# Little DOT MK III Mods??



## Frihed89

Can some of you please summarize the successful modifications (mods) you have made to your LD MKIIIs? I am not talking about tube rolling. I am talking about things like changing/substituting/adding/removing parts, such as capacitors, resistors, transformers, wire, etc.

 Maybe this pic will help of the top side of the board: 







 Here is the MK IV Per Sebastian's request. You can also cover this






 I found a pic of the bottom of the IV. The 22uf 400V (DC?) black caps look as if they are the coupling caps from what I can see of the bottom, but it's hard to see. Take a look: oops, maybe they are input caps. The small tubes are not the output tubes, are they?

 Where are all the experts!


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## SebastianL

Quote:


  Originally Posted by *Frihed89* /img/forum/go_quote.gif 
_Can some of you please summarize the successful modifications (mods) you have made to your LD MKIIIs? I am not talking about tube rolling. I am talking about things like changing/substituting/adding/removing parts, such as capacitors, resistors, transformers, wire, etc.

 Maybe this pic will help of the top side of the board: _

 

Mods on the LD MKIV are welcome as well.


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## FallenAngel

Those 220uF/200V look like output caps - my first suggested upgrade.
 0.22uF coupling caps are a close second.


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## SebastianL

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Those 220uF/200V look like output caps - my first suggested upgrade.
 0.22uF coupling caps are a close second._

 

Replace them with Black Gate or Auricap? What effect will it have soundwise?


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## SebastianL

LD MKIV circuitboard:





 It comes with Solen and Rubycon (and Mallory) caps and ALPS-27 potentiometer. Though on the Little Dot spec. site is says that it's got: "Nichicon, Rubycon, and German WIMA/ERO capacitors"


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## Frihed89

Find out the caps through whih the most signal passes: On the MK 1V, there are in a row: the 2 blue mallories, next to them, 2 small yellow caps, and then do big red "orange drop"-like looking things(?). Is there a picture of the bottom of the board?

 The two round black ones...I just saw them. I have no idea. 

 get the make and impedance and voltage specs from all the caps. You can then reference tham and find out the construction, and by then someone should be here that knows what they are doing?


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## FallenAngel

For interstage coupling - Russian Teflon TF3 0.22 at about $8 each, best bang/buck
 Output caps - your choice, aren't too many "great" options.


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## MikePio

Great thread, have been waiting for one like this... I have a LD MKIII and would love to mod it a bit, I will wait for more entries, Cheers,


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## Frihed89

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_For interstage coupling - Russian Teflon TF3 0.22 at about $8 each, best bang/buck
 Output caps - your choice, aren't too many "great" options._

 

First of all, thanks for replying. Many owners need more information, though, to take cation because they lack your understanding and experience, such as:

 1. Are you refering to the LD iii or IV or both?
 2. Which caps are the inter-stage coupling caps?
 3. What is a "Russian Teflon" cap; how many Volts DC? (22uf is the capacitance), and where do you get them?

 Thanks again. Please continue helping


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## SebastianL

Negatron has supposedly done some 'major mod' on his MKIV and a 'mod' on his MKIII. I've been trying to PM him, but his inbox is full.
 Maybe he could comment on his mods?

 I agree, interesting thread.


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## SebastianL

Quote:


  Originally Posted by *Frihed89* /img/forum/go_quote.gif 
_The two round black ones...I just saw them. I have no idea._

 

The two black caps are Solen 2,20µFJ 400V caps of french make. Not bad caps at all, but I think both Black Gate and Auricap are better caps. Perhaps Vishay as well.


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## ulyses

What is the difference between little dot mk3 and mk2? They look have same components. In adition to this, would I try these mods for my little dot mk2?


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## Frihed89

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_The two black caps are Solen 2,20µFJ 400V caps of french make. Not bad caps at all, but I think both Black Gate and Auricap are better caps. Perhaps Vishay as well. 




_

 

Yes, but what do they do? They look about the right size to be coupling caps for the output tubes, but I can't see the connections on the printed circuit board. These are Metallized Polypropylene fast caps. Whatever they do, I would not replace them with an electrolytic of any kind. Some kind of PIO type might be better, like Auricaps, Jensen, Audio Note (not cheap even for copper foil), Mundorf silver in oil (all these cost money): The vintage Russian, K-40s on Ebay are cheap and sound very good. But, hey find out what this cap does first. You can change caps and have practically no influence on the sound.

 That's why it would be nice to have someone here who knows the circuit.


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## natrix

I have the MKIV - there is a 5 volt, 1 amp regulator which can be used to power a γ1 DAC. Tube amp with SPDIF input!


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## Dept_of_Alchemy

You can do the 6H30Pi mod so you can use the much better power tubes on the MkIII.


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## Olev

Quote:


  Originally Posted by *Frihed89* /img/forum/go_quote.gif 
_Yes, but what do they do? They look about the right size to be coupling caps for the output tubes, but I can't see the connections on the printed circuit board._

 

These are input capacitors on the MK IV, output capacitors are the large ones in the middle of the PCB with per channel having one large electrolyte with large Wima and smaller Vishay bypass forming the output capacitor.


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## SebastianL

Quote:


  Originally Posted by *Dept_of_Alchemy* /img/forum/go_quote.gif 
_You can do the 6H30Pi mod so you can use the much better power tubes on the MkIII._

 

That would be the Bullplug mod made by ethebull, right?


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## Frihed89

Quote:


  Originally Posted by *Olev* /img/forum/go_quote.gif 
_These are input capacitors on the MK IV, output capacitors are the large ones in the middle of the PCB with per channel having one large electrolyte with large Wima and smaller Vishay bypass forming the output capacitor._

 

That certainly make sense, because of their location. I only have the oictures to work from.

 Thank you my nordic friend. Help these people out. I put this topic op originally because I have a friend who is interested in possible modifications.

 If you-or anyone else- have experience, can you tell the owners which caps are worth changing, which are not, and what kind they can use as substitutes?


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## SebastianL

Quote:


  Originally Posted by *natrix* /img/forum/go_quote.gif 
_I have the MKIV - there is a 5 volt, 1 amp regulator which can be used to power a γ1 DAC. Tube amp with SPDIF input!_

 

A nice option if your source is a PC or a MP3 player.
 I guess the γ1 DAC requires very little power (300mA), but does the internal powersupply deliver sufficient current to drive both the amp and the DAC without affecting the performance of the amp?


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## Pricklely Peete

I modified mine but I hesitate to provide what I did as the chassis the MK III is shoehorned into is a major PITA to pull the pcb out of and then get it all back in again.

 You need the patience of a Saint IMO to work on this amp. 

 As Always YMMV.

 Peete.


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## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_I modified mine but I hesitate to provide what I did as the chassis the MK III is shoehorned into is a major PITA to pull the pcb out of and then get it all back in again.

 You need the patience of a Saint IMO to work on this amp. 

 As Always YMMV.

 Peete._

 

Now that we're warned, could you please disclose your modifications for us? I've had the pcb out on my _MKIV_ - a lot of screws had to be removed, but with a little patience it worked OK.
 I mean, this whole thread is about modifying a LD amp which in most cases would imply modifications on the pcb. If I want to mess with my amp it's at my own risk (hopefully I know what I'm doing or at least I can reverse the process).


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## Pricklely Peete

Sure OK.....as always the moment anyone pulls a tube amp board or opens one up the following warning applies... High Voltage is present and it is extremely dangerous so make sure your large caps are drained of voltage and current. You also void your warranty, obviously 
	

	
	
		
		

		
			





 I bypassed all the large value caps directly with .033uf 500V NOS K42Y0-2 Russian PIOs, changed the 68 ohm 2W grid resistor on the 2 power tubes to 121 ohm 3W Kiwame (for the 6H30Pi tube mod). I added 4 x Panasonic 1 ohm 3 W resistors to all four tube sockets at the filament V pins (to drop the V to as close to 6.3V as I could get it) as the V to these is unregulated and running higher than spec (my line V is 127V) which means additional heat and premature tube failure.

 I bypassed the WIMA 3.3uf 50V MKP output coupling caps with a pair of NOS T-3 Russian 0.1uf 600V Teflon caps that had to be slung underneath the chassis because of their size (big caps). That meant changing the feet on the MK III chassis to large brass cones (Audioselection I think....)

 I already use the king of power tubes with it, a costly pair of 6H30Pi-DR's from the 1980's with either Sylvania round getter black plates (6AK5WB mil spec) or Tung Sol 403B drivers. Other great tubes to use are Telefunken CV4010 Diamond bottom, Amperex PQ E95F (rare but outstanding), Mullard CV4015 large shield logo mil spec, Raytheon USN - Jan 6AK5 among others.

 Here a few pics of the mods......(sorry about the crappy quality, I had a really old cam at that time). The pics do not show the 1 ohm 3W resistors I added a few weeks later nor all of the .033uf 500V K42Y-2 PIOs (5 in total). The MK III review thread has details of another member pointing out the filament V mod that alerted me to the unregulated V being fed to the heaters. If your mains V is at 115 or 120V then you don't need to add those parts but my line V is always at 127V which put the heater V at around 6.9 or 7.0V which is a little too high. The addition of the 4 x 1 ohm 3W resistors dropped the line V about .5V or so getting it much closer to spec which dropped chassis temps and should make all the tubes last a normal period of time (closer to their MTBF spec). 














 All of these mods had a positive impact on the SQ of the MK III. Well worth the effort. Some future mods worth doing are subbing the 3.3uf 50V WIMA output coupling caps for a pair of Auricap 3.3uf or if you can find them a pair of PLIO K75-10 NOS Russian caps (2.2uf 400V). Of course you keep the T3 0.1uf 600V using them to bypass the K75-10's.

 Changing out the I/O wiring for some silver plated copper wiring or Mundorf silver/gold 23 awg hookup wire. Swap out the cheap brass/gold plated RCA jacks for CMC copper billet/gold plated types and finally change out the pair of 220uf 200V caps for Nichicon FG/KG or if you really want to spend some money Black Gates. The mains filtering caps could also be subbed for some higher quality units (computer rated CDE or Aerovox BHC). The 3 resistors of the PSU section could be subbed for high quality Mills types (5W max but 3W would be ideal). IRC makes terrific resistors for this application (the Mil spec stuff is very good and fairly cheap compared to Mills or Reiken). The generic metal film resistors could be subbed with Vishay/Dale (matched pairs would be a good idea for the signal pathways).

 Lots of things to consider.

 The MK IV could definitely benefit from the swap of the 2.2uf Solens for some better quality caps like the K75-10 PLIO/T3 Teflon combo or Mundorf Silver/Gold PIOs or any other high quality type. I'd also pull the WIMA box caps and replace those with same value types of your fav brand (size is a limiting factor obviously) but I've never found the WIMA sound to be anything special other than the Black Box WIMAs that cost a fair pile of dough (but would be ideal in this spot). Anyway just a few thoughts on this amp as I don't own one but have sent parts to another MK IV owner to try these suggestions out. (the K75-10 PLIO/T3 Teflon combo and some K42Y-2 .033uf 500V PIOs as bypass caps for the 5 large electrolytic caps ) That member is no longer active at HF so I have no idea how this mod turned out but it should be similar to the MK III in SQ.

 These are just suggestions and my own opinions so others results might vary depending on what parts used, soldering skill,execution of the mods, wire selected etc etc...

 Peete.


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## MikePio

Hey Pricklely Peete, 

 Thanks for the great MOD write up! I have one question, since I want to do one mod at a time... The 6H30Pi tube mod, ( I am new to this lol ) can I use the Kiwame 5W/120 ohms resistor? I might be mistaken, but doesn't a 120 ohm resistor be capable of 110 ohms to 130 ohms, giving a -/+ 10 lee way? The ones I have an option of getting are only 2W and 5W, so I am assuming the 5W would be o.k., since 3W is required? Thanks for your time, and once again, great job...


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## SebastianL

Hey thanks, Peete. Nicely done mods, now we're getting somewhere! 
	

	
	
		
		

		
		
	


	




 Execellent photos. Of course the chassis always puts a limit to the mods you can make, but Peete you seem to have found a (daring) solution 
	

	
	
		
		

		
		
	


	




 I see now what you mean about fitting it all back into the chassis. You've got a lot of wires there.

 Did you do the mods step by step in order to hear what each mod sounded like, or did you do it all at once since the pcb was out of the box anyway? And could you comment a little more on how the mods has changed the sound (overall and in particular)?

  Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_I already use the king of power tubes with it, a costly pair of 6H30Pi-DR's from the 1980's with either Sylvania round getter black plates (6AK5WB mil spec) or Tung Sol 403B drivers. Other great tubes to use are Telefunken CV4010 Diamond bottom, Amperex PQ E95F (rare but outstanding), Mullard CV4015 large shield logo mil spec, Raytheon USN - Jan 6AK5 among others._

 

I don't want to get too off topic here (since there's already a 128 pages thread dedicated to LD tube rolling), but with my Unison Research amp the EL34 power tubes makes a HUGE difference. From the dull JJs (Tesla) to the brilliant Svetlana and the rich sounding Electro Harmonix.

 Also, is it not right that if you short-circuit the power cable, you automatically drain the amp of voltage and current?
 Just a tip in stead of having to wait 30+ minutes for the power to run out.

 Thanks also for sharing your thoughts on upgrades for the MKIV model.
 The MKIV already comes with CMC gold plated RCA jacks though 
	

	
	
		
		

		
		
	


	




 SebastianL


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## Pricklely Peete

Quote:


  Originally Posted by *MikePio* /img/forum/go_quote.gif 
_Hey Pricklely Peete, 

 Thanks for the great MOD write up! I have one question, since I want to do one mod at a time... The 6H30Pi tube mod, ( I am new to this lol ) can I use the Kiwame 5W/120 ohms resistor? I might be mistaken, but doesn't a 120 ohm resistor be capable of 110 ohms to 130 ohms, giving a -/+ 10 lee way? The ones I have an option of getting are only 2W and 5W, so I am assuming the 5W would be o.k., since 3W is required? Thanks for your time, and once again, great job..._

 

I believe the originals are 2W...I used 3W to give me some headroom in the parts spec. I'd stay at 120 or 121 ohm. Email David though since I think the newer MK III's may already be 6H30Pi ready.

 Peete.


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## Pricklely Peete

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_Hey thanks, Peete. Nicely done mods, now we're getting somewhere! 
	

