Sound by Doc

I've been accumulating gear for decades, and it's time for me to start letting some go. I love electronics and guitar, although my skill with the latter is much weaker than my skill with the former! I am a retired physics teacher.

Some notes about vacuum tubes:

Our shop uses two computer-controlled stations of the finest vacuum tube testers available, the Amplitrex AT1000.
In contrast to almost all vintage tube testers, the AT1000 tests electron tubes at their actual operating point, up to 500 volts on the plate! Nearly all vintage testers used proportional testing - testing a tube at a small fraction of its operating voltage and extrapolating to its real-world performance. Since tubes are inherently nonlinear, a test at full power is much more revealing of problematic tubes. The AT1000 also features regulated power supplies and digital measurement, so it is reliably calibrated at all times.

The testers are operated in FIXED bias mode, which is more selective to weed out used or weak tubes. Tubes that test as New Old Stock are described as "tNOS," and the range of test values will be shown in the listing. Be careful, because some disingenuous or uninformed vintage tube sellers who use the AT1000 list GM and plate current results from AUTO bias mode, which masks decreases in emission (caused by depletion from use) by forcing plate current to match specifications even if bias voltage is dramatically out of specification. AUTO bias mode is not appropriate as a tool to learn whether a vintage tube's emission has been depleted.

That being said, premium used tubes may be further tested in AUTO bias mode in order to learn more about their performance and possible application in your circuit. In those cases, test results for Fixed and Auto bias will be included with your purchase.

Tubes that test NOS may have been used, but they are electrically indistinguishable from new vintage tubes according to manufacturer data sheets. We define this as within 20% of bogey values for all tested parameters. This is consistent with original European and USA manufacturing tolerances and is also consistent with other trustworthy vintage vacuum tube shops, like Brent Jessee: http://www.audiotubes.com/nosnote.htm. Tubes that test NOS (tNOS) are guaranteed not to fail for 60 days after purchase. Abuse of the tube is not covered by our warranty.

Combining shipping is a very good value! We usually ship tubes within 24 hours.

Shop Website

Tax Policies