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Old 22nd July 2011, 10:05 PM   #591
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1KHz 1W 8Ohm
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Old 25th July 2011, 07:15 AM   #592
ak4396 is offline ak4396  Germany
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Default 8Ohm 1W :-)

8Ohm 1W :-)
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Old 25th July 2011, 07:21 AM   #593
ak4396 is offline ak4396  Germany
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Default 8Ohm 1W k2 k3 THD

8Ohm 1W k2 k3 THD
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Old 31st July 2011, 03:38 PM   #594
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Default I try again...

Hi Tazz, let me guess your output stage:

It's like rev 1, and rev 1 is the attached pic, but with:

1. Zener replaced with resistor Rxxx (rev 0 used TL 431)
2. R2=R6, C4, VR left out, R1 chosen to provide symmetric drive for a given load, Rxxx and R5 (Nelsons grab box... ;-)))

Can you post your solution with your schematic - measurement looks beautiful. Can you post measurement with different loadspeaker loads??? (In my opinion a weak point)

Regs, Dirk
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Old 31st July 2011, 06:59 PM   #595
NYCOne is offline NYCOne  United States
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Quote:
Originally Posted by HVfanatic View Post
Hi Tazz, let me guess your output stage:

It's like rev 1, and rev 1 is the attached pic, but with:

1. Zener replaced with resistor Rxxx (rev 0 used TL 431)
2. R2=R6, C4, VR left out, R1 chosen to provide symmetric drive for a given load, Rxxx and R5 (Nelsons grab box... ;-)))

Can you post your solution with your schematic - measurement looks beautiful. Can you post measurement with different loadspeaker loads??? (In my opinion a weak point)

Regs, Dirk
I've asked NP directly, and he's OK with having DIY designs for a J2 clone posted in the forum. He does not want a J2 official schematic out, but short of that, he's indifferent to DIYers posting their creations.

In light of the above, I suspect we will be seeing a few schematics in the next few weeks.

I'll leave it to the folks who made the designs to post them, but I've been privy to a few J2 clones.

Hopefully, the designers will feel comfortable moving this DIY amp forward via the forum.
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Old 31st July 2011, 07:32 PM   #596
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I just looked at the thread and there was some new discussion. I'm always looking forward on papas opinion on the possible solutions presented. I always like to understand more...
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Old 31st July 2011, 08:07 PM   #597
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I did not use a voltage reference but an optocoupler to set the bias the led senses the current passing through the upper fet source resistors and the phototransistor actuates the vgs seen by the upper fet in order to set and maintain the bias. A comparatively large capacitor in parallel takes care of the AC content and limits any adjustment of the bias to very low frequency.

If it is okay with NP I can post my schematic wich I believe is fairly close to the real j2 in a weeks time or so.
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Old 31st July 2011, 08:24 PM   #598
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I would also like to see it in a PN... ;-)))
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Old 31st July 2011, 09:50 PM   #599
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Quote:
Originally Posted by NYCOne View Post
I've asked NP directly, and he's OK with having DIY designs for a J2 clone posted in the forum. He does not want a J2 official schematic out, but short of that, he's indifferent to DIYers posting their creations.
Just for clarity, I find the lack of an official schematic discourages commercial
cloners, so there is no such thing.

Better that you guys exercise your DIY muscles anyway.

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Old 31st July 2011, 10:19 PM   #600
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Maybe tomorrow I draw a new approach with explanations... ;-)))

Papa will laugh at my silly ideas!
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