Anyone Wrecked a Vibrochamp?

[bcmatt]

Hi,
I have a BF Vibrochamp clone, and will likely try building an express or liverpool some day, but for now, I am wondering about using my vibrochamp's stuff to change it into something a bit more TW-ish.
Has anyone had any thoughts on this before? These are my questions:

Is there some sort of simple changeover I could do, using the output stage that already exists (6V6 and 5Y3), and using the 2 12ax7's that are in the preamp? (it has a second because of the tremolo circuit)

If I needed to add another 12ax7, does that pose any voltage type problems aside from the simple work of drilling another hole for a 3rd tube socket?

Is there someone who has already done this, that has good pictures or explanation of all they did?

[muchxs]

I built a killer Vibro back in the '80s, it was a Boogie (ish) thing with 2x6L6 and a solid state rectifer. Fuchsaudio stuffed a Dumble conversion in one back when Andy still did conversions. If you hike over to the Dumble pages you'll see it's a popular amp to butcher.

A couple tips... go easy on the stock power transformer, it's pretty weak. Switching to a solid state rectifier takes a little load off and frees up a socket. You can easily build a Derailment type thing in that package, the only oddity is that the stock control panel is labeled volume bass treble speed intensity, your speed (change the pot of course) becomes a midrange control with intensity left over as a blank hole, a master volume if you're not a traditionalist or a presence control if you figured out what to use that extra octal socket for.

If you swap the stock iron for upgraded iron like Dave Allen's oversized Champ transformer and a Hammond 125CSE your possibilities are wide open.

A Trainwreck combo will give you trouble. Fuchsaudio knows how to make it work correctly. Andy Da Man!! If you really must have a speaker in there upgrade to an Eminence Legend 105 and cut the baffle to make it fit.

Steve Liberty (sliberty, Freedom Amps) builds some killer single ended 'Wrecks.

Look at the Derailment. It's not exactly what you want but it's in the same ballpark.

[mlp-mx6]

Dave at allenamps.com has an upgrade PT for the VC. Here is the text from his page.

Upgrade Power Transformer for BF/SF Champ™, VibroChamp™, Bronco™, and Princeton™. 310V-0-310V @ 150ma, 6.3V at 4.5A, 5V at 2A. 50V bias tap, center-tapped heater winding and internal hum shield brought out to a lead for grounding. 2" by 2-1/2" mounting centers, 5.1lbs. Unit is approximately 1" taller than a stock transformer. Now supports the use of both 6L6 and EL34 power tubes (with proper socket wiring). Cool running M-6 lamination steel.

Probably a good idea if you're completely rebuilding.

[bcmatt]

I should probably point out that my Vibrochamp is actually a Ceriatone kit that I had built, and it is in a pretty big combo cab with a Celestion G12H. (It is still a head cab style amp chassis though). I can switch for other 12" speakers that I have as well, or just use the head with a different speaker cab, so I'm not too worried about that part of it. I'm not sure exactly how tough the Ceriatone Transformers are compared to the originals, but will that have an affect on what I can do?
My main guidelines for actually doing this would be if I can do something sing the transformers and chassis that I already have. It has no faceplate right now, so I don't care about switching pots, controls and jacks to be different things.
ButYa, I'll se what I can find as far as Steve Liberty's Single ended designs.

[Richie]

there is a marshallized champ type thing called the BEAST.. you can find the info and sound clips on SEWATT and 18watt.com.. i think Mark Huss has some clips somewhere too.

http://www.sewatt.com/node/13360

[bcmatt]

there is a marshallized champ type thing called the BEAST.. you can find the info and sound clips on SEWATT and 18watt.com.. i think Mark Huss has some clips somewhere too.

http://www.sewatt.com/node/13360

Thanks for the link. I will look around a bit more on SEWATT. The Beast is interesting but, but I think I want more of the trainwreck style of distortion; something with a few gain stages (not as much of the "all at once" distortion). I do have a couple of 12ax7s I can use in my layout (I'm thinking of ditching the tremelo circuit for an added gain stage, and I think I'd like to keep the rectifier tube and the current output stage.
Do you guys think I am asking too much? Or is it actually simpler than I am making it out to be? It's never simple, is it?

