These are absolutely, without a doubt, the finest tubes that can be purchased for the Torpedo.
They are able to push the Torpedo 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.
NOTE: Because of the rarity of these tubes and a current non-audio demand (see below), Beezar is offering these tubes only in tested and matched pairs for Torpedo customers only. For special singles resulting from a poor match or defect, please contact Beezar directly.
Flowery language aside, there's no free lunch with these tubes:
- As stated, they are rare and the non-audio demand is current.
- They can 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.
As always, Beezar 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. If possible, please limit your replacement requests for a tube that rings for a long time.
Beezar will cheerfully replace it.
As with other Beezar tubes, each tube has been personally checked for defects, 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.
Current Beezar stock consists primarily of Telefunken, Amperex, and a mix of other manufacturer's tubes.