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Old 25th February 2011, 11:35 PM   #1
diyAudio Member
Join Date: Nov 2006
Smile 7 channel Preamp

Well, here it is -- I 'completed' the 7 channel preamp several months ago, and I have been too busy listening to music and movies to share it.

Forgive my tardiness!

It is driving an X3 and X250, and meets my modest requirements that it be incredibly detailed and quiet enough that I can't tell if the system is on from my listening chair.

The circuit is a jfet XCCCCSBOSOZ. Basically "metalman's circuit" with various changes to resistor values and transistors. Also, I put back in "P5" for gain control, which metalman's circuit did not have.

Here are a few pictures:
Attached Images
File Type: jpg 2010_NOV 113.jpg (466.4 KB, 142 views)
File Type: jpg 2008_1207 003.jpg (470.7 KB, 132 views)
File Type: jpg 2008_1207 020.jpg (465.5 KB, 129 views)
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Old 25th February 2011, 11:41 PM   #2
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Here are a few more pictures:

Attached Images
File Type: jpg Input and main board.jpg (471.0 KB, 124 views)
File Type: jpg Outputs.jpg (456.8 KB, 123 views)
File Type: jpg Volume control.jpg (474.4 KB, 91 views)
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Old 25th February 2011, 11:42 PM   #3
6L6 is offline 6L6  United States
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Holy cow, that's totally wicked!!

I would love to see more photos as well as a block diagram and schematic. Is it balanced?


Last edited by 6L6; 25th February 2011 at 11:44 PM.
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Old 25th February 2011, 11:46 PM   #4
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You might be able to tell from the pictures that the volume control is only half complete. One signal output ground on the XLR outputs is connected to signal ground. If I ever finish soldering up the other 7 deck 17 position rotary switch, then it will have true balanced outputs. I could not hear a difference with the balanced outputs though, so this is pretty low on my list of things to do.

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Old 26th February 2011, 05:29 AM   #5
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Location: Phoenix, AZ
WOW! But I don't think you have quite thick enough aluminum for the enclosure.



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