily being worth it. Don't get me wrong--their iron is really nice, but the prices are steep. For a wee tiny 5 watt SE I agree there are other good sources. A PT's job is only to provide a stable set of voltages. A choke is just an inductor--if the values are correct and it can handle the current, use whatever works. The real personality is in the OT. I've tried 4 OTs in my main prototype, and they all sound "good" but they all sound different, some of them very much so.

I found an enlarged photo of the MM kit, and it looks like there are only a few components to change, aside from the rebuild of the PS. I suppose any good champ or GA-5 circuit could be tweaked for tone.

Just for hoots, check out this Valve Junior that's on eBay.

[unklmickey]

...I remeber that a big issue was with the gounding and heater noise. Heaters are DC & one would assume that'd make them less susceptable to noise issues but in their case this isn't true....

the early combos were not DC heaters.

the heads and (to the best of my knowledge) the later combos are.

the early combos had a totally crap printed board layout, that had heater traces running right along side signal traces in the preamp section.


some folks were successful in re-routing the heaters via twisted wires instead.

and referencing the ct of the filament transformer to a positive voltage instead of ground.

all this, without using a DC supply for the heating current.

http://users.telenet.be/svokke/valve%20 ... 20mods.htm

even with all the warts, these amps were an incredible value, when you consider the price.....$100 for the head only, $140 for the combo.