Cheer and cheerful 24/192k DAC

FTGV

Make that Cheap and cheerful.

I spotted this little kit while surfing ebay and thought that it appeared to have a lot of potential if important erea's were given special attention.Since niether of my current DAC's have 192k capability this looked like a economical way to try the few high sampling downloads that I have stored on my PC at their full resolution.

The kit I purchased did not include the chassis,transformer ,connectors etc.
It came with a blank PC board with the exception of having the three SMT IC's already soldered (the DAC,DIR and logic).All the other parts to populate the board are included .For the price the parts are of decent quality but since they are standard hole through types they are much easier to find suitable higher quality substitudes,which ofcourse is what I did.Since board real estate is at a premium there is no room for exotic film caps etc.

I opted for Nichicon HE and UCC KME's for main filter caps.I used Panasonic FC's for local decoupling, bypassed by Panny stacked films. WIMA film's were used the PLL filter and BC polyprop's for the lowpass filter.I also substituded the LM78/79 regulators with the lower noise MC variants.Nothing exotic but definately a few notches above the stock parts.

The DAC circuit itself is as simple as it gets.There is no USB input or sample rate convertor ,instead input is via SPDIF into a Cirrus CS8416 DIR followed by an AKM4396 dac chip then to the low pass filter/output buffer.AKM is one of the biggest makers of DAC chips but these are mostly found in higher end soundcards.On paper atleast the AKM4396 is an excellent DAC and appears to be the equal of the dual differential 24/192k offerings from Cirrus and Burr Brown.

However it is my opinion that it is the analog section that can have an even greater influence on sound quality than the specific data converter used.The opamp included with the kit is the archaic 5532.Not the worst sounding device around but far from the last word in resolution.I find it on the soft slightly dark side sonically.I will be replacing it with a pair of discrete class A opamp's similar those marketed by Burson.

Also in an atempt to not adversly affect the signal - noise performance and preserve all those 24bit's of resolution I will be placing the little toroidal transformer in it's own separate chassis to prevent the possibility of any 60hz hum being coupled into the output.


I found a Hammond case with ideal dimensions for the PC board.

steveinaz

Cool!!!

FTGV

steveinaz wrote: »

Cool!!!

Thanks to you I recieved atleast one reply.I guess this speaks to my popularity in these parts as being that of p*nis at a **** slumber party.HeHe

Anyway here is the finished product.It worked flawlessly at first power up without any extraneous noises or smoke.:biggrin: I have been doing some listening with an LM4562 opamp installed since the discrete units are not ready to go yet. First impressions are extemely positive, sounding open and airy and detailed but with a slightly lightweight bottom end.I expect things to change(hopfully for the better)when I get the other opamps installed.

As for futher mods I plan to install a pulse transformer to provide isolation from the PC and maybe some further power supply tweaks.
The retina damaging ultra intense blue LED's used for power and sample rate indication will be toned down or changed to green and red respectively.

All said and done I think this is a great little board with an excellent lay out and very conducive to modifications. I'm very pleased with the results considering my total outlay of approx.$70 ($40 kit ebay,$30 digi key)not including parts I already had on hand.I can highly recommend the kit for someone looking to try an inexpensive DIY unit.

I can provide a link to the ebay seller if anyone is interested.

Poee7R

Looks good man, and I agree with the blue led's, toss em for sure.

I was really excited while reading, until I came to the part about no usb input. Im looking for a diy dac myself, but Im interested in building one for a pc rig, so I need USB or Ill have to add another component.

So I have two questions, can a usb input be added without much of a problem? (not sure on the premise of adding a usb input and wether or not it is even possible without it being better to go with a different unit)

And second question... Ive looked at all the pics a few times now, where do you stick the tube? :biggrin:


Dave

FTGV

Poee7R wrote: »

I was really excited while reading, until I came to the part about no usb input. Im looking for a diy dac myself, but Im interested in building one for a pc rig, so I need USB or Ill have to add another component.

So I have two questions, can a usb input be added without much of a problem? (not sure on the premise of adding a usb input and wether or not it is even possible without it being better to go with a different unit)

There is a very similar kit(see link) that adds a USB input, however since it is of non async. variety so that input will be limited to 16bit/48k.
Otherwise if you desire hi res capability via USB you'll need an external solution.The other main difference that I can see between this and the board I purchased is the DAC chip , a Cirrus CS4398 vs the AK4396,though they are similarily spec'd.
http://www.ebay.ca/itm/CS8416-CS4398-192Khz-24Bit-DAC-USB-Coaxial-Assembled-/260814783037?pt=LH_DefaultDomain_0&hash=item3cb9c5c23d

And second question... Ive looked at all the pics a few times now, where do you stick the tube? :biggrin:

It so happens that I do have a suggestion as to where you can stick that tube.:eek:

heiney9

Fred, very cool. Can you build me one?

