These are absolutely, without a doubt, the finest tubes that can be purchased for the original Torpedo I headphone amplifier. (See my other Ebay listings) They are able to push the Torpedo I into another level of quality and performance. Some have said that these tubes make a Torpedo sound as good as a $1,000+ amplifier - they are that good.

Flowery language aside, there's no free lunch with these tubes:

1. As stated, they are rare and the non-audio demand is current.  They are being harvested worldwide to restore 1940s-1950s computers based on these tubes.  They are used as high-usage, long-life replacements for the 6J6.
2. They may tend toward microphonics, which cannot be determined by a tube tester.*

The history of this tube is that they were manufactured for the early computers and calculators. The IBM CPC was one of these. Here's a link from the Valve Museum: Valve Museum - E90CC (5920) The data sheet for this tube type even states that these tubes are not for audio, but after using many several pairs of different manufacture for months, the only reason for making that statement is that the manufacturers did not want to be liable for the potential microphonics.

* Beezar Audio will replace a microphonic tube. However, because of the rarity of this tube, please try to be accommodating. Some microphonics can be easily tolerated, perhaps echoing slightly only when you tap the tube or the amplifier directly. Other microphonics can ring for several minutes. Despite this, a microphonic tube may sound very, very good.  If possible, please limit your replacement requests for a tube that rings for a long time and is realistically not tolerable. Beezar Audio will cheerfully replace it those cases.

As with other Beezar tubes, each tube has been personally checked for defects, tested on a B&K 747B, the glass cleaned, and the pins straightened/cleaned. Further, because these tubes are offered in pairs, only - they are also matched. As a side benefit, these tubes are tall enough that they can be swapped without removing the Torpedo case lid.  See my other listings for the Torpedo 1 headphone amplifier.

Please contact me if you want pairs of tubes or more in matched mfr and matched tested output.  I will typically need an extra $2 per tube to provide matching, since it means extra work and cuts down on the numbers of tubes I can sell because of the unusable mis-matches.

** I will refund excess shipping charges for multiple quantities. **

NOTE: The photo is representative. These will ship in either their original boxes or plain white ones.