6SN-7's, do you own an Amplitrex Tube Tester?

OTL Asylum

OTL, Output Transformerless Amplifier User Group.

Posted by Cousin Billy (M) on January 20, 2015 at 05:25:36

In Reply to: RE: 6SN-7's posted by Catastrofe on January 7, 2015 at 05:20:23:

I can't stress strongly enough how important a great tube tester is. The Amplitrex allows us to test in both fixed bias, and continuous bias mode. In continuous you get a true reading of how a tube behaves, especially as it warms up.

You start by testing in pairs. Look to see how the left and right banks age. Upon completion you total the readings from each bank. Don't just total GM. Voltage V is just as important. The first thing you'll notice, over time, the banks equalize themselves. What a great amplifier the MA-1 is.

Since your strongest 6AS7's do more work, they age a little quicker. After time things start to balance. Pay attention to have the same number of newer stronger tubes per bank.

I have never replaced all the tubes at once. Be careful to add up the totals of each banks tubes. It is preferable not to have one side stronger than the other. Placement in the bank appears not to make a difference.

Years ago Jack Williams commented that while GM is important, make sure the V (for voltage) is also well matched. Discard any run away tubes. These are the one's that just keep rising while under testing. I'll guess that I encounter one out of every twenty I test.

This post is made possible by the generous support of people like you and our sponsors:

Follow Ups Full Thread

Topic - 6SN-7's - throwback 07:18:11 12/28/14 (16)

Tung-Sol roundplates! I'm quite late to this discussion, and you've probably done... - jeffreybehr 16:33:34 03/21/16 (0)

RE: 6SN-7's - throwback 20:24:09 01/04/15 (7)

RE: 6SN-7's - throwback 07:39:39 01/05/15 (3)

RE: 6SN-7's - Catastrofe 05:20:23 01/07/15 (1)

6SN-7's, do you own an Amplitrex Tube Tester? - Cousin Billy 05:25:36 01/20/15 (0)

RE: 6SN-7's - Lew 07:51:55 01/05/15 (0)

RE: 6SN-7's - Lew 07:24:22 01/05/15 (0)

RE: 6SN-7's - Cousin Billy 04:04:23 01/05/15 (1)

Quick ebay search - Cousin Billy 05:14:20 01/05/15 (0)

If you have a 5-driver-tube MA-1 - Ralph 12:06:40 12/31/14 (5)

RE: If you have a 5-driver-tube MA-1 - MP 06:44:51 09/09/23 (0)

RE: If you have a 5-driver-tube MA-1 - throwback 10:19:03 01/04/15 (0)

RE: If you have a 5-driver-tube MA-1 - Banat 09:09:22 01/01/15 (2)

Hi, Banat…. - Lew 08:19:08 01/02/15 (1)

RE: Hi, Lew - Banat 12:38:07 01/02/15 (0)

RE: 6SN-7's - Lew 20:30:21 12/28/14 (0)

Follow Ups

6SN-7's, do you own an Amplitrex Tube Tester? - Cousin Billy 05:25:36 01/20/15 (0)

Post a Message!