For owners of SM3623+SM5843+PCM58 DAC DIY kit

Well, we bought two of them and both has the same fatal for sound error: instead of -12V analog supply for PCM58 there's only -5V. It still works but completely out of parameters. You can easily check your KIT for this BAG - just compare resistors value near 3xLM317 stabilizers and if they all the same ( blue-white-black-black = 690 oHm and red-red-black-black= 220 ohm) then you are in :) ! Or just check U on pins 9 or 20 of PCM58. Please, note that LM317 is POSITIVE stabilizer but in spite of this it is in NEGATIVE configuration (on attached picture there's stabiliser on right side of board just near the 3300uF Kenwood (Elna) capacitor). All you have to do is to change resistores value: 690 ohm on 1,3 kOm and 220 ohm on 150 ohm (1%) and you will be suprised :) !
Also this DAC has no deemphases filter witch means that some old CD's will reproduce overtuned high frequency noise. I will make passive filter later and let you know.
 

Attachments

  • pcm58.jpg
    pcm58.jpg
    23.4 KB · Views: 1,323
To be more precise

As this post reffered to another forums too I want to define more exactly:
The PCM58 chip has four power supplies: +5v digital on pins 2 & 13 and -12 analog on pins 9 & 20. Negative supply on pins 9 & 20 goes direcrly from "-" of diode bridge (checked red on attached picture) and output of LM317 (checked red) positive regulator that responds on -12V attached to the "common" ("ground"). This is correct configuration.
The only thing is that person who assemble this DAC put incorrect values of resistors to this regulator. If you read on pins 9, 20 the same -5v as on mine board then change resistor from OUTPUT pin of marked LM317 to ADJ pin to 150 ohm (1%) and from ADJ pin to ground to 1300 ohm (1%). After doing that BEFORE you'll put the mains on UNPLUG carefully the PCM58 chips from their sockets, then put the mains on and check your voltage on pins 9 or 20, it has to be someting like -12,1 v (and it's O.K. between 11 - 13V as max permissible as meanwhile you are happy with -5v :) ). If it's O.K. then put PCM58 back at their homes and now compare the sound with your favourite CD. Enjoy!
 

Attachments

  • pcm58 dac.jpg
    pcm58 dac.jpg
    66.5 KB · Views: 1,155
Enable deemphasis filter

To make deemp filter enable resolder pins 15-16 of SM5843 on mother board and adapter. Connect pin 16 of SM5843 to pin 16 YM3623. Connect pins 17, 18 of SM5843 to the "ground" (pin 8). Now you deemphased ;) (if you do really need it). I have some CDs with deemp, for example Jethro Tull "Too Old To Rock'n'Roll... so I made it.
To be more precise we have to connect pins 17,18 of SM5843 to pins S1,S2 of YM3623 but I didn't check board yet.
The most important thing is that I want to change filter SM5843 to PMD100 as it outperforms 5843 in sound reproduction + HDCD (I also have some CDs :angel: ). But I dont know how to do that as far as I'm newcomer in digital. Please, help to configure correct! I can check SM5843 configuration. Anyone?
 
flshzug said:
i think hand selected matched pcm58's should make more obvious difference ? Arent those dac pin compatible with something better?

+++++ Shure, you are right, matched PCM58 will make a deal but I don't know where to get them. As for the dac chips - I have D/A converters on PCM63P-K also and on PCM1702 and on TDA1543. I also had Audio Alchemy with HDCD but sell it as I don't like the "sound" of Analog Device chips. And TDA1541 with ten ;)crowns also do not makes any attractive to me. Thats why I want to try HDCD filter in PCM58 DAC as far it already sounds very good to me ( seems like better then PCM63P-K :confused: ).
 
More fan from fabulous DAC ;)

Well, PMD100 sits down right in the place of awful (as people talk) SM5843. As far as I'm beginner in digital it "costs" me time overlot, but it finally works. The main very helpfull thing is that SM5843 chip has onboard pull-up resistors inside and designers of this DAC didn't connect them to the board. Furthermore we have 74HC04 with free legs to invert XTI from YM3623 (oA pin 8). So I did the connections and now I'm in HDCD decoding (with de-empasis of course) ! Sounds different but my main aim achieved.
 

nX3NTY

Member
2009-07-04 6:33 am
Sorry if I bump up an old thread, I just found out this and register just because of it, it looks like I have similar board like you and also similar problem! Gonna fix mine soon, is there any other tweak I should do to it? I have some old Bee Gees and Carpenters old CD, should I do the de-emphasis thing?