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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. ryencoke
    Thanks for the info!
  2. odinsride
    Hi, I am having a problem with my new Little Dot I+ and WE 408A tubes.  The amp does not seem to work when I put the jumpers on the 408A side as described in the instructions.  I tried the 408A tubes with the jumper set to 6JI position just to see if the tubes work, and they seem to work okay, but when I put the jumper to the 408A position, nothing happens.  The tubes don't even warm up.  Wondering if it's a defect in my unit or if I'm doing something wrong.  I've noticed on youtube videos that other Little Dot I+ have an actual switch there, but mine simply has a jumper setting instead.
    I did the following per the instructions:
    Original jumper position for K1/K2:
    408A   x [ x x ]   6JI
    New jumper position for 408A tubes:
    408A   [ x x ] x   6JI
    Hope my little diagram makes sense, the square brackets are the jumper.  I can take pictures if it would help as well.
    EDIT:  Here are some pics of what I have if it helps - https://www.dropbox.com/sc/jsw77ffcgbay1ts/AAD2nJxScXU0-V3NCMyZRTIHa#/
  3. i luvmusic 2
    Did you removed the jumper from both J1 and J2?
  4. odinsride
    J1 and J2 jumpers were already removed from the factory.
  5. i luvmusic 2
    How i wish i can help you But my LD 1+ was butchered see....
  6. i luvmusic 2
    I was looking at the manual and it looks like it's just a matter of removing J1 and J2 then switch to 408.I never have a 408 tube so i never tried this setup. 
  7. odinsride
    Yeah I did exactly as the manual says but just seems like when switched to the 408A side I just get no sound.  The unit powers on but that's it.  I'll post on the littledot forums to see if they can maybe replace my unit or something.  Btw, your LD looks absolutely insane lol, I have no idea what I'm even looking at (brand new to this stuff)
  8. gibosi
    It does seem that something is wrong with your amp. The only thing this jumper does is switch the heaters between 6.3 volts and 20 volts. The fact that the tubes don't even light up in the 408A position indicates that the heaters are not connected to a voltage source. Other than rechecking your connections, it might be best to contact David ( little.tube @ gmail.com ) to see if he can help.
    Good luck!
    odinsride likes this.
  9. odinsride
    I emailed David and unforunately he is not able to help since I did not purchase the LD I+ through an authorized vendor.  I ordered a cheap multimeter to do some of my own troubleshooting with my limited knowledge of electronics.  I'm not sure what I'll be able to do, but at least I can still use the LD I+ with stock 6JI tubes.  Bummer that I can't get the 408A's up and running.
    Edit: Another thing I wanted to mention - as I said before the 408A tubes work (and sound great!) when the jumper is in the 6JI position.  Is it okay to keep using them like that? I only tried it out for a minute to see that they work, but if it's okay to use them with the jumper in the 6JI position I'd be happy with that.  
  10. gibosi
    Since your amp is brand new, I suggest that you contact the vendor and ask that your amp be replaced.....
    In the meantime, a simple thing to try is swap out the two computer jumpers for a another pair. It is unlikely that they are defective, but it is certainly worth a try.
    And once you have a multimeter, if you are very careful, you can try to measure the heater voltage at the socket and at K1/K2.
    Good luck! :)
    odinsride likes this.
  11. odinsride
    Ok so I got my multimeter.  The reading between heater pins 4 and 5 when the jumper is set on the 6JI side is ~7.2v, which I'm not sure if that's correct or not since you stated they should be 6.3v in that position.  Now the fun part comes - I switched the jumpers over to the 408A side, this time with the bottom cover of the amp removed and facing up, and as soon as I turn it on I see smoke.  When I take a closer look with a flash light, I see that pin 5 of the right heater has been over-soldered, and the solder is connecting with the leftmost (408A side) K1 jumper pin.  So yeah, I will definitely be sending this back for a refund and will order my replacement directly from LD so I get warranty coverage.  Thanks for the help guys...I'm off to a rough start with audiophile equipment so far, but I won't give up :)
  12. gibosi
    Congratulations on solving the problem! It's a shame that your amp is defective, but it is very fortunate that you decided to roll 408A tubes now, and not a year from now, so you are able to make a strong case for a refund.
    7.2v is a little high, but that is not surprising. The LD heater voltage is unregulated, so if the AC voltage coming out of the wall is a bit high (not at all uncommon) the heater voltage will also be high. Plus, with no tube plugged in, there is no load on the heater circuit. Typically, with a tube plugged in, the reading at the pins will be a bit lower. Anyway, nothing to worry about.
    And IMHO, your decision to purchase your next amp directly from LD is a good one. They have one of the best warranties in the business.
    odinsride likes this.
  13. plus9paradox
    Just got a pair of Tektronik GE 6AU6 8425 and man are they amazing without even burning in yet! Will post more details after I am able to listen for a while. I soldered pins 2 and 7 together inside the amp :) I think its a lot more ideal than the wire jumper method. 
  14. i luvmusic 2
    You should try Yugoslavia 6HM5.
  15. plus9paradox
    Are they comparable in sound? I am thinking about grabbing a set of the Tung Sol 6AU6 as well and possible another pair of these tektronix to hold onto just in case. 
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