[Ctritical Bill]

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.

 

[buldogge]

Hey Bill...Thanks for the reply.
 
The amp will be arriving tomorrow.  It has an issue with left channel static and mono delivery on the HP jack...so...there is a good chance I will have it apart anyway.  I figured I might as well try my hand at some positive mods at the same time...
 
Of course, it could be as simple as the usual broken wire at the volume pot!
 
I'm wondering why no one has moved the transformer off the chassis or at least made a new loom to enter the back, to make pulling the PCB out easier.
 
Could you recommend a source for the caps?
 
Can you explain why the input caps don't need to be there (complete modding newb here)?  What gauge/type wire to replace with?  Straightforward 22AWG solid copper...or...???
 
Thanx again,
-Mark

 

[buldogge]

I know this thread is mainly for MK III mods...but since mine hasn't arrived yet, I figured I would take another look at my MKII.
 
Tuns out it is a V 1.0, the caps are Nichicon, Wima, and the Ero MKT1822s mentioned above.
 
Thoughts???
 
TIA
-Mark

 

[Ctritical Bill]

If you are going to move the transformer then the case is of little use ( and you would have to lengthen all the wires ). You would be better off getting a tube amp kit off ebay. They cost very little and you can mod them any way you like and then fit a case to suit.
 
The input caps are there to filter any DC from the source so if you are confident that your source doesn't have any DC on the output then the caps aren't needed. Just google 'measuring DC offset' and you will get lots of info on how to measure it and then you can decide if you want to go ahead and remove the input caps. I just use solid copper wire from a CAT5 network cable but anything will do as it is only line level signal it is carrying.
 
There are lots of choices for caps, you'll just have to do some research. Just be aware that they need to be small enough to fit in the case; that will limit your choice. I am a fan of russian NOS caps, they can be had for little money and they sound good but they tend to be large. Again google is your friend and ebay will take your money.
 
I think with Little Dot amps if you get an early production board you will probably get what is advertised on their website. As they run out of parts they seem to just put in whatever they can find. I have 3 Little Dot amps and internally none of them are the same as the ones they advertsie on their website.

 

[buldogge]

Thanx for the reply Bill.  I found the Eros and the Russian PIOs you used on eBay...Trying to figure out the Mundorfs, are these correct?:

 
TA
-Mark
 
 
Quote:

  If you are going to move the transformer then the case is of little use ( and you would have to lengthen all the wires ). You would be better off getting a tube amp kit off ebay. They cost very little and you can mod them any way you like and then fit a case to suit.
 
The input caps are there to filter any DC from the source so if you are confident that your source doesn't have any DC on the output then the caps aren't needed. Just google 'measuring DC offset' and you will get lots of info on how to measure it and then you can decide if you want to go ahead and remove the input caps. I just use solid copper wire from a CAT5 network cable but anything will do as it is only line level signal it is carrying.
 
There are lots of choices for caps, you'll just have to do some research. Just be aware that they need to be small enough to fit in the case; that will limit your choice. I am a fan of russian NOS caps, they can be had for little money and they sound good but they tend to be large. Again google is your friend and ebay will take your money.
 
I think with Little Dot amps if you get an early production board you will probably get what is advertised on their website. As they run out of parts they seem to just put in whatever they can find. I have 3 Little Dot amps and internally none of them are the same as the ones they advertsie on their website.

 

[Ctritical Bill]

Yes, they are the ones but those in the picture are 630v. You only need 250v and they are much smaller so will fit.

 

[buldogge]

Ahhh...250v, got it.
 
TA
-Mark
 
Quote:

  Yes, they are the ones but those in the picture are 630v. You only need 250v and they are much smaller so will fit.

 

[buldogge]

I received the MKIII with "issues" today.  
 
I was on my way out the door, but I popped off the front cover to check the pot and HP jack...no obvious faults, although the pot wiring is a spindly thing, isn't it?!  
 
I then popped in some Russian power tubes and some Zenith 6DT6As that I don't care about and fired it up.  I heard the static in the left channel that the seller listed...played with the left driver tube/socket and it got much worse...played with it again, popped it out and back in and eliminated the static...methinks there is bad/cold solder on the pins of the socket/pcb...???  
 
I'll pull it out tonight and have a look and also look at the caps used.  I did look thru the bottom holes and see that it is a V 2.0 board....so, anyone with V 2.0 that has input on mods/caps that worked well for them, I would love to hear about it.
 
TIA
-Mark

 

[buldogge]

OK...So I got the MK III apart tonight.  I ended up cutting the 22 AWG power wires from the transformer...I think I will run them out the back of the cube and thru the back panel...it will make pulling the board much easier.
 
Attached are (2) pics showing the two halves of the board.  My V2.0 appears to be just like Bill's, except the bigger caps between the tube sockets are tall blue Nichicons not the slightly shorter brown ones on Bill's.
 
Also, the 7 pin sockets were solidly soldered...both left and right socket have a lot of play in the socket body itself...is this normal???
 
Given the caps shown in these photos...does Bill's swaps still make sense...any other recommendations?  Any opinion on Sprague 730Ps for the coupling caps?
 
TA
-Mark
 

 

 

[Ctritical Bill]

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.

 

[Koukol]

Can anyone tell me if the RCA outputs on the back are by any chance balanced?

 

[buldogge]

Well...Routing the power wires out the back of the transformer box and thru the back panel worked out well...gives more room to pull the board out the back.
 
However, the fragile wires of the volume pot broke one after the other...I de-soldered and re-soldered them all and ended up with a scratchy pot.  
 
Anyone know a good (US) source for one of those JST 5-pin connectors and pins?
 
Recommendations for a new pot (US again, would be nice)??
 
Since I'll be down for a bit...I'm thinking I'll change the PS bypass caps to Russian PIOs and the outputs to Mundorf M-Caps, unless anyone has other (reasonable) suggestions...???
 
TIA
-Mark

 

[Koukol]

  Well...Routing the power wires out the back of the transformer box and thru the back panel worked out well...gives more room to pull the board out the back.
 
However, the fragile wires of the volume pot broke one after the other...I de-soldered and re-solders them all and ended up with a scratchy pot.  
 
Anyone know a good (US) source for one of those JST  5-pin connectors and pins?
 
Recommendations for a new pot (US again, would be nice)??
 
Since I'll be down for a bit...I'm thinking I'll change the PS bypass caps to Russian PIOs and the outputs to Mundorf M-Caps, unless anyone has other (reasonable) suggestions...???
 
TIA
-Mark

I take it you don't know the answer to my question.

 

[buldogge]

 
I take it you don't know the answer to my question.

I don't think it's possible to have balanced RCAs.  
 
The RCA pre-amp output is controlled by the volume pot and is equal in power to the HP jack output.
 
-Mark

 

[Koukol]

 

 
I take it you don't know the answer to my question.

I don't think it's possible to have balanced RCAs.  
 
The RCA pre-amp output is controlled by the volume pot and is equal in power to the HP jack output.
 
-Mark

Ok, thanks Mark
I knew it was a long shot but I had to ask since I googled and couldn't find the answer.