	
	
		
		

		
		
	


	




 Execellent photos. Of course the chassis always puts a limit to the mods you can make, but Peete you seem to have found a (daring) solution 
	

	
	
		
		

		
		
	


	




 I see now what you mean about fitting it all back into the chassis. You've got a lot of wires there.

 Did you do the mods step by step in order to hear what each mod sounded like, or did you do it all at once since the pcb was out of the box anyway? And could you comment a little more on how the mods has changed the sound (overall and in particular)?



 I don't want to get too off topic here (since there's already a 128 pages thread dedicated to LD tube rolling), but with my Unison Research amp the EL34 power tubes makes a HUGE difference. From the dull JJs (Tesla) to the brilliant Svetlana and the rich sounding Electro Harmonix.

 Also, is it not right that if you short-circuit the power cable, you automatically drain the amp of voltage and current?
 Just a tip in stead of having to wait 30+ minutes for the power to run out.

 Thanks also for sharing your thoughts on upgrades for the MKIV model.
 The MKIV already comes with CMC gold plated RCA jacks though 
	

	
	
		
		

		
		
	


	




 SebastianL_

 

Thanks !

 I did the mods in two stages. First I changed out the grid resistors for the 6H30Pi mod and listened to that for a few months then pulled the amp apart again to add the mods I talked about.

 The SQ improvements were 3 fold in nature. better bass response and extension. Much quieter SNR due to extra smoothing of the mains filtering caps (lowering ESR as well) while the output coupling cap bypass added some much needed details to the signal output. Overall I'd say the SQ gained resolution and refinement without upsetting the tube magic in the mids. A decent quality mains cable and decent quality RCA cables were the final touches.

 I don't think shorting the mains leads (L + N) is a good idea...you need a bleeder network installed on the mains filter caps or use a device that does the same thing mounted on a stick or plastic wand. You parallel a 150K 1W resistor across the +- terminals of each large cap and then measure them with a DMM to make sure all the voltage has been bled safely off the caps. I'm not 100% sure of the resistor value but you can google it and find out for certain.

 I believe the Mk IV CMC are one step below the ones I suggested. Here's a link to the ones I'm talking about

Charming Music Conductor-CMC-805-2.5CU,,cmc-audio,Tube Socket,cmcaudio,banana,spades,binding posts,rca jacks,rca plugs

 Peete.


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## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_
 I believe the Mk IV CMC are one step below the ones I suggested. Here's a link to the ones I'm talking about

Charming Music Conductor-CMC-805-2.5CU,,cmc-audio,Tube Socket,cmcaudio,banana,spades,binding posts,rca jacks,rca plugs_

 

I believe you're right, but I'm fully satisfied with the 'standard' CMC rca's in my MKIV amp. They are _very_ tight with my Neutrik jacks. To upgrade these would be a waste of money. LD has done an excellent job there.


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## natrix

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_A nice option if your source is a PC or a MP3 player.
 I guess the γ1 DAC requires very little power (300mA), but does the internal powersupply deliver sufficient current to drive both the amp and the DAC without affecting the performance of the amp?_

 

It sounds good to me. With a minimal "E" config (coaxial SPDIF to analog only) I measured it on an HP E3610A lab power supply at 12mA when at 5.00 volts. The 5 volt regulator on board is rated to 1A, so unless it is already at or above 98.8% capacity I doubt there should ever be any trouble.


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## SebastianL

Just had a thorough look inside my MKIV just to be _very disappointed _discovering that the caps are not of the brands mentioned by Little Dot.
 The 'Solens' 3.3µF are marked 'Phenix HiFi'. They look a lot like Solen but with a different (although similar) logo. I've done a search and couldn't find them anywhere. They could be produced by Solen though.
 Neither are there any Rubicon or Nichicon caps. Only Nippon Chemicons.

  Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_(size is a limiting factor obviously)_

 

I'm now investigating the components I'm considering as substitutes, and SIZE DOES MATTER! Now I see why you chose the untraditional positioning of the caps outside (underneath) the box. Mundorf 3.3µF caps are much too large to fit in anywhere. Also I think the Mundorfs are much too expensive (€95 each) compared to the pricerange of the Little Dot amp. For that kind of money I'd rather buy another amp to begin with.

 One last thing: any suggestions on a power cable upgrade?


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## MikePio

Hello everyone, 

 I have a newbie question, Regarding the 6H30Pi Mod, from looking at the PCB pictures I cannot find which resistor to change! There are many! If anyone can specify where this resistor is, and how many of them, since I only has six of these resistors... Thanks for your time! Cheers, 

 -Mike.


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## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_I bypassed the WIMA 3.3uf 50V MKP output coupling caps with a pair of NOS T-3 Russian 0.1uf 600V Teflon caps ...._

 

According to this picture of the MKIII pcb, the WIMAs are 2.2 uF and not 3.3uF, right?


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## Pricklely Peete

On mine they were 3.3uf but I can't be sure what value they are for all the MK III's. The MK IV uses/or used to spec 2.2uf 630V Solens (whatever brand you have in yours now I forget).

 Peete.


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## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_On mine they were 3.3uf but I can't be sure what value they are for all the MK III's. The MK IV uses/or used to spec 2.2uf 630V Solens (whatever brand you have in yours now I forget)._

 

The world famous 'Phenix HiFi' 
	

	
	
		
		

		
		
	


	



 2.2uf *250V* (not 630V).


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## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_ I'd also pull the WIMA box caps and replace those with same value types of your fav brand (size is a limiting factor obviously) but I've never found the WIMA sound to be anything special other than the Black Box WIMAs that cost a fair pile of dough (but would be ideal in this spot). 
 Peete._

 

Peete, about the WIMA Black Box caps, are there different types? On a thread elsewhere on the web someone advised to get WIMA Black Box _film and foil and not metallised!_
 The ones I've found are Metallized Polypropylene. Will they do?
WIMA audio Capacitor

 -Sebastian


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## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_The generic metal film resistors could be subbed with Vishay/Dale (matched pairs would be a good idea for the signal pathways)._

 

Could you point out which resistors are in the signal path on the MKIV (or on the MKIII for that matter)?
 I enclose a photo of my MKIV with two groups of resistors that I think are in the signal path (A & B). My marking of the A group shows both left and right channel whereas group B only shows one channel.

 -Sebastian


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## SebastianL

Pricklely Peete,
 what kind of wire did you use for the extension of capacitors you placed outside the box? Or what wire would you recommend?

 Sebastian


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## Pricklely Peete

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_Pricklely Peete,
 what kind of wire did you use for the extension of capacitors you placed outside the box? Or what wire would you recommend?

 Sebastian_

 

I used some bog standard 20 awg OFC copper hook up wire I had left over from another project. If the MK III was easy to take apart I'd change it to the stuff I now have (in abundance), Mundorf Silver/Gold but 22 awg solid silver or 22 awg stranded high quality copper is more than good enough. Whatever you can lay hands on for a decent price should suffice. Keep in mind the amp is low cost so no crazy expensive wire is necessary.

 Peete.


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## Pricklely Peete

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_Could you point out which resistors are in the signal path on the MKIV (or on the MKIII for that matter)?
 I enclose a photo of my MKIV with two groups of resistors that I think are in the signal path (A & B). My marking of the A group shows both left and right channel whereas group B only shows one channel.

 -Sebastian_

 

The resistors in the gain network (via the slider selectors) are I believe in the signal pathway. Order and then match pairs of 1% tolerance or better Vishay/Dale..Holcro or Caddock. Email David and ask for the other spots that should be considered and the Wattage ratings. I know the PSU resistors LD used to spec (just the Mk IV/IVSE) were barely adequate and caused quite a few MK IV's to fail but I believe Sword and David have addressed this issue. IMO though you can get very good quality power resistors (with tighter tolerances 1% vs 5%) for not a lot of money. Might as well right ? What value are the 2 yellow metal/poly film caps in the pic ? I'd also replace these (if they are Hovland then don;t bother...but I doubt they are).

 Peete.


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## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_The resistors in the gain network (via the slider selectors) are I believe in the signal pathway. Order and then match pairs of 1% tolerance or better Vishay/Dale..Holcro or Caddock. Email David and ask for the other spots that should be considered and the Wattage ratings. I know the PSU resistors LD used to spec (just the Mk IV/IVSE) were barely adequate and caused quite a few MK IV's to fail but I believe Sword and David have addressed this issue. IMO though you can get very good quality power resistors (with tighter tolerances 1% vs 5%) for not a lot of money. Might as well right ? What value are the 2 yellow metal/poly film caps in the pic ? I'd also replace these (if they are Hovland then don;t bother...but I doubt they are).

 Peete._

 

I already mailed David about this and I'm waiting for a final reply (first off he replied about the risk voiding the warranty etc.)
 The two yellow caps are german ERO 0,47µF +/- 10% 250V and I ordered some Russian K42Y-2 PIO caps to sub them.
 As yet I have replaced the four WIMA caps with danish Jantzens and after some burn in, they did their job. The lacking of high treble is gone, which for me was a huge issue. The MKIV box doesn't leave much space, but I managed.
 When I first got the MKIV I was quite dissapointed with the sound considering all the fuss and hype about this amp on this forum. Little 'tube' sound, lacking high treble, mushy bass and so on. Now things are looking better with my first mod.
 As soon as the Russian K75-10s arrive I will try to swap the original noname (Phenix HiFi) caps and give it a listen. Eventually I will try to substitute these with Ampohms or mayyyybeeee Mundorfs.


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## SebastianL

Btw. I have my eyes on Kiwame resistors for PSU as well as signal path.


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## SebastianL

These are the resistors in the signal path on the MKIV according to David:





 To quote David: "The only resistors that you should change are the ones in Group A, which are the gain resistors."


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## SebastianL

"It's best to overengineer and choose the highest wattage you can find. The signal resistors in circle B will not really make much of a difference, but replacing the gain resistors in A may make a marginal improvement."

 Quote David of Little Dot who's been very helpful as always 
	

	
	
		
		

		
		
	


	




 -SebastianL


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## sonda2008

Hello SebastianL,
 Any news from the "war zone"? 
	

	
	
		
		

		
		
	


	




 Probably I'm not the only one who is checking this thread every now and then to see the progress in your LD modification 
	

	
	
		
		

		
		
	


	



 Best of luck!
 sonda2008


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## Pricklely Peete

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_"It's best to overengineer and choose the highest wattage you can find. The signal resistors in circle B will not really make much of a difference, but replacing the gain resistors in A may make a marginal improvement."

 Quote David of Little Dot who's been very helpful as always 
	

	
	
		
		

		
		
	


	




 -SebastianL_

 

Get some Caddock or Holcro 1/2 W or 1W (tighter tolerance the better) matched pairs for the gain sections.There is no need to go above 1W with 1/2 W being ideal in this particular part of the circuit. 
 Partsconexxion offers matching services for a small fee...they have a great selection of high quality parts to choose from.You could ignore the gain pairs that you never use and just concentrate on the pairs that you do use or change them all. The difference in cost is only 10 or 15 bucks.

 Every little bit helps even though David seems to think not a lot can be gained...I disagree..generic metal films in the signal path can do some SQ damage that can be repaired with high quality great sounding replacements. The K75-10's used in conjunction with the T3 Teflons is a fabulous combo...it's my personal fav but the caps are huge and present an installation dilema (as you know from my efforts). Fortunately it's a minor dilema easily solved 
	

	
	
		
		

		
		
	


	




 The sub of the cheap Eros poly film for K series PIOs is a worthy upgrade. You've already noticed how pulling the WIMA's for something better can make a big diff. Personally I don't know why people like WIMA...I think they sound like crap (except the Black Box types which are PIO...
	

	
	
		
		

		
		
	


	




) in the signal pathways . Don't forget to bypass all the large filter caps with small value 250V or better PIOs.

 Anyway good job thus far on the mods Sebastian ! I look forward to hearing how each step progresses and what you think of the results 
	

	
	
		
		

		
		
	


	




 EDIT: The large resistors in the B section of the photo look to be 2W...I would go with no less than 3W in these spots, again get the pairs matched and the tightest tolerances you can find. 

 Peete.


----------



## SebastianL

Quote:


  Originally Posted by *sonda2008* /img/forum/go_quote.gif 
_Hello SebastianL,
 Any news from the "war zone"? 
	

	
	
		
		

		
		
	


	




 Probably I'm not the only one who is checking this thread every now and then to see the progress in your LD modification 
	

	
	
		
		

		
		
	


	



 Best of luck!
 sonda2008_

 

Hold on! I’m still in the progress of modifying my MKIV. But things are definitely going my way.

 By now I have more or less followed the suggestions laid out by Pricklely Peete substituting the WIMA MKS4 caps with Jantzen Superior Z-caps. The Jantzens was my own choice though, since I’ve heard a lot of good reports about them. Furthermore they are a Danish product and I bought them in a store just down the road from where I work. Buying them was an easy task. However installing them wasn’t easy at all! There is very little space inside the LD box. Perhaps that’s why they call it LITTLE dot 
	

	
	
		
		

		
		
	


	




 Subbing the WIMAs with the Jantzens (the first mod I did) made a HUGE difference on the SQ. WOV! The annoying lack of treble (the biggest issue for me) was gone. Now, a lot of clear treble – maybe adding a tad too much emphasis on the high frequencies. But I was so content I was about to stop the modding process. However I had already bought or ordered a lot of other components. Thus, I went on tweaking.

 Next step was installing the Russian K42Y-2 .033µF 500V PIOs as coupling caps on the five big electrolytes on the back of the PCB. Also I subbed the two yellow ERO 0,47µF with Russian K42Y-2 0,47µF PIOs. Last step this time was exchanging the output wire w. some expensive AudioNote AN pure silver wire (solid core and very stiff – a bit difficult to work with, but the advantage is that it gets a strong grip on the front lid).
 This (so far) last step brought it all back into balance. At this point once more I’m hesistating on continuing the mods because I am SO satisfied with the result: transparence, even balance throughtout the spectre, great stereo perspective, good depth, great dynamics. This is what I expect from a tube amp. I could easily live with this modded amp forever! (considering the money and time spent).

 Once I’ve done all of the mods I will elaborate my statements and and draw a final conclusion. So far I’m very happy with the overall sound. Much more refined than the standard MKIV amp I received.
 Note that I use Sennheiser HD650 with this amp which is very important to take into consideration when reading this report. The above mods might not suit other headphones at all. Just this weekend I tried a pair of HD800 with my modded MKIV and I preferred my own HD650+MKIV combo. The HD800 sounded much better with some other equipment (a HeadAmp GS-X).

