Asymmetric double triode as used in old Ampegs.
Q: When does a preamp tube become a Premium Selected tube?
A: All preamp tubes labeled Premium Selected have passed the following tests:
- Low Noise Test
- Microphonic Test
- Gain Test
- Sonic Tests
- Shock Tests
- Listening Tests
- Balanced Output Test
TAD Premium Selected/Highgrade tubes are guaranteed for a period of 6 months (according to terms of warranties)
for the quality criteria mentioned above.
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