[buldogge]

  Looks like you got an early one with decent components. Lots of Wimas there which aren't bad for a cheap capacitor. Can't tell what you have for the power supply bypass though.
 
The soldering on the tube sockets looks okay so if you are still getting noise on one channel that goes away when you move the tube I would closely inspect each pin socket to see if anything looks unusual.

Hey Bill...Not sure what caps these are?  Do you think it would be worth swapping the Russian PIOs in here, and the Mundorfs 1ufs upfront???
 
TIA
-Mark
 

 

[buldogge]

OK...So the PIOs are in...getting ready to install the Mundorfs this evening.  
 
While I have the board out of the chassis again, is there any good/easy way to provide a better chassis ground???
 
TIA
-Mark 

 

[buldogge]

OK...The Mundorfs are in as well.  Redid the rear ground wire/solder, thru the board, just to be safe.
 
Everything sounds really nice...
 
Only odd thing is that after the new pot and caps, it seems I need a bit more gain than previously...to achieve the "same" volume...???
 
-Mark

 

[buldogge]

Ok..Anyone out there still???
 
Yeah or nay or changing the WIMA .22s?  To what?  More Russian PIOs (K42s?), Vitamin Qs, Jantzens (do they make 250v?) ???
 
Did anyone end up pulling the 2.2 WIMAs upfront and replacing with solid wire instead? (assuming I understood that exchange earlier in the thread)
 
 
TIA
-Mark

 

[bharat2580]

how do you actually open up the thing..

 

[derbigpr]

  how do you actually open up the thing..

 Point a magic wand at it and hope for the best.

 

[bharat2580]

 

 Point a magic wand at it and hope for the best.

ok now can we talk sense again.

 

[derbigpr]

 
ok now can we talk sense again.

 
Remove the tubes, undo the 4 screws on the front panel, and the PCB pulls out.

 

[bharat2580]

Remove the tubes, undo the 4 screws on the front panel, and the PCB pulls out.

Thanks. What about the rca and the supply ?
Are those connected via a long wire or something ?

 

[buldogge]

Thanks. What about the rca and the supply ?
Are those connected via a long wire or something ?

The wiring isn't terribly long.
Be particularly careful of the thin/fragile wiring on the volume pot...I replaced both my pot and the wiring harness (RC battery harness).
 
If you're going to be doing a lot of modding, you might consider extending the wires to the transformer (or even re-wiring it with a harness to make removal easier)...I extended them, externally.
 
Be very careful when pulling the pcb/tray out they the back...it requires some wiggling and the wires are pretty packed in there.
 
Good luck!
-Mark in St. Louis

 

[carlosgab]

Would an ALPS RK27 fit the mkiii as a replacement for my stock volume pot?

 

[SonicJedi]

This amp isn't really suited to modding because of the cramped case but if you have one and want to mod it then there are benefits in changing the caps and maybe some of the resistors.
This is my modded board :



I have changed the output bypass caps to 1uf Mundorf Mcaps, the coupling caps are MKT1822 from my LD MkIV, and the power supply bypass caps are russian K40Y-9 paper-in-oil. I also changed the input resistors to some Dale ones as I had them spare but don't expect that to have made much of a difference.
The amp now has improved clarity, soundstage, and a better sense of ambiance. Only changes I might make now is to remove the input caps and replace them with just a piece of wire as I have found that works well in other amps I have modded. Also I will be replacing those two 5W cement resistors in the power supply to metal oxide ones simply cause they are better and it is quick, cheap, and easy to do.

These are the caps I removed :



The brown ones are the output bypass caps - no name ( I guess no one wanted to own up to making these ).
The yellow ones are the power supply bypass - Carli 47nf but both of mine measured below 40nf which is close to the 20% tolerance.
The blue ones are the coupling caps - Rifa.

All of these are cheap junk and shouldn't really be in an audio amplifier. The Little Dot website shows a version 1 board and mine is version 4 and it looks like they have been cutting costs. My board was a Wima-free-zone, not that they are the greatest caps but better than what was installed.

So underneath all the cheap components I think there is a good amp waiting to get out and simply changing a few caps will make a great improvement. Just be aware you need to choose caps that will fit in the confined space.

