Pair of Gold Pin 6922 Amperex USA for RCA [Lot E]

$100.0 Buy It Now or Best Offer
free,30-Day Returns

Seller Store coffeedj
(1153) 100.0%,

Location: Corvallis, Oregon
Ships to: US,
Item: 276774890644

All returns accepted:ReturnsNotAccepted
Amperex:Amperex
Type:E88CC 6922
6922:6922
Country/Region of Manufacture:United States

Old Stock Audio sells the finest vintage tubes and components.WE ALWAYS SHIP PREMIUM PRODUCTS PRIORITY MAIL.ALL our premium products are guaranteed, with replacement or refund. Please see our Primer on testing below to understand how we test. International Returns: Returns must be paid for by the buyer. Please contact us before taking action so we can work out the best plan. Products must always be verified before refunds.________________ FOR SALE: Pair of 6922 AMPEREX USA GOLD PIN made for RCAOn the tube tracer this pair of tubes tests perfect and near perfect for matched sections. Quantity: 2 tubes in this listing. History: Most of these tubes came from a single collector and were stored in a warehouse since the late 1940’s. Therefore, not of all the boxes are in good conidion–and if not they are replaced with either a white or other box. Specifications: Testing at plate voltage of ~100, grid: -2.0V, expected current: ~10.0 ma plus or minus 5%.(Plate voltage varied between 100-110 during testing. All tubes tested at or better than NOS) Note: The 6922 / 7308 / ECC88 are a higher voltage version of the 6DJ8The 6DJ8 is limited to 125V Plate to Cathode, the 6922 is OK to 250V Tube A: 11.5, 11.4 ma 1962 Date CodesTube B: 10.6, 11.4 ma 1963 Date Codes THANK YOU FOR YOUR PURCHASE!!!_____________________________________________ How to test vacuum Tubes. Vacuum tubes must be tested in the manner they are to be used if you want to know how they will perform. For this reason a standard vacuum tube tester is nearly useless to qualify an audio tube. Low power audio tubes and pre-amp tubes (like the 12AX7, 6DJ8, 12AU7, 6922, 12BH7, etc.) are best qualified on a tube tracer. The traces will allow you to see the operation of the tube over the entire working spectrum, literally an infinite region of points. A tube tester looks at ONE single point, and may show a pair of tubes to be identical when in fact it is only an accident that it measures that way!! I have a number of examples of tubes that tested perfectly NOS on a tube tester, but when put on the tube tracer you could see that one channel had completely failed. For power tubes (like the 5881, 6V6, 6L6 KT66/88 EL34/84 etc.) the best method to qualify is to put them into a pure Class A circuit, according to the RCA handbook specifications, and measure the current draw. Often the current match method is used for pre-amplifier tubes, but this is not as good as tube tracing for low current tubes like the 12AX7. Pre-amplifier tubes are voltage devices, so matching the current is not as important as matching the grid/voltage trace. Over time, NOS pre-amp tubes will break in and change their current draw, but they will retain the curve matching characteristic. Higher power pre-amp tubes like the 12AU7 or 5687 can be matched with current draw or tube tracing, depending on how it is used. For example, a 12AU7/12BH7/12AT7/5687 etc. running as a cathode follower usually delivers high current to drive something like a transformer phase splitter or direct output. In this case the current draw match at 80% of listed maximum would be best. If you know what you need, let me know when you order and I’ll make sure to test the proper way for you. Finally, what does a 1% or 5% or 10% match mean on a vacuum tube. Often you will see guarantees of a match within 1%. While this may be true, tubes age and break in, and it is unlikely to hold that close of a match over time. A 5% voltage difference in gain results in less than 1/2 of a dB of output difference. Since the definition of 1 dB is that it is the smallest change noticeable to the human ear, 5% is a sufficiently good number for matching. The question was asked: why not measure and state the mutual or transconductance? The answer: It is not a value that gives you meaningful information, if the tubes already test in the manufacturers specification range. In addition, conductance changes based on circuit topology. Here is an example that helps understand: You can swap a 12AX7 (conductance=1600, gain=100) with a 5751 (conductance=1200, gain=70) with no audible difference, except that the 5751 is a little quieter due to the lower gain. You have to very slightly tweak the volume up, to compensate–that is all. For good quality tubes, the conductance difference will be minimal from the perspective of circuit performance. Further more, selecting tubes on the basis of a single transconductance reading does not guarantee uniformity across the entire working range–this is the same Tube Tester error mentioned above. Conductance is very valuable when designing a circuit–but the designer uses the average manufacturer stated value and expects that tubes will perform in a range around that value. For the user, you want uniformity in the working range, and/or matched current draw at a proper representative power. That is what we supply. Often people ask how long tubes will last. This is a question that is nearly impossible to answer on any specific tube. NOS tubes will have an average life based on power drawn and internal design. For example, some Western Electric switching tubes used for over 100 years still perform like a brand new tube. The rule of thumb is, power output tubes may need changing every 6 months or last 5 years–depending on how hard they are pushed, or how long they are used. Guitar amps are a lot harder on tubes than audio amplifiers. Preamplifier tubes will last longer–12AX7’s may last 15 years, while 6SN7’s may last only 3-5 years, again based on current draw. My circuit designs usually run tubes at levels that are very friendly. Some designers (and I can name a few) like to run everything right at the rails, so my designs will need far fewer tube replacements over time in comparison to theirs. There is no real merit to either design–it’s all a matter of choice and listening preference. To Summarize:1. Never trust a tube that is tested only with a tube tester, for audio purposes.2. Don’t pay extra for matching (on a tracer or class A circuit) to the 1% or 2% level.3. Only buy tubes from sellers that are willing to stand behind the product. 4. All Old Stock Audio tubes are tested using either a tube tracer or Class A circuit – you can buy with confidence and a full satisfaction guarantee.

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