Vibrochamp owners - favorite OD/distortion?

[andrew_k]

I just bought my first all-tube, PTP amp -- a '78 silverface vibrochamp. Picking it up this week, woo!

I know a couple of guys here have these, or have had them. What's the best mid-gain drive pedal to go with it?

[cheeb]

None. 

But sometimes I like to use a TS7 modded for less gain.

[gez]

I have a silverface vibrochamp.  Beautiful tone, though new tubes/recap might help bring out the best in it.

For OD I use a CMOS based circuit.  If you can stand the volume, you can get an amazing tone by using the OD as more of a booster (which is why the CMOS sounds great as there's plenty of headroom to drive the amp).  It really sings and sustains.  Bloody loud though!

[m-theory]

You'll want to swap the speaker, check the tubes, and replace the filter cap, if that hasn't already been done.  The OE speaker is pretty much useless, imo.  The tubes may or may not be ok...you'd have to have them tested to be sure.  If they're original, they could very well still be good, since they're probably RCA, and because these amps generally didn't get used a whole lot.  If the filter cap can is original, it should be replaced, because electros dry out after about 15 years. 

You might also have to consider installing a 1k 5 watt resistor across the cathode, to limit current.  The SF champs, although built with the exact same schematic and components as BF models, tended to run very high current across the 6V6.  I've read that this was due to different transformers being used in the SF models, but I don't know that for certain.  The problem presented with this excessive current is that it makes the amp sound terribly flubby and loose, and also cooks the tube very quickly, especially when pushed with a pedal.  Common safety warnings definitely apply here.  In fact, you're best off having a qualified tech go through the amp anyway, just to make sure it's up to snuff before you start pounding on it.

As for pedals, a good overdrive works well, and I also like a mosfet boost, but my favorite way to run this amp is to just plug straight in and crank it. 

[andrew_k]

Thanks for the tips guys, I really appreciate it!
The amp should be fine, it's had all electros replaced other than the cap can (m-theory: can you recommend a good brand if I need to replace this?). Bias resistor is swapped for 1k 5w to fix the high current across the 6V6 and the valves are tested as good, but I have a NOS JAN 5751 coming for v1 as I want to experiment.
The speaker is the original Oxford, at this point I'm planning on getting a weber sig ceramic 8 and packing the original away.

[kurtlives]

I just built one...

I really like it clean or with a light smooth overdrive unit.

It sounds great cranked though, mine has to be pushed real hard for it to break up. I also have a mini switch to remove the tone stack. This adds lots of gain and mids.

[drewl]

Yes the silver face versions ran higher voltages which runs them very hot, it'd be better to lower the voltage to get it to sound like the tweed ones, but we're not talking radical changes.
There's some quick easy mods, like disconnection the tone stack or feedback loop to get these to sound killer, search the web they're easily found.

Weber makes a great replacement speaker for these, try running one into a large cab and you'll really see or hear how great these amps are.
I've found simple boosters or tubescreamer type pedals are all that's neede to get a bit more grind out of the stock circuit, but almost anything sounds good through it, it's a very pedal friendly amp.

[gez]

it's had all electros replaced other than the cap can (m-theory: can you recommend a good brand if I need to replace this?).

My memory is a little hazy, but I'm pretty sure the following is correct.  In mine there were a couple of superfluous holes drilled in the chassis either side of the can.  The spacing exactly matched the screw holes of some heavy-duty tag strip I had.  I bolted it in place, connected the relevant terminals together with a single wire and grounded it to the chassis.  I was then able to connect some large Spragues (Watford Valves sell them - can't remember the variety) horizontally and they just fitted.  I'd disconnected the can from the ciruit, but I left it in for aesthetic purposes.

[gez]

PS  When I did change the filter caps the speaker tightened right up (mine is stock).

[m-theory]

The amp should be fine, it's had all electros replaced other than the cap can (m-theory: can you recommend a good brand if I need to replace this?).

I can't imagine going through the trouble to replace all electro caps and leaving the most important one stock.  That's goofy.  Filter caps have a huge impact on tone when they go south. 

I went the route of gez as well in mine, because the cap can was about $30-$35 at the time.  I'm not sure what they run right now, but probably more than Sprague.  At any rate, you should be able to find it here, though you may have to ask what part number it is. 

http://www.tubesandmore.com/


I've read good reviews of the Weber sig for that amp.  Mine has a Weber alnico, and it sounds fantastic.  I hesitated spending twice as much on the speaker as I had spent for the amp, but I couldn't find a single comment anywhere that suggested that it wouldn't be worth it.  gez is correct, of course, that replacing that filter cap is going to improve the amp a great deal on its own, but that OE Oxford isn't much to right home about, and, after 30 years, it's bound to have fairly loose cone material anyway. 

[gez]

but that OE Oxford isn't much to right home about, and, after 30 years, it's bound to have fairly loose cone material anyway. 

Yeah, it's always been a worry what the hell I'm going to do when it finally goes.  Sounds like those Webers are the way to go (thanks for the tip).

[m-theory]

Sounds like those Webers are the way to go (thanks for the tip).

I'm sure there are others worthy as well, but I personally can't say enough good about the P8Q (different number now) that I've got, and I keep reading very strong comments about the sig 8 as well.  Additionally, Ted is a terrific guy to deal with...I've never been led astray by him, he responds very quickly to questions, and on one occassion, he went far beyond his call to help me out with something that he really had no need to eat on his own, so I'll always be a strong advocate for him.  He's a true stand up guy with some terrific products. 

[cheeb]

+96 on the Weber

[drewl]

You can find those cap cans cheaper nowadays.
Weber might have them, they have alot of parts.
The can in my '73 is still good fwiw.

[andrew_k]

Hmm... maybe the cap can has been removed already; is that what this means?

The death cap has been removed and the earth line ground directly to the chassis.

lol @ "death cap"

[m-theory]

The can in my '73 is still good fwiw.

Any tube amp older than 15 years should have filter caps replaced.  They're only conidered reliable for about 15 years, after which time, they could literally fail at any time, and often take out the tube and transformer when they go.  Sure, you'll find some that are 40-50 years old, or more, but that doesn't mean that they're "good."  Aside from saving your amp from potential disastrous failure, a filter cap job on an amp older than 15 years will provide a dramatic improvement in tone.  It's like taking a blanket off the speaker. 

Btw, you cannot tell by looking at these caps, can type or other, whether they're any good or not, unless they're physically deformed or leaking.  The cans are doubly impossible to visually diagnose, because the actual caps are inside the can. 

[m-theory]

I have to add, after a recent O/D build, that I've got a brand new "favorite" for this amp.  I built a booteek T/S variant yesterday, plugged my Lester into it, set the output almost maxed, the tone at about 2:00, and the gain at about 10:00, and the amp on about 4.  Holy crackers...I've never heard that little amp breathe that much fire!  I'm not generally a huge O/D fan myself, because I generally get my O/D from my amps, but this circuit, driving my humble little VC, sounded simply amazing.  Very impressive (and very loud!).

[andrew_k]

m-theory: if the amp is said to have had the "death cap" removed and the earth line ground directly to the chassis, does that mean I don't have a cap can and don't have to worry about that part of the equation?

Regarding b00teek tubescreamers; it's good to hear they play nice with the VB; I built one yesterday in anticipation of the amp's arrival 

[m-theory]

does that mean I don't have a cap can and don't have to worry about that part of the equation?

No.  I may be mistaken, and I'm no amp tech by any means, but I don't believe that amp would've had a "death cap," and it should've come with a 3 prong cord.