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Post by donnyp on Mar 1, 2007 17:45:39 GMT -7
1) Anyone out there know how many milliamps the GTE-34LS's in the SRZ-65 Limited Edition should be biased at? I'm getting a reading of 32 Milliamps on tube #1 and 26.5 Milliamps on tube #2.
2) Also, I found an old Mullard GZ-34 and installed it in the SRZ. The bias remained very close to 32 milliamps which was the reading I got with the stock Sovtek GZ-34 it came with. Can I assume that the old Mullard is a good functioning rectifier tube if I get the same bias readings?
Thanks!
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Post by myles on Mar 1, 2007 18:26:57 GMT -7
1) Anyone out there know how many milliamps the GTE-34LS's in the SRZ-65 Limited Edition should be biased at? I'm getting a reading of 32 Milliamps on tube #1 and 26.5 Milliamps on tube #2. 2) Also, I found an old Mullard GZ-34 and installed it in the SRZ. The bias remained very close to 32 milliamps which was the reading I got with the stock Sovtek GZ-34 it came with. Can I assume that the old Mullard is a good functioning rectifier tube if I get the same bias readings? Thanks! First .... if you have about 450 plate volts, 35-36mA is about the range where I would start. You can fine tune from there. Second .... if the Mullard makes sound come out of the amp it is a good tube. Third.... you are about 20% apart on the two tubes. This is almost considered not matched. Your tubes will wear faster, there will be more hum in the background, and you will loose sustain. This is probably an issue because one of the tubes bounced in shipping or was mishandled at some point. But ....... since we are talking SRZ-65, and I am making what may be an incorrect assumption but think this is a new amp .... and the amps have not been out that long .... and the output tubes carry a 90 day warranty (preamp tubes are six months ... 180 days) .... then I would call Rick Benson toll free at GT at 1-800-459-5687 and tell him you talked to me and I told you to call him because the tubes "are not matched" and he will replace the duet under warranty. Tell him you want E34LS #6's. You could see 3mA spread at idle or less. On a curve tracer and operating they would be exactly matched across the entire operating range. 6mA spread it too far off match and not typical at all of GT processed tubes. Happy playing.
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