MSB Link DAC III Mods

rgbeach

Active Member
I recently purchased an old, circa-2000 MSB Link DAC III - just the base version, not Gold or Nelson - and having the basic power supply, not the P1000. For those of you that have read my various posts, you'll know that I like finding older, good quality (OK, sometimes not so good quality) gear and refurbishing/restoring/reusing it. Often times it's less expensive, but I mainly do this because it bothers me to see so much good stuff tossed in the trash bin. I also enjoy working on the gear, and I learn along the way.

Anyways, my intention with this DAC was to modify it according to Dan Wright's guidance from the early 2000's. His formal documentation has been gone from the web for a long time, but I managed to find this: https://www.audioasylum.com/messages/digital/5078/msb-link-dac-mods-all-i-know-for-now-instructions. It mostly centers around using better parts in the signal path and in the analog (op amp) and DAC supplies.

I chose to replace all the electrolytic capacitors on the board, the regulators, rectifiers, and bypasses for the supplies, and the resistors in the signal path. The BP electrolytics were replaced with Wima film MKS, and the bypasses with Wima film MKP. All resistors replaced with Vishay / Dale RN60D. Electrolytic capacitors replaced with Elna Silmic II, except for the big power supply filters which were Nichicon KS. A previous owner had replaced the stock op amps with TI MC33078, so I kept those in there. My parts list is attached.

In total, there are 40 parts to replace (42 if you include the op amps). Fortunately, I had all the capacitors on hand, except for the big filter caps, as well as regulators, and the rectifiers. Even with buying 20 of each value of resistor, my parts order was less than $40 shipped.

Here is the stock board removed from the chassis:
20180415_070951.jpg


Notes:

1) On the power supply side, the filter capacitors, bypass capacitors, and rectifiers were all replaced for the +5V DAC and +/-8V Analog (op amp) supplies. The +/-8V regulators were replaced with +/-12V to better drive the op amps. I ~ doubled the capacitance/voltage for the filter capacitors, going with 6800uF/50V Nichicon KS. There's no space on the board for these, especially with the HexFred rectifier diodes in place, so I mounted these upside down on the chassis and secured them in place with a glue gun. Also, the Wima MKP film bypass capacitors were too big to it in the existing through holes, so I drilled new holes into the board.

20180419_221844.jpg

2. On the output stage, the electrolytic capacitors on the supplies to the DAC (PCM1716E) and op amps were replaced with Elna Silmic II of the same values, the BPs replaced with Wima film MKS, and all resistors replaced with Vishay / Dale RN60D. Dan suggests removing C40/56, but that is not necessary if you adjust the jumpers on J16. By rearranging the jumps you can disable that part of the post-DAC filtering. At some point in the future, I may try swapping op amps with OPA2134 or the like.

20180419_221830.jpg

3. I replaced all remaining electrolytic capacitors on the board with Elna Silmic II, and most of these are for the +5V digital supply to various ICs. Also replaced resistors on the digital inputs, ad removed resistors on the analog outputs to ground, per Dan's instructions.

4) Lastly, the base Link DAC III comes with a phase inverter switch on the back, which essentially controls the phase inter jumper pins on J14. However, it also disables the "Digital Zero Option", which controls when a digital signal overrides a signal from the analog inputs. With the Digital Zero Option enabled i.e. a jumper across it's pins, when a digital input is plugged in and turned on, the digital inputs override the analog inputs. However, with the Zero Option disabled i.e. no jumper across it's pins, the digital input only overrides the analog inputs when music is playing through the digital inputs. The ramification of this is that the DAC would switch back to the analog inputs when one song ended, and then switch back to the digital input when the next song began, and the switching relays are pretty loud. So, I shorted the leads from the Digital Zero Option, and thereby enabled it to prevent the switching.

Here's the board after modifications mounted back in the chassis:

20180419_221813.jpg


It was a pretty easy project. There's a lot of space on the board and it's mostly pretty easy to work with. I did have to use a desoldering wick extensively to remove all the solder from the regulators, as well as some of the other parts. The board is double-sided, so many/most of the parts are soldered on both sides of the board.

The end result was good in that it still worked :) and it sounds pretty good. I can't say if it made any improvement over it's stock state, but it was a fun project, I learned a little bit more, and this DAC should now last for another 20 years!
 

Attachments

  • MSB Link DAC Parts List.pdf
    331.3 KB · Views: 40
So didn't they produce this DAC with a power base? Did you get that as well?

The P1000 PowerBase was a separate upgrade, which I believe works with many of the early MSB Link DACs. Unfortunately, the person I bought this from did not have the PowerBase, so I'm using the basic power supply.
 
Back
Top Bottom