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Adcom GFA-565 replacement circuit board
- Thread starter krellmk
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Hi, Chris Hoppe of Hoppe's Brain here.
I do actually have test results, in a blog post. I'll add them to the product page.
https://hoppesbrain.com/2022/11/08/ebfa-565-versus-bfa-565-validating-a-new-design/
I do actually have test results, in a blog post. I'll add them to the product page.
https://hoppesbrain.com/2022/11/08/ebfa-565-versus-bfa-565-validating-a-new-design/
Uh-oh ... a bot ? @WOPL Sniffer
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Interesting idea. How would you do this? I can think of two ways..
1. Feed one amp channel an inverted signal, say, from the cold output of a balanced preamp.
2. Feed a single-ended signal to both amp channels, but connect one in inverted mode by sending the signal to the negative side of the long-tail-pair at the input.
The GFA-565 is mono, so this could be done, but there would need to be a speaker wire jumpering the negative outputs together, so they are common-ground.
Although I'm not sure the 565 could be modified to produce an inverted output.
Option 1 is better and could be done with any amp with common ground.
Power would be the same as when bridging. A pair of GFA-565's would be somewhere around 1100 watts into 8 ohms!
1. Feed one amp channel an inverted signal, say, from the cold output of a balanced preamp.
2. Feed a single-ended signal to both amp channels, but connect one in inverted mode by sending the signal to the negative side of the long-tail-pair at the input.
The GFA-565 is mono, so this could be done, but there would need to be a speaker wire jumpering the negative outputs together, so they are common-ground.
Although I'm not sure the 565 could be modified to produce an inverted output.
Option 1 is better and could be done with any amp with common ground.
Power would be the same as when bridging. A pair of GFA-565's would be somewhere around 1100 watts into 8 ohms!
I run my Counterpoint amps such that the hot is left; cold is right and ground floats at the amp end. Speakers attach to the red terminals only, noting polarity. I should Re-wire them with an XLR jack but now I use some custom cables with XLR to twin RCA at the amp end.
But despite the fine sound distortion is rather high in these amps, due to the tubes.
If costs get high (as they do) then the Benchmark amps are the answer.
But despite the fine sound distortion is rather high in these amps, due to the tubes.
If costs get high (as they do) then the Benchmark amps are the answer.