 Also to anybody who might want to mess with this amp: heed the warning from Pricklely Peete “the chassis the MK III is shoehorned into is a major PITA to pull the pcb out of and then get it all back in again. You need the patience of a Saint IMO to work on this amp.”!!!
 He is so right!! Warning goes for the MKIV as well.

 regards, Sebastian (a happy modder)


----------



## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_ The K75-10's used in conjunction with the T3 Teflons is a fabulous combo...it's my personal fav but the caps are huge and present an installation dilema (as you know from my efforts). Fortunately it's a minor dilema easily solved 
	

	
	
		
		

		
			





 Peete._

 

Already got a pair of K75-10's. They are indeed _HUGE!!_

 Sebastian


----------



## SebastianL

Mods that are comming up: replacing the resistors and the Phenix HiFi caps once I receive the parts. I ordered some AmpOhm caps and some Kiwame resistors.

 Sebastian


----------



## Budley007

I doubt that I will ever own one of these amps. Nevertheless, this thread has been both enjoyable and informative. Thank you very much for your effort and time, folks.


----------



## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_Personally I don't know why people like WIMA...I think they sound like crap (except the Black Box types which are PIO...
	

	
	
		
		

		
		
	


	




) in the signal pathways . 
 Peete._

 

You're not the only one 
	

	
	
		
		

		
		
	


	




:



> Quote:
> 
> 
> Originally Posted by *Daroid* /img/forum/go_quote.gif
> ...


----------



## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_Get some Caddock or Holcro 1/2 W or 1W (tighter tolerance the better) matched pairs for the gain sections.There is no need to go above 1W with 1/2 W being ideal in this particular part of the circuit. 

 -----

 EDIT: The large resistors in the B section of the photo look to be 2W...I would go with no less than 3W in these spots, again get the pairs matched and the tightest tolerances you can find. _

 

To which degree should the resistors match? +/-10% or just as close as possible?


----------



## Frihed89

I would forget about the resistors, given the gains you've made, and see if there isn't anything you can do for the power supply to smooth the voltage better and/or make the rails bigger. Also, i am guessing it's SS rectified and he may have cut some corners, but you know I am not an LD owner.

 I am really happy to hear about your successes.


----------



## Pricklely Peete

That is what the bypass caps for the large electrolytic caps will do Frihed89. There is only so much room in this chassis although I do believe the resistors in the signal path DO make a noticeable difference and are worth the effort and expense.

 Sebastian...what I mean by matching is having both resistors measure the same value (if you need 4.7 ohms then a pair of 4.7 ohm resistors are culled from a batch as a matched pair). Tolerance has to do with how close to the stated value the parts actually are + or - .1 %/1%/5% etc...matching is making sure you haven't got a wide variation in value that when used in the gain section would yield a balance mismatch if the resistors are way off.

 Peete.


----------



## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_I already use the king of power tubes with it, a costly pair of 6H30Pi-DR's from the 1980's ....
 Peete._

 

Peete, how important are these expensive tubes? Did you do a direct comparison with the standard Sovtek 6H30s or the Electro Harmonix 6H30s? What are the differences soundwise, bass/treble extension, stereo perspective, depth, transparency, dynamics?
 All in all are they really worth the huge price tag?
 A local danish constructor of tubeamps with more than 20 years of experience, tells me that all the 6H30 type tube are exactly the same, made at the same factory. They only put different stamps on the tubes to justify the high pricetag.
 He knows the specs of the 6H30 by heart - he's that much into tubes!
 Of course I know that reportedly the 6H30Pi-DR's have been through intensive testing to meet mill. requirements, but are they worth it?


----------



## SebastianL

This is what I'm talking about:
 "hello TG,

 Jean Cristophe Morrison, the in-house tube wizard
 at New Sensor has tested the Saratov against the 
 Sovtek. He told me that they are axactly the same.
 From my own tests I agree with him.
 In some application the Sovtek is better because of lower microphony.
 BAT uses the original russian 6H30P-DR and not the Sovteks to realize a higher price."
6H30Pi variants [Archive] - diyAudio


----------



## Frihed89

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_That is what the bypass caps for the large electrolytic caps will do Frihed89. There is only so much room in this chassis although I do believe the resistors in the signal path DO make a noticeable difference and are worth the effort and expense.

 Peete._

 

OK. You are the boss!


----------



## SebastianL

For those interested, by now I have done all of the planned modifications. Latest modification was subbing the output caps with the Russian PIO / FT3 Teflon combo. After the initial harshness had disappeared I did a comparison with the Ampohm caps and I did not notice any significant difference.
 But according to my guide through this venture of modding, Prciklely Peete, the Teflons take about 700 hours to do a full burn in (the Ampohms as well take a long time).

 Thus I’m in the tedious process of burning in the output caps the next couple of months. It wouldn’t be fair to draw any final conclusions until then.
 But so far I can say that I’m very satisified with the mods I’ve done. Subbing the WIMA caps with the Jantzens being the most significant upgrade.

 Discovering that exchanging the resistors was very difficult, I gave up less than halfway through this particular mod. The problem is that the existing pinholes in the PCB for the standard resistors were too small for the larger Kiwame and Holco resistors and I wouldn’t risk damaging the PCB. I managed to install a few Kiwame resistors in the signal path (both L and R of course). Luckily the three standard 5w ceramic resistors were quite large and I had no trouble replacing them with Kiwames. I measured of all the Kiwame and Holco resistors before installing them, and I managed to get matched pairs or very close to matched pairs with all of them. They were all very close to the stated value. Maybe I will eventually install the rest of the resistors with some sort of pin extension. That will have be a holiday job when I have nothing else to do since it’s a real PITA!

 Some time ago I also replaced the original Sovtek 6H30П–EB with a pair of very cheap mil. spec. 6H6П. IMO a huge upgrade. Much better bass response and bass extension. (This is a bit off topic, I know) They sell for cheap in bundles on eBay.


----------



## Pricklely Peete

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_This is what I'm talking about:
 "hello TG,

 Jean Cristophe Morrison, the in-house tube wizard
 at New Sensor has tested the Saratov against the 
 Sovtek. He told me that they are axactly the same.
 From my own tests I agree with him.
 In some application the Sovtek is better because of lower microphony.
 BAT uses the original russian 6H30P-DR and not the Sovteks to realize a higher price."
6H30Pi variants [Archive] - diyAudio_

 

Your source is correct there is no sonic difference between the Sovtek or the EH Gold Pin. They are both built the same way with mostly the same materials. The DR's are another animal compared to the new production 6H30's, the NOS DR's are far better constructed and sound a little more extended and in control of the bass. The treble region has a little more sparkle with the mids being very smooth/creamy without sounding syrupy. I bet the Teflon/PIO caps are contributing a great deal to the overall sound so it's tough to gauge how much of the effect is attributed to the tubes or the new parts.....but,
 It's been a while since I compared the NOS DR's vs the Sovteks ( I have both) so allow me to reacquaint myself with my LD MK III and I'll get back to you guys in few days with some fresh listening evaluations to report.

 Good job thus far Sebastian, taking on a mod of this scope is commendable 
	

	
	
		
		

		
		
	


	




....the hard part is waiting on the burn in of the Teflon/PLIO cap pairs. It's fun to listen along the way and take mental notes during the process.

 Keep us informed as to your thoughts and progress 
	

	
	
		
		

		
		
	


	




 Peete.


----------



## SebastianL

Quote:


  Originally Posted by *Pricklely Peete* /img/forum/go_quote.gif 
_Your source is correct there is no sonic difference between the Sovtek or the EH Gold Pin. They are both built the same way with mostly the same materials. The DR's are another animal compared to the new production 6H30's, the NOS DR's are far better constructed and sound a little more extended and in control of the bass. The treble region has a little more sparkle with the mids being very smooth/creamy without sounding syrupy. I bet the Teflon/PIO caps are contributing a great deal to the overall sound so it's tough to gauge how much of the effect is attributed to the tubes or the new parts.....but,
 It's been a while since I compared the NOS DR's vs the Sovteks ( I have both) so allow me to reacquaint myself with my LD MK III and I'll get back to you guys in few days with some fresh listening evaluations to report.

 Good job thus far Sebastian, taking on a mod of this scope is commendable 
	

	
	
		
		

		
		
	


	




....the hard part is waiting on the burn in of the Teflon/PLIO cap pairs. It's fun to listen along the way and take mental notes during the process.

 Keep us informed as to your thoughts and progress 
	

	
	
		
		

		
		
	


	




 Peete._

 

I tried the 6H6П before I did the Teflon/PIO mod and it definitely had a serious impact. The 6H6П is not the leanest tube out there (soundwise), but that's what I like about it. Suddenly the acoustics of my classical recordings became much more apparent. The character of the room - much more like a vivid concert feeling. Tending a _little_ bit towards the magnificent Stax combo I heard some weeks ago.

 Anybody did a comparison between the 6H6П and the DRs?


----------



## KMASCII

Quote:


  Originally Posted by *SebastianL* /img/forum/go_quote.gif 
_Subbing the WIMAs with the Jantzens (the first mod I did) made a HUGE difference on the SQ. WOV! The annoying lack of treble (the biggest issue for me) was gone. Now, a lot of clear treble – maybe adding a tad too much emphasis on the high frequencies. But I was so content I was about to stop the modding process. However I had already bought or ordered a lot of other components. Thus, I went on tweaking._

 

I've ordered some caps to sample and swap for the WIMA's in my stock LD MKIII. Although I'd appreciate any added clarity and imaging, your comments about a prior lack of treble worry me a bit. I'm not wanting to take my LD any closer to a solid state sound than it already has. If anything, I'd look to toning down the lower high frequencies just a tad.

 I listen to a mix of rock & acoustic through HD650's with GE 5654 5stars and 6H6n's. These are the tubes I'd finally settled on, and I find this combination just a smidgen bright at times. Other tubes I've tried turned out to be just a little dark or unrevealing for my liking.

 I guess I'm looking for a more tubey sound, if you will. I wonder if I'll have to revisit some of my other tubes should replacing the WIMA caps expose too much of the highs. I'll try to remember to report back on my experiment and experience.


----------



## SebastianL

Quote:


  Originally Posted by *KMASCII* /img/forum/go_quote.gif 
_I've ordered some caps to sample and swap for the WIMA's in my stock LD MKIII. Although I'd appreciate any added clarity and imaging, your comments about a prior lack of treble worry me a bit. I'm not wanting to take my LD any closer to a solid state sound than it already has. If anything, I'd look to toning down the lower high frequencies just a tad._

 

Did you do a thorough burn in of the LD? It takes quite a while before the final sound settles in.
 After the upgrades that I made, the amp doesn't sound like solid state. Still got the tube sound. In fact, before the upgrades I was disappointed with the lack of 'tubey' sound, and I think it will be difficult to kill that altogether.

 I apologize for not posting a full report of the final results concerning the upgrades. It's due to lack of time. I'm still meaning to make a final conclusion once I get some time to do so.


----------



## Max F

Quote:


  Originally Posted by *KMASCII* /img/forum/go_quote.gif 
_I've ordered some caps to sample and swap for the WIMA's in my stock LD MKIII. Although I'd appreciate any added clarity and imaging, your comments about a prior lack of treble worry me a bit. I'm not wanting to take my LD any closer to a solid state sound than it already has. If anything, I'd look to toning down the lower high frequencies just a tad.

 I listen to a mix of rock & acoustic through HD650's with GE 5654 5stars and 6H6n's. These are the tubes I'd finally settled on, and I find this combination just a smidgen bright at times. Other tubes I've tried turned out to be just a little dark or unrevealing for my liking.

 I guess I'm looking for a more tubey sound, if you will. I wonder if I'll have to revisit some of my other tubes should replacing the WIMA caps expose too much of the highs. I'll try to remember to report back on my experiment and experience._

 

While I can't comment on the mods i can comment on the tubes. Those 5 stars are on the bright side. Definately check out some Mullard tubes either the EF95 or EF92 varieties (for more tubeyness). Also, look for some Raytheon or Sylvania 6ak5w type tubes for a more balanced, but revealing sound. I would do that before trying the mods - much easier.


----------



## SebastianL

Quote:


  Originally Posted by *Max F* /img/forum/go_quote.gif 
_ I would do that before trying the mods - much easier._

 

I totally agree. If you haven't done some tube rolling, that would be the first thing to do. The only reason why I ventured into this insane modding project, is because I'm such a stubborn ass. If the tube rolling doesn't do it for you, go ahead with the caps. But heed the warning - it's a troublesome job because of the shoebox design.


----------



## SebastianL

Originally Posted by SebastianL:
_Subbing the WIMAs with the Jantzens (the first mod I did) made a HUGE difference on the SQ. WOV! The annoying lack of treble (the biggest issue for me) was gone. Now, a lot of clear treble – maybe adding a tad too much emphasis on the high frequencies. But I was so content I was about to stop the modding process. However I had already bought or ordered a lot of other components. Thus, I went on tweaking._
  Quote:


  Originally Posted by *KMASCII* /img/forum/go_quote.gif 
_I've ordered some caps to sample and swap for the WIMA's in my stock LD MKIII. Although I'd appreciate any added clarity and imaging, your comments about a prior lack of treble worry me a bit. I'm not wanting to take my LD any closer to a solid state sound than it already has. If anything, I'd look to toning down the lower high frequencies just a tad._

 

If I haven't done so before, let me correct myself. Now, after the new caps have settled in the Jantzens _aren't_ a tad too bright! Just clearer than the WIMAs.


----------



## KMASCII

Gotcha SebastianL, thanks. This grasshopper needs to learn patience actually 
	

	
	
		
		

		
			





.

 My MKIII is the version 2.0 pcb. So I've oredered the 6H30's. I've got about 90-100 hours on the amp. About 50ish hrs on the tubes I'd quoted. I have other tubes from the EF91, 92 & 95 families. One of the reasons I'd settled on the GE 5stars, which are the brightest of any I've used, is the detailing. They've been the best at imaging for me.

 Alas, tax return season = upgraditis/mod season for me. But at this time I've got the MKIII paired with LD DAC_1 tolinked to my computer. It's surprising how much cleaner and clearer WASAPI out (Win vista & 7) is compared to ASIO (Win XP). Who'da thunk.

 Anyway, great thread, big fan of my MKIII and great work you guys.

