# Modifications to a 6X4 rectifier tube circuit



## ed2000 (Feb 16, 2007)

I have shown the circuit below. Can the circuit be modded to use the 6X4 rectifier with more common preamp tubes and an EL84 instead of the way it is now? The chassis is from a 'Northland Canadian III' combo.
Looking at the pics is it worth the effort or should I scrap the idea of making a cute little Vibro Champ Wannabe


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## Wild Bill (May 3, 2006)

ed2000 said:


> I have shown the circuit below. Can the circuit be modded to use the 6X4 rectifier with more common preamp tubes and an EL84 instead of the way it is now? The chassis is from a 'Northland Canadian III' combo.
> Looking at the pics is it worth the effort or should I scrap the idea of making a cute little Vibro Champ Wannabe



Anything can be done, Ed. It's all a question of whether or not it's worth the trouble. I can't tell you anything from the pictures 'cuz I HATE looking at pictures! It's just too damn much time and effort to try to figure out a circuit from a picture. A real schematic can almost instantly tell you what you need to know but a picture just makes a tech's head hurt!

Tell us the tube lineup. That will tell us what we have to work with. I warn you, however. If you are new at this trying to help you make major mods to an amp is like trying to help a guy rebuild his engine over the telephone, when he's never ever opened the hood of a car before! No matter how much you want to help the guy it just gets too frustrating!


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## ed2000 (Feb 16, 2007)

tubes: 3 - 6AV6
1 - 6AQ5? writing on the chassis not clear, tube not labelled
1 - 6X4

I would guess the 6AQ5 would be the power tube
One 6AV6 controls tremelo and the other 2 are preamp.
The chassis pic has the tubes labelled.

How comparable are the 6AV6 to 12AX7 ?
The 6AQ5 has a similar appearance to the EL84...interchangeable?
I'll try to draw a schematic showing components around the tubes.


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## nonreverb (Sep 19, 2006)

This is a single power tube amp. The 6AQ5 isn't interchangeable with the 6BQ5..I'd guess this thing'a about 4 or 5 watts output. Probably not worth going to the trouble to convert the rectifier to anything than what it is as it not going to make an improvement IMO.


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## Wild Bill (May 3, 2006)

ed2000 said:


> tubes: 3 - 6AV6
> 1 - 6AQ5? writing on the chassis not clear, tube not labelled
> 1 - 6X4
> 
> ...


NRvrb is right, Ed. You have one power tube. A 6AV6 is like 1/2 of a 12AX7. So essentially you have a Fender Champ style amp with a tremolo section added.

This is about all you can do. You see, the amp is designed for these tubes and this power level. That means the power transformer can only supply enough to do this job and the output transformer can only handle 4-5 watts of power. They won't be able to handle being asked to do more.

Mind you, Champ style amps can sound great! I'd put a decent speaker in it and leave it alone!


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## madkatb (May 14, 2009)

The 6aq5 has all the same numbers/voltages/etc. as a 6V6 but a top B+ of 250V. So it's a slightly lower powered Champ-style with tremolo. You'll have to trace out the circuit and compare the schematic to a Vibrochamp.


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## ed2000 (Feb 16, 2007)

The sensible thing to do is get decent tubes and run it as is. As I said it sounded good and crunchy just before it went silent. Is the 'Tube Store' local to the GTA?
Are the resistors shown in the pics wirewound?


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