This Champ is ridiculous. No sane person would ever spend so much time and money on such an inexpensive small amp, would they? It is irrational.
I got the amp in Sacramento in 2005 from the estate of a woman who bought it new in 1971 along with her new electronic organ. The amp sat in her living room, occasionally singing church music, for 35 years. The picture above was taken the day I brought it home.
It was the coolest little amp I had ever heard for harp, but I just could not leave it alone. First I tried several new input tubes, and that is when I learned that the 12AT7 tube is a terrible tone generator and the 5751 is great. The Champ is a good test bed for things like that because its circuit is so simple.
Next I replaced the speaker with a Jensen reissue P8R. Hated it. Then I altered the baffle so it would accept a 10-inch speaker and tried a Jensen P10R. Hated it. I tried several other various speakers and finally settled on the Weber 10A-1250 with H dustcap. Now we were getting somewhere. The Champ settled into that configuration for several years.
Then one day I lost my mind and decided to trick the amp out more. (Read: spend more money on it.)
First I installed a pot in the negative feedback circuit so I could adjust it to find the optimal mix for crunchy tone. I discovered the optimal mix was ZERO, so I removed the NFB circuit and the pot (which was mounted on the back part of the chassis) and used the hole where the pot had been to mount a line out jack.
More tube swaps followed, finally ending with the 5751 in the input section, a vintage black plate GE 6V6 in the power section, and an NOS “Coke Bottle” Sylvania 5V4G rectifier. Again, the Champ settled into this configuration for some time. It was sounding GOOD.
But not good enough. So I asked Bruce Collins at Mission Amps to voice the tone stack for harp using NOS Soviet K40Y paper in oil tone caps. Big improvement, but I wasn’t finished quite yet. A few months later Bruce installed a Hammond 15-watt output transformer and a choke. There! The amp was finished. A sleeper amp, with big punch and crunch in a small package.
Which brings us to today. Before guitar player Steve Mignano headed off to tour with Cassie Taylor and the Soul Cavalry he gave me a Warehouse Veteran 10-inch speaker and said, “It crunches like a motherf---er.” Hmmmmm, this I had to hear.
I looked around for a 10-inch cabinet and finding none I decided to swap it into my Champ, removing the nice Weber alnico speaker. The Weber speaker made the Champ darker and warmer, and Steve was right: The Veteran speaker crunches like a mutha with a brighter, raspier tone. It’s fun. Ratty!
I really don’t know how much I have invested in the Champ now, but it is a ridiculous amount – certainly more than the value of the amp. I have learned more about harp amp tone from the Champ than from any other amp. It is now the amp I have owned longest. Purists might sneer at me for altering a classic but it has been a blast. And the amp is a little beast.
Choke and Hammond 15-watt transformer
The silver bullet-shaped Soviet military PIO caps
Rectifier and power tube; Warehouse Veteran speaker
I saw an interesting mod for an amp that I'm considering that installs a talk box into the case without interfering with the rest of the set up. Once I get my car fixed I'm going to buy myself an old megaphone and give it a shot. I have no idea if it's possible to use a talk box and a harp together, what with the tube running into your mouth, but I'm going to give it a shot.
I don't think you're crazy at all Rick. I sold my silverface 'cuz it wasn't ballsy enough for me, but I strongly believe that modding a Champ gets you extreme portability ( 'cuz it's so small ) with the sound you want. I wouldn't have sold mine if I had gone to the lengths you have. I don't think there's a cuter, more classic looking little amp out there.
Last Edited by on Oct 27, 2012 9:55 AM
YIKES!!! I am sure am glad the Vibro Champ belongs to my wife and I'm not allowed to touch it. But this reminds me, I have a new 5751 I need to go plug into my old Peavey and see what it sounds like.
I was swapping amp stories recently with an unknown (to me) harp player at a get-together, telling the happy story of my most recent antique tube amp acquisition, and his response was, "did you get the mic with it?". I don't think he was being snide, but instead offering an astute and subtle suggestion. I am now looking for "THE MIC". I have enough amps.
To be honest Rick, the problem is not the tinkering you are doing...... its the tinkering that you encouraging the rest of us to do! I bought a VHT Special 6, so far after reading your threads, I have changed the valves, modded the circuit and after a throw away comment from you last week I have now fitted a Lil Buddy speaker! I don't know how you sleep at night!
I need to join Amps Anonymous... Yes friends it started with a Honeytone. I then moved to something with a 10" speaker. I am now looking at something with two or even four 10's. My wife has threatened to pack her bags, but I figure to play the blues I need to suffer. It can only help my tone....
My SF Franken-twin / Super Sex [six] has been "under the knife" (or is it soldering gun?) at least as much as your Champ. I may not have spent quite as much on it though. Got it as a naked chassis at a garage sale ten years ago for $15 bucks or so. Had it re-capped by someone who cold-soldered a joint or two - then started 'learning on it' myself.
I did spend some coin on an ebay blonde twin cab , cut a crude reducer ring to mount a 10" next to the twelve, - then went a little looney "in the laboritory" (cue Borris Karloff voice).
At it's modded peak it had a cathode/ fixed bias switch, a pentode/quasi triode switch and a variable feedback pot, not to mention higher value signal path caps and lowered plate voltage on the pre's. It sounded good that way - even though cathode biasing did not turn it into a little low watt valco, and I rarely had a chance to crank it to the crunch point. When some intermittent cutting out started to happen it fell way down on the 'b' list for bench time as I started working on other amps.
When I re-did my bench and finally made a usable chassis caddy, I got around to trouble shooting the monster - but not before returning it to something close to stock. Gone are the bias and pentode switches. I finally found a loose - actually non existant solder joint on one of the tube pins. (I forget which now).**
It is back in it's kick-ass glory now. It doesn't crunch easily but it's got major cajones. Like a Harley on a slow cruise, even when it's not blasting, you can feel the power.
Still - I'll futz with it some more when I get a chance. Having heard how much difference cold biasing made on my Bassman, - Im gonna re-wire the Silverface balance pot to be a Blackface style bias pot.
Hey - that's the beauty of Silverfaces. They are nearly indestructible, they are capable of great tone, - and they aren't precious collectibles like Blackfaces are.
** Had I done the Mullet one's (Gerald Weber) chopstick test thoroughly I would have caught the problem a lot sooner.
Last Edited by on Oct 27, 2012 1:19 PM