 Edit: btw, the photos on the Little Dot site are the version 1.0 pcb by the looks of it. My pcb version 2.0 looks different than those posted on their site. I'll post some photos of mine at stock.


----------



## KMASCII

Just to be certain. In the attached diagram these caps are output caps that are in parallel... right? 
	

	
	
		
		

		
		
	


	




 Cap 1 is, I believe, a Chemi-con 220uf 200v (there's no brand markings on the caps). Cap 2 is the WIMA MKS4 0.68uf 160v.

 Thanks.


----------



## bigdirty

hey guys, following this thread Ive had some fun modding my mkIII. I started off removing the parts from the cramped confines and placed them in a cheapo hammond aluminum case. Ive got v2 of the board.
   
  Input caps -                 4.7uf Mundorf Supreme
  Interstage coupling -     0.22 K75-10 pio   (this mod seemed to be the most bang for your buck)
  Output caps -              0.68 K40y-6 pio
  Audio Note Tantalum Resistor in the gain section.
  Alps Blue Velvet 100k Pot
   
  With these mods, listening to music has never been so enjoyable. 
  Thanks for this thread.
   
  Now I have a question regarding the large electrolytics in the post above.  Im using my mkIII only as a preamp, no headphone use. I emailed David regarding subbing the electrolytic for a film cap and asked if a smaller value could be used. "yes a smaller value can be used"  but when I asked about a specific value I didnt get a reply.  
   
  Not using the headphone output, how low can i go with the value of the large electrolytic?   (Chemi-con 220uf 200v) 
   
  Ive got some 0.01uf k72, 0.22uf k75, 0.68uf k40, and some 1.0uf film caps kicking around. Can any of these be used?
   
  Any input would be appreciated
   
  thanks for your time
   
  big


----------



## SebastianL

I know this is a little late but FWIW I would say yes, the two caps are in parallel. I'm not that familiar with schematics but judging from the way signal runs it must be a parallel connection.


----------



## SebastianL

Quote: 





kmascii said:


> Just to be certain. In the attached diagram these caps are output caps that are in parallel... right?
> 
> 
> 
> ...


 

 I know this is a little late but FWIW I would say yes, the two caps are in parallel. I'm not that familiar with schematics but judging from the way signal runs it must be a parallel connection.


----------



## SebastianL

Bump


----------



## Ice Max

Hey, is there anyway to remove the circuit board from the case without desoldering everything? that seems the only way to get it out for me. I have a MKIII with a v1.0 board


----------



## bigdirty

Quote: 





ice max said:


> Hey, is there anyway to remove the circuit board from the case without desoldering everything? that seems the only way to get it out for me. I have a MKIII with a v1.0 board


 


  you should be able to pull the board out enough to work on it. remove the potentiometer connector from the front of the board. pull the board out the back.


----------



## SebastianL

Quote: 





bigdirty said:


> Quote:
> 
> 
> 
> ...


 


  That's right. You will be able to work on the board without desoldering. However this method leaves you very little space as the board will not be completely free of the case. There's a risk that you will damage some wires or components. I ended up desoldering the wires to the PSU, the potmeter and the input & output connectors. Trust me this will save you a lot of trouble - otherwise it will be a true PITA.
  The wires to the PSU come with a colorcode. Be sure to note where each color go.


----------



## Ice Max

Thanks. I just need to replace the resistors in the back so I can use 6H30 tubes without damaging the amp and killing the tubes prematurely. these have enough wattage and ohms correct? http://www.radioshack.com/product/index.jsp?productId=2062295&filterName=Type&filterValue=1-watt+resistors#


----------



## SebastianL

Quote: 





ice max said:


> Thanks. I just need to replace the resistors in the back so I can use 6H30 tubes without damaging the amp and killing the tubes prematurely. these have enough wattage and ohms correct? http://www.radioshack.com/product/index.jsp?productId=2062295&filterName=Type&filterValue=1-watt+resistors#


 

 I would't know about this as I have the LD MKIV amp. However the 6H30 tube or 6H6 (my favourite) is an excellent choice. You won't be disappointed. Try to email David at Little Dot, he usually answers very quickly or try the littledot forum which is up and running again.


----------



## Stevebol

Quote: 





ice max said:


> Hey, is there anyway to remove the circuit board from the case without desoldering everything? that seems the only way to get it out for me. I have a MKIII with a v1.0 board


 


 I ended up cutting all the wires to the transformer and labeling them but I wouldn't recommend doing it. My LD MK III had a hum and one of the large caps had come loose. I'm going to make a larger cabinet for it. A couple wires to the volume pot came loose so I had to cut that.
  This is going to be a big pain in the butt but I like the sound of the amp.


----------



## SebastianL

Quote: 





stevebol said:


> Quote:
> 
> 
> 
> ...


 
   
*I told you so!!!* And I agree that this amp sounds good - with some modding of the caps.


----------



## Ice Max

Phew, Finished all the mods I needed to do to my MKIII, now for the hard part: getting it back in the chassis! Anyone got tips on getting it back in all in one piece? I broke two wires that i had to re solder so far, and I'd rather not have any more causalities. everything is still soldered to the transformer, and it just seems IMPOSSIBLE to get things back in their place. getting this thing back in makes pulling it out seem easy!


----------



## SebastianL

Quote: 





ice max said:


> Phew, Finished all the mods I needed to do to my MKIII, now for the hard part: getting it back in the chassis! Anyone got tips on getting it back in all in one piece? I broke two wires that i had to re solder so far, and I'd rather not have any more causalities. everything is still soldered to the transformer, and it just seems IMPOSSIBLE to get things back in their place. getting this thing back in makes pulling it out seem easy!


 

 I've managed to get the board back into the chassis of my MKIV about a dozen of times, believe it or not. But I ended up prolonging two of the wires to the transformer by simply soldering a little piece of extra wire onto the existing wire. This made the task much easier and doesn't affect the sound IMO. As I've mentioned before it really helps if you desolder some of the wires before you start working on the board. The signal wires aren't hard to solder back on only the wires to the transformer.
  How the people who assemble this amp manage to do it is a complete mystery to me 
	

	
	
		
		

		
			




   
  I don't recollect if I've mentoned it already but I also removed the two caps that sits right before the headphone out (a pair of 3.3µF Solen look-alikes on the MKIV) and replaced them with a straight hookup wire. My electronics engineer friend told me they only serve the purpose of preventing the amp from blowing up if you feed a DC signal _INTO_ the headphone out. As I'm not likely to do that and as we all know that a capacitor sometimes is a necessary evil it's better to avoid it if possible. And so far my amp hasn't blown up and I get the benefit of avoiding the enormous russian K75-10 caps that Pricklely Peete suggested.
  Exactly what these look like on the MKIII I don't know but I think they are the two red ones near the headphone out - probably WIMAs.


----------



## Skooks

I have a LD Mk III and I have changed both the driver and power tubes to M8100/CV4010 and 6H30. So far, that's all I've done, but it is sounding really good driving my Denon D2000 phones with the new JMoney ear pads and re-cabled with Moon Audio Blue Dragon.
  I might purchase the HE-5LE phones. But, will the LD Mk III drive them? Or, does it take more current to get them to really sing?
  If you could help me out here, I'd sure appreciate it.
  Thanks...
  Hugh


----------



## SebastianL

Quote: 





skooks said:


> I have a LD Mk III and I have changed both the driver and power tubes to M8100/CV4010 and 6H30. So far, that's all I've done, but it is sounding really good driving my Denon D2000 phones with the new JMoney ear pads and re-cabled with Moon Audio Blue Dragon.
> I might purchase the HE-5LE phones. But, will the LD Mk III drive them? Or, does it take more current to get them to really sing?
> If you could help me out here, I'd sure appreciate it.
> Thanks...
> Hugh


 
   
  I haven't tried the HE-5LE with my LD amp but I've tried them with my MAD Ear+ which I would say produces about the same amount of power. Though I know the 6H30/6H6 tubes are able to produce a lot of current I wouldn't know for sure. My MAD Ear+ had to be turned all the way up to just get them to play at a decent level. These cans are VERY hard to drive and I don't think I would recommend them with the LD. In stead I can wholeheartedly recommend the Audez'e LCD-2 which is also an orthodynamic can like the HE-5LE. The synergy of my LCD-2 and my modded LDMKIV is nothing less than a miracle! It's at least on par with the best STAX equipment at less than 1/3 of the price.
  Also the HE-5LE is a very forward sounding can. The music is coming from within your head while the LCD-2 is much more laidback with music playing in front of you and thus doesn't create listening fatigue. On top of this the LCD-2 is very easy to drive.
   
  It's interesting that you like the 6H30 powertube better than the 6H6P. While I don't own the MKIII amp and only listened to it briefly the 6H6P tubes outperforms the 6H30P-EV in my MKIV amp by a great margin IMO.


----------



## sonda2008

Hi guys! Some time ago I decided to check what’s in my MK III. I dismantled the front panel and a couple of wires connected to the pot fell off. I have no idea how to fix it  Could you provide some schematics how to wire the pot to the main board please? I wouldn’t like getting rid of the amp since I spent small fortune on the tubes. Please help!


----------



## davidjasondiaz

is this thread still alive?


----------



## sonda2008

I hope so!


----------



## SebastianL

Quote: 





sonda2008 said:


>


 



> Hi guys! Some time ago I decided to check what’s in my MK III. I dismantled the front panel and a couple of wires connected to the pot fell off. I have no idea how to fix it  Could you provide some schematics how to wire the pot to the main board please? I wouldn’t like getting rid of the amp since I spent small fortune on the tubes. Please help!


 

 On my MKIV the pot is soldered directly onto the board to four soldering points with no wires attached.
   
http://www.littledot.net/forum/viewtopic.php?f=9&t=815&sid=30a6313093903f4c3755ff2a4900334e
  This links to the Little Dot forum website. More specifically the MKIII. There's a lot of pictures there showing both sides of the board. Maybe you can figure out where they are missing. Logically it should be somewhere near the cutout. Exactly where each wire go I don't know. They each have a different color right?
 You could try to email David of Little Dot. He's usually apt to answer questions.
little.tube@gmail.com
 or try to pm Prickleley Peete.


----------



## sonda2008

Thank you sir!


----------



## SebastianL

Of course another option is to post your question directly on the LittleDot.net forum. When you do get an answer please share with us the info in this appropiate thread


----------



## rh495140704

it is good


----------



## Pricklely Peete

Hey Sebastian........hows the MK IV and the LCD-2 working for you ? Any more changes to the amp since the last round of mods were talked about ?
   
  I lent my Mk III to another head fi'er (at the last meet I attended, Fall 2010) and woudn't you know it I haven't heard back from him for over 4 months now....last time we talked he was enjoying the modifyed Mk III vs his stock Mk III to a great degree. Hopefully I hear from him soon...I kinda miss the little guy (my MK III). Jeez I hope that head fi member is alright.....
   
  Peete.


----------



## SebastianL

Quote: 





pricklely peete said:


> Hey Sebastian........hows the MK IV and the LCD-2 working for you ? Any more changes to the amp since the last round of mods were talked about ?
> 
> I lent my Mk III to another head fi'er (at the last meet I attended, Fall 2010) and woudn't you know it I haven't heard back from him for over 4 months now....last time we talked he was enjoying the modifyed Mk III vs his stock Mk III to a great degree. Hopefully I hear from him soon...I kinda miss the little guy (my MK III). Jeez I hope that head fi member is alright.....
> 
> Peete.


 

 Hi there Peete,
   
*the modified MK IV and LCD-2 combo is a KILLER!!!*
  I have two other serious amps to compare with. My canadian Mapletree MAD Ear+ Purist HD and my german Violentric HPA V181 (balanced). As much as I love the Violectrics dynamics, exact details and transparancy I prefer the LD MKIV with the right tubes. These are mainly the russian 6J1P-EV or U.S. Tung-Sol 6AK5W (1950's) input tubes and russian 6H6P power tubes. All NOS tubes.
  Just before I bought the LCD-2s I read that they didn't go well with tubes. NOT true. The SQ is everything I have ever dreamed of. Nothing less. I could go on elaborating my impressions if I had the time. All I can say is: my search is over.
   
  Some more here in my previous posts:
http://www.head-fi.org/forum/thread/439449/little-dot-mk-iii-mods/75#post_7376692
http://www.head-fi.org/forum/thread/439449/little-dot-mk-iii-mods/75#post_7260946


----------



## Stevebol

Quote: 





sonda2008 said:


>


 



> Hi guys! Some time ago I decided to check what’s in my MK III. I dismantled the front panel and a couple of wires connected to the pot fell off. I have no idea how to fix it  Could you provide some schematics how to wire the pot to the main board please? I wouldn’t like getting rid of the amp since I spent small fortune on the tubes. Please help!
> 
> Hey Sonda, that's exactly what happened to me. I need a close-up pic, or something, to see how the potentiometer is wired. Could someone post a close-up of the pot and how it connects to the circuit board? Even something hand drawn would be great.


----------



## sonda2008

Stevebol,
   
  Looks like the soldering quality is very poor not only on my MKIII. My clumsiness did not help either I guess  I think I figured out the pot wiring. It works fine... sometimes... well... I loose the left channel when I touch the pot in an improper manner  I had some problems with the pot before and I assume it got damaged during the process of rewiring. I’ll check my soldering job later but I’m quite confident I did a decent job with my soldering iron.
   
  Here is a key/legend for the rough sketch I did:
  O – orange
  WO – white orange
  B – brown
  WG – white green
  G - green
   
  Bear in mind I have never consulted the wiring with anyone and it is my educated guess only. Do not attempt this at home unless you are entirely sure and confident bla bla bla... 
   
   
  http://img848.imageshack.us/img848/8601/copyofdsc05647.jpg
  
  http://img405.imageshack.us/img405/7887/copyofdsc05652.jpg
  
  http://img641.imageshack.us/img641/3722/copyofdsc05763.jpg


----------



## KMASCII

Your wiring looks correct. On my version of the MKIII there is a five pin socket soldered to the circuit board. The pot then plugs into the surface socket with a five pin harness being wired from the pot. Also different is my wire colors: red, blue, brown, green and black.
   
  But I believe the outside green and orange wires on yours, which solder to the circuit board, do output to the pot. And the inside striped wires are inputs from the pot. And the common ground is or course the circuit board's center soldering point. Although the circuit board has the L and R printed to distinguish between left/right channel soldering points, there's no indication for the in & out from the pot.
   