H9

P.s. I don't surf the DIY Mods and Tweaks forum on a regular basis otherwise I would have seen it sooner.

FTGV

heiney9 wrote: »

Can you build me one?

Sure if you send me the parts I can assemble it.

agfrost

Looks nice, Fred. Please keep updating as time goes on/as you continue to massage it.


Jay

TECHNOKID

Great job GV, thanks for sharing with us.

SCompRacer

Nice job Fred! One area I am not finished with yet is DAC's. Oh, and a TT plinth project.

FTGV

Thanks ag,TK and Rich.

I have the discete opamps installed.Since two are required I needed to adapt the mini PC boards on to an 8 pin DIP header so that it would fit into the standard IC socket. Initial impressions are of greater weight in the bottom end with a more refined top end but still with a somewhat uptilted response in comparison to my regular DAC.

Face

Nice job Fred! But where are the tubes? :biggrin:

Is it direct coupled?

FTGV

Face wrote: »

Nice job Fred! But where are the tubes? :biggrin:

Can't get em to fit in the dang IC socket.:frown:

Is it direct coupled?

Yes.

FTGV

Adding a pulse transformer for the SPDIF input is last tweek planned for this unit.Transformer coupling provides galvanic isolation which is particularly important when the DAC is used with a PC's coaxial digital output.It will effectively isolate the DAC from any noise artifacts (like from the computer's switching supply) and eliminate the possibility of a ground loop.

The transformer is a Newava S22083 http://www.newava.com/pdf/S22083.pdf and sourced from Digi key for <$10.
I recommmend it as a possible upgrade for any DAC that does'nt have one on it's coaxial input (such as the original MF V-DAC).

After installation I believe I'm hearing a smoother and more detailed high end with a better sense of space.
Overall the more I listen to this little DAC the more impressed I am with it's ability to reveal the little details and nuances from well recorded acoustic guitar tunes from the likes of Al DiMeola,Justin King,Alex Degrassi,Clapton.Etc.It digs deep but IMO without becoming unaturally hyper detailed.
Obviously manufacturer hyperbole but AKM refer to the 4396 as the "miracle dac" because it is claimed that it's hi frequency noise levels are similar to a good R2R DAC and substantially lower than competitors delta -sigma chips .
How much this contributes to the excellent resolution I'm hearing I'm not sure .

drselect

Nice looking work Fred.
Might have missed it but where is the link for were you got the initial kit from?
Also you mention adding descrete opamps could you please provide a little more info about them?

SCompRacer

jinno1, nice try. Reported.

SCompRacer

Awesome work Fred! I too would like to know more about your discrete opamps. I'm a believer in them. I'd also like you to give me a working with small coax class...nice job on the braid grounds! No way you cut it; you, what's the right word, un-braid or de-braid it, right? I have an air bearing tonearm to rewire using some 1/8" coax. One end goes to a small PCB in a tight place. Maybe I'll send it to you!

george daniel

Very nice work Fred--with your skills and talent,,I'm sure this was childs play to you.Me,,,I'm a "paint by the numbers" guy. :biggrin:

FTGV

drselect wrote: »

Nice looking work Fred.
Might have missed it but where is the link for were you got the initial kit from?

Thanks,variations of this kit are available from a number of vendors here is the link to the one I purchased from.http://www.ebay.ca/itm/NEW-Hi-end-DAC-24-BIT-192K-HZ-AK4396-sc-/200613201099?pt=LH_DefaultDomain_0&hash=item2eb57a84cb

Dont let the source and price fool you,the quality of the PC board is very good and the DIR and DAC IC's are the real deal not counterfits.

I'm now working on another one ,the one I linked to in post#5 http://www.ebay.ca/itm/120768083816?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

It is near Identical with the exception of adding a USB input(16bit/48k adaptive mode)and swapping the AKM4396 with a Cirrus CS4398.For this version I will be using a completely separate power supply for the digital and analog sections,(each with their own AMVECO mini toroid transformer)and high performance shunt regulators for the analog.
The pretty black and gold PC boards are the shunt reg's.

