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Old 22nd November 2012, 11:13 AM   #3521
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yes
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Old 24th November 2012, 07:02 PM   #3522
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Hi All,

Getting close to finishing my dual mono F4 clone. It's only been powered up for about an hour and I was listening to it for 15 min or so. Sounds great with the tube pre-amp that is also mostly done. I'm going to let the F4 run a few hours on the bench and re-adjust the bias and offset in preparation for a full listening session tonight. HP339 is saying THD: ~0.0078% at 1 watt into 8 ohm. Real number is likely lower than that as I think the notch filter on the HP needs some work.

The case is the diyaudio deluxe 4u.

Anyway, thanks to Papa and everyone else for all the info you've posted to this site. Without it I'd still be listening to store bought stuff.
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Last edited by willamp; 24th November 2012 at 07:17 PM. Reason: adding info for clarity
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Old 24th November 2012, 07:38 PM   #3523
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every stereo F4 deserves proper XLR on back plate

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Old 24th November 2012, 07:50 PM   #3524
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Quote:
Originally Posted by Zen Mod View Post
every stereo F4 deserves proper XLR on back plate

Don't worry. 30 minutes with a saw and I can switch the RCA to XLR if/when I need to.
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Old 24th November 2012, 07:55 PM   #3525
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Here's a question for ya

Look at the second waveform in my picture, 1st post (1st waveform is 1khz input). This is the HP distortion monitor output. This the signal sent to the meter after the notch filter. See how much fundamental frequency is in the signal? Shouldn't that have been removed? and isn't it throwing my measurements off?

thx
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Old 24th November 2012, 10:09 PM   #3526
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well - you must explain your measurement method , so we can decide what's lousy - your building , or measurement skills

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Old 25th November 2012, 10:09 AM   #3527
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Well, lets disregard my analyzer question, probably not the right forum for that.

As for the F4: first listening session last night was most enjoyable. It sounds great in my system. Just what I was looking for.
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Old 14th December 2012, 01:53 AM   #3528
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Quick one: are two 2*26v 120va transformers good to power the f4?

I still have them lying around but am not sure regarding too high voltage and too low power...
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Old 14th December 2012, 06:15 AM   #3529
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120VA is limiting factor - you'll need to decrease bias

also - Jfet's are approaching tricky voltages - you'll need to take care of their Idss .....

so - either degeneration or cascooding
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Old 14th December 2012, 07:37 AM   #3530
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