Buying the Forte 1A kind of killed my Aleph budget, but I have plenty of parts available to make an amp of some other kind. I've been thinking about it a lot lately (instead of doing homework assignments, projects, etc.)... I've always loved the X-SOZ and the Zen-lite... and I would love to have both combined into one. This will turn into my Christmas break project.
Attached is a first-draft schematic. I have an old 30-0-30 transformer that is big and heavy (probably 10 pounds or more). I don't know the VA rating, but I think it'll be sufficient. I figure after it gets loaded by four FETs, it's recitified voltage will settle in at around 80VDC, which is what I included in the circuit. I could drop it some more with a CRC filter (which I'll probably do).
I don't have the spare money for huge heatsinks, so this won't be a 20W monster SOZ, it'll be more like a 2W version. Would these heatsinks be suitable if I put one FET per sink? I figure with one 150W light bulb, the idle current will be around 700mA per FET, which is low, so each will then dissipate 50-60W. At the moment, I am leaning toward a single rail supply over a double. Any reason why I shouldn't do this? I am also unsure of the value to use for the input pot. I really want to include it because I would like it to be an integrated solution. This was a big problem with the Forte; I had to build a separate passive preamp (oxymoron?) so I didn't deafen myself. I am currently thinking about IRF230 for the FETs, it I can find them.
I have a pretty good general idea of where I'd like to go with this, but I really wonder... would it be worth it? I'll only get about 2W, which is totally fine. I usually listen at about 50-60dB through my 102dB 1W/m speakers, so I am only using milliwatts anyway. But, will this be a good, clean 2W, or will it be loaded with distortion? Thanks for any pointers.
Attached is a first-draft schematic. I have an old 30-0-30 transformer that is big and heavy (probably 10 pounds or more). I don't know the VA rating, but I think it'll be sufficient. I figure after it gets loaded by four FETs, it's recitified voltage will settle in at around 80VDC, which is what I included in the circuit. I could drop it some more with a CRC filter (which I'll probably do).
I don't have the spare money for huge heatsinks, so this won't be a 20W monster SOZ, it'll be more like a 2W version. Would these heatsinks be suitable if I put one FET per sink? I figure with one 150W light bulb, the idle current will be around 700mA per FET, which is low, so each will then dissipate 50-60W. At the moment, I am leaning toward a single rail supply over a double. Any reason why I shouldn't do this? I am also unsure of the value to use for the input pot. I really want to include it because I would like it to be an integrated solution. This was a big problem with the Forte; I had to build a separate passive preamp (oxymoron?) so I didn't deafen myself. I am currently thinking about IRF230 for the FETs, it I can find them.
I have a pretty good general idea of where I'd like to go with this, but I really wonder... would it be worth it? I'll only get about 2W, which is totally fine. I usually listen at about 50-60dB through my 102dB 1W/m speakers, so I am only using milliwatts anyway. But, will this be a good, clean 2W, or will it be loaded with distortion? Thanks for any pointers.
Attachments
The distortion is very dependent on the current, less so on
the voltage, so you want to look for a balance there. When
I do development work, I often just use a variable supply
sao that I can dial it in most easily. In your case, an existing
fixed ~40V supply and a Variac ($39 cheap) would assist you.
the voltage, so you want to look for a balance there. When
I do development work, I often just use a variable supply
sao that I can dial it in most easily. In your case, an existing
fixed ~40V supply and a Variac ($39 cheap) would assist you.
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