New AD1862 R2R Dac Build. and Compariison to off shelf Dacs.

[niss_man]

Hi Guys

 

I just had a sneak peek of a new Dac I have just finished building over here. 

So here is  a few pics of the final product which I'm pretty proud of.

A little background to this project. I wanted to try a R2R afterliving with delta sigma dacs for a few years(Audio GD NfB-28 )and (Diy najda active crossover/dac here). The nfb28 having the reknowned sabre ES9018 chip and the najda being a diy Deqx 8 chanel active dsp with blinged up power supplies. 

 

I got my hands on a used PDX dac.. thanks @scumbag. I originally heard the PDX when I was just getting into the audio..pile scene at a few gtg's down the Gold Coast and at Mike Lenehans.

I couldn't say no to the PDX and so grabbed it. I fell in love with the sound of the PDX and experienced my first R2R type dac with Tube output stage. I was going to modify the power supplies to bling up the PDX to get the maximum I could out of it, but after a bit of thinking, decided to design and build my own R2R Dac. Originally I was going to use the PCM1704/02 chips as the PDX but they were quite hard to come buy so I went for an Analogue devices top of the line AD1862 as found in some high end Denon (DCD-1650) and Teac (Vrds-25) and others. I also sourced a PMD100 oversampling chip favoured by many and decided to use the AD844 output stage georgehifi likes to rave on about (no harm in trying).

 

1st up the design of the circuit I will share here.

 

 

And then the PCB design sent of to Pcb Way in China which did quite a good job I must say.

 

Even got Enig plating (gold plated).

 

Cheers

 

Simon

 

 

 

I'd also like to thank @Gieseler Audio Clay for helping me out with multiple questions about the Pdx and Dac design in general. I know you have plenty on your plate and to take time to help me out I am much appreciative.

Edited February 12, 2017 by niss_man

[Guest scumbag]

Simon,

 

Very interesting. Keep the information coming! I see the PDX lurking in the shadows below your Zeus DAC. I sense an inevitable comparo.

 

Mark

Edited February 12, 2017 by scumbag

[niss_man]

Some more pics of the final product

3 minutes ago, scumbag said:

Simon,

 

Very interesting. Keep the information coming! I see the PDX lurking in the shadows below your Zeus DAC. I sense an inevitable comparo.

 

Mark

haha yes. Will post some more pics first up.

Here it is with a few other Dacs to keep it company. Sorry about the mess but as a diyer there seems to be a never ending pool of wires, test instruments, tools and open covers lying around the place.

 

 

A close up with the populated PCB. As usual there is always some silly little mistake I make on the first batch of boards. In this case, I didn't quite get my talking happening between the CS8414 receiver chip and the PMD100 chip. There are a few pins you tie high or low (5/0V dc) to enable different communication protocols between chips. It wasn't anything major and can hardly be seen. I had to lift a pin from the CS8414 and tie it to Gnd as can be seen by the blob of solder between 2 pins. The CS8414 is the surface mount one on the top left.

 

 

Here is the whole lot. I have used extremely low noise power supplies (these are muchmuch better than generic 7805 and 317 regulators). The Rcore transformer powers a few things.

1- The 5Vdc supply using TPS7A47 regulators (the veroboard). Powers the CS8414 receiver and the PMD100 chips.

2- The dual +/- 12Vdc powers the AD1862 Dac chips.

3-  Another 9Vac secondary on the Rcore is going to a power supply on the Dac board (white wires). They get turned into 5Vdc for the switching relays and also a separate low noise 3.3Vdc to separately power the Usb-I2s(amanero) converter instead of using the noisy power from the usb bus.

 

The 2nd torroid transformer powers the Salas shunt power supply on the right hand side for +/- 15Vdc for the AD844 output stage.

 

This may all a bit of overkill like bringing a machine gun to a knife fight but we want these things to be the best they can be don't we?

 

 

You will notice this is DC coupled as well so no capacitors in the circuit to flavour the sound. The output is on the RHS of the Dac board.

Here is the Salas shunt power supplies which are raved on about over on Diyaudio.

 

The Front and sides are made from some beautiful wood I got from Tasmania. "Spalted Rainbow Sassafras".  The middle front is some copper bus bar I had from my previous project so used some in this to match up.

 

Previous projects. One on top right is a lightspeed attenuator with remote control and 3 inputs. Thanks again to @georgehifi. 

The sexy box on the bottom right also using Spalted Rainbow Sassafras is my own designed poweramp I did last year.

If you want to know about that project just ask and I might start a new thread.

 

Side shot. Enough wood for you @Luc?

 

So this has Coax, optical and usb input.

