[wushuliu]

I did some searching through AC to see if there was any info on the recent spate of DAC kits out of China/HK that are very popular on other forums. I didn't find much info at all so I thought I would add some info as well as easy mods to get improved performance.

The most documented are the 24/192 upsampling boards offered by Gigawork and Snow48-6. Both are reliable sellers with speedy (for HK overseas) shipping.





This one comes with USB/Coaxial/Toslink input, upsampling board, and a high quality R-core transformer. Best bargain. These DACs use cs4398 chip and come stock with 5532 opamps. The opamps are not soldered and are therefore swappable.

http://cgi.ebay.com/Gigawork-24-192-Up-sampling-DAC-DA-CONVERTER-w-USB-kit_W0QQitemZ120540707231QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item1c10c9399f




This one is cheaper with no USB, no upsampling, and no transformer.

http://cgi.ebay.com/NEW-BIG-24bit-192Hz-HI-FI-DAC-DIY-KIT-ASSEMBLED-MODULE_W0QQitemZ140389033636QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item20afd6a6a4




This guy is the cheapest but requires the most modding. I would recommend sticking with one of the above.

http://cgi.ebay.com/24bit-192KHz-DAC-DIY-KIT-FULL-ASSEMBLED-KIT_W0QQitemZ230445112086QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item35a7995b16


Apparently you can request a completely built version of the first kit with a nice aluminum enclosure for $250 shipped. There are pics on the Aussie forum linked below.


The general consensus seems to be that stock/opamps mod they compete w/ retail anywhere from $600 to $2k range. Once you add transformer outputs, however, all bets are off and you open the vortex that is audio nirvana. Not bad for $150 inc. power supply.

There are quite a few threads out there on these:

This aussie thread is a good one w/ pics and info

http://www.stereo.net.au/forums/showthread.php/16138-My-new-dac

For masochists, the Diyaudio thread is a monster at 250 pages:

http://www.diyaudio.com/forums/digital-line-level/137976-experience-diy-dac.html



I’ll come back to add more info once I’m done w/ the B1 tutorial.

[Mariusz]

THX Wushuliu. 
We need more of these IMHO.


Cheers
Mariusz

[avionic]

Wushuliu, I can't read any more of your threads. Every time I do I end up spending more $$. Seriously though I will be following this one with great interest.

[HT cOz]

Very cool thread    I can see a future B1-DAC combo.  These threads have me thinking I really need to get in on the action.

[wushuliu]

Yeah, I'm *real* happy with mine. I am waiting for the nice new transformer that now comes with the kit (I have the older one that's not so great quality), then I will start the tutorial. I also have very inexpensive Edcor transformers coming for the output so I am really, really excited.

[jb]

Based on component choice and PCB layout, I would avoid the first two. Cirrus Logic, the company that makes the CS8416 S/PDIF receiver chip, gives very specific recommendations regarding components and layout to maximize performance and minimize jitter. Locating the CS8416 on a daughter board and using through-hole passive components is contrary to Cirrus’ advice.

The general consensus seems to be that stock/opamps mod they compete w/ retail anywhere from $600 to $2k range. Once you add transformer outputs, however, all bets are off and you open the vortex that is audio nirvana.

Are you kidding? Not with the crap power supplies and voltage regulators. A poorly implemented Sigma-Delta DAC is more like audio hell.

[wushuliu]

Based on component choice and PCB layout, I would avoid the first two. Cirrus Logic, the company that makes the CS8416 S/PDIF receiver chip, gives very specific recommendations regarding components and layout to maximize performance and minimize jitter. Locating the CS8416 on a daughter board and using through-hole passive components is contrary to Cirrus’ advice.

Are you kidding? Not with the crap power supplies and voltage regulators. A poorly implemented Sigma-Delta DAC is more like audio hell.

Yeah, well it must have froze over cause it sounds pretty good down here!

[Atlplasma]

I purchased the big Gigaworks DAC in 2009. I'm using it with my Mac Mini music server over USB. So far it's been very reliable. I've also purchased the parts for the DIY output mods but haven't gotten around to putting them in.

[wushuliu]

Tutorial


Ok, let me start off by saying that there are quite a few mods out there for these kits. I am only covering what I consider to be the easiest as I am lazy and believe in getting the most with the least amount of work.

Also, it goes without saying to please be careful and I am not responsible for anything that may go wrong. Proceed at own risk, etc.

These mods pertain to the first two kits; Power supply pertains to the R-core provided for the first kit (and the second I'm sure if you ask the seller)

I will focus on 3 choices: Stock, opamp/cap mods, and output transformer mods.

