DIY DAC....is this any good

[portreathbeach]

Thanks again abraxalito for your help.

I have done a bit more reading into various DAC chips and receiver chips and due to having a good knowledge and experience with PIC microprocessors and various other digital devices, I have decided I would like to try and make a DAC instead of buying the eBay one. I think it is better to learn by building from scratch.

I see why the 1543 and 1545A chips are not interchangeable, as they run 2 different formats or protocols from the receiver chip.

I found a site that implements a CS8412 and a TDA1545A.....

Match Made in Heaven: Batteries and Non-OS DACs

You can get CS8414 chips on eBay which are pre-soldered onto DIP adapter, so I think I may try it. Please could you have a look at the schematic on this site and tell me what you think. I understand most of it apart from the string of diodes on the LM317! I've used LM317 chips before, but not like this. Is the ADJ (pin 1) connected to the top of the series of diodes, or is it just crossing?

If I were to use the schematic on this site and I did parallel some 4515A chips, do I need to change any of the resistors on the output?

Sorry for all the questions, the internet is a great source of information, but sometimes it has way too much and can be misleading.

 

[portreathbeach]

I just found another similar schematic:

This one uses a 1543, so to use a 1545A, I would have to set the mode of the CS8414 to output EIAJ, correct? I'm still not sure about the power supply and how to parallel the chips though

 

[abraxalito]

I have done a bit more reading into various DAC chips and receiver chips and due to having a good knowledge and experience with PIC microprocessors and various other digital devices, I have decided I would like to try and make a DAC instead of buying the eBay one. I think it is better to learn by building from scratch.

I used to think so too but in recent years I've changed my mind. The satisfaction I find comes from the feedback loop - build something, listen and see how it sounds. Building totally from scratch means a long delay before you can get to listen, so enthusiasm tends to lag a bit there (maybe I just have ADD ). Modding something that works straight out of the box means you can try a fairly simple tweak - like removing those two green caps - and get practically instant feedback. I've found such tight loops are the real essence of learning by doing.

I've also used PICs in the past but these days I'm sold on ARMs because they do so much more (the 32bit PICs are quite good though I must admit but I don't see a long-term future for MIPS).

I found a site that implements a CS8412 and a TDA1545A.....

I'll take a peek and get back to you on that in another post.

Sorry for all the questions, the internet is a great source of information, but sometimes it has way too much and can be misleading.

No apologies required for questions If there's something I'd suggest to improve DIYA in general it would be fewer claims made and in their place more questions asked

 

[abraxalito]

Websites can indeed be misleading...

Back to the link you cited. Almost the only thing I agree with that guy on is that Monica Bellucci is a babe. On technical stuff I'd barely give him the time of day.

Down and dirty - he's got a string of diodes hanging off his LM317. I'm wondering why he'd do that - diodes have a really poor dynamic impedance and putting several in series compounds this. But then I notice he credits Thorsten for the idea - this is where the plot thickens considerably coz Thorsten is pretty switched on about DAC design and I hesitate slightly whenever I cross swords with him

Fortunately he provides the link to what Thorsten actually said and it turns out to be quite different from what he's implemented. The diodes are the same but the original suggestion was to run several hundred mA through them - this lowers their impedance quite nicely. Yet our Monica fan has set the output current of his LM317 at 52mA (1.25V/24R) - barely enough to power the TDA1543, leaving nothing over for the diodes to act as shunts. Add to this his choice of 1mH inductors in the receiver power supply leads me somewhat reluctantly to just one conclusion - give him a wide berth.

 

[bcmbob]

I hope this isn't hijacking - but this kit is giving excellent results with the mods developed by Dario I. The thread is very long but there are some good comparisons to other DIY and commercial DACs

DAC 2496 (AK4393)+CS8416+AK4393+5532 Kit | eBay

http://www.diyaudio.com/forums/digi...2496-ak4393-dac-kit-cs8416-ak4393-5532-a.html

The bare PCB with pre-mounted SMD chips is also available from the same vendor. It is an easy to build solution with top end sound and I am suggesting it only if you are not confining the scope here to the unit in the first post of this thread.

