Wolfbane Posted March 6, 2016 Share Posted March 6, 2016 This is what RCA came up with in the later half of the 1950's to make that happen: Quote Link to comment Share on other sites More sharing options...
mike stehr Posted March 6, 2016 Share Posted March 6, 2016 Nice tube tester...I could only imagine the going rate for one of those. Quote Link to comment Share on other sites More sharing options...
Wolfbane Posted March 6, 2016 Author Share Posted March 6, 2016 Nice tube tester...I could only imagine the going rate for one of those. I've used a few of the laboratory grade testers including the Amplitrex AT-100, Triplett 3444 and both the early and late versions of the RCA WT-100A. For precisely matching tubes I prefer my WT-100A. Especially if you own multiple tubes and/or tube equipment. I use the Triplett 3444 as my field tester and have borrowed my friend's AT-100 for testing my VT-4C/211 tubes. If the RCA Tester was still being made today it would retail for $6,000 US dollars. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted March 6, 2016 Share Posted March 6, 2016 That would be a great way to make a database for all the tubes in your collection. In fact you would need to make a database if you wanted to get into that 1% match. I have four EL-37 Mullard's I'd like to test on a machine like this to see how close they are. They power my two Fisher 80-AZ mono amps. I don't even own a tube tester at all, but who knows, maybe some day I'll drop some coin on one. Doubtful it will be anywhere near this caliber. Quote Link to comment Share on other sites More sharing options...
Wolfbane Posted March 6, 2016 Author Share Posted March 6, 2016 That would be a great way to make a database for all the tubes in your collection. In fact you would need to make a database if you wanted to get into that 1% match. I have four EL-37 Mullard's I'd like to test on a machine like this to see how close they are. They power my two Fisher 80-AZ mono amps. I don't even own a tube tester at all, but who knows, maybe some day I'll drop some coin on one. Doubtful it will be anywhere near this caliber. Perfectly matched pairs/quad, etc. are not required for most tube equipment. Some amps allow single tube bias, other by channels. some self bias. I don't know what Brent Jessee charges. If you were up here in the GWN, and local, I could test them for you. I like to test a tube the first time on the WT-100A and then my Triplett 3444 and then cross compare my results between the two. You can also use the RCA Tester to check other calibrated tube testers to see how accurate your test results are. I have two of the WT-100A Units, an early unit and a late unit. If we start driving south to our place in AZ more often I may at some point haul one of them down with me. It weighs ~80lbs and takes up at least 1/2 of my car's trunk though which would make a hauling it on a long trip a painful process. 1 Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted March 6, 2016 Share Posted March 6, 2016 Having tubes which are "matched" using the tester shown above (or any tester which uses only a single operating point) can be very misleading. Yes, in push-pull amps it can make it easier to set the dc balance of the output stage. As to performance under signal conditions, such matching ensures nothing at all. We also need to remember that tubes, even from the same production run, will not age identically. So, after some number of hours, one tube may be quite different from the other. The only way to truly match power tubes is with a curve tracer (a fairly rare entity these days), and the only company I know of which uses one is AEA. And, for small signal tubes, or output tubes used in single ended amps, I personally think that matching is unnecessaryhttp://aeaaudio.com/tube-testing/http://aeaaudio.com/matching-tubes-with-a-curve-tracer/Maynard 1 Quote Link to comment Share on other sites More sharing options...
toolz Posted March 6, 2016 Share Posted March 6, 2016 Very informative. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 7, 2016 Share Posted March 7, 2016 Good old Brent Jessie he has been made go too guy for vintage tubes for 15 years. Very honest and stands behind what he sells. I sure would like to get my hands on one of those RCA tube testers for my collection. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 7, 2016 Share Posted March 7, 2016 Having tubes which are "matched" using the tester shown above (or any tester which uses only a single operating point) can be very misleading. Yes, in push-pull amps it can make it easier to set the dc balance of the output stage. As to performance under signal conditions, such matching ensures nothing at all. We also need to remember that tubes, even from the same production run, will not age identically. So, after some number of hours, one tube may be quite different from the other. The only way to truly match power tubes is with a curve tracer (a fairly rare entity these days), and the only company I know of which uses one is AEA. And, for small signal tubes, or output tubes used in single ended amps, I personally think that matching is unnecessary http://aeaaudio.com/tube-testing/ http://aeaaudio.com/matching-tubes-with-a-curve-tracer/ Maynard I pretty sure Brent uses a curve tracer also... Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 7, 2016 Share Posted March 7, 2016 That would be a great way to make a database for all the tubes in your collection. In fact you would need to make a database if you wanted to get into that 1% match. I have four EL-37 Mullard's I'd like to test on a machine like this to see how close they are. They power my two Fisher 80-AZ mono amps. I don't even own a tube tester at all, but who knows, maybe some day I'll drop some coin on one. Doubtful it will be anywhere near this caliber. Perfectly matched pairs/quad, etc. are not required for most tube equipment. Some amps allow single tube bias, other by channels. some self bias. I don't know what Brent Jessee charges. If you were up here in the GWN, and local, I could test them for you. I like to test a tube the first time on the WT-100A and then my Triplett 3444 and then cross compare my results between the two. You can also use the RCA Tester to check other calibrated tube testers to see how accurate your test results are. I have two of the WT-100A Units, an early unit and a late unit. If we start driving south to our place in AZ more often I may at some point haul one of them down with me. It weighs ~80lbs and takes up at least 1/2 of my car's trunk though which would make a hauling it on a long trip a painful process. Actually basic matching is technically required for best performance with output tubes regardless of biasing arrangement...in other words you don't want wildy mismatched tubes which is what you get if you order them unmatched. Basically you end up with the rejects that could not be matched which is never a good thing.. Quote Link to comment Share on other sites More sharing options...
Wolfbane Posted March 8, 2016 Author Share Posted March 8, 2016 Having tubes which are "matched" using the tester shown above (or any tester which uses only a single operating point) can be very misleading. Yes, in push-pull amps it can make it easier to set the dc balance of the output stage. As to performance under signal conditions, such matching ensures nothing at all. We also need to remember that tubes, even from the same production run, will not age identically. So, after some number of hours, one tube may be quite different from the other. The only way to truly match power tubes is with a curve tracer (a fairly rare entity these days), and the only company I know of which uses one is AEA. And, for small signal tubes, or output tubes used in single ended amps, I personally think that matching is unnecessary http://aeaaudio.com/tube-testing/ http://aeaaudio.com/matching-tubes-with-a-curve-tracer/ Maynard The RCA WT-100A Tester (above) can test filament current to 10 amps AC (up to 30 watts) 250MA DC maximum filament current. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted April 3, 2016 Share Posted April 3, 2016 I still play around with my Hickok 600a tube tester, trying to measure if my tubes are getting tired or if they are matched well ( I run both 2A3 and EL34 PP amps in my systems). Not sure it is really good enough for accurate matching, but it at least shows when two tubes are not near each other so I don't pair them. T Quote Link to comment Share on other sites More sharing options...
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