Little Dot MK8SE / MK6 Super Mods (All verified mods are on first page)

Discussion in 'Headphone Amps (full-size)' started by redge78, Sep 26, 2015.
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  1. gug42
    I still watn to add some modifications :wink: Really I have 8 nice audyn capp waiting !
    Your post and pictures are really apreciate because give me some exemple ! thx
     
  2. coinmaster
    [​IMG]
     
  3. baronbeehive
    :)
    What's up?? Is there nowhere that you can pick up a set of pliers lol?

    Jump in your batmobile this minute to your nearest neighbourhood DIY shop and get one............ or bring in Superman to finish the job!
    :)
     
  4. gug42
    Hello,

    Thank you for asking news :)
    Well I've done nothing on the little dot :frowning2:

    But I have design my own amp : an SE of 4 Watt, based on KT66 and E186F :)
    Building will start next month ! :)
     
  5. baronbeehive
    That's good news..... Good Luck!
     
  6. gug42
    If you need plan or peace of gears used, don't hesitate to ask :)
     
  7. 3ggerhappy
    Hi all posting it here:
    Just found out my little dot mk viii has channel imbalance just realize this when I use it as a pre on my speaker setup. Volume pot issue I think, problem is the volume does not equalize when I turn the volume up. Now Can anyone point me(link if posible) for a compatible replacement for the pot? stepped attenuator if posible? Is it even possible to replace it? Please advise to those with the know how
     
  8. SonicTrance
    Hi @3ggerhappy
    You wont fit a balanced stepped attenuator inside the mk8 without some modifications. Easiest thing to do is to replace the pot with fixed resistors and change the volume digitally from your PC/Mac or music player.
     
  9. Maxx134
    Maybe Easier to check the tiny (10k I believe) input grid resistors after the volume and possibly change them out to either adjust or correct difference.

    IMO, changing out the volume is going to be really small advantages if any.
    Money better spent elsewhere in this Amp..
     
    Last edited: Oct 15, 2017
  10. MrCurwen
    Absolutelu do not do this. The 10k resistor is a voltage divider for NFB insertion. It's value is not trivial.

    I second Sonics proposal.
     
  11. Maxx134
    I thought I answered this.
    I strongly disagree to change the volume pot.
    It is a sore waste of money as it is hard to find better replacement without expense.

    My initial intention and suggestion was to correct the imbalance of the channels,
    Not remove them.
    Yet if the NFB is to also be of concern,
    Then it may very well be the NFB resistors that are off, as they are at such a high value that they can most likely be the culprit of mismatch.
    And so should be checked for similarity of both sides.

    Another likely problem area could also be the tiny gain switch as well?
    It sets gain by changing value of the NFB resistors with parallel resistors .
    I am contemplating to bypass this gain switch,
    since I do not use both settings.
     
    Last edited: Nov 16, 2017
  12. Mogos
    Hi Guys!
    I have a question.
    Lately one of the current meters started to show higher values than usual.
    On the start the value is the same on both meters (as below).
    [​IMG]
    After around 2 minutes the value reises up to
    [​IMG]
    It is connected with the tubes. That's for sure. But what can this mean?
     
  13. SonicTrance
    Probably a tube thats going bad. Have you switched left channel to right channel and see if the problem moves with the tubes?
     
  14. baronbeehive
    Pleased to say my LD is up and running again!

    I haven't bothered to see what was wrong up to now because I've been enjoying my little speaker amp too much but there are times when headphones come in handy, like in the middle of the night for example, and I was missing my LD!

    I found out the problem which was another of those little annoying problems like the last time with the wire, only this time it was a bad solder joint which I noticed pretty much straight away, in fact I remember mentioning it before, on one of the WCF caps. I checked the trace to tube pin2 which revealed the problem was a lifted pad. I fixed this but the problem was still there so I took out the board again, getting good at that and putting it back again with Sonic's tip using an insulated screwdriver. The reason I didn't fix it properly first time is because the board is multi layered and has a different trace on the back with one leg of the WCF cap being connected to one leg of the 330ohm resistor, this couldn't be seen from the component side! Confusing LOL!

    What obviously caused it was when I rearranged the parts inside into their final positions which probably disturbed the dodgy solder joint. Suffice it to say problem sorted, and thats 2 amps that I've fixed now, this one and my speaker amp. Feeling pretty good and its thanks to you guys, you've trained me well!

    Just got to get the switch back in and the the driver tube bias adjusted and we're away!

    .......

    Edit:

    Well not quite...... I've rectified the fault with the faulty circuit, and the amp powers up with both meters showing equal current..... however having plugged in the headphones, there's no sound. I suspect the safety protection circuit kicked in when I had the problem with the amp. I've checked the fuses and it's not that so I need to know about this protection circuit.

    How do I locate and fix it?
     
    Last edited: Dec 22, 2017
  15. gug42
    Sorry to ask here ... but you've been so helpfull ....and seems you are the guys for this question :ksc75smile:

    Well I have a MKP 4 pins capacitor for bypassing an electrolytic one, and I don't know how to wire the 4 pins .. I don't want to take risk .... and I don't find any clear schematics on google ..
    The capacitors are : https://www.mouser.fr/productdetail/871-b32778p6356k000

    Any help please ? Did I wire the two left legs and the two right legs ? An another options ?

    Really hope you can answer me ... don't want to blow things :ksc75smile:

    Well a little schematics, the second would be my guess :
    Caps-4-pins-Wiring.PNG
    Thank you in advance !
     
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