Sunfire Classic Vacuum Tube Preamplifier - Manual (Page 22)

22
User's Manual
Changing the phono stage gain
The following gain changes may be
performed by experienced electronic techni-
cians. Your Sunfire Dealer may be able to
recommend a good service/repair shop.
Factory set gain of MM Phono is 40 dB.
The gain may be changed as follows:
36 dB - change R 11 and R 35 to 3.9 K ohms
40 dB - R 11 and R 35 are 2.4 K ohms
44 dB - change R 11 and R 35 to 1.5 K ohms
These resistors are located on the circuit
board close to the Phono stages. They are
identified by white ink lettering. Changing
these resistors will simultaneously increase
the gain of the moving coil phono stage, i.e.,
by the same four dB increments.
Factory set gain of MC Phono is 60 dB.
The gain may be changed independently of
MM Phono as follows:
60 dB - Stock R4 and R28 are 62ohms, 1/2W
65 dB - change R4 and R28 to 33 ohms,1/2W
70 dB - change R4 and R28 to 18 ohms,1/2W
Changing the input impedance
of the phono stage
Change the jumper position on the
headers labeled J6 & J9 to the value recom-
mended by your phono cartridge manufac-
turer. Most moving magnet cartridges work
best at the 47k setting. Moving coil cartridges
typically work best at a lower setting.
Tube type and location
Phono Board
V1 6DJ8 or 6922 MC amp
V2 6DJ8 or 6922 MC amp
V3 6DJ8 or 6922 MC amp
V4 12AX7 MM amp
V5 12AX7 MM amp
V6 6DJ8 or 6922 Infrasonic amp
Line Board
V1 6DJ8 or 6922 Contour amp
V2 6DJ8 or 6922 Line amp/Bal amp
V3 6DJ8 or 6922 Line amp/Bal amp
Note: 6922 Tubes are preferred as they
have less noise and microphonics than 6DJ8s
Appendix
Appendix