 

 

 

 

 

 

 

 

[niss_man]

Some boring oscilloscope shots. Unfortunately I dont have a distortion meter but maybe at a later stage I will learn how to use a sound card to do the same thing.

 

1000Hz- 0db 

 

10KHz

 

14KHz

 

20KHz you can see the stair effect happen hear at these extreme frequencies. Perfectly normal.

 

Here are some square waves thrown in for good measure. These arent pure flat as you might expect but these are what you would see on any cd player. Square waves are made of harmonics which reach into the MHz and as cd's only go to 22Khz they don't have the ability to show any better. We don't listen to square waves anyway. @Nada you wanted to see these.

 

 

 

[Nada]

Awesome project! Such excellent  design and execution. Congratulations. How did you learn to make your own PCB designs?

[niss_man]

4 hours ago, Nada said:

Awesome project! Such excellent  design and execution. Congratulations. How did you learn to make your own PCB designs?

The oracle google taught me. and the other oracle you tube.  Of course I've only scratched the surface being an amateaur and I seem to always make a little mistake on my first batch, but as always with this diy stuff there is a bit of a buzz when it is up and running and sounding nice. 

[Guest scumbag]

Sh*t, I wish I could get that out level of knowledge out of Google!

[pete_mac]

Great work mate!

[niss_man]

Here are some general observations of the sound of this Dac compared to the others. Not a review as such and definitely not in the same league as Cafad's reviews.

 

 

Simdac (thats the name I've given this one)

 

I read somewhere ages ago that a member @bhobba (i think) said that he would put dacs as his second most important thing in a system after the speakers. After listening to this I would agree (well third, room, speakers, dac).

The immediate thing to come to mind when firing this one up is Bass, impact, speed, energy. All are things that most people generally relate to when using a R2R type dac. "Musicality" and "Prat" are a result of this I think. If I turn up my lightspeed pre volume to maximum on idle (no music) I get pretty much zero noise change from the speakers (well maybe ever so slightly when the ear is 1cm away but virtual stuff all).  So that says to me it's got a pretty damn low noise floor (maybe those power supplies payed off?). The simdac seems to be able to reproduce great harmonics and texture to the music and you seem to be able to get into the music just that slightly more. When flamenco guitar is played I can imagine the texture of the fingers on the strings a bit better, with saxophone I can hear the valves slightly more and with male vocals I can hear a chestiness and depth that are slightly more than before. Is it the low noise floor or the R2R'ness (new english word) of the Dac, I tend to think it's a bit of both. 

Ballsy. Yes that had to go in bold as this thing has it in spades. This is what creates the impact. It seems to want to create all of the music. What I mean by that is the leading edges are sharp and easier to drive. A drum hit may sound like it was hit by a light weight on my audio Gd sigma dac (mind you it is still there on the audio gd). With the leading edges of the music all there on the Simdac, it sounds like drums are struck by Evander Hollyfield. Mind you when the music asks for gentle it can give gentle, but when it wants impact, you can sometimes feel like your being blown through your lounge chair and into the back wall.(thats the type of energy this thing can reproduce).

     

PDX The pdx made me fall in love shortly after listening to it. It has the characteristics of the Simdac, but with the tube output stage it has gained that tubeyness to the sound. The leading edges are more rounded and soft making the music a bit less impactfull but the general R2R'ness is still there , texture, musicality, prat, engagement etc but just in slightly smaller numbers. Dare I say it but to me it seems the valves (colour the sound). Where as the simdac seems to reproduce everything exactly what is in the music, the PDX rounds the leading edges a bit and changes it. Mind you this isn't a bad thing as it can be slightly more generous to poorer recordings than the Simdac because of this.

    Because the simdac is so good at reproducing what is in the music, shit (poorly recorded) music turns extra shit and well recorded music turns extra well if you know what I mean.

The tubes, in the PDX are more forgiving to poorly recorded music.

                Now I don't know whether this is normal  or not, but when turning the volume to maximum on no music, the PDX has the highest noise floor of the lot (I can hear the noise floor at the listening position 3.5m away), That said it is still extremely enjoyable to listen to albeit it can get a bit little muddled when the music gets busy compared to the simdac (and maybe even the audio gd). 

 

Audio GD: The noise floor of the Audio Gd is lower than the PDX and and close to the sim dac (2nd in this bunch). The audio gd is a Sigma delta dac (does that make a difference?). It is highly detailed but seemed to have not as much impact. Less engaging (almost boring in comparison to the other 2). It makes you sit there and listen to the detail but it didn't engage the emotional core as much as the other 2. Playing Joe Satriani "Always with me Always with you", the whip crack sound had less impact on the same volume.