[bcmatt]

Steve Liberty (sliberty, Freedom Amps) builds some killer single ended 'Wrecks.

Look at the Derailment. It's not exactly what you want but it's in the same ballpark.

Yes, I think the Derailment is close to what I am looking for.

[Richie]

You might ask Allyn also, he has done a SE wreck.. i think he posted some pics somewhere..

[bcmatt]

So, this is what I have come up with so far for the layout:
It is basically just me trying to replace the vibrochamp preamp with the Express preamp. However, You will notice that there are 3 loose wires and probably some mistakes. I am quite unsure of what exactly I should be doing with the "Presence" components, B+ connections, and the second half of the 2nd 12ax7s connections in general.
Anyone have any thoughts? I'd like to have a clear plan before I actually start butchering my champ.[/img]

[muchxs]

I am quite unsure of what exactly I should be doing with the "Presence" components, B+ connections, and the second half of the 2nd 12ax7s connections in general.
Anyone have any thoughts? I'd like to have a clear plan before I actually start butchering my champ.

At a glance... I should take a long look before commenting...

The typical presence scheme is in the NFB on a plate to plate amp. This is SE, SE usually doesn't have a presence control. You have a couple options, eliminate the presence control and plug the hole on the front panel or add a master volume to use the extra control postition. Real Trainwrecks don't have master volumes. Yours is neither a real Trainwreck nor a real Champ so I wouldn't worry.

I know I mentioned presence, if you converted the amp to 15-18 watts plate to plate with two output tubes a presence control an easy addition.

Trainwrecks use three triode stages in the preamp. The fourth section is a waste of a section, it not used. We gain freaks hate to see a perfectly good triode go to waste. If you want to make your amp a little more complicated you can use the extra section as a cathode follower. I like the way your layout is simple even compared to a stock Champ.

If that wire to pin 5 of your 6V6 just dangles sound goes nowhere, that's your grid input. You want to bleed a lot of preamp gain to the ground with between a 75k and a 220k resistor then feed your power amp what's left. Like magic you should have sound. If the amp isn't stable or it sounds harsh bleed more gain to the ground. Or wire your master volume in there, keep the bleeder to the ground to limit overall gain.

Real Trainwrecks don't use grid blockers. Try a 33k grid blocker on the input, it might make your life easier later.

[bcmatt]

Cheers. Thanks for the help Muchxs. I think I will drop the presence like you say.
Your also right that it does kind of bother me to not make use of a possible gain stage. I'll come back to this in a few days. I'm thinking I should actually draw out the actual schematic as well, to help sort some things out.
I will definitely be working through all your suggestions as well.
Thanks!
Matt

[bcmatt]

oops, double post

[bcmatt]

Ok, I'm finally back; taking a few more kicks at my proposed project. I hacked away at the schematics and came up with this:

http://bp3.blogger.com/_4u9l5q2yFBA/...h/SE+Wreck.GIF

I don't know if this would work, but hopefully someone can tell me. You can see I ditched the presence control like suggested. Also, the component values coming out of the last 12ax7 cathode are the champ values and not the express values (even though the style of drawing might lead you to believe otherwise). Is this what I would want? Also, these B+ connections out of the first two 12ax7 plates; can they be connected like that (before the filter caps with those 100k resistors)?

For now I only put in 22k off the input, because I was going off (a wrong) memory of what you suggested, but I would likely change that to 33k.

I think I would also try master Volume, but I'm just starting with this to see if I'm on the right track.

[invalidcd]

I did the same thing to a champ the and it sounded great, it was very clean and not very loud , so I changed the 6V6 to an EL84 and it screams. it will be worth the extra hole you have to drill trust me . ill try to post a schematic also getting rid of the mid pot and replace it w/ a 33k or 10k fixed resistor and also i would suggest leaving the bass at 1M,b/c in amps this small , tone stacks suck up a lot of gain.

[invalidcd]

Hear is the schematic for an el84.