A guide to building the Pass F4 amplifier.

[cal3713]

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.

[Norrlands Guld]

Originally Posted by cal3713

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.

[cal3713]

Originally Posted by Norrlands Guld

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.

[ggetzoff]

NG,

Great work!

[Norrlands Guld]

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?

[ggetzoff]

Originally Posted by Norrlands Guld

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

[Norrlands Guld]

Originally Posted by ggetzoff

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.