Head-Fi.org › Forums › Equipment Forums › Computer Audio › LKS Audio MH-DA003
New Posts  All Forums:Forum Nav:

LKS Audio MH-DA003 - Page 36

post #526 of 554
Quote:
Originally Posted by penguin140369 View Post
 

 

2) Thanks for identifying the 0.01uF cap, I will source a suitable replacement. In the picture, the northernmost terminal of this (missing) cap appears to connect to Pin 8 of the regulator. Are you able to determine what the southernmost terminal connects to? I ask as I think the copper trace may be damaged here, and it may no longer be a suitable soldering point for terminating the 0.01uF cap.

 

Not sure what you are getting at, post a photo with a markup of the area you are talking about

 

 

Quote:

If you had the choice, b0bb, would you try out the MkII version (the one with the ES9028 chips) or stick with the older model? Both are still available, it seems.

 

The mods I have described are for the 9018. The 9028 is an unknown quantity.

post #527 of 554

Hi b0bb

 

Sorry for not being clear.

 

I have marked up the image below.

 


The green square shows the location point of one of the solder points for the missing 0.01uF cap. I cannot tell from the trace what it connects to. I would like to know this, because the solder point is quite damaged.

 

Thanks.

post #528 of 554

Hi b0bb, ignore the above request - after some clean-up the copper trace is still usable as a soldering point.

post #529 of 554

Dear b0bb,

 

LKS already announced in recent days of a debut MH-DA004, the 9038pro dual model, the price goes up to 9800 RMB. I wonder what the DIY enhancement works or not for not harsh sound. Specially major issue is on the XO model, 570 or 950? May be I should ask for a socket to ease the swap work of the LKS build and Head-Fi recommended. What is your suggestion? I guess it is a difficult question to answer. Your idea is appreciated any way.

 

 

fjc36

post #530 of 554
Quote:
Originally Posted by fjc36 View Post
 

Dear b0bb,

 

LKS already announced in recent days of a debut MH-DA004, the 9038pro dual model, the price goes up to 9800 RMB. I wonder what the DIY enhancement works or not for not harsh sound. Specially major issue is on the XO model, 570 or 950? May be I should ask for a socket to ease the swap work of the LKS build and Head-Fi recommended. What is your suggestion? I guess it is a difficult question to answer. Your idea is appreciated any way.

 

 

fjc36

Post a link with the information.

 

The MH-DA004 has not been officially announced.

 

The best info I can find is the site below:

http://nxtmarket.info/item/546362464272

 

At a cost of  9900 RMB, this makes it about 1800-2000 USD after distribution overhead costs are added.

 

The DAC itself looks like a variant of the MH-DA003MkII Discrete.

DAC chips have heat sinks attached which is consistent with the 9038 having higher output current up to 128mA vs 32mA for the 9018

 

The Digital part of the power supply is different (upper right on the photo)

 

XO is the Crystek CCHD-575-50, the 50ppm version is the cheapest model in the 575 family.

LKS should have spent the extra cash to get the 20 or 25ppm variant as they seem quite attached to this XO.

 

The 575-50 made the MH-DA003 sound way too harsh, this made this dac marginally better than the Gustard X20 in unmodified stock form.

 

I think LKS lost a lot of potential customers this way given the Gustard is 2/3rds the cost.

 

The 4pin to 14pin  DIL socket footprint for a bigger XO is still there so replacing the 575 should not be a big issue should it become necessary.

post #531 of 554

Dear 0b00,

Thanks for the reply. LKS shows the new model of new DAC; 9038pro dual on the Tao Po net, so, it should be official. Your interpretation is correct. They do mention few points like upgrade the USB board than the original Amanero, that  add up the cost of RMB 600, 9400 to 9900.  They do mention about the current  increase from 30 mA to 100 mA according to the DAC 9018/9028 and 9038. So in MH-DA004, discrete I/V is supplied not as a option. OP is gone. The newest DAC and the discrete OP must increased the cost to 2000 RMB.

LKS mentions redesign and upgrade the power supply. They insist on use CCHD-575, (They should have read this forum).  I like to ask to put a XO socket before delivery, and switch all WIMA to be MKP or KP grade. if this is the final debut, it is indeed more costly. Wish it is worthy. I could translate the Chinese here at vital part, if needed. Or you have a translation machine already.  What is the crystek XO you recommend? Why not let me  ask them to supply an extra XO during the purchase. The extra service and cost can be negotiated (two XO).


Edited by fjc36 - 3/13/17 at 12:54pm
post #532 of 554
Quote:
Originally Posted by fjc36 View Post
What is the crystek XO you recommend? Why not let me  ask them to supply an extra XO during the purchase. The extra service and cost can be negotiated (two XO).

 

CCHD-950X

 

This is a starting point for experimentation and not a recommendation, it worked well with the 9018, the 9038 might behave completely differently so that is the downside.

 

LKS made a really strange choice using the large electrolytic for the XO regulator.

They look like Nichicon MUSE audio caps, this compromises the performance of the TPS7A47 regulator.

The MUSE caps perform very very poorly at the 100MHz range, most of the work is done by the small ceramic cap, the brown one on the side.

 

I normally expect to see low ESR solid polymer caps here.

 

LKS may have done this to dull out the sharp and harsh presentation of the 575-50.

 

I have marked the caps with the red "X" below, they probably need to be removed and replaced with regular solid polymer caps if the XO is swapped as the 950X does not require such drastic measures to bring it back into line.

post #533 of 554

Thanks for the review, b0bb. Your comments, plus the very high output current of the new Sabre chips, have put me off upgrading to the 004 version.

post #534 of 554
Quote:
Originally Posted by penguin140369 View Post
 

Thanks for the review, b0bb. Your comments, plus the very high output current of the new Sabre chips, have put me off upgrading to the 004 version.


