Aleph "MJ" using SemiSouth SJEP120R100 outputs - diyAudio
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Aleph "MJ" using SemiSouth SJEP120R100 outputs

Posted 8th August 2010 at 09:29 PM by Tea-Bag
Updated 9th August 2010 at 12:34 PM by Tea-Bag

So I believe I am finished with the Mini-A version modified for SemiSouth R100 output. The MJ is not in reference to Michael Jackson, rest his soul. Simply a reference to Mosfet input, JFET output.

Technical pieces:
R8 is a 1K pot. This allow for some DC offset adjustment.
R18, This affects drain current to differential pair. This value is lowered. I chose 220R resistor since I have a bunch of them. Papa presented this as needed on mod's in general for the lower VGS of the R100 (~1.5v)
R19, gate resistor to Power JFET R100. This is lowered to 47R. We see with F1J and F2J that gate resistors are lower.


Rail Voltage is +/-24v
Source voltage is .425v and is largely determined by the 100K pot settings and heatsinks on hand. The real value of the pot is ~ 70-80k here. I let the IRF240's run no higher than 65c and R100's no higher than 70c.


Sound

Previously I had R18 at 392 default and R19 at 220. Once I changed these The sound became even smoother, with detail and resolution improving at the same time. Before their was a touch of glare. Now the midrange blooms as we expect. I feel the project is now worthy of sharing. It's got a fairly 'fat' bottom end, and of course not the control of the F5, but is close in resolution, and offers a more mellow smoothness. I wanted to do this as a simple and low cost implementation voltage output using R100's and also take advantage of the higher dissapation of the IRFP9610's. They run a bit hotter now.

Included is modified schematic.

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