FTGV

SCompRacer wrote: »

I'd also like you to give me a working with small coax class...nice job on the braid grounds! No way you cut it; you, what's the right word, un-braid or de-braid it, right?

After stripping off about a 1/2" of the outer insulation I just gathered the shield to one side and twisted it into a braid for easy soldering.The opamp's were pulled from another otherwise defective piece of equipment,they are dual differential Class A using bipolar transistors vs the Burson's which use fets.

Thanks for the kind words Mike and George.

praedet

I actually need to try that transformer technique on my DAC. What is the second blue part with the transformer?

FTGV

praedet wrote: »

I actually need to try that transformer technique on my DAC. What is the second blue part with the transformer?

Thats a 220nf poly cap to block any miniscule DC that might find it's way on to the data line.


Here is a link to the Digi-key part# for both the transformer and cap.
http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=CA&KeyWords=470-1003-ND&x=21&y=14
http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=495-1106-ND

Face

I refuse to drink the Kool Aid

FTGV

Face wrote: »

I refuse to drink the Kool Aid

As always nice to here from you and thanks for the kind words.

FTGV

To add some versatility to the DAC I purchased this little USB transceiver/DAC board which will allow me to also use my lap top.The board is based on the Burr Brown PCM2704 which is a USB reciever,SPDIF transmitter and basic 16 bit stereo Delta Sigma dac all on one IC chip.USB is limited to 16/48k adaptive mode operation and the board includes a pulse transformer on the SPDIF output. While certainly outclassed by newer USB chips it is completely adeqate for use with a lap top for streaming internet radio or itunes etc.It also does a credible job with flac files via J River Media Center. (operating in WASAPI mode).I installed the PC board in a small plastic case which makes for a very compact and portable unit.I used a 75 ohm BNC for SPDIF output and since the PCM2704 also has a stereo analog voltage output I included a pair of RCA connectors thus making it a complete self contained USB DAC.While sound quality is compromised using the on board DAC it is very convenient for times when my daugther wants to hook her lap top into a rig.

heiney9

My Keces DA-151 uses the PCM2702 (very similar) for USB and the designer basically said the same thing. Not state of the art but when implemented correctly the strenghts can be exploited and the weaknesses minimized and so far what I'm hearing out of the Keces is really, really good. Careful attention to the power supply and a seperate clock helps to improve performance a lot.

Three words describe the Keces; effortless, cohesive, dead quiet.

Enjoy Fred, nice work as usual.

H9

Face

Great job Fred.

FTGV

heiney9 wrote: »

My Keces DA-151 uses the PCM2702 (very similar) for USB ....

Yeah Brock from what I gather the two chips differ only in that the 2704 has an SPDIF (and I2S) output so can function as just a USB -SPDIF convertor to feed a separate DAC ,with the 2702 you must use the on chip DAC.I could have put it in a larger case and used a nice regulated power supply but with this unit convenience and portability trump ultimate sound quality.

Good to see you have found a DAC you like for your office rig within your budget.

SCompRacer

As usual, high marks Fred! Fox crystal....hmmmm, I see a trend here.:cheesygrin:

I see you added a test port. I have them same fittings on my oscilloscope.







:cheesygrin: I know, I know, BNC, a true 75 Ohm connector.

FTGV

SCompRacer wrote: »

Fox crystal....hmmmm, I see a trend here.:cheesygrin:

Thats what came already installed.Not sure of the freq.stability spec.

FTGV

I built up another one of these simple little DAC's so that I can do a comparison of two different D-A chips to see if I could discern any audible differences.Of course the quality of the power supplies and the analog output stages play a large roll but I'm curious to see if I can hear any differences between equally spec'd chips from two different companies.Namely the Cirrus CS4398 and AKM AK4396 both are 24bit/192 k Delta-Sigma differential voltage output devices.Other than the addition of a 16/48k non async USB input on the Cirrus board the two are near identical thus making it an apples to apples comparison.Both very similar PC board layouts,the same power supply scheme,and use the same Cirrus CS8416 digital input reciever.
As with the original AKM board I used Panasonic FC series electrolytics for local decoupling ,and Panny stacked film's for supply bypassing.
Aswell a BNC connector is used to assure proper 75 ohm termination impedance and a pulse transformer provides galvanic isolation from my PC's soundcard.The main filter caps in the second board are UCC's vs Nchicon's in the first.

As the pics show I used another though slightly larger version of the cute little Hammond cases.After I'm finished with the comparo I will use the extra chassis space to beef up the main filter capacitance with the addition of an auxillary PC board with 4x 3900uf.