------
Hey Critical Bill, your post has been immensely helpful! I did notice something however, that I hope you can help address.

The 0.047uF (47nF) yellow Carli caps in the photos appear to be safety line caps marked and rated as X2. I am not by any means an expert, but they seem to be filtering DC from the power supply. You replaced those with PIOs which are not rated as safety X2.

Does this matter, and is it a safety concern? From what I read, these should not impact the sonic character of the amp.

thank you!

 

[SonicJedi]

Hey folks;

I went ahead and modified my Little Dot MKIII based on the information I got from this thread. Here's what I did, and then I'll go over the results.

My upgrade project will be in two parts; primarily because the procurement of parts and shipping got split up. In the very first attempt, I am changing the 4 x signal caps which in my case were Vishay / ERO 1840-3 0.22 uF 220v. I have the v4.0 circuit board on my LD MKIII.

I replaced these ERO with 4 x 0.22 uF 450VDC MUNDORF M-CAP® EVO OIL. The biggest factor in choice of Mundorf caps was their size. They have long leads, and can be mounted horizontal or vertical.

In the second step, I'll be replacing the output bypass caps with Mundorfs 0.68uF, and the PS bypass safety caps (which currently are some generic crap) with Vishay x2.

My primary use of LD is as a preamp with Odyssey Khartago Extreme Amp. Just upgrading the signal caps has made a dramatic improvement. The sound stage is holographic now. There is breadth, and depth in it. The high registers have a beautiful slight coloration which is a trademark of Mundorfs. The lower end is tight, and bass is bone dry and comes with a thump. Midrange is still lush. There is a little bit harshness to the mids right now, and I suspect a little burn-in will fix it. The above results are from 2 hours of burn-in.

I can only imagine what results second have of the project will bring!

Will update once done.

 

[SonicJedi]

Alright. Done with the second stage of upgrade. This is what I did in this part:

1. Replaced the two crappy electrolytic generic looking things with 2 x 0.68 Mundorf Mcap Evo Oil Aluminum.
2. Replaced the PS bypass generic looking crap with 2 x 0.47 Vishay MKP X2

It took me good 2.0 hours to do this minor upgrade, since Mundorfs are big, and it was a challenge to close it back. I ended up unsoldering all wires, got the board in, and then pulled in each direction and attached wires on each end. I ended up taping the leads because they may touch the sides. But, once in, there's good 1 mm space between the LD bottom and the caps - so all good.

Results:
After the initial upgrade of the 4 x .22uF Mundorf Evo Oil Aluminum coupling caps, the sound became really thin. So much so that Louis Armstrong sounded like Stevie Wonder. I am exaggerating a little bit. But really, the lower mids completely disappeared. I suspected that the caps were too small, and it was acting as a filter, by truncating lower frequencies. The bass became boomy. The highs were brilliant, airy and spacious.

I suspected because of those generic caps, there was something off. So, I ended up up upgrading the PS bypass caps as well.

After this upgrade, the mids are back! The highs are airy. The piano notes seem to hang in the air as they decay, it's beautiful. Louis Armstrong sounds like himself again.

One thing that has changed though, and that's baffling is that the volume is too low now. So I had to adjust the gain to 4, by toggling the switches. Before the upgrade, I was driving it by having the pot set at 12'0 clock. Now, I am getting the same volume at 3'O clock. Not sure what's the cause.

The sound's great though! Also, the noise floor has sank quite a bit, and there's much less ambient noise.

Here's a photo of the board:

 

[SonicJedi]

OK...The Mundorfs are in as well. Redid the rear ground wire/solder, thru the board, just to be safe.

Everything sounds really nice...

Only odd thing is that after the new pot and caps, it seems I need a bit more gain than previously...to achieve the "same" volume...???

-Mark

I've been playing around with the output caps, and it seems like that you going from 0.68uF to 1uF may be the culprit. My crude understanding is that a bigger cap takes longer to charge, and during that cycle amp loses amplification. Since it's happening quite fast, so overall gain is lost.
I may be completely wrong on the science, but using a 1uF cap did the same for me. Perhaps someone more knowledgeable can explain the science here.