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RE: BOM deviations and operating points ...

These are the changes I made to RH84 ver. 2 schematic.

Mostly based on the parts I had at the time and the fact that I was converting another circuit.

R1 = 400K , R2 = 220, R3 = 20K, R5 = 400K, R6 = 180

C1 = .1uF, , C2 = 33uF, C3 = 50uF

D1 = (2) 6.2V Motorola zener diodes in series

B+ = 302VDC T1 = 5K/8

Operating Points: all DC voltages

EL84: P = 293, g2 = 292 K = 10

12AT7 P = 124 K = 1.3

THD = 1.52% @ 1.17W RMS & 2.43% @ 2.75W RMS 3W RMS before clipping

THD measurements @ 1KHz with sine wave input

Summary: I should have build first on a breadboard to make measurements easier to take and followed the signal circuit schematic as per the design ver. 2 using a higher quality OPT than AES PT-31.

That being said, the subjective listening experience was more than good enough on 811B or a set of Magnavox 2-way horns.

I will not make advisements on the power supply configuration, but I did use a LOW DCR type - not low in uF.

Thanks to all for their contributions to this thread.



Edits: 01/24/15
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