[Noob Alert]
I have a number of NOS EL34s that I need tested so I can run them as matched pairs in a pair of Quicksilver Mid Mono amps. (My pair of amps have pin jacks to allow for meter use in setting the bias of each pair of power tubes.)
Due to Murphy's Law of Moving (stuff is never in the right box) I no longer have the data sheets. The shop I purchased the tubes from is no longer in business. So I looked at tctubes.com. Their Standard test includes current draw (mA) and transconductance (Gm) in the actual readings (upon request) for each tube. In requesting a quote they also supplied me with a sample AT1000 data sheet (attached) for a typical EL34 which would be part of their Premium test.
a) Is the data in the Standard test sufficient for me to match up the tubes to a reasonable extent?
b) Or would it be necessary (or even worth the doubled cost per tube) to get their Premium testing done?
TIA for any comments or suggestions. 🙂
I have a number of NOS EL34s that I need tested so I can run them as matched pairs in a pair of Quicksilver Mid Mono amps. (My pair of amps have pin jacks to allow for meter use in setting the bias of each pair of power tubes.)
Due to Murphy's Law of Moving (stuff is never in the right box) I no longer have the data sheets. The shop I purchased the tubes from is no longer in business. So I looked at tctubes.com. Their Standard test includes current draw (mA) and transconductance (Gm) in the actual readings (upon request) for each tube. In requesting a quote they also supplied me with a sample AT1000 data sheet (attached) for a typical EL34 which would be part of their Premium test.
a) Is the data in the Standard test sufficient for me to match up the tubes to a reasonable extent?
b) Or would it be necessary (or even worth the doubled cost per tube) to get their Premium testing done?
TIA for any comments or suggestions. 🙂
It would be best if the tubes have already been broken in for a couple of hundred hours first before the testing,
to stabilize their characteristics. Your amps can only adjust the output pair's total current, not each separately.
These amps should have the output tubes closely matched for DC plate current at their nominal operating points.
Also for lowest distortion, they in addition should have similar transconductance as well. Unless you have at least
a dozen tubes of the same mfr, there may not be good matches.
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I'd just go with the standard testing - that is, unless you plan to run them at a voltage that's outside of the expected 'bogey' tube testing parameters. And even then..
TC does a great job, and if the situation dictates, they will test under pretty much any conditions you ask.
TC does a great job, and if the situation dictates, they will test under pretty much any conditions you ask.
Agree with this. TC uses an amplitrex which will test at working voltages to give the most reliable results. As long as the tube is given a good 20 minutes to heat up before the test it will be very accurate. If you can find someone local with a Maximatcer that is the second best tester to use. A tester that uses real world voltages make the difference.
In fact, they have 2x Amplitrex plus a large complement of vintage and custom test gear, all specific to tube testing. TC knows their stuff, and has enough experience with the various types, styles and vintages to know how and what to expect from them. Depending on the type, age etc. they may run each tube several times - once on arrival, once in the middle of the conditioning process and then again for a final test.
Between tests, the tubes may be left to 'cook off' (on heater only, or at light bias) for hours or even a day or more, until they are happy that everything is stable and they can collect good data. You're getting what you pay for.
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