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Tube Amp Building - Tweaks - Repairs / Re: AB763/6V6Plexi amp kit questions/advice
« Last post by acheld on October 21, 2025, 04:12:58 pm »Agree with Tubeswell's advice. Schematics really are the language of choice . . .
Don't make the mistake of using these. You're talking about a build which would use a Hammond 290BX, or similar. The Concert tranny (290EX) weighs in around 8 lbs (as opposed to the BX @ 5+ lbs), and is good for 275 mA of B+ power (as opposed to the BX providing about 130 mA IIRC). If you don't use much of the rated current, you will need to drop the voltage with big dropping resistors in power supply. This wastes power, adds heat, and your build will be much heavier than you want. So yes it can be done, but in the long run it is not worth it. Many of us have made this mistake . . . it's a natural thing to do!
As for switching power supplies, no reason why it can't be done. Plenty of high power SS amps use these successfully. It's all in the specifications -- can it supply the current you need at the required voltages without introducing noise?
Here's a link to Hammond's guitar amp spec page: https://www.hammfg.com/electronics/transformers/classic/290. I use this before every build. They (and Edcor, and others!) have many other transformers, but the 290 series is the most common in tube guitar amps.
Quote
I have the transformers from the Fender Concert 1980s 60 watt amp.
Don't make the mistake of using these. You're talking about a build which would use a Hammond 290BX, or similar. The Concert tranny (290EX) weighs in around 8 lbs (as opposed to the BX @ 5+ lbs), and is good for 275 mA of B+ power (as opposed to the BX providing about 130 mA IIRC). If you don't use much of the rated current, you will need to drop the voltage with big dropping resistors in power supply. This wastes power, adds heat, and your build will be much heavier than you want. So yes it can be done, but in the long run it is not worth it. Many of us have made this mistake . . . it's a natural thing to do!
As for switching power supplies, no reason why it can't be done. Plenty of high power SS amps use these successfully. It's all in the specifications -- can it supply the current you need at the required voltages without introducing noise?
Here's a link to Hammond's guitar amp spec page: https://www.hammfg.com/electronics/transformers/classic/290. I use this before every build. They (and Edcor, and others!) have many other transformers, but the 290 series is the most common in tube guitar amps.