Our Tube Test Equipment

Most common tube testers give results only for emission or transconductance at low voltage - unrelated to the manufacturer’s spec sheets or any amplifier operating points. Trustworthy sellers test with equipment like the AVO testers, computerized cardmatics, or the Amplitrex. These are still rare to see in the marketplace, and have limitations on voltages, currents, tube types that can be tested, conditions for test, etc.

Our tester is a Laboratory Tube Tester. We can test anything, any way we like, up to 1kW and/or 3.5kV on the plate. Combined with good methodology, this means precision test results (<1% accuracy) and REAL matched tubes. While I cannot guarantee the subjective sound of the tube (as this is dictated by your system and where you place the tube in your system), you can be confident that you’re getting an excellent quality part.

Our equipment and methodology will outperform all of the following testers (and more) for accuracy, number and type of tests performed, as well as operating range that can be tested:
AVO 160, Mk II, Mk III, IV, VCM 163; B&K 607, 650, 700, 707, 747; Eico 666, 667, 635, 625; Funke W19; Heathkit TC-1/2, TT-1; Hickok 533, 539C, I-177, TV-2, TV-3, TV-4, TV-7, TV-10, 123A Cardmatic, 600A, 6000A, 752A, 800A; Hickok / Western Electric KS-15560-L2, KS-15750-L1, KS-15874-L2; Jackson 648-S; Maxi Matcher; Neuberger RPG375; RCA WT-110A, WT-100-A; Russian Military L2, L3; Sencore Mighty Mite, TC162, MU150; Triplett 3414, 3423, 3444

Our Tube Test Methodology

All tubes first have their pins cleaned/resoldered as needed before being tested for gas/leakage/shorts.

Tubes are then allowed to preheat, warm up to full operating temperature at datasheet specifications, then allow all readings to stabilize. We also operate both halves of a dual triode (or other multi-section tube) at full voltage and current during testing. This is done to allow for thermal stabilization: when you operate a tube, it’s structure changes shape as it heats up. These changes manifest as changes in transconductance, plate current, power output, and gain (mu), so to even get an accurate reading of a tubes parameters, it must have all sections operated at full test voltages/currents until those readings stabilize.

In addition to socketing, our test setup consists of multiple low noise regulated DC power supplies, low noise precision 1khz sine generator, and a precision load testing jig. All readings taken either directly or via a 1 ohm 4-wire 0.5% wire wound resistor using shield/guard probes with a calibrated HP 3456A 6.5-digit digital voltmeter.

If a set of tubes are advertised as “matched”, the seller must have tested the tubes at real world operating conditions and list values <10% for both transconductance and plate current for each section of each tube (as well as power output if they’re output tubes). If you don’t see those values, the tubes you are buying are NOT matched. TV-7 or similar tester values are not acceptable on their own.

About The Tubes We Sell

• ALL tubes failing tests for residual gas/leakage/shorts/”life”, with below TV-7 minimum/<50% of datasheet/unstable transconductance, or with unstable operating points under full power dissipation are destroyed.

• A tube will only be listed as “new” if it is or was in the original box, otherwise it will be sold “tested as new” (if it tests as new, anyway). As for a minimum “good” test value, I will be rejecting any tube that has less than 50% of the data sheet transconductance or full power output.

• The transconductance of most new tubes can be +/-25% of the value listed on the data sheet, therefore a tube can be considered as meeting new spec if it is within this range.

• Power output tests, used in conjunction with transconductance, will indicate if a tube is used and will be listed as such.