1. Stock

There is nothing that needs to be modified or added to the stock kits. You can swap opamps at your leisure. All you need do is attach the power supply and then plug in the inputs and rca's as you see fit. Be sure to consult documentation re: dac switches and jumpers for the different inputs. The seller should have provided a cd w/ the necessary info. Now you can go straight to the Power Supply Transformer section below.

2. Opamp/cap mods

The Goal : get rid of some bypass/filter caps next to the dac, jumper them, replace output caps

Startin' w/ these guys





Now if your board has different color capacitors or slightly different values, don't matter. There'll
be 4 of them and they need to go.

Important: This solder on this board is finicky. I do not recommend applying the soldering iron to the bottom of the board. In my experience the pads tend to melt or just disappear into the board. So I recommend working only with the top side.

What I did was rock each cap back and forth until they broke off. (Given the finickiness of the board I wouldn't worry about 'saving' them so you can put them back in. It'll be more trouble than it's worth unless you're a pro with an adjustable temp workstation, etc.)

Then I bridged each side of each cap positive and negative side with some solder. You can also use a piece of wire, etc.




Next, Output caps

This may be tricky w/ the rca inputs in the way. I recommend pulling those out of there as they're very flimsy, and using some decent rca inputs and wire. Chances are to accomodate an enclosure you'll have to anyways...

Output caps can be replaced with the cap of your choice. The holes require small leads, so I clipped off thin leads from spare resistors and soldered them to my cap leads.



In the rear you'll see I also replaced the caps before the second opamp. Whether you want to try this is up to you. Since the layout of these boards seem to change every six months, some boards may not even have them.

That's it!

I found this mod to be far superior to the stock sound. Clears things up a lot.

You can also try some of Dave's mods below: getting rid of those 4 bypass caps, getting rid of the second opamp and jumping the bypass caps that sit before it. Jump the pins to keep mute relay (see his post), and losing the output caps altogether.

This is a good option as it doesn't involve replacing any of the caps, just pulling stuff out and jumping with wire, etc. And losing the second opamp is a plus


to be cont'd

[wushuliu]

Line Output Transformer Mod

Next up is the output transformer mod. This is also fairly easy.

1) You bypass opamps altogether.

2) Minimal contact w/ the board, reducing risk of screwing something up while (de)soldering.

2) Since you don't need the opamps you won't need to use the ~ 12v -0- 12v part of the power
supply, only the ~9v-0 part (see Transformer/PS section below). So basically you can run out to Radio Shack or digikey or wherever and use a cheap 9v transformer, buy the kit w/o transformer from ebay and save money to use towards the *line output* transformers.

Next, Getting signal from Bypass caps

This is what you're going for. Here's a great basic pic from diyaudio:




and a diagram (applies to both Left and Right):






You will need resistors and caps for the filters. You can start with ~500ohms for R1 and 1nf
for C1 and then adjust up or down to taste. I also recommend PRP or Takman resistors. They are cheap
and I think preferable to the usual dale, etc. in this application. Or better yet, compare for yourself.

Let's get started.


You want to solder in the 4 signal wires. They will go the transformers and from the transformers to your RCAs

In the Opamp mod section I showed the 4 Bypass caps by the dac chip that were tossed. Same
applies here. However, instead of jumping them we will be drawing the audio signal.

From Left to Right the signal goes: R-/R+/L+/L-

You will only need to deal with the positive (unstriped) side of each one. Like so:




I still recommend rocking the caps to break them off, thus avoiding full desoldering on the bottom side of the board. Then use tweezers to pull out the leads. Much easier and reduces iron time on the pads.

Also, the dac chip is removeable. So if you feel a little cramped during this part, gently pull up the dac chip from its sockets...

When you're done, should look like this:




That's it for the board. Phew. Now you can be butterfingers all you want with the output transformers!


Which Output Transformers?

A wide bandwidth (20hz - 20khz or higher) 500/600:500/600 is a good start. The average price for a pair is ~$100 - 150. American-made Edcors, however are a budget alternative. Not a huge amount of feedback on their quality, but it's a reputable company.

Most Popular

UTC/TRW A-20

http://cgi.ebay.com/Pair-UTC-A-20-Input-Transformer-500-500-Ohm_W0QQitemZ310206172473QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item4839ba8d39



Cinemag - ~$56 ea.