    With this dac I could handle music louder, for longer than any of the other 2 dacs and it seemed to make you want to turn the music up to get the musicality and forcefullness of bass etc there. 

The other 2 dacs didn't need the volume as high to give the same impact so they would be good for guys who play there music at a lower volume.

 

Wifeyness: Whilst gardening outside with the front door open to hear the music I ask my wife Kylin what the music sounds like (worst question an audiophile can ask his wife I know). She says it has more bass. Yes, yes it does. I think with both the simdac and PDX, because of there character they tend to project the sound at long distances much better than the other 2 dacs I have(audio gd, and diy Deqx, both delta sigma types). The energy in the sim and pdx doesn't degrade as easy over the longer distances I think.

 

Conclusion:  Simdac- Pros: Balls, energy, drive, impact speed, textural details. music reproduced as it is recorded. Don't need as high volumes. 

                                     Cons: Can be bit too much balls, impact, speed if your not used to it. music reproduced as it is recorded (needs good recordings)

 

PDX- Pros: Valveyness , can live in the music easier for longer as a result of slightly less leading edge impact. slightly more generous to poorer recordings. still good at low volumes

Cons: Less leading edge impact, noise floor, can get muddled in busy music

 

Audio Gd NFB-28-  Pros: Most generous with the poor recordings, good detail. Excellent alrounder.

Cons: Needs high volume to get bass and impact happening (may be a good thing for some). Not as engaging. Not as good at a distance.

 

I won't bother giving scores here but I think we can get the general gist. If you want an excellent alrounder that can play all types of music and recordings go for the Sigma delta. If you like your music with a ton of energy, drive and true(imo) to the recording my simdac wins. If you want one with slightly less energy and drive while still retaining  a good amount of texture (or for people who like valves), the PDX is for you.

 

PS: I intend to lend the dac around to a few guys in the QLD audio club (or maybe have a gtg here, too hot atm though), and get some other opinions on this thing as well. Once it comes back I will sell one or two of my other dacs. 

 

 

    Cheers

 

Simon       

   

         

Edited February 13, 2017 by niss_man

[Listener]

50 minutes ago, niss_man said:

PS: I intend to lend the dac around to a few guys in the QLD audio club

 

I would not do this Simon, you might not get it back!

 

Nice work.

 

Steven.

[niss_man]

10 minutes ago, Listener said:

 

I would not do this Simon, you might not get it back!

 

Nice work.

 

Steven.

Haha. I know a good heavy thug who can force the situation for me.  

[Nada]

Quote

The sexy box on the bottom right also using Spalted Rainbow Sassafras is my own designed poweramp I did last year.

If you want to know about that project just ask and I might start a new thread.

 

Yes please to a new thread on your poweramp.

[niss_man]

The sexy box on the bottom right also using Spalted Rainbow Sassafras is my own designed poweramp I did last year.
If you want to know about that project just ask and I might start a new thread.

 
Yes please to a new thread on your poweramp. [emoji4]

I will start a new thread for that in a week or two.

[rockeater]

Any project with PMD100 is a good project.

I thought they were no longer available so I never looked for one. Where did you get yours from and how much was it?
 

[niss_man]

I searched the diyaudio classifieds section.

[Nada]

@niss_man  I wonder if there is any DC offset on the outputs?

 

Also if you want a great alternative USB input look at the new Audial USB board that can bypass the PMD100 and feed the AD1862 right justified data direct with very low noise. This will  allow you to play NOS ,HD or use your computer to up-sample and filter to your tastes.

[niss_man]

45 minutes ago, Nada said:

@niss_man  I wonder if there is any DC offset on the outputs?

 

Also if you want a great alternative USB input look at the new Audial USB board that can bypass the PMD100 and feed the AD1862 right justified data direct with very low noise. This will  allow you to play NOS ,HD or use your computer to up-sample and filter to your tastes.

I have a trimmer on the ad1862 circuit to put 0 offset into the ad844. I also have optional trimers on the ad844 and the lme49710. I have 1-2mV at the output so I haven't even bothered installing my option trimmers,

 

  I have a diyhk ad1862 NOS board which I was using before I got to put this together. I must say I don't think there is really a great deal of difference between the 2 but have not tested side by side. Maybe at some stage I will build another dac box with power supplies and install the NOS one to do a comparo. 

   The audial sounds interesting. I found the amanero great as you can modify the firmware which I had to do to get it working with the slower clock rate old school PMD100 chip. Can also choose Right justified etc.  Can you do that with the Audial USB board?

