Time for a new DAC project....
As a response to the growing number of over-priced DIY DAC projects, Kurt von Kubik and me decided, to use the experiences from our Reference DAC, and develop a new DAC.
The idea is that this DAC should match commercial DIY DAC's, which is normally based on Op-Amps.... That's why we will also use op-amps.
In contrast to many commercial DIY DAC's, this one will not just be a DAC-PCB without analog stage and PSU. It will be a full DAC design, including Complete PSU, digital stage and and analog stage. Even connectors onboard.
And in contrast to thoose telling you, that a DAC-board without PSU and analog stage will cost you 300-600$, we are beeing more realistic.
We aim for a total price of 199$ including PCB and ALL components. PSU, DAC and analog stage all included.
Since we do not believe in the idea of seperate boards connected by screw terminals in High End audio, everything is placed on 1 single board! Just plug in 115 or 230 VAC, and you are running!
The project will be 100% open source, with links to component suppliers. Just to give all of you an idea of how low cost such a design really is... Even though some manufactures tell you something different
During the R&D of our Reference DAC, we found that the best performing DAC on the market (Sonic performance), is CS4398 from Crystal Semiconductors. So the choice is really easy... The new DAC will be based on this chip.
We will use CS8416 SPDIF receiver (Market leader) and SRC4192 Sample rate controller.
In general, we will use high quality components, like Wima foil capacitors, Panasonic FM series electrolytics, 1% resistors and so on.... All the things that manufactures try to tell you, will cost a fortune.... Still, our target price is max 199$. And still... 100% open source!!
Since this is a project under R&D, we will accept good ideas.. So keep them comming....
As a response to the growing number of over-priced DIY DAC projects, Kurt von Kubik and me decided, to use the experiences from our Reference DAC, and develop a new DAC.
The idea is that this DAC should match commercial DIY DAC's, which is normally based on Op-Amps.... That's why we will also use op-amps.
In contrast to many commercial DIY DAC's, this one will not just be a DAC-PCB without analog stage and PSU. It will be a full DAC design, including Complete PSU, digital stage and and analog stage. Even connectors onboard.
And in contrast to thoose telling you, that a DAC-board without PSU and analog stage will cost you 300-600$, we are beeing more realistic.
We aim for a total price of 199$ including PCB and ALL components. PSU, DAC and analog stage all included.
Since we do not believe in the idea of seperate boards connected by screw terminals in High End audio, everything is placed on 1 single board! Just plug in 115 or 230 VAC, and you are running!
The project will be 100% open source, with links to component suppliers. Just to give all of you an idea of how low cost such a design really is... Even though some manufactures tell you something different
During the R&D of our Reference DAC, we found that the best performing DAC on the market (Sonic performance), is CS4398 from Crystal Semiconductors. So the choice is really easy... The new DAC will be based on this chip.
We will use CS8416 SPDIF receiver (Market leader) and SRC4192 Sample rate controller.
In general, we will use high quality components, like Wima foil capacitors, Panasonic FM series electrolytics, 1% resistors and so on.... All the things that manufactures try to tell you, will cost a fortune.... Still, our target price is max 199$. And still... 100% open source!!
Since this is a project under R&D, we will accept good ideas.. So keep them comming....
How about USB interface?? We are a bit doubtful about implementing a USB interface on the DAC.
Basically, an USB interface would make the DAC very flexible. The trend goes towards computer based audio. In that light, USB is almost mandatory.
But then again.... Connecting a PC through a USB connection, will create a galvanic connection between PC and DAC, which will cause massive noise injected into the DAC. That's reality, also in commercial DAC's (Even though they forget to tell you ).
So the question is.... Do we want USB or not??
We could skip the USB part, and add an extra TOSLINK interface. Even though TOSLINK is much worse performing than electrical SPDIF, TOSLINK is much better than common available USB interfaces. And then you are galvanic seperated = No Noise injection from the PC.
This just requires a TOSLINK interface on the PC. But this seems to be more common these days.
What is your opinion on this??
Basically, an USB interface would make the DAC very flexible. The trend goes towards computer based audio. In that light, USB is almost mandatory.
