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Darkvoice 336i & 336SE Tuberolling PartII

Discussion in 'Headphone Amps (full-size)' started by heatfan12, Jul 31, 2008.
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  1. JKDJedi
    Good start. Curious how all the JAN tubes you have compare to the grey glass.
  2. JKDJedi
    Any idea what year this tube might be? The dates are rubbed off and can barely make out the two digit code it has, G5 or 33, what grabbed my attention was the old RCA logo before they changed it in the 50's, 60's?
    Last edited: Aug 26, 2019
  3. sennfan83261
    If "G5" is indicated on that 6SN7GT (it looks that way to me), then it is a private-brand non-OEM tube with a shipping date of June, 1945 (see "2. RCA DATE OF SHIPMENT" in the source below). From 1936-1945, RCA tube date codes went by "Letter-Last Digit of the Year-E," where the "E" is indicative of an OEM shipment. If the terminal "E" is missing, then it is a non-OEM shipment. Hope this helps!

    Source: http://pax-comm.com/rcadates.pdf

    EDIT: For old RCA tubes, the "G5" on your tube is the date code, lol. No other date should be indicated thereon.
    Last edited: Aug 27, 2019
    JKDJedi likes this.
  4. JKDJedi
    I had a dual setup planned to share with you guys but that experiment didn't pan out, I had planned to roll a dual 6BL7s in the 6AS7 slot as mentioned in the 6AS7 thread. The Darkvoice might not be able to handle the 3amps this setup would pull ( vs the 2.5 amp 6as7 tubes draw from it) So a member suggested (6BL7 thread) to just roll a single tube in the 6AS7 slot) I have and am surprised this works. And sounds better than I expected. Does not get hot since it's only drawing 1.5 amps. Volume is now at 12 to 1 o'clock as you would suspect from the smaller push but no distortion or added hiss at all....very quiet.
    IMG_20190830_172230.jpg IMG_20190830_172238.jpg 00100lPORTRAIT_00100_BURST20190830172329526_COVER.jpg
  5. volly
    Very cool experiment bro, congrats on the sound! The tubes look clean aF!

    I've now settle the the 6080WA JAN RAYTHEON NOS and a Tung Sol Dumont USA 6SN7GTB, very happy with the combo and I have a RCA 6080 to try out later but for now this is it but I might look at the 6BL7's a try! Thanks for sharing bro!

    JKDJedi likes this.
  6. Xibipiio
    Thanks for trying that for us!
    I’ll definitely give it a shot, as I have a few 6SL7s around. I wonder how a 6BX7 would do in in 6AS7G slot?
  7. JKDJedi
    Not sure about those tubes, and still haven't given up on the dual setup, they messed up on my adapter from China, so currently talking to some dude in Bulgaria to have a custom one made for me.
  8. Keno18
    @JKDJedi, I think you had asked about using a turntable with the DV. I just set up one with mine with a phono preamp and it sounds great. So yeah, it works.
    DarkDrummer and JKDJedi like this.
  9. Slade01
    Would you happen to know if the VT-99 carries the same designation weight as a VT-231? Meaning, is it just labeled that way to indicate military use but the same construction/production specs as regular 6F8Gs?
  10. JKDJedi
    I was wondering the same...seems to be just that. A military designation. Read your question again... Your asking if these tubes are built different from the consumer versions..
    Last edited: Sep 4, 2019
  11. Slade01
    Fascinating history of tubes. So I came across something from Sylvania had akin to a newsletter that provided cross listings of military designations (e.g. VT labeling) to its consumer counterparts especially during the war times where commercial suppliers may have been called upon or needed to provide replacements at various locations in the country. So I suppose the inference is that they are the same tube in construction and specifications. I am not completely 100% on this of course, but right now, that is what the i'm led to believe so far.
  12. Slade01
    Yes, was questioning if VT tubes were build differently than consumer. Based more of what I have come across, the VT is just another label, but same construction. I guess I got caught up in the idea when I first read about military grade tubes with the 6080s, where the 6080W- variants are more rugged in construction and said to last longer, etc., so and that maybe true for those tubes, but not for the "VT" series. So I get it in my head that anything military designated may or could be different in design. But for the 6F8Gs and VT-99, they seem to be one and the same.
    Last edited: Sep 4, 2019
    JKDJedi likes this.
  13. JKDJedi
    I think anything with a VT is just a label for the military. RCA for example, t(have a more rugged design which are the 5692.) their VT tubes are same as consumer tubes, probably the same across the board with all manufacturers.
    Last edited: Sep 4, 2019
  14. sennfan83261
    This. From looking at the 6SN7 reference thread, only JAN and 6SN7W variants have been mentioned to be potentially different from that of their civilian counterparts, the former being stress tested (just a small batch of the lot though) and the latter supposedly having a 10,000hr life (debatable). Then again, with Sylvania 6SN7W metal bases, I've seen complaints [TubeMaze.info] about how quickly the user's supposedly NOS tubes fizzed out on them. Makes me wonder about the reliability of these tubes for mission critical operations back in the day (hello transistors!). Then again, the ones on the market could simply be rejects found in a dusty warehouse somewhere and marked up and advertised as NOS, rugged military-grade tubes when offered for sale.

    Bottomline: who knows? ¯\_(ツ)_/¯
    Last edited: Sep 4, 2019
    Slade01 likes this.
  15. JKDJedi
    So I finally got the nerve to grab a GEC tube, a pair actually, I'll post thoughts on the tube when they get in. :wink:
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