No output from Little Dot MkII++ headphone amp

[12bitsoul]

Hi all
I acquired a pre-owned Little Dot MkII++ headphone amp some time ago which was needing some new tubes, one of the drive tubes was missing and the power tubes didn't appear to lighting up when the headphone amp was turned on. I've finally got around to purchasing a full set of replacement tubes which I installed today, but despite the headphone amp powering up, the power LED illuminating, and all 4 of the tubes lighting up, I cannot manage to get any audio output to my headphones. I have checked for obvious things and I am definitely connecting the audio source to the inputs of the headphone amp and I have tried connecting different audio sources including the line output from my hi-fi amp and also the line output from my MacBook Pro. I have tried different cables. I have even tried different sets of headphones but still no signal, even with the volume of the headphone amp turned up full. Has anyone here ever encounter a similar problem or have any idea as to what the problem may be? Any assistance or suggestions would be greatly appreciated.

 

[zizzyhead]

I don't own this but I've read that there are jumpers in the case that are adjustable. If you haven't already it may be worth while to take a look at those. It's conceivable that one could be not fully engaged. Or possibly needs to be set differently for your tubes. Be just a thought.

 

[12bitsoul]

I don't own this but I've read that there are jumpers in the case that are adjustable. If you haven't already it may be worth while to take a look at those. It's conceivable that one could be not fully engaged. Or possibly needs to be set differently for your tubes. Be just a thought.

Ah yes, good point. I shall make that my next stop and take a look at those switches and jumpers.

 

[12bitsoul]

I have taken a look inside of my Little-Dot MKII++ and have located the jumpers present for Ch1 & Ch2. However, I can only find the manual online for the Little-Dot MKII and Little-Dot MKIII. Is the operation and set up for the MKII++ exactly the same at that as the regular MKII?

Also, in the manual for the MKII and the MKIII it mentions about the two red DIP switches that control the gain of the amplifier but I cannot seem to locate any such switches in my MKII++. Do I need to go to Spec Savers or were these switches absent in the MKII++ version?

 

[zizzyhead]

Hopefully someone else will chime in here, as I mentioned I don't own one of these. Maybe someone on here has a manual???

 

[silent-circuit]

I have an original MK2, but I bought it second hand - don't know if they usually come with a manual but mine did not.

 

[12bitsoul]

Even if there are some hidden switches in my MKII++, I assume that even on the lowest gain setting that there will still be some audio passing through to the headphones when the volume control is turned up. I have tried those internal jumpers connected and also removed but in both cases, still no audio. Hoping that someone here can point me in the right direction.

 

[12bitsoul]

Hopefully someone else will chime in here, as I mentioned I don't own one of these. Maybe someone on here has a manual???

Anyone here own a LittleDot MkII++ or access to a manual as I'm still trying to establish the difference between this and the regular (non ++) MkII.
I'm just trying to confirm exactly what tubes and jumper settings are required for my MkII++ along with any other details that may help me in fault finding the problem I'm having, but only able to find the manual for the regular MkII for reference and there may be significant differences between the two. Any assistance or insight would be greatly appreciated.

 

[zizzyhead]

What tubes did it initially call me with? You had said one of the tubes was missing when you got it. If you have a set for one of the channels (or one preamp and one main) tube that it originally came with you might try using the old set in one channel and a new set in the other. Then you can try switching combinations of old and new tubes if that doesn't work. I have a kit built amp that I thought was broken when I first got it but turned out to be a bad tube. Also if the tube types don't match spec then it may not work. That's why I recommend using at least one of the old set. If you end up getting sound out of one of the channels when doing that at least you'd know that it was the new tubes. Good luck.