Your tubes have been fully tested on a computer-regulated, USA-made Amplitrex AT1000 on Fixed Bias setting with like new, NOS results (tNOS). Here's what that means: to qualify for this listing, several stringent conditions must be met: The plate current must measure between 36 mA and 54 mA AND transconductance must measure between 3280 uMhos and 4920 uMhos, consistent with original 1943 RCA, Sylvania, GE, and/or Tung-Sol datasheet specifications for new tubes of this type. The tubes must also show no shorts, show a gas current less than 4.5 mA, and a heater-to-cathode leakage of less than 10 microamps (10 uA). The tubes might have mechanical wear or have the label rubbed off - these are very old! Used-testing tubes are available in a separate listing at a significant discount. Every tube you receive from Sound By Doc is guaranteed against failure for 60 days after purchase, an industry extreme!
OPTIONS (use offer feature in Reverb):
Want a regular white box? $1 extra per tube
Want a tube that's packed in its original box? $3 extra per tube
Want the test results recorded on your box, too? $3 extra per tube
Want two tubes that match one another within 3% for GM? $10 extra per tube
Comfortable with a tube that has tape at the base? Save $1 per tube
Comfortable using a replaced guide pin? Save $1 (and get the replacement guide pin included, installed!)
Reverb Buyer Protection
Reverb has your back if your item is lost, damaged, or doesn't match its description. Simply report any issues within 7 days and we'll help you get a full refund.Learn more about Reverb Buyer Protection.
| Listed | 4 years ago |
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| Condition | Very Good (Used) Very Good items may show a few slight marks or scratches but are fully functional and in overall great shape.Learn more |
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Product safety information may be available here.



















