Rare Platinum Matched Pair Sylvania 7N7 Frankenstein Tall Boy Tubes, T-plates, Racetrack Micas. These Sylvania 7N7 Frankie's are great sounding tubes.


7N7 tubes were developed by Sylvania and are equivalent to 6SN7 tubes (with adapters).


One tube was branded as CBS Hytron and the other was branded as Philco, but both tubes were manufactured by Sylvania - as most 7N7 tubes were manufactured by Sylvania (other few by National Union). Lettering on most 7N7 tubes is normally in bad condition due to the fact that it is very easy to come off the glass - the worst of all tubes, even if you just take a 7N7 tube out of its box, some print might just come off due to contact with the box.


Tubes are tested on our military TV-7D/U mutual conductance (Gm) tube tester, which was recently restored and calibrated by Dan Nelson - the King of TV-7 series tube tester restoration and calibration. TV-7D/U test results (also refer to photos for measurements):

  •  Tube 1 Gm: 84 / 90    
  •  Tube 2 Gm: 88 / 88   

* Minimum good for 7N7 tubes on TV-7D/U is 50 (65% of NOS), so

    Below 50 = Low testing tubes
    50 - 77 = Good tubes
    77 and above = NOS tubes

So these two tubes test strong, above the NOS level. Also, tubes are Platinum Matched, tightly within 7% of mutual conductance.

No shorts, no leakage, no gas, no loose base.

Both tubes also have been sound-tested on our modded Dark Voice 336SE headphone amplifier. They sound fantastic, no microphonics, no hissing / crackling / or other noises. Background is dead quiet.

Tubes will come with generic white tube boxes.



Shipping:

  • Tubes will be shipped by Canada Post Small Packet by Air, unless otherwise specified. It normally takes 5 - 10 days to get to US addresses (2 days within Canada, 1 - 3 days on US customs clearance, and 2 - 5 days within US via USPS Priority Mail).
  • Combined Shipping is welcome, if multiple items are purchased. If items have been paid separately, we will refund any savings from Combined Shipping.



International Buyers - Please Note:

  • Postage displayed here is for USA and Canada only. Folks in other countries, please contact us first to inquire about the actual postage so that we can add the country and its corresponding postage to the listing. No shipping to China, India, Indonesia, Vietnam, Italy, Russia, and so on due to lots of reports on lost packages at customs.



Return Policies:

  • Returns will be accepted within 14 days of delivery, provided tubes are in their original conditions - no damages to tubes, factory tube boxes (if there are), or print on tubes; no drops in tube mutual conductance (to prevent abuse); and no removal of our unique stamp on tube glass.
  • Buyer pays for the return shipping cost.
  • To discourage tube trial there will be a 10% restocking fee. Serious buyer only!
  • All our tubes will be imprinted with our unique stamp on the glass. Please do NOT remove the stamp, or else tubes will not be considered ours and return will be denied.