But then again.... Connecting a PC through a USB connection, will create a galvanic connection between PC and DAC, which will cause massive noise injected into the DAC. That's reality, also in commercial DAC's (Even though they forget to tell you
).So the question is.... Do we want USB or not??
We could skip the USB part, and add an extra TOSLINK interface. Even though TOSLINK is much worse performing than electrical SPDIF, TOSLINK is much better than common available USB interfaces. And then you are galvanic seperated = No Noise injection from the PC.
This just requires a TOSLINK interface on the PC. But this seems to be more common these days.
What is your opinion on this??
Yeap.... Firewire would be NICE! But we do not want to create something that needs a lot of programming. And that would be the case with Firewire.
I did work on Firewire some years ago, when I was working with R&D at Bang&Olufsen. Trust me... It's not suited for DIY
Also I see the trend moving away from Firewire. It seems like Firewire never really got the foot in.
Maybe we should consider enhancing the performance of the USB interface, since this is more suited for DIY....
I did work on Firewire some years ago, when I was working with R&D at Bang&Olufsen. Trust me... It's not suited for DIY
Also I see the trend moving away from Firewire. It seems like Firewire never really got the foot in.
Maybe we should consider enhancing the performance of the USB interface, since this is more suited for DIY....
Looks good. I like the concept. One thing you might consider for the folks that want to tweak is to make some solder headers for alternative analogue stage connection. That way you have your solution out of the box, which I'm sure will sound good, but the ability to tweak and compare without ruining it as well.
Just a couple questions/comments. Why do you have that a zener diode on the spdif input? Shouldn't you have a proper pulse transformer there instead? As for the issues associated with a usb interface, you could overcome this by using an optocoupling stage, either between the computer and the receiver chip or, on the serial data stream from the chip to the DAC. The analogue power supply seems a little incomplete, you seem to be missing some clamping diodes, as well as your sense and return grounds should (ideally) be shown independent. I have a +/- 15V small signal audio power supply design that could easily be used for this project. It includes optically operated solid state relays to switch power to the chips. Also decoupling capacitors on the NE5532's; the 150uf electrolytics could be replaced with 4.7-10uf tantalum for equivalent, if not better performance. You're also using a DAC with balanced outputs, I'd put a couple of OPA1632's to buffer those, and offer a nice set of balanced outputs on this unit as well.
@ Sergery:
Point taken! We agree that a op-amp based analog stage is not ideal! I would prefer a discrete NFB design. That's why we made this DAC http://www.diyaudio.com/forums/digital-line-level/138230-dac-project-completed.html
This op-amp based DAC, is mostly a reaction to the growing numbers of commercial op-amp based DIY DAC's. We just want to finish it, instead of selling something almost done.
But I agree! I will add a header, to connect an external analog stage.
@ rsbonini:
The zener on the SPDIF, is actually a ESD protection. This may not be needed. I have not yet seen any commercial DIY DAC's with such a protection. I will leave it on the schematic and PCB, and let the builder decide, if he/she wants this protection.
We dont use pulse transformers, since these will be a major source of jitter. We have done quite a few listening tests to confirm the bad effect of pulse transformers.
Where would you place clamping diodes?
About Gnd, this is taken care of in the PCB layout.
Feel free to post the schematic on this +/-15V PSU... If this could upgrade the performance on the DAC, it is very interesting.
About decoupling, we did try different tantalum capacitors, with extremely low ESR. But the Panasonic FM outperformed these in sonic performance.
Generally we do not use balanced output. But I will consider this....
All i all... Nice suggestions... Keep them comming.....
Point taken! We agree that a op-amp based analog stage is not ideal! I would prefer a discrete NFB design. That's why we made this DAC http://www.diyaudio.com/forums/digital-line-level/138230-dac-project-completed.html
This op-amp based DAC, is mostly a reaction to the growing numbers of commercial op-amp based DIY DAC's. We just want to finish it, instead of selling something almost done.
But I agree! I will add a header, to connect an external analog stage.