  A while back I sent my MKIII for a short fall while I had the face plate detached which pulled the wiring from the pot. 
	

	
	
		
		

		
			





 I ended up using a heavier gauge wire because those that were the original wires were much too fragile, being much too light a gauge for my liking.


----------



## sonda2008

I removed the original wires (red, blue, brown, green and black) together with the white socket. The wires I used are solid core CAT5 ones.


----------



## sonda2008

KMASCII, have you tried any mods yourself?


----------



## KMASCII

I have. I swapped out the 3.3uf and 0.68uf WIMA's for equivalent Auricap's and Obbliggato's respectively. Both caps fit nicely, with thin foam packing, into the side bulges of the case. As well, I swapped the 220uf Nippon Chemicon, which were on the output side, for some equivalent, but higher voltage, Nichicon's. Since I'd torn the original Alps pot from the wiring I decided to also swap that pot out for an Alps 947G, which is physically larger. Now I have to extend the front plate out with a block of wood. Unfortunately I'm dealing with seepage flooding in my shop (ah... spring-time) otherwise I'd have fashioned a new mount for it by now.
   
  On the power wiring side, I replaced the wires and am going to route the power wires out the rear of the transformer housing and down into the top-rear of the case. I disliked the way the wires were originally routed through the floor of the transformer housing and into the top of the case, with no grommets to protect the wires from the sharp machined edges. I''m going to employ grommets and a split wire loom in my rerouting to tidy it all up.
   
  In terms of the capacitor swapping, I found that I've improved the clarity of the treble frequencies. Doesn't sound quite as harsh in the highs now, I don't think it was really grainy before, just a bit harsh. Still has plenty of detail though. Nice match for the HD650's.


----------



## sonda2008

Would it be possible to use 50k attenuator instead of 100k pot in my MKIII?
   
  Edit:
 Like the one from the link bellow:

 http://cgi.ebay.com/DACT-Type-21-Stepped-Attenuator-Potentiometer-50K-300B_W0QQitemZ120473999989QQcategoryZ3280QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D10%26ps%3D63
   
  They seem to be identical size wise. I’m asking specifically about 50k because if it is not drop-in replacement I might use it in another project later on.


----------



## KMASCII

The pot you're looking at is a "stepped attenuator" pot. Besides meaning incrimental volume changes, as opposed to gradual, they're suppose to offer other benefits in sound quality. But someone else will have to give you advice on this as I know not how stepped pots work. I don't think there is any problem using a lower impedance pot though, other than greater volume.


----------



## sonda2008

I took some pictures of the circuit board of my MKIII v2.0 today and I think (pardon my ignorance) there is something missing on the board. There is one brown 33uF 250V cap in the middle of the board. Looks like there should be two of them. There is nothing on the other side of the board. There is nothing rattling in the housing either  Am I missing something? Can anyone confirm there should be only one cap there?
   
  And if you could take a look at the components of my MKIII and suggest some element swapping to upgrade the SQ? Preferably something cheap and easily obtainable on eBay.Thanks 
   

   
  Sorry for the crooked picture. It’s actually made of 2 different photos. I couldn’t pull the board out far enough to take one nice shot.


----------



## sonda2008

[size=11pt]Today I visited my local shop with electronic stuff. There is nothing I mean absolutely nothing in terms of caps or resistors mentioned in the LD mod thread  The only things I could scavenge were some LEDs. From top to bottom:
 - original blue
 - orange
 - superbright white
 - superbright orange[/size]
  

   
[size=11pt]I think I’ll stick to the superbright orange.[/size]
   
[size=11pt]Can anyone help me with Ebay suggestions?[/size]


----------



## Stevebol

Hey Sonda, thanks for the pics. It should be a big help and I'm going to get started trying to put my LD back together. I haven't decided on the enclosure yet but I'll probably go with a simple wood box and put the transformer and tubes on top.


----------



## SebastianL

Quote: 





sonda2008 said:


> I took some pictures of the circuit board of my MKIII v2.0 today and I think (pardon my ignorance) there is something missing on the board. There is one brown 33uF 250V cap in the middle of the board. Looks like there should be two of them. There is nothing on the other side of the board. There is nothing rattling in the housing either  Am I missing something? Can anyone confirm there should be only one cap there?
> 
> And if you could take a look at the components of my MKIII and suggest some element swapping to upgrade the SQ? Preferably something cheap and easily obtainable on eBay.Thanks
> 
> ...


 

 Concerning the 'missing' brown capacitor you could check the board to see if there are two empty soldering holes. (Probably close to the existing capacitor). Every component in the design should have a small text printed just next to where it's placed in the design (like '100K' for a resistor or '33uF 250V' for a capacitor). So if there is only one text with the '33uF 250V' printed you shouldn't worry.
   
  Here you can see the LD MKIII board but it's the vers. 1 so it's not much help as there can be significant changes in the design:
http://www.littledot.net/forum/viewtopic.php?f=9&t=815&sid=ae7df9704ce470031d3523cbaf8f435d
   
  Of course you can always drop David a line for help. He's usually quick with an answer.


----------



## sonda2008

Quote: 





sebastianl said:


> Concerning the 'missing' brown capacitor (...)


 
   
  There are holes for additional cap and there is description on the circuit board. That's why I was asking. See the blow-up below.


----------



## jdg711

Looks like all you need to do is to stand up the existing 33/250, and then decide if it's supposed to have another one in the unoccupied space.
   
  I'd check with David at Little Dot on this. He usually responds quickly.


----------



## SebastianL

Yeah, but the strange thing is that if a component is missing and not replaced with a wire there should be a break in the signal path = no sound (for that channel). On the photo it looks as if some of the solder joints of the resistors have been tampered with. Did you buy it second hand?


----------



## sonda2008

Quote: 





jdg711 said:


> Looks like all you need to do is to stand up the existing 33/250, and then decide if it's supposed to have another one in the unoccupied space.
> 
> I'd check with David at Little Dot on this. He usually responds quickly.


 

  
  I was told that there  is supposed to be only one cap there.


----------



## sonda2008

Quote: 





sebastianl said:


> Yeah, but the strange thing is that if a component is missing and not replaced with a wire there should be a break in the signal path = no sound (for that channel). On the photo it looks as if some of the solder joints of the resistors have been tampered with. Did you buy it second hand?


 
   
  I bought it from David on eBay. Amp was shipped directly from China. I have never made any modifications to the circuit board myself. Many solder joints (most of them actually) do look messy.


----------



## KMASCII

My board is the same version as your's sonda. And mine has just one cap too. Whereas the boad is printed for two capacitors. I'm pretty sure this is related to the power supply end of things. I was under the impression this difference between the v1.0 and v2.0 boards had to do with the 6H30PI compatibilitiy. I could be mistaken though.


----------



## sonda2008

Quote: 





kmascii said:


> I'm pretty sure this is related to the power supply end of things.


 

 It makes sense.


----------



## sonda2008

Is there any room for improvement on my adapters?

 http://www.head-fi.org/forum/thread/301219/review-of-the-diy-6h6n-to-e182cc-5687-tube-adapters-bullplugs-for-ld-mkii-mkiii-headphone-amplifiers/45#post_7527150


----------



## sonda2008

Would it be possible to substitute WIMA 0.68uF 160V with the Russian K42Y-2 0.47uF 250V PIO cap?


----------



## sonda2008

Project frankenstein. Hopefully I'll be able to close the chassis


----------



## twc5964

I've had my MK III about 5  years. I use it more as an additional preamp than a headphone amp with my home stereo and especially with a  modified " JBL On stage 400"  ipod speaker(used as a tv speaker for my cable box which does a great job considering it's small size)  . The only mod I've done is parallel a pair of .22uf Audio Cap Thetas to the Eros .22 caps and .68 Auricaps to the Wima .68 caps and it certainly helped clean up the sound and make it a bit more dynamic.


----------



## KMASCII

Yes, and although the WIMA caps are a decent sounding cap, they were sounding just a bit grainy to me. Once I swapped the WIMAs for Auricaps & Obbligatos the treble became more controlled and cleaner.
   
  As a side note, I haven't come across an answer as to whether these output caps are in series or parallel. By the circuit board tracings they look like they're in series, but I don't know for sure.


----------



## Ponczomarinero

Mods done 
   
  Both of capacitors in LD III (0.22uF, 0.68uF) replaced with Russian PIO K40Y9. Signal cable from input connectors to the board replaced with silver one. Sounds very detailed now. Soundstage much bigger. Highs appears and they are clear. Now I need to think is it to bright or not. 
   
  Anyway has anybody replaced resistors for better one? Specially on REV2 board which I have. It wood be lovely to post some photo of rev2 board with marked resistor ind capacitors on signal path.
   
  Matt


----------



## jdamico

Will share my mods on my LD mk III.
   
  First of all, one of my goals was not to change the external aspect of the LD mk III with cables running in and out and or external caps or components.  The LD mkIII internally have aprox 3.5cm height with aprox. 2.3cm over board space height to accomodate components and aprox 1cm available for extra components on the reverse side of the circuit board.  This is a pretty restrictive size to make mods, but finally succeeded.
   
  I focused on the main problems (from my point of wiew and stricly IMHO) that are the input and output caps.
   
  My Litte Dot arrived on 2013 and doesnt came with any WIMA cap.  The input cap was a Polyester one ("3,3k N5 MMK 50" printed on it) don't know the brand (maybe kemet or Rifa).  The output cap is a 220 uF electrolytic (high temperature and high expected life) bypassed with a cheap polyester metallized film cap (chinese CL21 "CL21 684J 250V" printed on it).
   
  So, first of all I wanted to replace this caps, taking care of the size in order to fit them into the enclosure without problems.
   
  I selected WIMA MKP Polypropylene caps (the other option for me were obbligatos but the size was some how a trouble and wanted the shortest leads as possible to reduce inductance at high frequencies).  Also selected another bypass capacitor, the well known Vishay MKP 1837, to bypass the WIMAS.  I used this combo in the past and for me is a winner.
   
  The short lead problem (on board through hole designed) of the WIMA's was succesfully solved using uninsulated 24-26 AWG butt splice connectors from farnell (crimped and also with a little soldering "drop" in the open middle of the connector).
   
  Finally the Mods:
  Input cap:  WIMA MKP10 3.3uF 250V bypassed with Vishay 1837 0.068uF 150V
  Output cap: same stock electrolytic cap bypassed with two other caps both in paralell, one WIMA MKP4 0.68uF 250V + Vishay 1837 0.1uF 150V.
  220uF/16V capacitor of the driver tube substituted with Rubycon 220uF/35V ZLJ series (105°C - 10000 hours).
   
  The WIMAS were fitted in the main side of the circuit board and the Vishay on the reverse side (Vishay's are very little).
   
  In the future plan to change the 100K Alps 16 (16mm diameter) with a 100K stepped pot (21mm diameter), my initial physical measurements says that will fit well (the pot is fixed on the aluminium front panel but is very close to the circuit board edge and pot diameter space available is very restricted).
   
  If I can find some very good aluminium electrolytic pencil shaped (max 2.1mm diameter) 220uF/250V like Jensen, maybe will try to substitute as well in the future.
   
  Initial impressions:
  From the very beggining and after some burn in time 20-40 Hrs I have to say that the highs are much clearer and the grainy sound heard in some recordings almost dissapeared.
   
  My conclussion is that this mod results in a worth while work.
   
  Will try to post some pictures, but I'm new to this forum and maybe this feature is not enabled to me now, but soon...


----------



## jdamico

Have to say that all the internal components on board in the Little Dot MK III are 85°C or 105°C long life ones, but never measured more than 45°C with my tester in the hottest point of the external enclosure side (very close to the tubes), even after  hours of use.
  Tubes generates heat but they can dissipate directy to the surrounding air and I can't find any overheat problems that can shorten the expected life of the components, even assuming that internally there is more temperature (of course) that exernally (I assume that after hours of use the temperature gradient internal-external should be little, no more than 5 degrees).


----------



## jdamico

After some hours of listening I found that Vishays 1837 get too much brilliant in the highs and are a not good by-pass cap for electronic signals (maybe if used at very little values of capacitance this trouble will improve).
I like clear and open highs (not birilliant) and tried another by-pass combinations with cheap (non-boutique) caps.
Found that the best for me is the following:
Input cap: WIMA MKP10 3.3 uF  bypassed with Obbligato Gold 0.047 uF
Bypass for the output electrolytic stock cap:  Obbligato gold 0.68 uF
After 50+ hours of listening this combo shows clear mids and highs that makes the sennheiser HD650 sound really magnificent.


----------



## GCooper

Here's a question for folks interested in modifying their LD III amps:
   
  Decades ago my uncle owned the biggest tv/radio sales and repair shop in town. He insisted that tube equipment needed a separate stepped "on" switch arrangement for the filament supplies. He claimed it would extend tube and equipment lifespan vs. an "on" switch that gave an audible thump.
   
  Should tube amps have a two-stage on switch? Or is this out there in the land of hand-loomed at midnight by virgins gold wiring harnesses?
   
  Thanks
   
   
  FWIW, I wish the amp had a deep red or amber "on" LED. The blue is almost painful at night. A volume control with arbitrary markings from 1-11 would be a nice touch too.


----------



## SebastianL

Owning the LD MKIV for several years now as well as other tube headphone amps I have never experienced an audible thump while powering up any of these 
	

	
	
		
		

		
			





.
  Guess it's because a headphone amp doesn't draw as much power as a speaker amp. However I'm sure that a separate switch arrangement for the filament wouldn't hurt. But how or where would you find the space to put it? The stupid little shoebox doesn't leave much room for improvement.
   
  Concerning the dreadful blue LED I swapped it with a red LED because the blue one was driving me crazy. Be aware that LEDs come with different light intensity. The red one I bought is quite dimmed. For some reason all chinese equipment come with blue LEDs. Makes it easier to tell them apart though 
   
  Disclaimer: Mind you I have limited knowledge about electrical design. I'm just talking from experience. (just one tiny shock hazard so forth).


----------



## derbigpr

Problem with the MKIII I had is a faulty volume pot, I think. Read below to see the whole story and say if you think the volume pot is a problem too.
   
  For a short version of the question... which volume pot should or can I buy?  Should I just get the same Alps 16 100KAX2 as stock, or is it worth while to upgrade to a better pot?
   
