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Old 5th May 2013, 04:34 PM   #11
6L6 is offline 6L6  United States
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permaneder - The important question is 'how much bias can you attain, on both N and P sides, with zero offset?'

Reduce pots to zero.

Increase resistance a few turns at a time on both sides until you get some (perhaps 100mV) bias.

Trim offset to zero. (whatever it takes on bias pots)

Increase both pots evenly again and increase bias another 100mV

Trim offset again to zero

Repeat until you can increase bias no more, with zero offset.

--Spend time with kids first. Amplifier can wait.
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Old 5th May 2013, 04:51 PM   #12
NicMac is offline NicMac  Italy
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permaneder, did you test the K2013/J313 "Juma" F5 version that you made PCB's for recently? That one is next on my build schedule
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Old 6th May 2013, 06:31 PM   #13
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Quote:
Originally Posted by 6L6 View Post
permaneder - The important question is 'how much bias can you attain, on both N and P sides, with zero offset?'

Reduce pots to zero.

Increase resistance a few turns at a time on both sides until you get some (perhaps 100mV) bias.

Trim offset to zero. (whatever it takes on bias pots)

Increase both pots evenly again and increase bias another 100mV

Trim offset again to zero

Repeat until you can increase bias no more, with zero offset.

--Spend time with kids first. Amplifier can wait.

Thanks @ Zen Mod and 6L6.

I was too impatient and dumb to find proper settings. Had to learn that it needs to proceed step by step and in very small steps furthermore...
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Old 6th May 2013, 06:41 PM   #14
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permaneder, did you test the K2013/J313 "Juma" F5 version that you made PCB's for recently? That one is next on my build schedule
NicMac, no. I have to match MOSFETs first. Each 50 of the P and N types should be sufficient to find close quintets.

Last edited by permaneder; 6th May 2013 at 06:57 PM.
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Old 6th May 2013, 08:18 PM   #15
6L6 is offline 6L6  United States
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permaneder - Did your amp bias properly?
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Old 6th May 2013, 10:10 PM   #16
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by permaneder View Post
Thanks @ Zen Mod and 6L6.

I was too impatient and dumb to find proper settings. Had to learn that it needs to proceed step by step and in very small steps furthermore...
admitting to being dumb is first step for not being .......... dumb



you'll find more than few biasing tutorials for F5 , if you search with some patience
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Old 7th May 2013, 05:49 PM   #17
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permaneder - Did your amp bias properly?
I just fiddled about one channel. Setting idle current and offset works like you and Zen Mod described. Didn't make a final setup as the amp is still lying on the bench. I will do it next weekend probably...

Thank you again for your kind assistance.

Last edited by permaneder; 7th May 2013 at 05:51 PM.
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Old 7th May 2013, 08:24 PM   #18
Zen Mod is offline Zen Mod  Serbia
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Old 19th May 2013, 06:27 AM   #19
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I just fiddled about one channel. Setting idle current and offset works like you and Zen Mod described. Didn't make a final setup as the amp is still lying on the bench. I will do it next weekend probably...

Thank you again for your kind assistance.
The F5 is running in its cabinet since about 30 hours at a bias current of 1.3A. Both bias and offset keep very stable. The offset voltage is slowly drifting < +- 1mV on both channels. The heat sinks should be able to dissipate a bit more. So I'll increase the bias to 1.5A or so and will see, how it behaves.

In comparison, I prefer the M2 or F6. Yet, my F5 becomes more and more "round", smooth and singing after these few hours.

Thanks again for leading me to the path of enlightement...

It's only Rock 'n' Roll, but I like it

Last edited by permaneder; 19th May 2013 at 06:42 AM.
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Old 19th May 2013, 10:43 PM   #20
generg is offline generg  Germany
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Happy it worked now......!

Some pictures of F6 or F5?

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