This matched pair of RCA Radiotron / RCA CUnningham Radiotron round plate type 56 triodes was tested on our Paul Hart-calibrated TV7/U for shorts, gas and transconductance. There were no shorts or gas.
Tube One measured 52 while Tube Two measured 53 where minimum (65%) is 37.
Tube One has an silkscreened base while Tube Two's is engraved Both tubes have banded-cross, top-mica getters; solid black plates; dimpled foil getters and excellent flashing.
Lastly, a word of caution: In the heading these tubes are listed as 6SN7 substitutes; they are actually 2.5 volt 6J5 substitutes. (A 6SN7 is two 6J5s in one bottle.) This requires a dual adapter to give the equivalent of one 2.5 volt 6SN7. This is only possible if you have an amplifier in which you can change the filament voltage from 6.3 to 2.5.
WE HAVE SCORES OF THOUSANDS OF VACUUM TUBES. IF IT'S NOT LISTED, WE MAY HAVE IT. PLEASE ALSO SEE OUT ETSY SISTER SITE "LOWTECHTWOO" AND/OR CALL OR TEXT US AT 202-372-6931 IF YOU DO NOT SEE WHAT YOU NEED OR HAVE ANY QUESTIONS.
1. MOST FORMS OF SHIPPING -- EXCEPT MEDIA MAIL -- ARE AUTOMATICALLY INSURED UP TO $100. ETSY PURCHASE PROTECTION COVERS ITEMS UP TO $250 IN VALUE. IF AN ITEM IS MARKED "DELIVERED," AND YOU HAVE NOT ACTUALLY RECEIVED IT, THE FIRST STEP IS FOR YOU TO CONSULT YOUR MAIL CARRIER TO GET THE EXACT COORDINATES OF THE DELIVERY AND ARRANGE FOR YOUR ITEM'S RETRIEVAL. IF IT APPEARS THE ITEM HAS ACTUALLY BEEN STOLEN, IT IS YOUR LOSS AND YOUR RESPONSIBILITY TO FILE A REPORT WITH THE POSTAL INSPECTOR. ETSY MAY REIMBURSE YOU EVEN IF IT WAS STOLEN, BUT THAT DEPENDS ON THE LUCK OF THE DRAW.
2. MOST OF THE TUBES WE SELL ARE OVER 70 YEARS OLD. WE CANNOT GUARANTEE FOR FAILURES AFTER POWER UP AS THERE IS NO WAY TO DETERMINE HOW TUBES WILL INTERACT WITH YOUR ELECTRONICS OR IF THEY WERE MISTREATED IN TRANSIT; NOR IS THERE A WAY TO DETERMINE WHETHER THEY MAY HAVE FATAL FLAWS! WE CAN ONLY TEST FOR THE PARAMETERS MENTIONED ABOVE. WE CANNOT TEST FOR CATASTROPHIC FAILURE. IF A TUBE FAILS AFTER YOU GET IT, IT IS YOUR TUBE THAT HAS FAILED. THERE IS A .1 % CHANCE THIS MIGHT HAPPEN. BE WARNED. NO REFUNDS IN SUCH CASES.
3. IN OVER 9000 SALES, WE HAVE HAD A DOZEN OR SO LESS-THAN-FOUR-STAR REVIEWS OR HAVE LOST A CUSTOMER BECAUSE I REFUSED TO EITHER ISSUE A REFUND FOR A TUBE THAT WENT BAD AFTER IT HAD BEEN USED OR A BUYER KNEW NOTHING ABOUT TUBE REBRANDING AND CLAIMED THAT SOMETHING MADE BY TUNG-SOL AND BRANDED BY EMERSON WAS MADE BY EMERSON, AN ELECTRONICS COMPANY THAT NEVER MADE TUBES!
4. TUBES ARE GUARANTEED GOOD ON SHIPMENT. IF YOU FEAR DAMAGE OR LOSS OF PARCEL IN TRANSIT, PLEASE INSURE THEM! OUR SHIPPING RESPONSIBILITY ENDS WHEN THE PARCEL IS ACCEPTED AND SCANNED BY THE US POSTAL SERVICE. ETSY IS CLEAR ON THIS. SOMETIMES THERE ARE INITIAL SCANNING DELAYS. WE HAVE ACCESS TO THE SAME INFORMATION YOU DO AND IT IS YOUR RESPONSIBILITY TO DEAL WITH THE USPS SHOULD THERE BE DELAYS OR LOSS OF A SCANNED PACKAGE. PLEASE BE PATIENT FOR THE FIRST DAY OR TWO IF THE PACKAGE IS STILL MARKED AS "PRE-TRANSIT." WE SHIP THE DAY AFTER THE SALE IF THE SALE WAS AFTER 9:30 AM EASTERN TIME.
5. WE BUY TUBES IN BULK. 10-15% OF THEM ARE NOT SUITABLE FOR HIGH END AUDIO APPLICATIONS. THAT LOSS RATE IS REFLECTED IN OUR PRICES. I LISTEN TO THESE TUBES IN TUBE EQUIPMENT. SOMETIMES TUBES THAT TEST WELL HAVE PROBLEMS AND SOUND AWFUL. THAT IS ALL I CAN DO. IF THERE WERE A TEST FOR FUTURE FAILURE, I WOULD USE IT. THERE ISN'T. THERE IS RISK IN LIFE. THESE PRODUCTS ARE NO LONGER MADE. THERE ARE NO MANUFACTURERS TO TAKE PRODUCT BACK BECAUSE OF DESIGN FAILURES OR QUALITY-CONTROL ISSUES. THE PRODUCT DEVELOPMENT AND IMPROVEMENT CYCLE IS OVER.