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Old 14th May 2013, 10:18 PM   #1
RollE2k is online now RollE2k  Sweden
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Default FS: Balanced parafeed Pre-amp pcb's

I made myself pcb's to build my parafeed-linestage, and i now two spare boards left.
The line-stage pcb does have room for cascoded DN2540 CCS for each triode-half, two large coolers, common bias-resistor for both phases in each channel, LL1674 / LL1676 output transformers, and the signal layout is for dual mono (separate gnd for each channel) it is possible to put the two tube heaters in either parallell or series. built for 9-pin tubes with ECC88/6n6p/6h30p/6n1p pinout. No room for PSU, that you'll have to make separate pcb's for.
The circuit is like the Raleigh audio parafeed stage ( http://www.raleighaudio.com/figure_18.htm ) but with cascoded DN2540's as CCS. Schematics is now in post #6 below!

The PCB itself is 10x20cm, 1,6mm thick, 2oz copper and i made it possible to use risers if you want to mount the tubes in horizontal position.

I would want €30 for one board. Drop me a PM..

Click the image to open in full size.

Last edited by RollE2k; 26th May 2013 at 10:18 PM.
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Old 14th May 2013, 10:21 PM   #2
RollE2k is online now RollE2k  Sweden
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oh, and the transformer-pads are wired for series : parallell, which means 8:1 or 4:1 with LL1674 / LL1676.
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Old 15th May 2013, 02:38 PM   #3
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This sounds interesting and will probably attract much more interest with a circuit.
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Old 15th May 2013, 09:52 PM   #4
RollE2k is online now RollE2k  Sweden
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Sorry i totally missed that, but anyway it's pretty much the raleigh audio design, but with cascoded DN2540s as CCS. ( Figure 18 )
So now i've updated the first post, thanks for pointing it out!

Last edited by RollE2k; 15th May 2013 at 10:00 PM.
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Old 17th May 2013, 11:24 PM   #5
RollE2k is online now RollE2k  Sweden
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For those who would like great tube stage, with balanced OR unbalanced output, this is a really nice circuit!
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Old 21st May 2013, 11:19 PM   #6
RollE2k is online now RollE2k  Sweden
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Since i have gotten questions about the boards...
Here comes the exact schematics of the signal circuit on the boards...
NOTE: As said in the text above red squared input transformer is not possible to mount on this board, but is just pictured how to integrate.
Click the image to open in full size.
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Old 30th May 2013, 03:02 PM   #7
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And we try one more time!
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Old 11th June 2013, 11:55 AM   #8
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