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Author Topic:  question about Vibro Champ speaker
Chris Walke


From:
St Charles, IL
Post Posted 18 May 2017 11:15 am     Reply with quote

I have a mid to late 70s Vibro Champ with what I believe is the original speaker. I know the amp is rated at 5-6 watts.

I was wondering what the speaker rating is – what kind of output can it handle?
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Mike Schwartzman


From:
Maryland, USA
Post Posted 18 May 2017 2:33 pm     Reply with quote

I believe my Vibro Champ is 1976 0r 1977. It was still stock when I bought it in the early 2000's. The stock speaker was a very cheesy (cheap) ceramic 4 ohm speaker. I replaced it with a Jensen 8" 4ohm alnico magnet speaker rated at 25 watts and it was a very good improvement. Not cheap, but well worth it.

That amp was used for recording, but I put the same exact speaker in my buddy's Champ(non Vibro, but same era). He plays blues harp thru it and it still sounds really good after using it regularly for a couple of years now. Both amps being mid-1970's also got re-capped as well.
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Eric Philippsen


From:
Central Indiana, USA
Post Posted 18 May 2017 2:37 pm     Reply with quote

The power handling capacity of a Champ or Vibrochamp's speaker isn't much as I'm sure you know. Enough to handle the amp's output. Even so, it's not at all unusual to see either model with a replacement speaker. Realistically, the original speaker isn't something to write home about. Most likely it's an Oxford.

The mistake that's often made is putting an 8-ohm speaker in for the original 4-ohm. The amp will work but not as well.

Actually, most people are unaware that later silverface Champs and Vibrochamps ran with a higher plate voltage that earlier ones due to a different transformer. I've owned a lot of them over the decades and have two now. To my ears they sound better, which I realize is heresy to blackface owners.
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Steven Paris


From:
Los Angeles
Post Posted 19 May 2017 11:34 pm     Reply with quote

According to the "Fender Amp Field Guide" (http://www.thevintagesound.com/ffg/), the Blackface and Silverface Champs AND Vibro Champs all used the "AA-764" circuit. The schematics shown on that website, and in the "Tube Amp Book" all show plate voltages of either 342 volts or 350 volts. I'm sure it is possible that later ones did have a different transformer with a higher supply voltage. Do you have a link to a schematic showing this? The 6V6 tube will take up to 450 plate volts.
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Eric Philippsen


From:
Central Indiana, USA
Post Posted 20 May 2017 11:33 am     Reply with quote

While the AA764 schematic is the most common one referenced for Vibrochamps there is most certainly the AB764 schematic, listing a higher B+ voltage, for the later Bronco which was simply a V/C with a different faceplate. Although open to debate, it would be hard to argue it represents only the Bronco, a low end model. More likely, the AB764 also reflects silver face Vibrochamps and Champs.
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Steven Paris


From:
Los Angeles
Post Posted 20 May 2017 5:16 pm     Reply with quote

Thanks for the tip--yes, I see it on the Bronco schematic---they may have used a Deluxe Reverb power transformer, as the voltages are similar.
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Jack Hanson


From:
San Luis Valley, USA
Post Posted 21 May 2017 6:45 am     Reply with quote

The stock 8-inch Oxford is a little on the wimpy side. An aftermarket 8-inch 4-ohm Jensen, Jupiter, Mojo, or whatever, would be a definite improvement.

A hot trick with a silverface Bronco, Vibro Champ, or Champ is to install the chassis into a Musicmaster Bass cabinet with a 4-ohm 12-inch speaker, such as the 25-watt Jupiter.
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