CMOB - 2H

http://www.cinemag.biz/output/output.html

Altec 15356/A (on and off on ebay)




EDCOR XSM600 - ~$13 ea.

http://www.edcorusa.com/Products/ShowProduct.aspx?ID=327

These are just a few of the many to choose from. I also focused on options easily available to those
in the U.S.. Internationally there are Sowters, LLundahls, Monacors,etc. that are easier to find. You get the idea.

Now each transformer brand is different as far as their primaries (input) and secondaries (output to RCA). We want to follow the 5 or 600: 5 or 600 diagrams. In the UTC pic above for instance you can see the writing on the side:

Pins 1 and 6 = primary, signal from the board
      7 and 12 = secondary, signals to RCA
      3 and 4, 9 & 10 = Center Tap, you jump/connect these two w/ wire

So consult the transformer you have and if you have any questions just ask.

Now add the resistors and cap filter to the signal wires.

Just as in the diagram above.





then attach, solder, etc to appropriate pins on your transformer.






You can see the white output wires that are going to the RCAs. I did not take a close pic of the
1K, 1nf R-C filter but you can kind of see here. Just follow the diagram above.






There ya be. Not too tough was it?

[wushuliu]

Power Supply Transformer

The first kit comes with a R-core R26-34 transformer for the power supply. It is also available separately on ebay. It's a mad jumble of wires but you'll only be using some, not all.

Note: The wiring in this post pertains to US/115v only!

Stock/Opamp mod wiring

On the board you will see at the back two inputs for 7-10v and three inputs for (12 to) 15v-0-15v




For the 7-10v you will use the two brown wires

For the 15v-0-15v you will use a grey at one end, blue at the other, and BOTH in the center

Here is a great diagram  provided at diyaudio:



The remaining wires on that side should clipped/taped up and tucked away


For Output Transformer/No Opamps Mod

Since you will be bypassing the opamps completely, there's no need to worry about the 15v-0-15v
side. Nip/Tuck those away and just wire up the 7-10v with the two brown wires!


Primary/Mains

OK, please look at the diagram above.

Wire the Red and Green together for your LINE voltage

Wire the Orange and Yellow together for Neutral.





Remember this applies to 115v/USA only


You will want to add the Power switch to the Line of course.

The rest of the setup is up to you.

Here endeth the Lesson. Be Careful and Have Fun.

[wushuliu]

I purchased the big Gigaworks DAC in 2009. I'm using it with my Mac Mini music server over USB. So far it's been very reliable. I've also purchased the parts for the DIY output mods but haven't gotten around to putting them in.

I thought I read you bought the Altec 15356 transformers. I just got some on the 'bay...

[Atlplasma]

I thought I read you bought the Altec 15356 transformers. I just got some on the 'bay...

That's correct. I have everything I need for the mod but have been waiting for some downtime to take it on. I'd be curious to see how yours turns out.

Steve

[wushuliu]

IT'S ALIVE!









Gonna give it some time to settle and I have some higher quality parts coming to replace some of what's being used now.

First impression w/ these Altec transformers (and R-core transformer)  is that the sound is indeed more natural and very three dimensional compared to mod I had before and of course far better than stock.

I'll add pics and more info later on this week.

[stc4life]

I'm going to grab one of these and do some of the diy mods as well.  I might try to add the decware tube output too.

Is there an organized tutorial for the mods somewhere or are you referring to the lampizator site?  I I was worried I would have trouble following that website if all the PCB IDs are different on the "better boards," rather than the third one above, which it appears was the board used on the lampizator site.  I am a proficient solderer, but these types of mods are totally new to me, so I don't want to bite off more than I can chew:)

[wushuliu]

I'm going to grab one of these and do some of the diy mods as well.  I might try to add the decware tube output too.

Is there an organized tutorial for the mods somewhere or are you referring to the lampizator site?  I I was worried I would have trouble following that website if all the PCB IDs are different on the "better boards," rather than the third one above, which it appears was the board used on the lampizator site.  I am a proficient solderer, but these types of mods are totally new to me, so I don't want to bite off more than I can chew:)

This *is* (or will be) the only organized tutorial on this kit (as far as basic and transformer output mods). Otherwise you can slog through the 225 pages on diyaudio, which is where I draw my info. There are several kinds of mods for these boards. The Lampizator takes a different approach altogether and I won't be covering that (just looks too messy to me). My focus is on getting the most benefit w/ the least amount of work/mess. I'll have the pics and info up very, very soon.

[stc4life]

That's awesome.  Its noble of you to finally pull a tutorial together given how in depth and fragmented the discussion of this DAC has been on the numerous boards.  I look forward to hearing about your experience.

