Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › Little Dot I+ Tube Rolling
New Posts  All Forums:Forum Nav:

Little Dot I+ Tube Rolling - Page 101

post #1501 of 1934

This isn't specifically about tube rolling, but I'm having a problem with my Little Dot 1+. The right channel is massively distorted while the left channel seems just fine. I have swapped tube channels and the results remained the same. I have also swapped the fuses and that is not the problem. What do you think is the issue?

post #1502 of 1934

10 minutes after intalling it, the Audio-Gd Moon HDAM, is working.

 

First impressions? Totally constipated, but, since I´ve read that this HDAM takes forever in burning in, I´ll wait.

 

 


Edited by Mario_Fpolis - 7/28/13 at 4:20pm
post #1503 of 1934
Quote:
Originally Posted by Tus-Chan View Post

This isn't specifically about tube rolling, but I'm having a problem with my Little Dot 1+. The right channel is massively distorted while the left channel seems just fine. I have swapped tube channels and the results remained the same. I have also swapped the fuses and that is not the problem. What do you think is the issue?

 

By swapping tube channels, I assume you have swapped the tubes left to right and right to left, and you have also tried another set of tubes....

 

The only thing I can think of are the circuit board jumpers. Perhaps one of them has worked itself loose. Open your amp up and check two sets of jumpers:

 

1) the jumpers (K1 and K2) that select 6.3 volts or 20 volts, and

 

2) the jumpers (J3 and J4)  that select for low impedance versus high impedance headphones.

 

(I believe you are using EF95 tubes, so it is unlikely that you have J1 and J2 installed which allows the use of EF91/92 tubes.)

 

And while you have the amp open, push down on the op amp to make sure it is seated well.

 

Good luck!

post #1504 of 1934
Originally Posted by gibosi View Post

 

Thanks for your response. However, I opened up the amp for a second look and found something that I am nearly positive is the problem (or at least the symptom of one); there are two burnt/charred/ashen resistors on the right side of the circuit board. Orienting the amp so the bottom plate is removed, the amp is upside down, with the volume knob to the top right, the burned resistors are on the edge of the right side horizontally, middle area vertically on the circuit board. The burnt resistors are on the right side of the yellow bricks that are labeled "1J2A", or inbetween the first and second screws from the inside of the chassis on the right side of the case.

 

 

 

Judging by the resistor colors on the other channel, the resistors are rated at 10 ohms with a tolerance of 10%. I have circuit board V2.1, which is different from the circuit board used in picture #2, which is only used to display the location of the named screws on the side of the chassis.


Edited by Tus-Chan - 7/28/13 at 6:32pm
post #1505 of 1934
Quote:
Originally Posted by Tus-Chan View Post

 

Thanks for your response. However, I opened up the amp for a second look and found something that I am nearly positive is the problem (or at least the symptom of one); there are two burnt/charred/ashen resistors on the right side of the circuit board. 

 

Good detective work! If you don't mind my asking....  Do you intend to send it back to Little Dot for repair? Or will you try to fix it yourself?

post #1506 of 1934

I have no idea. I don't think Little Dot will even look at my amp if I'm not the original owner, and I only have passing soldering experience and no equipment to do so to boot. I might just take the thing to some random electronics shop and tell them to replace the resistors.

post #1507 of 1934

Good luck! And I, for one, hope you will keep us informed.

 

Cheers

post #1508 of 1934

Those resistors were probably pretty hot when you were running for an extended period at max volume considering how close they are to those transistors on the heat sinks.  They should be rated for some pretty high temperatures, but considering you were pushing the amp hard and they might have been slightly under-spec'd for the service... 

 

There is a good chance that you'll be back in business after replace the resistors.

 

 

Quote:
Originally Posted by Tus-Chan View Post

 


 

 

Judging by the resistor colors on the other channel, the resistors are rated at 10 ohms with a tolerance of 10%. I have circuit board V2.1, which is different from the circuit board used in picture #2, which is only used to display the location of the named screws on the side of the chassis.

post #1509 of 1934
Quote:
Originally Posted by Mario_Fpolis View Post

10 minutes after intalling it, the Audio-Gd Moon HDAM, is working.

 

 

So....  you purchased the Dual OPA with the standard extension lead and simply plugged it into your opamp socket? Very interesting!

 

Any further impressions?

post #1510 of 1934

Gibosi, 

 

Pretty much it, I borrowed from a friend, ask protection to the Godess of DIY and plugged it, hoping for the better.

 

Soud wise, still a long way in burning it, it remains very congested, the vocals like constipated, but I have a lot of hope in this HDAM.

 

The HDAM away form the cabinet is getting a lot of EFI and EMI, so I´ll put some copper tape around it, in order to achieve some silent background.

 

This week I´ll put my hands on a 627 and next week a good friend of mine with a HF-1 will be here in order to evaluate this HDAM and opamp, when the Moon module will be fully burnt, I presume.

post #1511 of 1934

Thanks for the update. The idea of an HDAM is very intriguing to me and I look forward to learning more about your experience with it.

post #1512 of 1934
Quote:
Originally Posted by whirlwind View Post

Congrats, it is a great little amp.....have fun.

Thanks, looking forward to its arrival... hopefully tomorrow. beerchug.gif

post #1513 of 1934

Little Dot is here.  I did a bit of A/Bing with the emu0202 headphone amp (I'm running the line out from the emu0202 into the Little Dot) and the difference is incredible, even just out of the box (with stock tubes and op amp).  I'm going to get accustomed to this setup before rolling in the Voshkod tubes...

post #1514 of 1934
Quote:
Originally Posted by Edgard Varese View Post

Little Dot is here.  I did a bit of A/Bing with the emu0202 headphone amp (I'm running the line out from the emu0202 into the Little Dot) and the difference is incredible, even just out of the box (with stock tubes and op amp).  I'm going to get accustomed to this setup before rolling in the Voshkod tubes...

 

Glad to hear you are liking it. And it only gets better as you begin to explore other tubes and op amps. :)

post #1515 of 1934

The Little Dot is out for repair, and hopefully will come back good as new (actually, better than new, considering I got it defective) by the time I am through my vacation. biggrin.gif

 

It's actually kind of a shame that I upgraded to a real Stax amp and no longer need this to feed my energizer.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › Little Dot I+ Tube Rolling