   
  Now, for the problem:
   
  I bought a used MKIII. Worked fine for a few hours, then left channel stopped working completely. Right channel worked fine. White RCA input signal didn't reach the headphones, but input going trough the red RCA did work.  So I tried replacing tubes, different power cable, different RCA cable, source, fuse, etc. Nothing changed, always right channel worked, left didn't. 
   
  So I opened up the amp and saw some cables fell off of the volume pot. While trying to get the volume pot off, I ripped off the rest of the cables.  Now I soldered them again, in the same order as they were before and as they should be soldered, and now the LEFT channel works, but the RIGHT one doesn't.  And its not the case of me soldering wrong channels, because now the WHITE rca input works, but the RED rca doesn't, so its the opposite to before.  My guess is the reason for that is my poor soldering, because it really is poor.
   
  Also, the volume pot sometimes seems smooth when turning, but sometimes its rough. Like there are spots that are rough, and not always on the same place, like there's something inside the volume pot moving around and screwing with the signal. I guess I'll just have to replace it.


----------



## jdamico

The little dot mk III  comes with a 100kohm Alps 16mm diameter Pot.  From new I had some issues with this pot, sometimes when turning + or - the volume knob it was some noise (bad contact scratching inside the pot) and so I decided to change it.
   
  At first I checked if  a bigger pot would fit in the Little dot little mkIII chassis and enclosure, and the conclusion is that the maximun body diameter allowed to fit is 21mm diameter.
   
  I found on ebay a DACT stepped pot 100K with 21 mm diameter from China ($12) and same kind of shaft.  I'm posting the picture here.  Very fine and good pot.
   
  I will strongly suggest to change the original pot to an stepped pot 100K 21mm diameter, all the noise when moving the knob disappeared and the sound is more accurate and tigth.  
  The cables in the LD are very thin and you have to desolder and solder carefully because the length also is constrained (can't cut to shorten the cable).  Of course you can make an entire new and strong cable, but this was not my goal.
  There is only one grounding cable and you have to insert a little copper "bridge" between L and R ground on the new pot before soldering the cable.   After soldering use a silicon hot glue gun to fill the place, this will add mechanical strength and galvanic isolation.


----------



## jdamico

After +250 hours can share the results of my mods (strictly IMHO).
   
  Input cap: WIMA MKP10 3.3 uF  bypassed with Obbligato Gold 0.047 uF
   
  Bypass for the output electrolytic stock cap:  Obbligato gold 0.68 uF  (didn't changed the output electrolytic stock cap because there is not enough space to do it without changing the whole Little Dot external aspect).
   
  Alps pot changed to DACT stepped 21mm body 100k pot.
   
  Output tubes:  stock russian (the best)
   
  Input (drive) tubes:  Tung Sol Jan 6AJ5 dated 1945
   
   
  The first 40hrs hours of listening are some how unpleasant:  The new caps sounded brigth (not bad but unreal), so is mandatory to give them some time to burn in.
   
  After 50+ hours things become better and better.  Input caps:  you get the best of both worlds:  Wimas tigth bass and obbligato's liquid, clear and beautiful highs.
   
  Pictures:  didn't remember to take pcb pics with the LD wide opened when doing the last mods, so they are taken only from the front
  without the aluminium front cover.


----------



## derbigpr

Quote: 





jdamico said:


> The little dot mk III  comes with a 100kohm Alps 16mm diameter Pot.  From new I had some issues with this pot, sometimes when turning + or - the volume knob it was some noise (bad contact scratching inside the pot) and so I decided to change it.
> 
> At first I checked if  a bigger pot will fit in the Little dot little mkIII chassis and enclosure, and the conclusion is that the maximun body diameter allowed to fit is 21mm diameter.
> 
> ...


 
   
   
  Thanks for this. I will have to change the cables on mine as well, because I already made them shorter...and now they're a pain to solder. They're also horrible quality. VERY thin, but at the same time, they dont bend, the isolation feels like plastic rather than rubber. I'll have to get a thicker wire. 
   
  In fact, I'm sorry to say this, the entire MKIII amp is of poor quality.  Not the aluminium case which looks good, but the inside is very badly put together. Very poor soldering,  wires are thin and brittle, half the solder joints are brown and rusty looking, etc. Not a nice sight when opening the amp.  It obvious why some amps cost more than others...and its not just their performance that matters. For example Nuforce HDP or Musical Fidelity V-CAN are so perfect looking on the inside, everything is precise and clean, like a swiss watch, while MKIII looks like it was built during a coffe break by someone who didn't really care much for it. Not to mention its impossible to get the components out without desoldering certain wires, which is totally ridiculous and makes any repair much more time consuming than it has to be.


----------



## jdamico

> In fact, I'm sorry to say this, the entire MKIII amp is of poor quality.  Not the aluminium case which looks good, but the inside is very badly put together. Very poor soldering,  wires are thin and brittle, half the solder joints are brown and rusty looking, etc. Not a nice sight when opening the amp.  It obvious why some amps cost more than others...and its not just their performance that matters. For example Nuforce HDP or Musical Fidelity V-CAN are so perfect looking on the inside, everything is precise and clean, like a swiss watch, while MKIII looks like it was built during a coffe break by someone who didn't really care much for it. Not to mention its impossible to get the components out without desoldering certain wires, which is totally ridiculous and makes any repair much more time consuming than it has to be.


 
   
   
   
  Yes, all you said is truth.  But for the price is one of the best performing headphone (and line) amps out there.  And if you have some soldering skills and love mods and tube rolling, can be a very satisfying thing.  The bad is the little enclosure with almost no additional space.
  Mine came with cheap chinese film capacitors (not even wima or another well known brand) and so decided to change them all.
  Electrolytics are a reasonably good standard for tube amps (long life, high temperature ones).
  In mine the solder joints are not bad but miserly stingy. The good is that this make more easy to desolder things.
  Good luck.


----------



## derbigpr

I have another question related to volume pot.  I decided I'll go with the classical Alps 16 100k pot, as stock inside the MKIII. But my problem now is, there seem to be many variations of alps 16 pot.  I found two types of 100k pot,  the 50W and 100W ones. I assume W means watts, but which one should I take?  Does it even matter? Prices are the same.
  Also, what kind of wire should I use to connect the PCB and the volume pot? Does it matter even? Can I use just any copper, insulated piece of wire or does it have to be special?


----------



## jdamico

Never saw something like 50W or 100W  in audio pots.    All audio pots of this kind are max 1/4 watt; typical 1/8 watt or less for sure.  Sorry, can't help you with this.
  Alps pot used in LD mk III is, as far as I know,  old stock not in production now, but there is a huge inventory in China.
  Most important things to select the pot are:  100Kohm, Type "A" (for audio),  stereo (X2),  max 21 mm body diameter,  shaft diameter 1/4"  (stepped pots with individual resistors for each step are the best for audio and lasts almost forever).
  IMHO any good insulated copper cable will do the work, but avoid more than 22 AWG gauge and more than 300V insulation if you don't want to figth to solder and to bend them inside the enclosure. Length of cables should be the shorter as possible but don't worry too much about it as with the quality of the potentiometer.


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## derbigpr

Quote: 





jdamico said:


> Never saw something like 50W or 100W  in audio pots.    All audio pots of this kind are max 1/4 watt; typical 1/8 watt or less for sure.  Sorry, can't help you with this.
> Alps pot used in LD mk III is, as far as I know,  old stock not in production now, but there is a huge inventory in China.
> Most important things to select the pot are:  100Kohm, Type "A" (for audio),  stereo (X2),  max 21 mm body diameter,  shaft diameter 1/4"  (stepped pots with individual resistors for each step are the best for audio and lasts almost forever).
> IMHO any good insulated copper cable will do the work, but avoid more than 22 AWG gauge and more than 300V insulation if you don't want to figth to solder and to bend them inside the enclosure. Length of cables should be the shorter as possible but don't worry too much about it as with the quality of the potentiometer.


 
   
   
  Sorry I meant 50 mW and 100 mW, not watts.  I'll try to find an acceptable wire in one of my old broken speaker amps. I bet there are wires inside that I could use.


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## jdamico

For LD mk III you can search on ebay for: DACT Type 21 Stepped Attenuator Potentiometer 100K 2A3 (let me clarify I don't have any relation with this seller and is not my intention to promote him).
  Not only will fit perfectly mechanical and electrical, but is a clear upgrade over the stock pot.  I'm using it, very happy with the results, and is my best advice.
  For short cables handling small currents I have a recycle trick: if you have an old and damaged computer case standard power supply, you will find that is plenty of 18 AWG 300 Volts cables of different colors.  You can cut and use them, they are very flexible and better than LD stock.


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## SebastianL

Nice job jdamico. Swapping or bypassing the caps really made a huge difference in my LD MKIV SE. One piece of advice though: be careful with the hot glue as it tends to melt once the amp gets hot. Especially close to the tubes. I glued my Jantzen caps to the pcb at first, but they all came off after a while.


----------



## derbigpr

Quote: 





jdamico said:


> For LD mk III you can search on ebay for: DACT Type 21 Stepped Attenuator Potentiometer 100K 2A3 (let me clarify I don't have any relation with this seller and is not my intention to promote him).
> Not only will fit perfectly mechanical and electrical, but is a clear upgrade over the stock pot.  I'm using it, very happy with the results, and is my best advice.
> For short cables handling small currents I have a recycle trick: if you have an old and damaged computer case standard power supply, you will find that is plenty of 18 AWG 300 Volts cables of different colors.  You can cut and use them, they are very flexible and better than LD stock.


 
   
   
  Ahhh, yea, I have loads of power supplys at home. I'll take them apart and have a look. Thanks a lot, i totally forgot about that.


----------



## derbigpr

Is it normal that when I start the amp, for the next 10-15 minutes there's slight ticking audible from the headphones? Its not loud, barely audible, it sounds like metal hitting glass, very gentle sound. Does that mean tubes might be ready for replacement?


----------



## jdamico

> Is it normal that when I start the amp, for the next 10-15 minutes there's slight ticking audible from the headphones? Its not loud, barely audible, it sounds like metal hitting glass, very gentle sound. Does that mean tubes might be ready for replacement?


 
   
  Sparkling inside tubes?
  Tubes should have near 2000 hrs of life (standard tubes, military made tubes will last even more). Make your own calculations based on your average listening sessions.
  Check the heater wires (6.3V from the transformer), maybe they have poor soldering and the tubes have a cold start.
  Also you can write to LD in their forum to have an answer direct from factory.


----------



## derbigpr

Quote: 





jdamico said:


> Sparkling inside tubes?
> Tubes should have near 2000 hrs of life (standard tubes, military made tubes will last even more). Make your own calculations based on your average listening sessions.
> Check the heater wires (6.3V from the transformer), maybe they have poor soldering and the tubes have a cold start.
> Also you can write to LD in their forum to have an answer direct from factory.


 
   
  No sparkling on the tubes at all, I was checking that very carefully. The clicking noises disappear after about 10-15 minutes.


----------



## SebastianL

It could be the tubes heating up if the room temperature is rather cold. I've heard sounds like this as well both from my LD and from my all tube speaker amp. If you hit the tubes gently with a fingernail while the amp is powered up, you are likely to hear a similar sound due to some microphony in the tubes.
Tube rings might help.


----------



## jdamico

SebastianL wrote: 





> Nice job jdamico. Swapping or bypassing the caps really made a huge difference in my LD MKIV SE. One piece of advice though: be careful with the hot glue as it tends to melt once the amp gets hot. Especially close to the tubes. I glued my Jantzen caps to the pcb at first, but they all came off after a while.


 
   
  Thankyou, At first I was afraid because heard lot of comments about sound smearing when bypassing caps, but the results are very pleasant and satisfactory, and of course the amp sounds better than the original stock amp.
  The hot glue or another insulation is horrible but necessary because the Obbligatos gold comes with external metal shield  and have to avoid the accidental touch between them and pcb solder joints and/or  component leads, but my LD never gets hot enough inside to melt the silicon.  I measured max. 60 celsius after hours at 75% volume knob.


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## lemonjelly

I've got the mk III version, which I use with a pair of HD650s, and have made quite a few changes since I first bought it (a couple of years ago).  I started with trying to change the caps - basically following this thread - but found that the case really was pretty bad to work in.  I ended up ditching the chassis for 1 that I built myself, that's about 3 times as big !  But for me it made sense as I wasn't really restricted by the cap size and it was much easier to do stuff and then change it again if it didn't work out.  Cos it'll be easier I'll put in the schematic of the original mkIII amp, and it might be useful for anyone as reference when modding (I did this pretty quickly but it should be correct).  I also about halfway along desoldered anything I needed from the PCB and went completely to point to point wiring (it meant I had more space and could position everything how I wanted).
  

  
 Cos I switched out the caps so long ago I can't remember that well the differences that they made, they were definitely all positive, but the biggest differences from what I remember were with the change of the 0.22s and the inclusion of the 3.3uFs as bypass in the power section.  Currently I have:
  
 Russian K40-9s PIOs (I think) as replacement to the 0.22s, 3x K75-10s 3.3uF bypassing each PS cap, ampohm tinfoil 0.047uFs to replace the same in the PS section, panasonic 470uFs to replace the 3 x 330uF PS caps, Rubycon 330uF to replace the 220uF caps, 0.1uF teflon FT3s as bypass for the Rubycons and 0.68uF K75-10s to replace the same in each section. 
  
 I also had a 3.3uF Jantzen superior as input cap in each section (replacing the 2.2uFs), but ended up taking them out entirely as Sebastian had earlier in the thread.  You have to be very careful of course if you're doing that cos from what I understand if your source has any DC offset, then this will get amplified and blow up your headphones basically...  I also kinda messed up the wiring on the volume pot, and found that as I use it with a HTPC/DAC set up pretty much all of the time I was happy to just use the volume on the PC.  So rather than buy a new pot, I soldered in resistors from the rca signal to ground and where the 2.2uF cap is.  I think I've got a 2k to the 2.2uF, and a 330 to ground (I found I used about a range of 6->8:1 ratio on the original pot).  The total value to use here from what I've read, seem to depend on the output impedance of your source (10 times that value seems to be the guidance).  I'm using a DAC exclusively, which has about a 50 ohm value, and so I thought to play it safe I'd go to around 2k.  I also just put in a single resistor of 80k instead of the gain resistors (the gains correspond to x3->69k, x4->83k, x5 ->150k, x10 ->470k).
  
