[b0bb]

  Hi B0bb, 
Are there anyway to reduce the supply voltage for the opamps in the output stage ? I tried 2 blue trimpot but it doesn't work.

There 4 trimpots, 2 by the regulators and 2 near the dac, which ones did you try?

 

[penguin69]

LKS mod update:
 
XO upgraded: Crystek 950
Output op amps upgraded: Burson double-sided discretes
I/V op amps upgraded: Ticha 994's
 
All sounding very good now. Far better than when I first acquired the LKS and listened to it for the first time (that was a very disappointing day).
 
Wondering what to focus on next in the upgrade path?

 

[b0bb]

 
LKS mod update:
 
XO upgraded: Crystek 950
Output op amps upgraded: Burson double-sided discretes
I/V op amps upgraded: Ticha 994's
 
All sounding very good now. Far better than when I first acquired the LKS and listened to it for the first time (that was a very disappointing day).
 
Wondering what to focus on next in the upgrade path?

There are a couple of options.
 
1)Replace the I/V resistors with Vishay TX-2575 Z-Foil  Metal foil resistors, 4 pcs needed.
Texas Components make these to order for about 10-15 USD each. I am using 0.005% tolerance, the gain of the I/V stage is purely detemined by the I/V resistor, the closer the match the lower is the distortion from the I/V conversion.
The temp coefficient is ±1 ppm/°C, the MELF metal film that is stock is ±100 ppm/°C

 

 
2) Replace the bypass cap for V_com. The existing electrolytic cap's leakage current is quite large, replace this with a low leakage cap like the yellow Tantalum bead cap shown in the above picture.
 
The stock 100uF Panasonic FM aluminum electrolytic cap has a leakage of 10μA, the Tantalum bead is 0.5μA
Th total current in the V_com reference is 100μA, so there is a 10% error from cap leakage with the stock cap.
 
Leakage current from electrolytic caps can vary wildly with temperature and the applied voltage, less so with Tantalum caps.
 
3)Replace the V_com trimpot with a Vishay Accutrim metal foil trimmer, these have very low temperature drift ±10ppm/°C, the stock Bourns has a temp coefficient of ±100ppm/°C.
 
V_com is the voltage reference for the D/A conversion, so a lot of things depend on this being  as stable and as low noise as possible.
 
4)The stock rectifiers can be replaced with low noise Schotttky types.

 

[dacusb]

Hi B0bb,
 
Can you help by giving me the link where to get the Tantalum bead 0.5μA?
Thanking you.

 

[penguin69]

There are a couple of options.
...

Thanks b0bb. These were the areas I was considering based on a re-read of the whole thread.

I'm actually pretty happy with the sound now. But that is no reason to stop.

 

[b0bb]

  Hi B0bb,
 
Can you help by giving me the link where to get the Tantalum bead 0.5μA?
Thanking you.

http://www.mouser.com/ProductDetail/Vishay-Sprague/199D107X9020F6V1E3/?qs=sGAEpiMZZMtZ1n0r9vR22R37xUugJl7tUjm7LYm%2fbeA%3d
 
100uF 20V tantalum bead.
7μA with 20V across the cap, this drops 10-15x (0.70-0.45μA) with 1V across the cap

 

[dacusb]

Hi B0bb,
 
Thank you for your reply. I will continue to upgrade my LKS accordingly.
I have the following problems using Singxer SU-1 and connect it to the LKS MH DA 003.
I connect the Singxer SU-1 to my LKS MH DA003 using HDMI/I2S ports. The setting on SU-1 is: Pin 2 and Pin 6-7 set to ‘on’. This works fine with PCM modes but become surprisingly unpleasant when I upsample music files (FLAC/WAV) to DSD modes using JRiver: the music from the left channel is switched to the right channel and vice versa (recently it seems that the sound becomes monophonic) There is also a loud “pop’ at the beginning/end of the song when I stop and re-start the music. How can I fix those problems?
I am very disappointed when Shenzhen Audio explained that is because of the LKS and not the Singxer and even suggested that I should replace the LKS using the Gustard X20 or PS audio dac instead which is ridiculous.

