Any opinions / reviews on Gemtune APPJ PA1502A

Discussion in 'Headphone Amps (full-size)' started by mortus, Sep 6, 2015.
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  1. DavidK35
    That 2nd adaptor you link I bought also but I did not like the open structure, so i emailed xulingmrs. He suggested to put heat shrink on it but i did not like that either, so I ordered a custom one with solid cover like all the others. Cost $15.90 + shipping, looks great. Should have pics shortly with custom base I made of solid Padauk wood + mounting feet to beef up its appearance.
    Maxx134 likes this.
  2. DavidK35
    So I just tried a Sylvania 14F7,
    And I did get back more gain.
    I am not sure which manufacturer you tried, but I am getting a more lively presentation over the "AF" type, and it sounds great.
    I seem to have replaced the slight relaxed nature of the "14AF7" tube, with a bit more "live" factor, while hearing more depth.
    So now these 14F7 are my favorites! Lol
    I probably need to try a Sylvania in the 14AF7[/QUOTE]

    Thats the great thing about tubes, there is a flavor to suit everyones taste.
    Last edited: Oct 18, 2017
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  3. baronbeehive
    I bought the adapter from the first link and its ok but looks a bit odd due to its shape.

    Just received my Tungsol 14AF7, and first impressions are very favourable, I will report back after a bit more listening. I took a bit of a chance with it buying it with no test data but it looks and sounds NOS so I think I got away with it. I also have bought an RCA 14F7 to see if it is indeed more forward sounding, if that's the case it should be OK because the RCA sound should smooth over that.

    I don't know how you came across these tubes but it looks like you are on to something here, I would never have thought of them as a 12AX7 substitute. I'm not sure about them all being rebranded Sylvanias though, the one I've got looks typical Tungsol construction, I've never seen a Sylvania like this before. If it was Sylvania it would have to be made in their factories and so I don't see how it could look like a Tungsol. I know that manufacturers used to get bulk orders to satisfy and often had to buy up other suppliers stock when they couldn't meet demand.

    I read somewhere that the loctals were produced when they needed a tube with shorter pins because the longer pin variety were picking up interference, so maybe they are actually an improvement.

    I've been finding that my system seems to be getting even better and more open sounding lately and wondered if it was because of the longer burn in time for the caps I put in, this is possible because I don't bother burning in now and just note any differences over time.
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  4. DavidK35

    Read about them years ago in Head-Fi & been using them ever since. The only thing you have to remember is, what heater voltage your amp is wired for. This will determine wether you use a 14AF7 or 7AF7. Sometimes the driver tube is 6v & power tubes 12v etc, you have to confirm with amp manuf. first. Part of the impetus with these was for airplanes in WWII, they were developed to prevent them from falling out during difficult manouvers that could happen with octals. But it required a new line to be set up for manufacture, so some, maybe not all would just re brand them but were made in the Sylvania factory. The only drawback if you can call it that is there is 3 basic flavors, however since IMO they are all better than any 6/12/SN/SL7 anyway, the problem is mute.
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  5. DavidK35
    p.s. I just replaced the 5670 tube in my dac to a 7AF7 with adaptor and WOW the Gemtunes is really amazing now. I informed the DAC manuf of my mod & he says I am the first to try this LOL.
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  6. Maxx134
    OMG can you imagine the poor sap that did a fancy maneuver and had his tubes fall out! lol.

    This is quite an eye opener for me to experience.
    Dam, now I wondering now how the 7af7 would sound on my bigger Amp which now using a 6SL7 type.
  7. baronbeehive
    Ha ha..... that's the last thing you want to happen in the middle of a tricky manoeuver lol.

    Looks like the entire mods thread will have to be rewritten.......!!
    There are many more tubes that could be used that have been ignored also. I remember John in the LD thread tried tubes similar to this which were also very good and cheap, but without re-reading the entire thread I can't remember what the tubes were.

    Edit: I think they were 6f6's. I remember trying the Raytheons.
    Last edited: Oct 20, 2017
  8. DavidK35
    A couple of pics for you.

