thread: ART Tube Opto 8
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Old 10th March 2020
Here for the gear

ART Tube Opto 8 Schematic REVISION

I noticed a mistake in the PREAMP schematic. The actual circuit drawing is correct, but I got dyslexic with one of the part numbers. The parts identified as 2SA790's are actually 2SA970's. This makes a big difference, because '790' is an actual part number....and they definitely won't work! They're Darlingtons...and the 970's are regular bipolars.

My noise problem, the reason I started this thread, was caused by these transistors. I replaced them with transistors I had in stock, some 2N5087's. The 5087's work fine and the repaired channel is just as low noise as the other channels.

I've attached the affected revised schematics. Just download the new files or mark the previous ones with the correct part number.
Attached Files
File Type: pdf Tube Opto 8 Preamp CH 1.pdf (54.6 KB, 7 views) File Type: pdf Tube Opto 8 Preamp CH 3.pdf (58.6 KB, 3 views)