 

[b0bb]

  Hi B0bb,
 
Thank you for your reply. I will continue to upgrade my LKS accordingly.
I have the following problems using Singxer SU-1 and connect it to the LKS MH DA 003.
I connect the Singxer SU-1 to my LKS MH DA003 using HDMI/I2S ports. The setting on SU-1 is: Pin 2 and Pin 6-7 set to ‘on’. This works fine with PCM modes but become surprisingly unpleasant when I upsample music files (FLAC/WAV) to DSD modes using JRiver: the music from the left channel is switched to the right channel and vice versa (recently it seems that the sound becomes monophonic) There is also a loud “pop’ at the beginning/end of the song when I stop and re-start the music. How can I fix those problems?
I am very disappointed when Shenzhen Audio explained that is because of the LKS and not the Singxer and even suggested that I should replace the LKS using the Gustard X20 or PS audio dac instead which is ridiculous.

Your SU-1 is configured to connected to the Gustard X20.
In DSD mode the Gustard expects the I2S channel mapping of the left and right channels to be reversed  as you have noted.
This might be why the vendor is taking advantage of the situation to sell you the X20
 
 
The bank of DIP switches can change the behavior of the SU-1 to make it compatible with the LKS, contact Singxer directly for the info on how to set it up .
LKS I2S channel mapping mode is the same in PCM and DSD.
 
http://www.singxer.com/contact.jsp
 
Ask Singxer about the pop at the beginning and end of the song, one reason is the I2S clock being started and stopped, keeping it on all the time might fix things.
Singxer might be able to give you more info.

 

[dacusb]

Thank you B0bb for your guidance. I will contact Singxer directly and will keep you posted about the progress.

 

[justbenice]

 
There 4 trimpots, 2 by the regulators and 2 near the dac, which ones did you try?

Hi friend !
I tried 2 trimpots near the Ticha opamps.

 

[b0bb]

  Hi friend !
I tried 2 trimpots near the Ticha opamps.

These trimpots adjust the DC offset/reference and not the supply voltage, you will need to reset the DC offset on the DAC
Recheck the DC offset by measuring the voltage on pins 1 and 2 on the XLR connector and adjust the trimpot to as close to 0 Volts DC as possible.
Turn the DAC off after doing that to finish the reset.
 
The trimpots near the regulator are the ones that adjust the output voltage.

 

[justbenice]

 
These trimpots adjust the DC offset/reference and not the supply voltage, you will need to reset the DC offset on the DAC
Recheck the DC offset by measuring the voltage on pins 1 and 2 on the XLR connector and adjust the trimpot to as close to 0 Volts DC as possible.
Turn the DAC off after doing that to finish the reset.
 
The trimpots near the regulator are the ones that adjust the output voltage.

 
You are alway very helpfull Thank you !

 

[kazcou]

A mini version of this DAC (LKS MH-003 MINI)

 
 

 

 
 
 
 

 

[dacusb]

Dear B0bb,
 
I went to mouser website and tried to find the correct Wima film capacitors MKP2, but the mouser page said there are 4 or 5 different ones and I have to select the right ones.
 
http://www.mouser.vn/WIMA/Passive-Components/Capacitors/Film-Capacitors/_/N-9x371?P=1z0wq52Z1yvq1jiZ1z0zldhZ1z0yl9vZ1z0yl9t&FS=True
 
Can you specify which ones is correct and how many of them i would need.
It seems not easy to mount them on the 4-layer board. Can you be more specific?
Thank you for your guidance.

 

[b0bb]

  Dear B0bb,
 
I went to mouser website and tried to find the correct Wima film capacitors MKP2, but the mouser page said there are 4 or 5 different ones and I have to select the right ones.
 
http://www.mouser.vn/WIMA/Passive-Components/Capacitors/Film-Capacitors/_/N-9x371?P=1z0wq52Z1yvq1jiZ1z0zldhZ1z0yl9vZ1z0yl9t&FS=True
 
Can you specify which ones is correct and how many of them i would need.
It seems not easy to mount them on the 4-layer board. Can you be more specific?
Thank you for your guidance.

8pcs of the following. The 63V ones are smaller but Mouser does not have those in stock.
http://www.mouser.vn/ProductDetail/WIMA/MKP2D031501H00KC00/?qs=sGAEpiMZZMv1cc3ydrPrF2Av7JKdyW4DCABnugoea9E%3d
 
NOTE:The existing 0.1uF MKS caps need to be removed, these are next to the Black Panasonic FM caps. On mine the place is re-used by a 100pF Corning CGW glass cap, the square black box.

 
 
You will need a desoldering iron for removal of the stock caps , solder braid is not recommended due to the large risk of damaging the board.
 
I mount mine under the board