Thanks a lot!
Heatsinks are 350x200x50mm. Do we think they will be cool enough for more bias like 300mV?
The modushop 5U 300mm deep enclosure has temperature coefficient 0,18 C°/W and works for me when ambient temp is under 30°C , bias 295mV. Do you have the coefficient for yours? Where did you buy them? Big heatsinks is hard to find.
Well noted. I do not have the coefficient number. Sorry. I know they are about 3.1kg each so there is a lot of material.
i did buy these:
??????? ????MC2620 ??? ???? ??????-???
FWIW, my setup is very low gain, I just have 3.5v to drive my single F4 and at times it blows me out of the room with an fairly inefficient loudspeaker. On top of that, my life has been spent in and around loud jet airplanes which has trashed my hearing. So, if its that loud for me the vast majority of forum members would be satisfied with a single F4 and just a few volts of drive.
I'm just saying.....
I'm just saying.....
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One done. One more to go!
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I didn't see what speakers you are running, but one day you might try detaching one channel in each monoblock from the power supply and seeing how having a full dedicated power supply to a single f4 board sounds. With mine, I found that to be the best/cleanest and eventually quit paralleling the two boards. At first I just shorted the input of the unused board, but when I permanently disconnected it, I found out that even running idle was impacting the performance of the other board.
Well noted. I might try that later on. I have German Physiks Unicorn MK2 speakers.
Your speakers look like a lot of fun. Would love to hear them. Definitely a significant step down in sensitivity from mine though, so ymmv in regards to using only a single board. My Coincident PREs are 94db @ 1w/m and don't drop below 8ohms. Congrats again on such a great build. Hope you love the f4s like myself and everyone else.
Norrland Guld Need Help!
Hi Team.
First amp went perfect. Biasing and offset all great
Second amp bias well on all transistor but the off-set is all over the place. Goes up and down at lower volt with the varaiac and when I start getting close to 230v the offset just goes way negative and out of adjustability.
Any suggestions? Can I have shifted the J-fets?
Hi Team.
First amp went perfect. Biasing and offset all great
Second amp bias well on all transistor but the off-set is all over the place. Goes up and down at lower volt with the varaiac and when I start getting close to 230v the offset just goes way negative and out of adjustability.
Any suggestions? Can I have shifted the J-fets?
Have you checked the orientation of everything? Can you get us some clear photos?
Start measuring the static values of your good amp as a reference, then check each one against the one that won't bias. You've got a wrong value or something not oriented right or a bad solder joint.
Fortunately, it's a simple, low parts count design.
Greg
I think the problem is solved. I disconnected the VU meter from the speaker terminal. Lets see how it goes now. Looks good so far.
Are 10-11 mA Idss measurements for the 2SK170 and 2SJ74 good enough for the F4?
Thank you!
Abe
Thank you!
Abe
