r27 as a pot to jack up the bias. more bias makes it sound better. but adds heat.
heat sink temp. the lower the better. nelson says 55 or 50 deg C.
here is what i would do. jack the bias up till the sinks are 50-55deg C and the fan noise is low enough to live with if you have fans.
the temp of the fets dosent make it sound diffrent (temp will change how the fets mesure so i supose it could but i couldnt hear it) but the hotter the chip the shorter it will last. or it could overheat and fail, then it will sound bad.
heat sink temp. the lower the better. nelson says 55 or 50 deg C.
here is what i would do. jack the bias up till the sinks are 50-55deg C and the fan noise is low enough to live with if you have fans.
the temp of the fets dosent make it sound diffrent (temp will change how the fets mesure so i supose it could but i couldnt hear it) but the hotter the chip the shorter it will last. or it could overheat and fail, then it will sound bad.
Many thanks! The enclosed fan is very silent with rear exhaust. I will see how heat at the stock bias is managed and take it from there. [I would like 8-10 degrees of spare cooling capacity for higher room temperatures during summer.]
Also, each heat sink will have 75 degree thermal cutoff switches to the mains in case of fan problems...
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Wise.
50 deg is very safe.
But I don't wanna pay ur ac bill! In the summer. I use mine in the winter only, kinda sad but I don't have time in the summer anyway.
Keep in mind the extra draw on your powersupply.
Don't fry your xformer. More curent will raise the ripple in your ps.
So in short... Find your sweet spot. Powersupply/heat/sound you like. good luck. Worth the time
Good point. I'm using one 400VA toroid per channel, each with 88,000 uF of Panasonics plus a couple nice nonpolars for good measure. Should be good there, no? 🙂
Rectifiers are FREDs - 3020s. They might be touchier...
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Off the top of my head I would say yes a bit higher would be ok.
Off the cuff math and spelling are not my strong suit.
400/secondary Vac = ROUGH current rateing.
Lots of fun to be had
Off the cuff math and spelling are not my strong suit.
400/secondary Vac = ROUGH current rateing.
Lots of fun to be had
let`s say i will use same heatsinking from actual aleph which holds 140w dissipation at 30C above ambient per channel
keep sissy IRFP240 happy at the bay , with no more than 40W of dissipation/per piece and no more than 55C at heatsink - where you can touch it with your palm
still thinking at that battery system ... and how my speakers are current hungry I guess it is better for them to lower the voltage and raise the current
maybe one day this dream becomes reality but this after I will find and substitute input fets ..
maybe one day this dream becomes reality but this after I will find and substitute input fets ..
One more detail before power-up, if you please... I accidentally ordered the wrong cap for C4 so made do with what was on hand: one used Elna SilmicII and one new Panasonic. I'm not sure of the role played by that cap, which parallels the 9.1v zener diode. So, wait and order new&good 10 uf caps, put in new&good 22uf caps, or forge ahead with whats in there now? TIA
ok...so after a long stand today arrived the new j74s from buzz.a very nice gift of two matched 10ma quads.afterall it looks like there still are nice people on who you can count on!!!
THANKS A LOT BUZZ!!!
THANKS A LOT BUZZ!!!
at 1.6 amps/fet bias the J`s have a little bit of control over the low spl, low impedance speakers which I have.sincerely didn`t heard them sound like this before, this is first listening impression but there will be more in the next hours..days
I have to adjust a little bit the offset and probably lower the bias
will do some ''real'' photos when I finish everything...everything except listening to music 🙂
I have to adjust a little bit the offset and probably lower the bias
will do some ''real'' photos when I finish everything...everything except listening to music 🙂
still have to drill holes for feet(Adam Hall 4909), input/output connectors(cmc silver type), top plate for cooling and for power on led, after I can say I have almost finished the amps
they do worth the waiting and the effort of the build
they do worth the waiting and the effort of the build
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