@ rsbonini:
The zener on the SPDIF, is actually a ESD protection. This may not be needed. I have not yet seen any commercial DIY DAC's with such a protection. I will leave it on the schematic and PCB, and let the builder decide, if he/she wants this protection.
We dont use pulse transformers, since these will be a major source of jitter. We have done quite a few listening tests to confirm the bad effect of pulse transformers.
Where would you place clamping diodes?
About Gnd, this is taken care of in the PCB layout.
Feel free to post the schematic on this +/-15V PSU... If this could upgrade the performance on the DAC, it is very interesting.
About decoupling, we did try different tantalum capacitors, with extremely low ESR. But the Panasonic FM outperformed these in sonic performance.
Generally we do not use balanced output. But I will consider this....
All i all... Nice suggestions... Keep them comming.....
Which i understand, unless some of the new USB chips get around it, requires programming.
dave
It would be nice to have the possibilty to implement a non-feedback discrete design. I don't like operational amplifiers - they likely are not running in class A and their bandwidth is very limited (to give the same distortion at high and low frequencies).
I don't like the series regulators -they are too noisy. I've been a fan of shunt regulators for audio. Maybe the power supply should reside on a board of its own?
I do agree with you, but op-amps do work in class A
You should go for the earlier design then.
It both features completely discrete analog design and shunts, in addition NFB technology and DC servo circuits.
The sound is stunning, but assembly is likely to fail because of complexity and a very compact layout. http://www.diyaudio.com/forums/digital-line-level/138230-dac-project-completed.html
Schematics are found on page 20
Unfortunately the thread was closed, because of ambition.
Last edited:
@ knutn:
As Kurt von Kubik says, you should go for our other project, if you are into fully discrete NFB design and shunt regulators.
This design is finished, after approx 4 years of R&D.
If you feel like trying this project, just let me know, and I will help you through. We may even supply you a PCB, since we have a few spares.
As Kurt von Kubik says, you should go for our other project, if you are into fully discrete NFB design and shunt regulators.
This design is finished, after approx 4 years of R&D.
If you feel like trying this project, just let me know, and I will help you through. We may even supply you a PCB, since we have a few spares.
What about galvanic USB isolation using the Analog Devices ADUM4160 chip?
I have just tried this kit based on the ADUM4160 and it works flawlessly.
Sorry but I fail to see the point of using opamps just like all the other fine sounding chinese DACs. The latter are bought by people that....disconnect the opamp section and add transformers/active discrete stages etc.
Why make a DAC that is equal to (cheaper) chinese products ? Make it better to show europeans still can design good stuff ! I just checked the schematic and it is nearly a 100 % copy of a chinese Ebay DAC that can't be beat in terms of price/quality ratio. Less work, less money so why bother making a copy of that ? Just because you did the work yourself ?
A friend of mine always says: "if you decide to make one yourself make it better than what already can be bought as it will be more expensive anyway".
Last edited:
I've never totally understood the bias against operational amplifiers. Just like discrete components you can design well with them, or you can design terribly with them. Properly implementing opamps can result in some extremely high performance designs. Personally I like mixed architectures. For example, I designed a phono preamp with a discrete input gain stage utilizing the ultra-low noise of super-matched transistor pairs in parallel. The filter stage was active, taking advantage of the gain structure and inherent feedback design of opamps. Why limit yourself to one or the other, take the best of both worlds. That was all a little off-topic though.
I'll rework that analogue supply for this project, just a couple questions though. I assume that either the receiver or the DAC itself have a signal sense output (either logic high or low). This can be used to turn the analogue section on or off, so do you want this feature included in the power supply? (if so, let me know what the logic voltage levels are)
I'll rework that analogue supply for this project, just a couple questions though. I assume that either the receiver or the DAC itself have a signal sense output (either logic high or low). This can be used to turn the analogue section on or off, so do you want this feature included in the power supply? (if so, let me know what the logic voltage levels are)
Compared to i.e. Cambridge DM, the powersupply is somewhat more ambitious in this project though.
Otherwise you have a point.
But the design is still not closed, and I´m trying to talk hurtig in to incorporating a discrete buffer after the op-amps to provide sheer power.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.