Pair Amperex USN CEP 6922 Vacuum Tubes - SOLD
Offered on behalf of a third party is a pair of Amperex USN-CEP-6922 vaccum tubes. These have gold pins and a halo getter. Tube #1 has an etched date code of *4L, and tube #2 has an etched date code of *3E.
I have gone to the extra effort of double testing these tubes on a Weston 981 III and Kaye Small Signal Tube Checker (just back from a checkup by George Kaye).
On the Weston 981 III, min (65%) value is 1350, making about 2075 “theoretical” 100% (Gm = 6X meter). The results are as follows (rounded off to the nearest 50):
Tube #1 1850/1800
Tube #2 1950/1900
These values are all within 10%, so these two can be considered a reasonably well matched and balanced pair.
As indicated above, I went to the added step of testing these on a Kaye Small Signal Tube Checker. For those not familiar with the Kaye Small Signal Tube Checker, this device was sold some time back by Kaye Audio, and provides an INDICATION (see my TERMS AND CONDITIONS below) of noise, microphonics, gain and distortion.
I do not use this piece of equipment very often, but it does provide what I believe to be useful information. UNFORTUNATELY, I DO NOT KNOW EXACTLY HOW THIS INFORMATION TRANSLATES INTO REAL WORLD PERFORMANCE.
The noise and microphonics tests are totally subjective as they involve actually listening (the unit has a built in headphone jack), and I do not have a lot of experience judging, but here is my view.
I define "noise" as the noise a tube inherently makes (after proper warmup). This often exhibits itself as pops, crackles and swooshing sounds. No amount of damping or anything else should affect this parameter, although the conditions under which a tube is run may make a difference (and it may change over time as the tube ages).
I define "microphonics" as the noise a tubes makes with external stimulus that I induce (like tapping), or where the tubes acts like a little microphone. This often exhibits itself as a ringing that can vary from slight that is transient (like a small bell), to excessive that is extended (or does not stop, like a gong). Tube damping, for example, might have an effect on microphonics.
In the Kaye, the tube sits out in the open, so is subject to all environmental stimulus (which has a negative impact on noise and microphonics). The Kaye tester instructions actually recommend to keep the tester away from sources of electrical noise, such as transformers and fluorescent lights (how do you do that in the real world), and even shield the tube from light.
By the way, I have NEVER tested a tube that was totally immune from some level of microphonic response.
To get to the point, I rate the tubes for noise and microphonics on a scale of 0-5, with 0 being worst and 5 being best. The results are as follows (triode 1/triode 2):
Noise Microphonics
Tube #1 3/3 5/3
Tube #2 5/5 5/3+
Just as a note, it appears that Triode #1 on the Kaye corresponds to Triode #2 on the Weston, and vice versa.
Tube #2 appears to be a bit better for noise and microphonics than Tube #1. These are clearly better than average, but not the best I have ever tested. My estimate is that a tube pro might sell this pair as line grade (not good enough for phono grade, but better than driver grade).
Again, however, I must stress that I have no idea how these tubes might perform under real world conditions in real world equipment.
The gain test is supposed to measure the gain of a tube in a class A circuit, cathode bypassed, with a -10 db 500 hz tone applied to the grid (please don’t ask me what this signifies), and involves reading a meter (spec for 6DJ8 type is 27db). The results are as follows:
Tube #1 28/28
Tube #2 28/28
The tube gain thus appears to be better than spec and balanced between triodes.
The output/distortion test is supposed to show the maximum output a tube can produce (measured in Volts, with spec being around 50) at 10% distortion. I do not, however, know how this might translate to sound. All tubes were above the 50 V mark on all triodes.
In any event, this apears to be a nice and balanced pair based on the test results.
I can provide additional information or pictures upon request.
GENERAL TERMS AND CONDITIONS – PLEASE READ CAREFULLY
Please note that these tubes are being sold ‘AS IS’, but I will guarantee against a material misdescription in the listing. In such event, I will refund purchase price less shipping upon return of the tubes in the same condition as sent.
PLEASE NOTE THAT I CANNOT GUARANTEE (OR EVEN REMOTELY PREDICT) HOW THESE TUBES WILL SOUND OR PERFORM IN YOUR EQUIPMENT. THE TEST RESULTS ARE ONLY PROVIDED AS AN INDICATION OF TUBE PERFORMANCE IN A VERY LIMITED (AND NON-IDEAL) ENVIRONMENT. OTHER THAN AS SET FORTH ABOVE, I EXPRESSLY DISCLAIM ANY LIABILITY WITH RESPECT TO THESE TUBES OR RESPONSIBILITY FOR YOUR USE OF THEM.
Money order/cashiers check/personal check preferred, but all (other than US Postal money orders) must clear my bank first. I also accept Paypal for convenience (but add 3% to the total for USA, and 4% to the total everywhere else).
Trade value might be considered, particularly for vintage EL34/6CA7 and 6550 tubes. In any event, feel free to propose something (tubes or audio equipment) and I will at least consider it and respond.
Shipping in the USA via US Postal Priority Mail is included. If you are outside the USA, contact me for a shipping quote.
Please check my feedback on Audiogon, Videogon and Ebay (ID=baileyler) and buy with confidence.