 Part of the reason I uprated the values of the caps above, was that those are the stock values for the mk IV (the 330uFs are 470 and 220uFs 330 in the IV).  Other changes between the IV and III are the 120 resistors are all replaced by 150s on the IV, and the EF95 heaters are regulated.
  
 Those changes were all good + I rolled tubes, settling on 6n6ps with the Mullard EF92 or the russian EF95s.  But from the rolling thread (which is great) and what they've discovered I ended up switching the drivers to a Tung Sol 6SN7.  The difference was immediately obvious, especially as far as bass and soundstage.  Everything seemed a lot more real.  The 6SN7 needs seperate power for the heaters so I just used a DC PSU I had (7.5V / 2A), which I found stayed stable at 6.35v when the tube was connected.  After I made the switch I decided I wasn't really ever going to use the EF95/92s again, so I actually replaced the 2 sockets with the single octal (no more wires going everywhere).
  
 After that I thought I'd have a play with some of the plate resistance/cathode bias settings for the 6SN7/6N6P.  For the 6SN7 the plate bias is set by the 33k/1W resistors.  I tried 40k, 16k and 10k.  I didn't really notice much difference with the 40k, a big change with the 16k (I felt as big as the original change to the 6SN7 from the EF95/92s) and from the 16k the 10k was worse.  With the 16k the sound stage seemed much better, and everything seemed more musical (toe tappability).  I then changed the cathode bias resistors (the 680 for the 6SN7), going up and going down.  I didn't really notice a huge difference sound wise.  I then tried led bias instead, wiring in an led to drop voltage instead of using a resistor.  This seemed to sound worse, but was probably because the led didn't have enough current to react linearly (the 6SN7 current was only about 3mA when the led really needs more than 5).  Finally I tried using 2xAA rechargeable Nimh batteries (about 2.7v in series).  This seemed to sound best to me (but the change wasn't as big as the change to 6SN7 or to plate resistor).  With the led and battery it's as simple as replacing the 680 resistor and 220uF cap with whichever you're using, and wiring the +ve to pin2 of the EF95 socket, and -ve to gnd.  With the 6N6P I didn't bother changing the plate resistor (which I think is probably the 120/1W R6 on schematic), but I tried different values for the cathode bias.  I settled on 200 eventually, after trying battery/led/100/87/150/200, I didn't like the led or battery, and there didn't seem a huge difference between the other numbers.
  
 Basically the above is changing the plate voltage, current and bias voltage of the tubes when you change the values.  You can look at the curves for the tubes you're using and see what operating point you want to aim for.  Generally increased cathode resistance means plate and cath v goes up, and current goes down, increased plate means plate/cath/current go down.  For the plate resistance I'm not certain but from what I've read it seems like it affects the voltage swing (i.e. bigger the more dropped over the resistor) and gain.  For the values I've got figures for, with plate resistance/cathode resistance:
  
 6SN7                                                                                                          6N6P                                                                             
  
 33k/680 (2.4v)       3.5mA @ 85v                                                                   120/120           18mA @ 107v
 33k/2.8v led          3.18mA @ 95                                                                  120/150           16.3mA @ 112v
 39.8k/2.8v led       2.86mA @ 90v                                                                 120/87             20.3mA @ ~100v
 39.8k/2k (4.45v)    2.225mA @ 118v
 39.8k/2.7v battery 3.44mA @ 69v          
 16.5k/2.7v battery 5.4mA @ 115v
 21.6k/2.7v battery 4.7mA @ 107v
  
 As well for the 6N6P I went to an external PSU for the heaters, and changed the cathode resistor to 200.  I found that sounded best and got figures for that of 16.5mA @ 128v, with the 16.5k/2.7v battery setting with the 6SN7.  Mods that I've been looking at possibly doing are a CCS for the plate on the 6SN7 instead of the resistor (but I don't really know enough at this point), and cheap chokes in the PS section in place of the resistors (I've got space on top of the amp).  I've also got a couple of 6AS7s on the way which will hopefully make a big difference.  I keep meaning as well to replace the signal resistors with something other than the generic metal film I have currently.
  
 Lonnnngggggg post, but I've had a lot of fun just trying different things with this amp - especially as a lot of these were pretty cheap to do - and of course I'm not suggesting that I understand everything that is going on.  I've been learning as I've gone on so if there is anything I've done that's really stupid I'd appreciate people saying, but at this point the amp sounds great with headphones or as a pre amp.
  
 Final edit:  thought it would be useful to include the pin changes for 6SN7/6AS7 for the 7 or 9 pin sockets (all taken from the rolling thread, so thanks to those guys).
  
 The 6n6p on the LD should be OK supplying up to about an amp, with the EF95s only able to put out 0.2-0.3A, so for the 6SN7s you can use the heater supply from the 6n6p socket, but otherwise for the 6SN7 in the EF95 socket, or the 6AS7s, you'll need an external power supply.  The 6SN7 pulls 0.6A, and the 6AS7s pull 2.5A, both at 6.3v.  You could potentially run 2 tubes from a 12v supply in series without a regulator (just make sure the current rating is high enough + check the voltage at the tube pins, 5.7-6.9v is OK).  I also ran 2 6080s (6AS7 types) from a computer PSU 12v line in series, but it wasn't happy and started cutting out.  But you're best buying a power regulator like this to make it all easier.  Currently I've got a 19v/3.5A laptop PSU with a regulator, running the 2 6080s in parallel @ 6.3v each.
  
 9 pin (6n6p)         6SN7/6AS7                6SN7/6AS7             7 pin (EF95)
 1 (A1)                      2                           1 (G1)                  1 (L)
 2 (G1)                      1                           2 (P1)                  5 (L)
 3 (C1)                      3                           3 (C1)                  2 (L)
 4 (Heater)                7/8                         4 (G2)                  1 (R)  
 5 (Heater)                7/8                         5 (P2)                  5 (R)
 6 (A2)                      5                           6 (C2)                  2 (R)
 7 (G2)                      4                           7 (Heater)             Ext. heater  
 8 (C2)                      6                           8 (Heater)             Ext. heater
 9 (Screen - Gnd)        -


----------



## TrollDragon

lemonjelly said:


> Lonnnngggggg post, but I've had a lot of fun just trying different things with this amp - especially as a lot of these were pretty cheap to do - and of course I'm not suggesting that I understand everything that is going on.  I've been learning as I've gone on so if there is anything I've done that's really stupid I'd appreciate people saying, but at this point the amp sounds great with headphones or as a pre amp.


 
 Most excellent testing and work!





  
 Nice Schematic as well, I have a hand drawn MK IV version that I cobbled together.
  


Spoiler: MK IV Rough Schematic


----------



## gibosi

lemonjelly said:


> Lonnnngggggg post, but I've had a lot of fun just trying different things with this amp - especially as a lot of these were pretty cheap to do - and of course I'm not suggesting that I understand everything that is going on.  I've been learning as I've gone on so if there is anything I've done that's really stupid I'd appreciate people saying, but at this point the amp sounds great with headphones or as a pre amp.


 
  
 Pictures! Do you have any pictures? Let's see this beast!


----------



## lemonjelly

It's not ready for public viewing - I need a new top plate - but I kinda did the same thing as with the Bottlehead Crack.  So a simple open base of wood with a top plate (currently just 5mm acrylic).  I'm expecting if I like the 6AS7s I'll probably then take the 6n6p sockets out too... the insides are definitely function over form as well, I'm all for short distances and ease of modification really.
  
 + great to hear from you guys, I've kinda read parts of the tube rolling thread, fantastic work in there + the 6SN7 made an immediate diff (hoping for the same with the 6AS7s).


----------



## LPP6

lemonjelly said:


> I've got the mk III version, which I use with a pair of HD650s, and have made quite a few changes since I first bought it (a couple of years ago).  I started with trying to change the caps - basically following this thread - but found that the case really was pretty bad to work in.  I ended up ditching the chassis for 1 that I built myself, that's about 3 times as big !  But for me it made sense as I wasn't really restricted by the cap size and it was much easier to do stuff and then change it again if it didn't work out.  Cos it'll be easier I'll put in the schematic of the original mkIII amp, and it might be useful for anyone as reference when modding (I did this pretty quickly but it should be correct).  I also about halfway along desoldered anything I needed from the PCB and went completely to point to point wiring (it meant I had more space and could position everything how I wanted).


 
 Thanks for a great post. Is that schematic for the LDIII circuit board v1 or v2?


----------



## lemonjelly

lpp6 said:


> Thanks for a great post. Is that schematic for the LDIII circuit board v1 or v2?


 
 Hi, mine was the v2.  I think the only difference was the plate resistor for the 6n6p was 68 in the old version (Rs 5+6 in the diagram).
  
 Edit:  Actually thinking about it maybe the 2 180 resistors in the power section were less than 5W on some of the mkIIIs (I remember seeing some burnt out), and the v2 has a single 33uF, where it used to have 1 for each channel.  I ended up using 2 33uFs, but originally between the 3.3k and 33k both channels were connected to a single 33uF (C6).


----------



## lemonjelly

Just an update after installing 2 x Thomson 6080s (6SA7 type) instead of the 6n6ps.  The current draw from my old config went from less than 50mA with the 6n6ps to over 170mA with the 6080s (over 80mA per 6080)... so I wanted to reduce that.  And the increased current also meant the 6SN7 tube was getting a much lower voltage because of the power loss in the power resistors (the 2 180s), so it went down to around 3mA from the 5+mA previously.  The main reason I wanted to reduce the current was to find a better operating point for the 6080s + the 6SN7, but I wonder how well the transformer handles the increased current (the largest current with an "official" upgrade of DRs + EF91s would be less than 100mA), and the power resistors are also seeing pretty large wattage:
 V = IR, so @ 170mA, V = 0.17*180 = 30.6v... so P = VI = 30.6*0.17 =  5.202W (ie exceeding the rating of the 5W resistors).
  
 And for anyone using the 6AS7s, I'd assume with the stock LD mk IV you might see less than 170mA (cos of the 120 resistors being replaced with 150s), but with the LD mk III I would possibly expect this current or higher (I had a larger cathode resistor @ 200 than the stock mk III which will have reduced the current a little).  These are assumptions though as I say... my amp is pretty far from stock at this point (although a lot of the values that matter are still the same), so YMMV.
  
 In the power section I ended up replacing the 360 resistance with 170 resistance, and increased the total capacitance from 1410uF to 2160uF to compensate a little for the increased ripple.  This gave me a little extra voltage for the 6SN7.  
  
 I also changed the cathode resistor on the 6080s from the 200 to 660 (2x330r @2W each), which then reduced the current draw to a total of about 130mA (around 58mA per 6080, with  4.5-5mA for the 6SN7 sections).  This sounds a bit better, although not really had much time to tell.
  
 Edit: forgot that you need to uprate the 220uF/16v caps in the cathode if you increase the cathode resistance much, I just put in the old output capacitors which are 220uF/200v.  With 660 resistance I've got 38.2v cathode voltage, with 135v plate reading, so overall the 6080s are running at ~ 58mA @ 97v (you subtract the cathode voltage from the plate reading to get the actual plate voltage as on the curves).


----------



## SebastianL

Hey wow lemonjelly. Thanks for the very comprehensive post!
 SInce my posts in this thread I've moved on to a solid state Questyle amp, but if  one day I find the time I'd like to try the 6SN7 modification as I have some of these tubes already.
 Keep up the good work


----------



## bbmiller

trolldragon said:


> lemonjelly said:
> 
> 
> > Lonnnngggggg post, but I've had a lot of fun just trying different things with this amp - especially as a lot of these were pretty cheap to do - and of course I'm not suggesting that I understand everything that is going on.  I've been learning as I've gone on so if there is anything I've done that's really stupid I'd appreciate people saying, but at this point the amp sounds great with headphones or as a pre amp.
> ...


 
  


trolldragon said:


> lemonjelly said:
> 
> 
> > Lonnnngggggg post, but I've had a lot of fun just trying different things with this amp - especially as a lot of these were pretty cheap to do - and of course I'm not suggesting that I understand everything that is going on.  I've been learning as I've gone on so if there is anything I've done that's really stupid I'd appreciate people saying, but at this point the amp sounds great with headphones or as a pre amp.
> ...


 
 Do you think from looking at the way TrollDragon draws the 6.3 volt portion of the power supply that in its on modified form the little dot MK four headphone amplifier uses AC rather than DC voltage and current to heat its tubes and an alternative way to modify this amplifier to supply more current to the power tubes would be to drill a hole in the chassis and simply remove the wires from the press and transformer supplying the 6.3 AC and replace it with the more hefty external AC step down transformer with no regulation or rectification?


----------



## bbmiller

trolldragon said:


> Nice Schematic as well, I have a hand drawn MK IV version that I cobbled together.
> 
> 
> 
> Spoiler: MK IV Rough Schematic


 
 Do you think from looking at the way TrollDragon draws the 6.3 volt portion of the power supply that in its on modified form the little dot MK four headphone amplifier uses AC rather than DC voltage and current to heat its tubes and an alternative way to modify this amplifier to supply more current to the power tubes would be to drill a hole in the chassis and simply remove the wires from the press and transformer supplying the 6.3 AC and replace it with the more hefty external AC step down transformer with no regulation or rectification?


----------



## lemonjelly

bbmiller said:


> Do you think from looking at the way TrollDragon draws the 6.3 volt portion of the power supply that in its on modified form the little dot MK four headphone amplifier uses AC rather than DC voltage and current to heat its tubes and an alternative way to modify this amplifier to supply more current to the power tubes would be to drill a hole in the chassis and simply remove the wires from the press and transformer supplying the 6.3 AC and replace it with the more hefty external AC step down transformer with no regulation or rectification?


 
 Hi, sorry not been watching posts so late reply... It looks like on the schematic TrollDragon has drawn he has the same config as I had on the MK III, he has the power led whereas as I don't as I took it out.  They both seem to use AC... I have seen where people have had voltage regulators on a mk IV so I assumed that it included some regulation (as I said above), but I don't really know, not having ever played around with 1.  
  
 If you want to replace the power wiring on a mk2/3/4 for a set of the tubes, it would simply be replacing the tube filament wiring with your own solution (like the laptop power supply with voltage regulator).  I would think from what I remember that you could clip the wires for whichever set of tube filaments you want to replace from the transformer (not too close to the transformer in case you want to use them again of course) which is on top of the case.  Then solder in your own power solution in their place, with the only problem being that you'd have to ensure you're sending a +ve and -ve wire to each tube (the 2 sets of tube filament wires on the mkIII had different colours, but each set of 4 was the same, so you might have to trace them in the chassis to ensure you do this).
  
