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Little Dot I+ Tube Rolling

Discussion in 'Headphone Amps (full-size)' started by mapstec, Sep 16, 2008.
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  1. sling5s
    I don't remember anymore but I did find my answers on Little Dot website.  The site has an Question and Answer section that covers general questions about tube rolling and opamps. 
     
  2. ryencoke
     
    There are several reviews of the LT1364 in this thread. I can't post links (I'm too new still) but look at the top of page 15 of this thread. And also you can use "search this thread" links at top and bottom of this page to find more.
     
  3. ryencoke
    Received my LD I+ today. It came so fast it beat all the tubes/op amps I ordered. So far 2.5 hours on the stock tubes and pretty impressed with it. Next I'll be trying GE 6DT6A which I found at a local store.
    Great dealing with David and incredibly fast getting it, less than 5 business days!
     
  4. gibosi
     
    Congratulations on becoming a member of the Little Dot club! :)
     
    I thought the RCA and Tung-Sol 6DT6A sounded better than the GE's, but I never compared them to the stock tubes and would be interested to hear your impressions.
     
    Cheers
     
  5. kvtaco17
    Spot on with the GE's being behind the RCA's and Tung Sol's... BUT lets not forget the Sylvania's lol
     
  6. boombobby289
    Has anyone rolled Op Amp AD8397?
    AD8397 is used as Op Amp in Hifiman HM-901.
     
  7. gibosi
     
    Searching back through this thread, I can't find any mention of this op amp, so you just might be the first.
     
    I think you should try it and let us know! :)
     
  8. boombobby289
    Has anyone tried to mix the different brand/maker but same family tubes ?
     
    For example, is it ok to mix one WE 408A tube and one GE 408A tube in LDI+?
     
  9. gibosi
     
    It is perfectly safe to do this. However, the WE and GE sound different. And so the tonality of the R and L channels will sound more different than normal.... But again, it is perfectly safe.
     
  10. boombobby289
    What about if I were mixed one Sylvania 408A and one Philips 408A? Some headfiers claimed both are equivalent.
    Any comment?
     
  11. gibosi
    Depends on the year they were manufactured. In the early 1980's Sylvania sold it's vacuum tube business to Philips. So if both were manufactured in the early 1980's, the Sylvania just before the sale and the Philips just after, then they are likely very similar. But a Sylvania manufactured in the 1960's is likely very different compared to a Philips manufactured in the 1980's. And of course this would also be true for GE tubes, or any other brand, manufactured 20 years apart.
     
  12. ryencoke
    Thanks gibosi!
    At the local store that was the only tubes I could find, so didn't have much of a choice unfortunately. As for comparing the GE 6DT6A to stock tubes, it takes me a little too long to switch the jumpers so I can't do a very good A/B test on them. Also found Westinghouse 6DT6A so I will compare them to the GE 6DT6A since that's just a quick tube swap. 
     
    Comparing GE 6HM5 to stock 6JI (on stock opamp):
    GE 6HM5 - Wide soundstage. Nothing harsh about them, very balanced. Only issue, I had 2 bad tubes with high frequencies coming in and out (even after 15hr burn in on them each). Luckily I bought 4 and other 2 were ok!
    6JI - Harsh treble

     
    Headphones used: NAD HP50
    DAC: HiFimeDIY Sabre U2 Async
     
    Also still waiting on the MUSES02 opamp and a few more tubes. Once that comes in I'll take some time to do some more comparisons. 
     
  13. gibosi
     
    I am not sure, but I don't think Westinghouse made 6DT6's. So I believe that the Westinghouse tubes were manufactured elsewhere and Westinghouse simply painted their name on them. You might want to take a close look. If they have the same construction as your GE's, then probably GE made them. If they look different, then perhaps RCA or another company made them.
     
  14. ryencoke
    Good question.
     
    #1 GE 6HM5 and #2 Westinghouse 6DT6A have identical white letters with the tube model and dots below (hard to see in pic).
    #3 and #4 are both marked GE 6DT6A but #3 made in Japan, #4 made in Canada. None of the 6DT6A look very similar in construction..
     
    http://i.imgur.com/vCUAZFc.jpg
     
    #1 - Left: GE 6HM5
    #2 - Middle: Westinghouse 6DT6A
    #3 - Right: GE 6DT6A
    #4 - Bottom: GE 6DT6A
     
  15. gibosi
     
    The dots on the Westinghouse is a positive indicator that this tube was manufactured by GE. The made-in-Japan GE was certainly not made by GE. And I suspect that #4 was not manufactured by GE either. My GE has ribbed plates, like your Westinghouse. The smooth plates on #4 suggest RCA.
     
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