[penguin69]

b0bb, a $0.30 mod. Genius!

http://www.surplus-electronics-sales.com/index.php?main_page=product_info&products_id=1131

 

[Ric Schultz]

b0bb,
Very cool....well, at least cooler. Is that Kapton tape underneath the heatsinks to keep the transistors from being shorted?

 

[b0bb]

Is that Kapton tape underneath the heatsinks to keep the transistors from being shorted?

Yes

 

[vick_v]

I have been looking into the MH-DA004 and noticed that the XLR output frequency response is listed as 20Hz-20kHz and many of the competing DACs list at least 50kHz limit. The top hit (on google) that sells the DAC confirmed the above.
Is there anything that can be done to up that limit to at least match my bookshelf speakers at 40 kHz. Or is it possible that the info is incorrect?
I know we can't hear that high of a frequency but I am looking to build a system capable of reproducing this range and find out for myself if it makes any difference.

 

[RickyV]

Hi bobb,
I am a F1 user and looking to upgrade the cchd-575-25 clocks to something better. Do you know of a better clock that will fit the pcb lands?
Also i had an idea to replace the clocks LDO (adp 151) with a pulsar power, very short leeds 1cm or so.

 

[b0bb]

Hi bobb,
I am a F1 user and looking to upgrade the cchd-575-25 clocks to something better. Do you know of a better clock that will fit the pcb lands?
Also i had an idea to replace the clocks LDO (adp 151) with a pulsar power, very short leeds 1cm or so.

NDK makes an alternative.
http://www.diyinhk.com/shop/audio-kits/35-ndk-nz2520sd-20ppm-ultra-low-phase-noise-oscillator.html

Phase noise is lower "on paper", I have not used it in the F1, and it remains to be seen if it can do a better job than the Crystek.

The performance of the F1 is limited by the capability of the DAC's SPDIF receiver, the crystal in the F1 merely has to be good enough to get the job done and the 575 is more than adequate.

You should post on the other threads dedicated to the Singxer to get a better sense of what works.

 

[RickyV]

Thanks bobb,
Yes sorry about that. I read this intresting threat yesterday and you were the perfict man for the question i had.

Happy modifing.

 

[dacusb]

Adding the Corning CGW caps in parallel with the opamp bypass (Panasonic FM) caps will bring out the midrange fullness. Use a value of 100-220pF, either the CY or TY series will work.

Hi b0bb,

Where can I get the said Corning CGW caps?
Thanking you very much.

 

[dacusb]

Next installment of my LKS MH-DA-003 mods

High voltage Schottky rectifiers, these devices are fast recovery, compared to conventional diodes these use the majority carrier conduction mechanism.

These are 100V 8A devices from Vishay.

Analog side.


Digital side

Hi b0bb,

Schottky rectifier diodes 100V 10A from Vishay part number MBRF10H100-E3/45 are out of stock at both Mouser and Digikey. Can you provide us with other sites where we can get them?
Thanking you very much.

 

[b0bb]

Hi b0bb,

Schottky rectifier diodes 100V 10A from Vishay part number MBRF10H100-E3/45 are out of stock at both Mouser and Digikey. Can you provide us with other sites where we can get them?
Thanking you very much.

RS Components or Farnell might stock these, check with them to see if they can help you

 

[justbenice]

For the last few days i tried the Dexa New ClassD opamps and found out it sound very accurate. The Burson V5D have sweeter sound but i like the Dexa more.

 

[Ric Schultz]

RE the new 004: I measured the temperature of the IV output transistors and directly on top of the Nichicon caps after an hour with the top off. The temps were 45 for the transistors and 43 for the caps.......way, way less than what b0bb measured with the cover on. I find that most gear sounds best with the cover off.....That is how I have all my gear. So, better sound and longer lasting caps without any mods. Just remove the cover. Helps if your DAC is out in air like mine ......if inside a small shelf then it will get hotter. Put it on top of your rack and with no cover and you are good to go......just don't spill any drinks in it.....he he. Just dust it out once ever six months....unplugged, of course.

A friend with the 004 tried the heatsinks on the transistors and reported closed down bad sound. I have the heatsinks and will try them sometime next week. I will report what I hear.

 

[penguin69]

I ran my 003 with the lid off also. Not so aesthetically pleasing to all, but a good way to keep temps down!

 

[b0bb]

The heatsinks are just an experiment to see if it can bring the temps down with the case closed, in reality they are far too small for a proper cooling job.
The temp reduction was better than expected so I will spend the time to rebuild the output stages for better cooling.

This is not a permanent mod and it requires a lot of adjustment and I did not add any links for the materials I used as a result.

Unless extreme care is taken, the temps in the center pairs can be as much as 10ºC higher than the ones on the sides due to the small size of the heatsinks.
I had to adjust the clamping force on mine a few times to get it to behave.
There should be less than 2ºC difference between the center of the transistor mounting hole and the top of the heatsink, if not the mounting is off.

The temps on both halves of the output stage transistor pairs have to be within 2-3ºC otherwise the gains on both halves of the differential output will be mismatched leading to changes in the sound.
Given the LKS layout, the inverting output runs hotter than the non inverting input on the left channel with the reverse effect the right channel, leading to truly weird effects.

 

[mb3]

The heatsinks are just an experiment to see if it can bring the temps down with the case closed, in reality they are far too small for a proper cooling job.
The temp reduction was better than expected so I will spend the time to rebuild the output stages for better cooling.

This is not a permanent mod and it requires a lot of adjustment and I did not add any links for the materials I used as a result.

Unless extreme care is taken, the temps in the center pairs can be as much as 10ºC higher than the ones on the sides due to the small size of the heatsinks.
I had to adjust the clamping force on mine a few times to get it to behave.
There should be less than 2ºC difference between the center of the transistor mounting hole and the top of the heatsink, if not the mounting is off.

The temps on both halves of the output stage transistor pairs have to be within 2-3ºC otherwise the gains on both halves of the differential output will be mismatched leading to changes in the sound.
Given the LKS layout, the inverting output runs hotter than the non inverting input on the left channel with the reverse effect the right channel, leading to truly weird effects.

I found this mod worked well for me - placing one heatsink across two transistors. The unit is now significantly cooler. see https://www.jaycar.com.au/to-220-clip-on-heatsink-6043-type/p/HH8503