It is very early days yet for the 004, LKS official mu-sound site does not list this dac and its availability is currently limited to China only as far as I can tell.

 

The output transistors would be running with a  bias current of between 50mA-70mA if it were to operate in Pure Class A over the entire output range, these transistors would be very warm to touch.

 

I would be watching to see how this dac does in customers hands in terms of DC stability.

The dac is assumed to be directly coupled from the 9038 to the output so it is quite important that the outputs remain as close to 0Volts as possible.

(This was the case with with the 9018)

 

The output transistors of the discrete opamp should have been mounted onto a common heatsink/heatspreader, this evens out the temp differences between the PNP and NPN transistors improving the DC offset.

It also improves thermal coupling between the 2 sides of the differential output.

 

This would have helped quite a lot in keeping thermal induced DC drift effects under control.


Edited by b0bb - 3/17/17 at 11:05pm
post #535 of 554

So, I will hold my breath, and wait for whats going on. bobb explained well about the officials, restrict sells in China only not world wide, something odd.

post #536 of 554

Below is a markup of the area around one opamp's output transistors.

 

The transistors are very close to the electrolytic caps, lets hope these caps are rated to 105degC.

 

The 2 transistors should ideally be on a common heatsink/heatspeader to reduce DC drift.

 

Assuming a voltage of 15V across each transistor and a bias current of 70mA (0.07A),

each transistor will be dissipating just over 1W,

this gives a total dissipation of 4W for each channel, 8W for the whole dac.

 

(The specs claim Class-A operation, I am wondering if the opamp truly operates in full Class-A over the entire range,

because of the potential thermal issues here. I hope LKS did the right thing and reduced the supply voltage to the opamp.

15V is the voltage used on the 9018)

 

This will be an area to keep an eye on the temperature rise, the caps may be cooked by the heat over long term.

Electrolytic caps have water in them, this will accelerate loss thru evaporation.

 

The layout of the output stage is quite odd.

Transistor package is TO-126/SOT-32 which has an exposed metal heat spreader on the transistor.

On this LKS layout it is facing towards the caps, this directs the heat towards the caps and this seems counterproductive to me.

 

Below is a picture of the TO-126 package

post #537 of 554
Quote:
Originally Posted by b0bb View Post
 


Post a few pictures after you receive the card, the Ebay vendors sometimes change the board layout.

 

Do not mod until the card is verified as working in the DAC.

 

Hi b0bb,

 

Here are pictures of the card.

Which parts do I need to mod, then?

Thanking you for your help and assistance, so far.

post #538 of 554
Quote:
Originally Posted by b0bb View Post
 

 

ES9018 DC level with no signal is 1.65V

 

As this voltage is present on both opamp input terminals this is known as the common mode voltage.

 

This parameter is documented for the Ticha 994 and the stock OPA1612

 

Ticha994: Handles up to 12V

http://www.sonicimagerylabs.com/products/product_images_docs/994Enh_Discrete_HD_OpAmp/994Enh_DiscreteOpAmp_Datasheet.pdf

 

OPA1612: Handles up to 13V (15V-2)

http://www.ti.com/lit/ds/symlink/opa1612.pdf

 

I think you should discontinue the use of the V5D as it is not able to handle a common mode voltage of 0.004V

Burson did not supply this info on the V5 datasheet.

I have info from Burson:

Hi Tomasz,

 
Our engineer reported that our V5 can have an input common voltage of up to 5V.
 
Best regards,
 
Alex
 
Burson Audiowww.BursonAudio.com | info@bursonaudio.com 
Supreme Sound Audiowww.SSAudio.com.au | opamp@bursonaudio.com
Follow Burson on Facebook and Twitter!
post #539 of 554
Quote:
Originally Posted by Tomus4 View Post
 

I have info from Burson:

Hi Tomasz,

 
Our engineer reported that our V5 can have an input common voltage of up to 5V.
 
Best regards,
 
Alex
 
Burson Audiowww.BursonAudio.com | info@bursonaudio.com 
Supreme Sound Audiowww.SSAudio.com.au | opamp@bursonaudio.com
Follow Burson on Facebook and Twitter!

 

That confirms the low DC tolerance of the V5D.

 

Burson's is correct in not recommending the V5D for use in the LKS.

 

Quote:
Originally Posted by Tomus4 View Post
2017-02-23 1:21 GMT+01:00 Burson Sales <info@bursonaudio.com>:
 
Hi Tomasz,
 
Based on your measurement below. our V5 and the audio imagery opamp are both not to blame. 
 
The problem is with the DAC chip.  This DAC chip is outputs excessive DC and it will burn up any field effect transistor designs.  In fact, this DAC places any down stream ampifier and speakers at risk if the DC continue to increase over time.
 
We will replace the defective V5-Dual for you.  That's not a problem. However, please don't use our V5D in this DAC anymore.  The customer can try our V5i-D which has higher tolerance for DC or he can use any opamps that are not based on Field Effect Transistors. (FET)
 
Best regards,
 
Alex
post #540 of 554
Quote:
Originally Posted by dacusb View Post
 

 

Hi b0bb,

 

Here are pictures of the card.

Which parts do I need to mod, then?

Thanking you for your help and assistance, so far.


Start with this post

http://www.head-fi.org/t/745032/lks-audio-mh-da003/105#post_12035366

 

Go back up to a few earlier posts to see how another person has done it.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Computer Audio
Head-Fi.org › Forums › Equipment Forums › Computer Audio › LKS Audio MH-DA003