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Blackface Champ

10/8/2003 5:55 PM
anonymous Blackface Champ
I'm thinking of this as a first build, but have a few questions first:  
The 5y3 is a tube right? It looks like it's only in the power section and not actually an output tube, could it be replaced with a transistor and not effect the tone? What would you recommend?  
Also are there any mods I could do for more gain? What does it sound like with a fuzz or od pedel?  
Finally what's the wattage output on it?  
Here's the circuit I am looking at in case there are different versions of it:
10/8/2003 7:19 PM
Chris ( CMW amps )

Hi ?  
If you do get a B+ from about 320 - 360 Volts using diodes then it's pretty ok .  
If you want more gain I recommend building a tweed Champ 5F1/Princeton 5F2A 'cause they don't have a treble-bass-tonestack so less gain-loss .  
The output is about 4-6 Watts and pretty loud connected to a 12" cab .  
Have a look at for some great 1st tube amp info .  
Keep on rockin' and be carefull with the high voltages ,  
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10/8/2003 8:17 PM
Man o'Blues
Yes, the 5Y3 is a tube - more specifically a rectifier tube. It can be replaced with a pair of diodes (1N4007's). Tube rectifiers are often used to generate 'sag' or compression, but in a single-ended amp like the Champ, tube recto's don't add any sag. So you can dispense with the 5Y3 and use the diodes without affecting the tone, as long as you keep the B+ around the same as the Champ running a tube recto i.e. 300-350V.  
Want more gain? Just "lift" the tone stack.  
Check out the "P1" project over at for ideas on your first build.
10/9/2003 11:50 PM
Re: Another opinion
"So you can dispense with the 5Y3 and use the [solid state] diodes without affecting the tone,"  
Just for the record, I sure haven't found that rectifiers sound the same, whether vacuum or solidstate, in class A amps.  
I hear the difference, and I bet you will, too, if you check it out. Does it matter? Your call. And it probably is better for a novice to build SS, for simplicity, but if there is a PT with enough heater over capacity, say .6A, then you could try a 6ca7 tube diode, later.  
10/10/2003 12:16 AM

6ac7? though the 6ca7 was the american equivalent of an el34? :D im sure it would work just fine w the 6ca7. :D:D:D:D:D:D:D  
10/10/2003 3:26 AM

Sorry, I meant 6ca4.  
10/10/2003 2:15 PM
Man o'Blues
I've built Champ-like amps with both silicon and tube rectifiers, but never got around to a/b'ing them in the same amp, which is a bit of a PITA since you'd have to adjust the B+ to the same levels to get a true comparison. FWIW, I never noticed anything negative or lacking with either rectifier type in class A amps.  
I'm curious though why one would sound better or different than the other in a Champ (assuming same B+) if rectifier-induced sag is nonexistent. Maybe I don't hear the difference because my mind tells me there shouldn't be one, when there actually is :)
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