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Old 27th July 2008, 09:13 AM   #1
mattjk is offline mattjk  United States
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Default Help a noob build Pedja Rogic's J-fet buffer

I have one of the original briangt gainclone kits. just got it working and while it sounds good, it is a bit rolled off and weak, dynamically. Same as I have encountered with any amp with a passive attenuator.

so in my searching, I came across Pedja Rogic's J-fet buffer. I want to build one into Peter Daniel's integrated amp case.

questions I had were,

1. Where do place this buffer in the signal path? I assume before the volume pot?

2. Can I use the 25k pot I have now, or do I need a different value?

3. The schematic calls for a 15+15v psu. Can I just add windings to my current 100va toroid?

4. Lastly, will the j-fet be susceptible to hum from the toroid? Will it need to be shielded?

Thanks in advance.
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Old 27th July 2008, 09:30 AM   #2
lineup is offline lineup  Sweden
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you put it after the pot
at the gainclone input
at least this is what i remember

have you read all the JFET Buffer pages at Pedja homepage?
Download:
http://www.pedjarogic.com/srp/gc3.pdf

http://www.pedjarogic.com/gc/index.html

http://www.pedjarogic.com/
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Old 27th July 2008, 10:49 AM   #3
Nuuk is offline Nuuk  United Kingdom
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And look for the recent thread where somebody is having PCBs made for these buffers.
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Old 27th July 2008, 11:07 AM   #4
mattjk is offline mattjk  United States
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found it, thanks!
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Old 28th July 2008, 09:33 PM   #5
mattjk is offline mattjk  United States
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Quote:
Originally posted by lineup
you put it after the pot
at the gainclone input
at least this is what i remember

have you read all the JFET Buffer pages at Pedja homepage?
Download:
http://www.pedjarogic.com/srp/gc3.pdf

http://www.pedjarogic.com/gc/index.html

http://www.pedjarogic.com/

Second link was very informative, thanks.

could not read the first pdf.
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Old 29th July 2008, 04:10 AM   #6
mattjk is offline mattjk  United States
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Anyone seen this?

http://www.passdiy.com/order.htm

Quote:
7/1/08

Watch this space - Pass Labs will shortly be offering PC boards for some of the DIY design projects.

First up is the DIY First Watt B1 buffered passive preamp, to be followed by the DIY First Watt F5 power amplifier.
http://www.passdiy.com/pdf/B1%20Buffer%20Preamp.pdf
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