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A guide to building the Pass F4 amplifier.
A guide to building the Pass F4 amplifier.
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Old 4th July 2020, 04:39 PM   #1971
cal3713 is offline cal3713
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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.
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Old 4th July 2020, 05:23 PM   #1972
Norrlands Guld is offline Norrlands Guld  Sweden
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Originally Posted by cal3713 View Post
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.
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Old 4th July 2020, 09:21 PM   #1973
cal3713 is offline cal3713
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Originally Posted by Norrlands Guld View Post
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.
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Old 4th July 2020, 09:36 PM   #1974
ggetzoff is offline ggetzoff  United States
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NG,

Great work!
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Aleph J, F4, DCB1, VHEX +, USSA-5, BA-3 Pre, DCG3, USSPA, Transcendent Sound Masterpiece (sold) TDA1541A D3 with Abbas I/V
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Old Yesterday, 12:49 PM   #1975
Norrlands Guld is offline Norrlands Guld  Sweden
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Default 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?
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Old Yesterday, 01:05 PM   #1976
ggetzoff is offline ggetzoff  United States
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Quote:
Originally Posted by Norrlands Guld View Post
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
__________________
Airline Pilot-If it's not Boeing I'm not going.
Aleph J, F4, DCB1, VHEX +, USSA-5, BA-3 Pre, DCG3, USSPA, Transcendent Sound Masterpiece (sold) TDA1541A D3 with Abbas I/V
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Old Yesterday, 01:53 PM   #1977
Norrlands Guld is offline Norrlands Guld  Sweden
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Quote:
Originally Posted by ggetzoff View Post
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.
 

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