[dBe]

I did some searching through AC to see if there was any info on the recent spate of DAC kits out of China/HK that are very popular on other forums. I didn't find much info at all so I thought I would add some info as well as easy mods to get improved performance.

The most documented are the 24/192 upsampling boards offered by Gigawork and Snow48-6. Both are reliable sellers with speedy (for HK overseas) shipping.





This one comes with USB/Coaxial/Toslink input, upsampling board, and a high quality R-core transformer. Best bargain. These DACs use cs4398 chip and come stock with 5532 opamps. The opamps are not soldered and are therefore swappable.

http://cgi.ebay.com/Gigawork-24-192-Up-sampling-DAC-DA-CONVERTER-w-USB-kit_W0QQitemZ120540707231QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item1c10c9399f




This one is cheaper with no USB, no upsampling, and no transformer.

http://cgi.ebay.com/NEW-BIG-24bit-192Hz-HI-FI-DAC-DIY-KIT-ASSEMBLED-MODULE_W0QQitemZ140389033636QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item20afd6a6a4




This guy is the cheapest but requires the most modding. I would recommend sticking with one of the above.

http://cgi.ebay.com/24bit-192KHz-DAC-DIY-KIT-FULL-ASSEMBLED-KIT_W0QQitemZ230445112086QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item35a7995b16


Apparently you can request a completely built version of the first kit with a nice aluminum enclosure for $250 shipped. There are pics on the Aussie forum linked below.


The general consensus seems to be that stock/opamps mod they compete w/ retail anywhere from $600 to $2k range. Once you add transformer outputs, however, all bets are off and you open the vortex that is audio nirvana. Not bad for $150 inc. power supply.

There are quite a few threads out there on these:

This aussie thread is a good one w/ pics and info

http://www.stereo.net.au/forums/showthread.php/16138-My-new-dac

For masochists, the Diyaudio thread is a monster at 250 pages:

http://www.diyaudio.com/forums/digital-line-level/137976-experience-diy-dac.html



I’ll come back to add more info once I’m done w/ the B1 tutorial.

I bought a couple of these and I have done the mods on the diyAudio forum + a couple:

Replaced the Philips diodes with 1A 100V schottkys

Added additional bypassing on the caps in the power supplies

Removed all of the coupling capacitors and replaced them with jumpers

Removed the buffer op amp and added 1/3 & 5-7 jumpers to allow the mute relay to still be used

Replaced the latching diode at the relay with a UF4007 (I have a million of them for guitar amps)

Replaced the output opamp with Gigaworks dual OPA627 daughter board

Removed the USB input assembly in totality

Mortite damped the upsampling daughter board

Lead damped the Crystal DAC and input receiver

I will be using the coax out only so I ordered Canare 75 ohm RCA's and plugs for the case

I will replace the output RCAs with Gigaworks silver RCAs

Both of the last mods will happen when I receive the cases that I ordered for the DACS

I have sourced cases with extruded side panels (w/card slots), plate top, bottom and end panels in natural aluminum.  They are sized to just let the board slide in and are nominally 12" x 5.35" x 3.5" to allow the TX, IEC inlet and all other goodies room to breathe.  I did not order the panels machined to allow for the end user to use any type of configuration they wish.  If anyone is interested in one of these cases, drop me a PM and we can talk. 

The DAC sounds quite good with these mods.  I'm using a Blue Jeans 1M RCA digital interconnect right now.  It is very open with great dynamics and very good detail and lacks any harshness.  It is musical and even though it is no match for my old Cary 306 it is more fun to listen to for extended periods.  Last word: my wife likes it the best.

I'll be rolling some digital cables of my own and several other manufacturers, including the Nady.

My .02

Dave

[wushuliu]

Thanks Dave. You got busy on that thing. Happen to have any pics?

[dBe]

Thanks Dave. You got busy on that thing. Happen to have any pics?

I went ahead and took some new pictures.  I forgot to shoot the new diodes, but, hey:  they are just diodes





This is an overview of the mule






This captures most of the mods in one picture






USB input area stripped.  I removed the 3-pin regulator in the bottom of the board






The replacement RCAs - Canare and Gigawork



I auditioned opamps:
   
    AD826 - forward and hard, almost brittle sounding
    OPA2134 - smooth but not very articulate
    LM4562 - woofy and vague sounding, hard to define some instruments especially in the mid
          to upper bass
    Twin OPA627 (Gigawork) - as always very good with nice bass and smooth yet detailed, very
          dynamic

There you have it so far.  The journey will continue............................... ......

Dave