    001 (3).JPG

    005 (3).JPG
  9. baronbeehive
    I know how you feel now, I've had the TS 14AF7's for a couple of days now and I can confirm what you guys are saying, it is a great tube. On a head to head with the TS5751 I would say that it is marginally less silky and more realistic and live sounding, the treble is marginally more extended and neutral sounding, and the soundstage is marginally more realistic and equally open sounding as the 5751. It is really great, I can't make up my mind however if it is better than the 5751 because I really love that silky sound, but I can vary this with a more live sound if I want to now so I will keep them both and I think I will rank them first equal for different reasons. I would say you couldn't go wrong with either tube but which one you go for depends on whether you like silky smooth, or live sound.

    This system is sounding fantastic.... and could get even better... I don't know if the tube is NOS but if it is then it has had no burn in yet!

    Your amp looks great with its wood base now btw!

    Edit: RCA 14F7 arrived today, plates are the same but matt colour instead of shiny, RCA has an extra rod from top to bottom, bottom mica slightly different, glass tube slightly smaller, looks in good condition, but no test results again.
    Last edited: Oct 24, 2017
  10. Maxx134
    I tried a Sylvania 14n7 the other day and it was very good,
    But not as impressive as the (Tung-Sol) 14AF7,
    or the (Silvania) 14F7 type.

    Then I took a look and saw inside the 14n7 was not using round plates,
    but the newer angled type you see in later/newer tubes..
    So that confirms to me my past experience that I prefer round plates as having an edge in realism.

    I just received a Tung-Sol 14F7 that I will try next.
    Last edited: Oct 24, 2017
  11. Mshenay Contributor
    I hate to ask this, but some things have come up in my life that have put a restriction on my time... I don't think I will be in a position to mod this unit my self this year. An I'd like to not have to wait till 2018 to start listening to it! That said I may need to reach out to some one to perform the mods in my place, which may be better. I might try my hand at building a cMoy BB as my first project rather than soldering and modding this tube amp...
  12. baronbeehive
    I think you're in for a treat my friend!

    Re: the RCA 14F7 which I got today, it is another wonderful tube, so it goes into my top 3: TS5751, TS14AF7 and now RCA14F7.

    I had a moment on another planet agin when I first tried it.... to do with the ambient music I had on as well as the tube, so to try to retain objectivity I went through my test tracks again. I expected it to have a nice musical balance being an RCA, but I didn't expect it to have great detail and soundstage, like the other 2 tubes. On that first piece of music I tried, the soundstage was wide, deep, and all enveloping, but this depends on the music and I think that the other 2 tubes are fairly similar. It gets more and more difficult to separate the small details between tubes when they are at this top level. As a 14F7 rather than a 14AF7 it has more gain as expected which makes it better for me but I didn't find it any more forward or harsh which I suspect is more down to the type of 14F7. Once again the realism is there, also I found it going down to really deep bass which is something that I hadn't noticed before, I may have just missed that before, but the bass was more of the type you feel rather than hear, it was that deep, and that makes the music very full sounding. The thing that made it difficult was knowing the construction was pretty identical to the TS14AF7, I didn't know if the RCA was really a Tungsol in disguise lol.

    So to sum up:
    1 - TS5751, treble has a silky sheen to it, very liquid, but still has the dynamics when needed, detailed, controlled, open soundstage
    2 - TS14AF7, still smooth, more neutral and extended treble, more live sounding, detailed, open soundstage
    3 - RCA12F7, this was the surprise. Smooth, detailed, fairly neutral, live sounding, open soundstage, I found it enveloping but mainly down to the music being played, extended bass.

    I would rate them equal, but my preference is for the TS5751, followed by the TS14AF7, then the RCA14F7, but they were all very close.

    Looking forward to your impressions of the TS14F7 Maxx!
    Last edited: Oct 24, 2017
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  13. wantech

    I am new,
    can I hook up speakers on pa1502a ? how ?
  14. baronbeehive
    No, I'm the only one on this thread that has the PA0901A speaker amp.
  15. benjisun
    Here is Mine with TungSol 6L6GC and JJ long plate 12AX7 gold
    Maxx134 likes this.
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