Hi I thought of buying the Adcom GFA -5xxx series amps with Mosfet output as they are available very economical prices considering their Chassis and FETs ( the Schematic looks more like PASS designs except Class AB with higher Voltage power rails. How good are they as a Garage amp ? Also can they be modified for more Class A output.
Welcome ideas and suggestions
kannan
Welcome ideas and suggestions
kannan
They would be a killer garage amp. Getting kind of dated compared to some of the newer pass designs. Not bad but just not as pleasing sounding as a lot of Pass's other stuff. My take on them is they are detailed, dynamic but have sharp edges to the sound. They do not have the same fitness as the pass labs/first watt stuff. More generic sounding. They are great amps with that being said.
From what I understand, Mr pass designed The GFA 555. After that, Adcom has been tacking on little tweaks here and there throughout their redesigns. So it's kind of a pass design. But not fully.
If you want more of a class A amp, I would probably sell the GFA5xxx to fund a build. Otherwise, there are a bunch of tweaks on the internet for them if you look around. You could try increasing the bias (it is adjustable) lowering the rail voltage with a different transformer etc.
From what I understand, Mr pass designed The GFA 555. After that, Adcom has been tacking on little tweaks here and there throughout their redesigns. So it's kind of a pass design. But not fully.
If you want more of a class A amp, I would probably sell the GFA5xxx to fund a build. Otherwise, there are a bunch of tweaks on the internet for them if you look around. You could try increasing the bias (it is adjustable) lowering the rail voltage with a different transformer etc.
Thanks for your response and I see lot more information pointing to GFA 555 as a better alternative than Mosfet cousins from Adcom.
I do not own 5xxx series amp but plan to get one for experimenting.
I do not own 5xxx series amp but plan to get one for experimenting.
Yeah, they are definitely fun to play with. Not meant to be as DIY friendly as these DIY-designed amps but they are still pretty easy to work on.
What speakers are you powering with it?
What speakers are you powering with it?
You'll find them very good for a garage amp. And if your welder breaks down the GFA 5500 speaker outputs can be used for stick welding...
GFA-5400 is pretty good once you stuff more caps in there, but with its factory heat sinks you can barely dial in 4W in class A. (stock is set at ~2W)