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I have a friends sf Champ here (circa 1979). This thing won't get much above a loud speaking voice before it starts clipping and the tone is quite thin. The original "Fender" 6v6 is tired and the stock ceramic "Fender" speaker is clearly a turd. My guy isn't concerned with keeping the amp stock as it's not currently a real collectible model and he'd like to get as much clean volume as possible and improve the tonality. He doesn't want to spend too much on this either.
My plan is to replace the stock speaker with a very efficient 10" (It'll fit, I've done it). I'll be revoicing the amp to eliminate useless low end that the small cabinet can't reproduce anyway and I'll bump the low mids. The stock tone stack is totally inappropriate for this amp.
These amps typically have 420V or more on the power tube. Since we're after a cleaner amp I'll use a big bottle that won't mind so much rather than reduce voltage for a 6v6.
I have plenty of tubes, but all matched pairs except for one el34 whose spouse died some years ago. I'd like to use it rather than break up another couple or buying a new tube. My obvious concern is filament current. The Vibro Champ used the same PT with another 12ax7 in the circuit. I know people have run 6l6's in Vibro Champs. That would be .75A more filament current than the standard Champ. Putting the el34 in this standard Champ will draw about 1A more current. Or, another .25A more than a Vibro with a 6l6 tube. My plan is to just install the tube, check filament voltage and burn it for awhile to see if the PT gets too hot. I'm just wondering if anyone here has ever done this and can confirm if it works or not.
Of course I'll be rewiring the socket and rebias for the el34.
There's no hum, but I'm going to rebuild the power supply and take other hum reduction measures anyway. I'll be adding a pi filter ahead of the rectifier so that I can add a 47uf cap to the plate supply (22uf after the rectifier 100r then 47uf), I'll rewire the filaments with a false CT referenced to the power tube cathode bias and I'll rewire some grounding to a more ideal scheme.
Should be a neat little amp.
My plan is to replace the stock speaker with a very efficient 10" (It'll fit, I've done it). I'll be revoicing the amp to eliminate useless low end that the small cabinet can't reproduce anyway and I'll bump the low mids. The stock tone stack is totally inappropriate for this amp.
These amps typically have 420V or more on the power tube. Since we're after a cleaner amp I'll use a big bottle that won't mind so much rather than reduce voltage for a 6v6.
I have plenty of tubes, but all matched pairs except for one el34 whose spouse died some years ago. I'd like to use it rather than break up another couple or buying a new tube. My obvious concern is filament current. The Vibro Champ used the same PT with another 12ax7 in the circuit. I know people have run 6l6's in Vibro Champs. That would be .75A more filament current than the standard Champ. Putting the el34 in this standard Champ will draw about 1A more current. Or, another .25A more than a Vibro with a 6l6 tube. My plan is to just install the tube, check filament voltage and burn it for awhile to see if the PT gets too hot. I'm just wondering if anyone here has ever done this and can confirm if it works or not.
Of course I'll be rewiring the socket and rebias for the el34.
There's no hum, but I'm going to rebuild the power supply and take other hum reduction measures anyway. I'll be adding a pi filter ahead of the rectifier so that I can add a 47uf cap to the plate supply (22uf after the rectifier 100r then 47uf), I'll rewire the filaments with a false CT referenced to the power tube cathode bias and I'll rewire some grounding to a more ideal scheme.
Should be a neat little amp.
And I don't expect more watts for the plate voltage. I just figured I could use it with a big bottle it rather than reduce it for safer 6v6 operation.
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