Greetings fet-fetishists, I come to you from the far-away lawless-wasteland of the Tubes/valves forum. I found a neat big heatsink-box type of enclosure in an e-waste bin at work (I think this was a big battery charge controller?) That I figured would work well for a Pass type build. Each side has a heatsink that measures approximately 1 7/8" x 3 1/2" x 8", and the opening inside is about 8" x 6" x 3" high. (Pictures attached)
I like to use tubes for gain, and am always working on something new, but the front end will likely end up something like an impasse, or similar with a source follower output for a nice low output impedance. This is the easy part, really.
So, for what I'm thinking, the F4 "crippled" or the push pull burning amp output stage is what I want to build. I know going with jfets up front for the buffer on the F4 would be more versatile, but they are way too expensive for this project for me, especially if I'm already going to be building a preamp that can drive the output stage directly. Unless someone out there wants to slip a couple pairs in the mail for me, I would of course change my mind 😉
My main question, is would three output pairs per channel be fine on this heatsink? Basically built otherwise as per the F4 schematic. I understand that I can just crank the bias to keep the devices in a good temperature, but I'm not sure if they would need to be cranked down too far, and if I may be better off running two pairs per side hotter. I run 8 ohm speakers, and don't mind a small reduction in max power. For what it's worth, I plan on going with an Antek 300VA toroid, either 2x18 or 2x20, it will be a tight fit but not impossible!
Any ideas or comments would be appreciated!
(Special thanks to Zen Mod and their incoherent ramblings for making me look into pass designs further 😀)
I like to use tubes for gain, and am always working on something new, but the front end will likely end up something like an impasse, or similar with a source follower output for a nice low output impedance. This is the easy part, really.
So, for what I'm thinking, the F4 "crippled" or the push pull burning amp output stage is what I want to build. I know going with jfets up front for the buffer on the F4 would be more versatile, but they are way too expensive for this project for me, especially if I'm already going to be building a preamp that can drive the output stage directly. Unless someone out there wants to slip a couple pairs in the mail for me, I would of course change my mind 😉
My main question, is would three output pairs per channel be fine on this heatsink? Basically built otherwise as per the F4 schematic. I understand that I can just crank the bias to keep the devices in a good temperature, but I'm not sure if they would need to be cranked down too far, and if I may be better off running two pairs per side hotter. I run 8 ohm speakers, and don't mind a small reduction in max power. For what it's worth, I plan on going with an Antek 300VA toroid, either 2x18 or 2x20, it will be a tight fit but not impossible!
Any ideas or comments would be appreciated!
(Special thanks to Zen Mod and their incoherent ramblings for making me look into pass designs further 😀)
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2 pairs , except in case that these screws on top aren't M8 or M10 
there is no place for more
I believe that for even (just) 50W of heat per side , you'll need Babysitter in Summer time
there is no place for more
I believe that for even (just) 50W of heat per side , you'll need Babysitter in Summer time
You think a 200VA transformer would be good for two pairs per side? It seems that that would be fine, since it would be roughly half the VA draw at idle.
Just found that I have the lower reference voltage version of the TL431 on hand, the TLV431... Will it work in the F4? I'm assuming that it would need some parts value changes...
Add a quiet 120mm PWM fan at 10% speed on each side outside and you can go full power no problem. Forced convection is 10x to 20x higher than natural convection. Don’t fear fans.
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