 

Simon

[Nada]

2 hours ago, niss_man said:

I have a trimmer on the ad1862 circuit to put 0 offset into the ad844. I also have optional trimers on the ad844 and the lme49710. I have 1-2mV at the output so I haven't even bothered installing my option trimmers,

 

  I have a diyhk ad1862 NOS board which I was using before I got to put this together. I must say I don't think there is really a great deal of difference between the 2 but have not tested side by side. Maybe at some stage I will build another dac box with power supplies and install the NOS one to do a comparo. 

   The audial sounds interesting. I found the amanero great as you can modify the firmware which I had to do to get it working with the slower clock rate old school PMD100 chip. Can also choose Right justified etc.  Can you do that with the Audial USB board?

 

Simon

 

That's an impressive low offset out result. Well done.

 

I was looking at the diyhk ad1862 NOS board too but never went ahead with it. If youve got that you dont need the Audial USB. But to  answer your question the Audial USB does offer a direct right justified option for feeding the AD1862. Its a bit like Ian's FIFO and PCM option or the diyhk ad1862 NOS board you already have.

 

 https://www.audialonline.com/topics/usb-to-simultaneous-data-or-i2s-board/ 

 

 

Note for guys who like running balanced configurations, the Audial puts out paired data signals, with one inverted, to allow differential discrete designs using two of the mono AD1862 per channel to drop the noise floor a bit. What do you think of that design approach?

[niss_man]

18 hours ago, Nada said:

@niss_man  I wonder if there is any DC offset on the outputs?

 

Also if you want a great alternative USB input look at the new Audial USB board that can bypass the PMD100 and feed the AD1862 right justified data direct with very low noise. This will  allow you to play NOS ,HD or use your computer to up-sample and filter to your tastes.

You can see on the image the trimers for the ad1862 beside them and the optional trimmers I didn't need above the ad855 and lme chips above them. 

You would be able to make a nice simple dac with the Audial USB (usb only) using only dac chips and output stage, but I need other types of inputs as well. The price of the Audial is a bit ridiculous as well 170-180 euro, 230-250AUD delivered depending on the option of additional firmware!

[Nada]

4 hours ago, niss_man said:

You can see on the image the trimers for the ad1862 beside them and the optional trimmers I didn't need above the ad855 and lme chips above them.....

 

So you went with the LME49710 insteadd of the OPA627?

[niss_man]

Yep. Using the LME49710. OPA627 isn't really better or worse for that matter. Pretty much the same. The LME wins in the price department though. 

[bhobba]

Hi Guys

 

Yes I do believe the DAC is the next most important thing after speakers, and that is from a number of comparisons.

 

And yes the PDX is valvy goodness but outdone these days IMHO by some much more expensive DAC's like the Direct Stream which is why Mike and Clay don't make them any more.   I have one full house PDX available is anyone wants it.   I have been too busy to put it up for sale but if anyone wants it drop me a line and make me an offer.

 

Clay is upgrading the Konverter that won the DAC shoot-out a while back.   I have seen a  prototype - beautifully made - beyond beautiful actually - its constructed wonderfully.  How does it sound - don't know yet but its up against some tough competition like the Direct Stream Junior.  Undoubtedly comparisons will follow in due course.

 

Clay now makes what I consider THE value dac in its class at $750.00, the Klein.

 

But just today we may have a new value winner at about $400.00 - the Meridian Explorer 2.  OK with ordinary cables but today I was at Mikes checking out its MQA capability.  With top of the line cables the MQA was stunning - simply stunning.  Since it involves Mike cables I will do a  post about that part of it on his forum.  With the same cables is it better or as good as the Klein.   Don't know - but we will find out - but IMHO without the cables - not quite - even with MQA sources that it fully unfolds compared to 96k unfolding my suspicion is Clays DAC may still have the edge - but haven't done a comparison to be sure. I will be lending my Explorer to Clay and he can report and/or arrange a listening session to get to the bottom of it.  Don't worry even though Clay makes the Klein I am sure he will arrange something to remove any bias he may have.  It will likely appear on his sub-forum.

 

I will do a separate post about the Explorer but since its exceptional performance was only obtained with Mikes high end cables that part of it will be on his sub-forum.

 

Thanks

Bill

[Nada]

On 15/02/2017 at 4:12 PM, niss_man said:

Yep. Using the LME49710. OPA627 isn't really better or worse for that matter. Pretty much the same. The LME wins in the price department though. 

 

Whats the best place to get some LME49710?

[niss_man]

I got them at rs components here. I also got the ad844 at rs components as well. If you ever want to modify an existing current out dac of yours to the ad844 output stage I have plenty of boards left over here. These aren't boards for my dac, but separate 50mm x 50mm ones I made up to test with the NOS boards I got from Diyhnk. I would only ask $2 each plus postage for the boards. Cost me $20 for 10.  

[Nada]

Nice IV board