 Anyway only really looking as I've played around a bit more, and now have replaced all of the resistors with vishay etc, uprated some of them power wise, and installed constant current sources as the plate load for both types of tube.  I'm using 85ohm/5w vishay in the power section, 680/5w for cathode bias on the 6AS7s and some schottky SiC diodes as bias for the 6SN7 (2 total for 1.6v bias, but mainly cos I thought they dropped more voltage).  For the plate loads I have a CCS for the 6AS7s using TL783s with 20ohm resistors, and a CCS for the 6SN7 using LM317s with 240ohm resistors, so running at 62.5mA and 5.2mA respectively (guide I followed here: http://www.diy-audio-guide.com/constant-current-source.html).  I'll probably end up buying a couple of chokes + possibly 2 x power transformers, and then turn the amp into mono blocks basically.  Again all more for interest than anything, although each modification to the amp does seem to improve/change it to some extent.  
  
 Edit:  Increased 6SN7 bias to 3.2v, reduced current to ~4mA... added 4x of the schottky diodes in place of the bridge rectifier, changed the 6AS7 cathode bias to 2xLM317 (running pretty close to max voltage though so if anyone else was doing it probably use TL783s instead or similar) @62ma with 20 ohm resistors + put the 120ohm resistors back as plate load for the 6AS7s.
  
 2nd edit: added a 2nd LM317 in front of the 1s already there in cathode for the 6AS7s (to make a cascode)... changed grid leak resistors to 150k (from 470k) and doubled coupling capacitors to 0.47u.


----------



## TrollDragon

Thanks for all the great info and work you have done lemonjelly!

I am going to have a look at that CCS over on DIY.


----------



## lemonjelly

I'd definitely recommend the CCS's *(but not with the LM317/TL783 - see below)*, they seem to sound a lot better, are really simple/cheap and don't take much space.  Just remember about the voltage difference between input/output though - only 37v for the LM317 and 125v for the TL783 - on mine the TL783 is at about 90v or so with 5ma.
  
 Edit: An update on the CCS experiments and everything else.  I took all of the LM317s/TL783s out as they add noticeable background hiss.  I couldn't really tell with the headphones I use when trialling but with the HD650s/probably any good headphone it was too much.  When I first put the HD650s on after doing the CCS mods I couldn't work out why the background noise had increased so much, and went back reversing some of the mods, and eventually found that any of the LM317/TL783 in the chain - bias or load - introduced hiss.  This is probably why you rarely see people using these in CCSs... so I am eventually going to order some parts from the states and when I do that I'll order some IXYS45s and DN2540s and probably use those in a cascode, maybe with something else behind them.
  
 So I've gone back to resistor plate loads, with 4xSiC diodes (3.2v) as cathode bias for the 6SN7s, and 680 resistor/220uF for the 6080s.


----------



## TrollDragon

Thanks I will keep that in mind.


----------



## buldogge

Hey Guys...Looks like this thread hasn't breathed in awhile...but...I'm wondering if anyone has ever had to swap out the headphone jack on a MKIII?  
  
 Any major issues/suggestions/warnings?
  
 Also, has anyone moved the transformer to a remote position with wiring to a bus of some kind to facilitate easier removal of the PCB from the chassis???
  
 I might be picking up a MK III as a project to jump into some modding based on some of the findings/posts in this thread...the amp is currently acting mono at the headphone jack so I was thinking of replacing it and the volume pot to start before getting into the caps.
  
 Does anyone have a sorta "finalized" plot of mods they believe in for this amp?
  
 Any help is greatly appreciated...
  
 TIA
 -Mark in St. Louis


----------



## 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:


ctritical bill said:


> 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.
> 
> ...


----------



## 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:


ctritical bill said:


> 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

buldogge said:


> 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.
> 
> ...


 

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


----------



## buldogge

koukol said:


> 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

buldogge said:


> koukol said:
> 
> 
> > I take it you don't know the answer to my question.
> ...


 

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


----------



## buldogge

ctritical bill said:


> 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

bharat2580 said:


> how do you actually open up the thing..


 


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


----------



## bharat2580

derbigpr said:


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


 

 ok now can we talk sense again.


----------



## derbigpr

bharat2580 said:


> ok now can we talk sense again.


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


----------



## bharat2580

derbigpr said:


> 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

bharat2580 said:


> 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 (Mar 13, 2018)

Ctritical Bill said:


> 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 :
> 
> 
> ...



------
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 (Mar 17, 2018)

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 (Mar 20, 2018)

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

buldogge said:


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



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.


----------



## SonicJedi

I believe this will be my last post on the upgrades / mods. I had another go at it and changed the PS caps as well. I replaced the 3 x 280uF nippon chemi-con caps with 3 x Nichicon 330uF caps. I also bypassed the 0.68uF output caps with 0.01uf Vishay 1837. 

The results, which I credit mostly to Vishays, are astounding. The piano notes go high, and have weight behind them and they decay beautifully. The bass is still tight and authoritative with my Paradigm Studio 60v5. I am very happy with these changes. I haven't had a chance to try how this setup will sound with my Senn HD 700s. 

In summary, this is what I've replaced on LD MKIII v4 board:
1. Replaced the two crappy orange film generic looking things with 2 x 0.68 Mundorf Mcap Evo Oil Aluminum.
2. Replaced the PS bypass generic looking orange crap with 2 x 0.47 Vishay MKP X2 safety caps.
3. Replaced 4 x Ero 1840 0.22uF with 4 x Mundorf Mcap Evo Oil Aluminum 0.22uF.
4. Replaced 3x PS caps Nippon chemo-con 280uF to Nichicon 330uF. 
5. Bypassed 2 x 0.68 Mundorfs with  0.01uF Vishay 1837.

All of this fits in the case. Although, it takes forever to get things back in again. 







------------------

I


SonicJedi said:


> 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
> ...


----------



## blakean

Is it possible to test whether the Mk3 is working properly before I undergo the process of pushing it back into its casing? I have a hum issue that I'm trying to rectify and have taken the board out and would prefer not to have to do it again.


----------



## SonicJedi (Mar 28, 2018)

blakean said:


> Is it possible to test whether the Mk3 is working properly before I undergo the process of pushing it back into its casing? I have a hum issue that I'm trying to rectify and have taken the board out and would prefer not to have to do it again.



Unfortunately, I don't know the answer to this, and I personally wouldn't recommend testing it out of the casing due to safety reasons. However, I have couple of tips that may be helpful:
1. The hum: I had a hum and it turned out it was related to the power socket and ground issues. Once I plugged my DAC and LD to the same socket (via extension chord), so they were using the same ground, the hum went away. Also, I use my LD as pre-amp, and I saw the same thing when I connected it to the power amplifier. The solution was again connecting them to the common ground on the same wall.
But, since you already have your board open, make sure that the ground wire is soldered properly.

2. Closing the LD with relative ease:
I have found that the easiest way is to follow the following steps:
a. When putting the board back, make sure the only wires that are connected to the board are the power wires going to the power tubes, and the ground wire. All other wires at this point should be de-soldered and disconnected.
b. Insert the board from the back-side, and wiggle it pass the nut/bolt thing under the PS housing. I ended up using a plastic knife as a shoehorn to hold the wires down, and it works remarkably well.
c. Get the board out the other side, enough of the way so you can solder the power wires for the driver tubes. And then, the audio channel wires. This of course means, that you will already have to have the power wires for the driver tubes coming out of the other side, before you insert the board back in. Audio wires on the other hand are stiff and can be pushed in from either end when you are ready to solder them.
d. Now push the board back in and out the back-end about 1/4th of the board. At this point, you will solder the power cables to the caps, the power socket, and the audio signal cables to the RCA jacks.
e. Final step. Push the board back into it's place. Add 4 screws to hold the board up, and then connect the volume pot (assuming you have a socket based board).
f. Close the rear and front panels.

Good luck!


----------



## blakean

SonicJedi, thanks so much for this detailed and helpful response. I'm definitely going to give your method a try in the next couple of days.  

As for the hum, I did try different outlets (and different buildings) and had only the LD plugged in. So it appears that it wasn't a simple ground loop problem, which I originally thought it was when I bought the amp.


----------



## Boatmancalls

sonda2008 said:


> Stevebol,
> 
> Looks like the soldering quality is very poor not only on my MKIII. My clumsiness did not help either I guess  I think I figured out the pot wiring. It works fine... sometimes... well... I loose the left channel when I touch the pot in an improper manner  I had some problems with the pot before and I assume it got damaged during the process of rewiring. I’ll check my soldering job later but I’m quite confident I did a decent job with my soldering iron.
> 
> ...


Hi I realise it’s been a decade since you wrote this but could really do with some help with exactly the same issue.  Do you have any pics of the correct wiring on the potentiometer?  all the wires fell off as soon as I removed the front cover  
Many thanks


----------



## MIKELAP

Boatmancalls said:


> Hi I realise it’s been a decade since you wrote this but could really do with some help with exactly the same issue.  Do you have any pics of the correct wiring on the potentiometer?  all the wires fell off as soon as I removed the front cover
> Many thanks


Got a few pictures this from MK3 pot


----------



## Boatmancalls

Thanks so much for the reply.  My wiring colours look different to yours - I have Green, Blue, White, Black and Red coming out of the plug - which I assume corresponds to the 1-5 in the diagram above.  Time to get my soldering iron out and give it a try 

Thanks again


----------



## blakean

I needed this info a while ago. The wiring coloration (or lack of it) made the whole process a bit more time consuming than necessary, but I found that little colourful diagram that @MIKELAP posted to do the trick for me. This pot was a little trial-by-fire situation for an amateur solderer like myself. I ended up changing the wiring to solid colours just in case I ever have to do it again.

Good luck.


----------



## Boatmancalls

Thanks - yes my clumsy soldering will certainly be put to the test !! 

Thanks again

Simon


----------



## SonicJedi

Boatmancalls said:


> Thanks - yes my clumsy soldering will certainly be put to the test !!
> 
> Thanks again
> 
> Simon


Couple of suggestions:
1. email Sword Yang (little_dot at vip163.com) if you still need help. He's pretty responsive.
2. Take this opportunity to drop in a new and better quality pot. It will make a noticeable difference to your output. I recall that up to 21mm pot would work. Look for a 100k Alps original on eBay. Regardless of if you go for upgrade or not, make sure to fill and cover the wiring with silicone gel for galvanic isolation.

best of luck!


----------



## Boatmancalls

SonicJedi said:


> Couple of suggestions:
> 1. email Sword Yang (little_dot at vip163.com) if you still need help. He's pretty responsive.
> 2. Take this opportunity to drop in a new and better quality pot. It will make a noticeable difference to your output. I recall that up to 21mm pot would work. Look for a 100k Alps original on eBay. Regardless of if you go for upgrade or not, make sure to fill and cover the wiring with silicone gel for galvanic isolation.
> 
> best of luck!


Thanks so much for the help - just ordered a direct replacement and what I think is a better one from eBay 

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/362308916423

Fingers crossed


----------



## Andrew LB

SebastianL said:


> Quote:
> 
> 
> Concerning the 'missing' brown capacitor you could check the board to see if there are two empty soldering holes. (Probably close to the existing capacitor). Every component in the design should have a small text printed just next to where it's placed in the design (like '100K' for a resistor or '33uF 250V' for a capacitor). So if there is only one text with the '33uF 250V' printed you shouldn't worry.
> ...




Sorry for bringing up a decades old post but I took a look at my v2 board and and there is an empty capacitor slot and it’s does have the text underneath confirming that there should be another capacitor of the same size and type. I’m in the process of refurbishing and upgrading components on my mkiii after noticing two of the large 330uf caps were bulging.


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## SebastianL (Feb 20, 2019)

Andrew LB said:


> Sorry for bringing up a decades old post but I took a look at my v2 board and and there is an empty capacitor slot and it’s does have the text underneath confirming that there should be another capacitor of the same size and type. I’m in the process of refurbishing and upgrading components on my mkiii after noticing two of the large 330uf caps were bulging.



I'm sorry I can't quite comment on that as I have another version of the pcb - the mkIV. But as I said, try to email LD support they're usually responding.


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## Andrew LB (Feb 27, 2019)

Not sure if anyone found posted this already, but that connector for the volume pot that's on the main PCB is a JST XH series connector. I was considering replacing the header and wires with a better one but i think i may just solder the pot wires directly to the main PCB. The JST XH plug is just too loose for my liking.


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## Andrew LB

Is there a reason why you guys are using 0.47uf x2 film capacitors in the rear by the big electrolytics? The protection caps that came on my V2 were Carli .047k 275v MPX40/100/21 x2 film capacitors. I'm no expert but doesn't the K indicate 10% tolerance and the .047 indicate that it's .047uf? It says on the PCB under the cap 47n 250v. 47 nanofarads = 0.047 microfarads. Or am i completely missing something here? http://kaizerpowerelectronics.dk/theory/capacitor-code-table/


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## Andrew LB (Mar 8, 2019)

I changed out the four 16v 220uf caps on the signal side and replaced them with some Nichicon 16v 220uf FG (Fine Gold) audio caps. Sounds amazing. I also modded the back of the case and installed a new power socket/switch that also has integrated EMI Filter/Line Conditioner. I also got sick of the poor flexibility wires and decided to re-wire everything with some much higher quality 22ga copper 600v wire with silicone insulator. Only issue now though is the heater wires, which consist of 4 pairs. There is no marking to show + and -. I guess i could power it on without tubes and check the tube sockets using a multimeter. I found the this schematic and it just says HA and HB for the heater wires. No indication of polarity. Or is there no polarity on them? /confused.


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## Onik

Pricklely Peete said:


> Sure OK.....as always the moment anyone pulls a tube amp board or opens one up the following warning applies... High Voltage is present and it is extremely dangerous so make sure your large caps are drained of voltage and current. You also void your warranty, obviously
> 
> 
> 
> ...



I know it's really an old thread but I wanna ask does this mod also apply for MK II?


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## Seriosha

Hello, I hope this thread is still alive because I need a little help. Want to change the volume pot in my Little dot MKIII but I can't get it out, don't want to break anything but I don't know what to do after unscrewing the front panel, the pot seems fit in place by two little brackets, how to get it out without breaking anything?
By the way the pot in mine read 323G 50KAX2, so I was thinking about an Alps blue velvet  50K, right? Thanks in advance.


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