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RE: Amplitrex 1000 testing MA1 6SN7, matching

Posted by Cousin Billy (M) on November 10, 2008 at 14:52:51

In Reply to: RE: Amplitrex 1000 testing MA1 6SN7, matching posted by Lew on November 10, 2008 at 08:49:50:

Hello Lew

Yes, this is a computer compatible tube tester. I have not yet hooked it up that way, but when I have the time and the patience, it will be done.

I am still using it as a stand alone unit. I am very impressed so far. I have tested my 50 12SX7's. I have about 8 that are both very strong and perfectly matched. The best two pieces occupy V1a of each amp, the next best two V1b and so on. For V4 of each amp I have used the strongest, though not very well matched tubes. Is this OK?. iP Plate 8.8 and 9.6 on one (both have Gm of 3000), and 9.0 and 10.0 on the other (Gm 3000 and 3300). Would these tubes have been OK for V1a or b?. Should I use lesser strengthed but better matched tubes in the V4 position?. I figure these 'drive' the 6AS7's, so strength is more important then closeness.

Jack above seems to think it is the iP which is more important then the Gm. Do you concur?.

I have tested 40 6AS7's. The numbers are all over the board. When I reinstall them (After Ralph upgrades the MA1's with the MA2's power supply, I will be trying to run speakers which dip to 2.5ohms between 80 and 120Hz, please, no comments, I know I know I know, but there is no harm in trying), again, when I reinstall the6AS7's, should I add up all the numbers of each bank and try to balance them. Should I try to add up each row of each amp to the same numbers. Or am I just an excessive compulsive gone mad.

My MP1 mklll preamp has obviously 6SN7's. The front most tube on each side is the most important. These have RCA Grey glass. They are not very well matched 8.6 and 7.8, both with Gm of 3000 on one tube, and 7.2, 7.0, with Gm 2800 each. Is this OK, or should I put my best matched Chinese 6SN7's in this spot?.

All my 12AT7's test 50% with poorly matched sides. I will try to source better tubes.

Thanking everyone in advance.

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