 

[portreathbeach]

Thanks again for the reply. I do feel that I want to build a DAC from scratch now I've read into it a lot more. Have you any good schematics using 1545As?

 

[bcmbob]

Sorry, I don't. If you haven't been there already you might find some support and ideas on this thread. http://www.diyaudio.com/forums/audio-sector/187748-pushing-limits-tda1543-nos-dac.html#post2549622

 

[abraxalito]

Have you any good schematics using 1545As?

What difficulty level were you looking for? I haven't drawn up any whole schematics for my DACs over the past year or so, just have part schematics distributed through my notebooks. But I could cobble up something in a couple of days. My 4 montns old design I already mentioned has 8 DAC chips. The one I'm working on now is considerably more complex, with 19 chips - you can see the first prototype on the DAC sticky thread (post #33) - rather a lot of chips and wiring, but I'm simplifying it a little for the beta prototype

 

[portreathbeach]

I'm thinking maybe 8 DAC chips also. Any schematics, or part schematics would be greatfully received.

 

[bcmbob]

Let me poke my head in here again. That many DAC chips is an unfamiliar approach to me and maybe others. Can someone please give a short explanation of the benefits and theory involved?

Thanks.

 

[abraxalito]

Take a look at my blog for the prototype and an outline explanation for how I arrived at using so many DAC chips. Questions encouraged in the comments section.

diyAudio - DAC design and development

 

[bcmbob]

Thanks, looks very interesting. I'm off to study hall.

 

[portreathbeach]

abraxalito, did you have a look at the schematic I posted in post #22? Would this be a good start? I could replace the 1543 with a 1545A and change the mode of the CS8412 (CS8414) to output the correct format to the DAC. I would obviously have to use a 5 volt regulator to feed the 1545A, as the schematic shows an 8 volt feed.

Also, what about this circuit:

SPDIF audio DAC with CS8416 and TDA1543


Thanks again for your help

 

[abraxalito]

abraxalito, did you have a look at the schematic I posted in post #22?

I've looked now Its a reasonable start yes. I'll document the boards I have with partial DACs on and come up with my own schematics over the next couple of days...

I could replace the 1543 with a 1545A and change the mode of the CS8412 (CS8414) to output the correct format to the DAC. I would obviously have to use a 5 volt regulator to feed the 1545A, as the schematic shows an 8 volt feed.

Yes, all sounding reasonable. I use shunt regs (TL431) for CMOS DACs as they give lower output impedance at low currents, but I would normally have a series reg first, so you could keep the 8V reg.

Also, what about this circuit:

Gave it a quick scan, didn't notice any howlers Never seen a 10 DAC version before.

As regards sound quality - its dependent on getting the grounding right which isn't shown explicitly on schematics normally. I plan to draw up mine though to give grounding indications.

 

[portreathbeach]

I'll document the boards I have with partial DACs on and come up with my own schematics over the next couple of days...

That would be great. I think it could help a lot of others too.

As regards sound quality - its dependent on getting the grounding right which isn't shown explicitly on schematics normally. I plan to draw up mine though to give grounding indications.

When I am planning my different audio builds, I also like to sort the grounding out on paper first as I know how annoying ground loops etc. can be to sort out afterwards.

Thanks again

 

[marce]

Ground plane

 

[abraxalito]

When I'm modding NOS DACs which have ground planes I'll always disconnect things from the ground plane grounds and wire them explicitly using point to point and star grounding. Sounds better then.

 

[marce]

Even for the digital!

 

[abraxalito]

Not the pure digital (logic) but including the DAC chips.

 

[portreathbeach]

I have been reading the pdf documents on receiver chips, CS8412, 14 and 16 and want to know if there are any advantages/disadvantages of each chip. I notice that CS8416 can have multiple inputs and can be selected on the RXSEL pins whereas the CS8414 only has 1 input, this wouldn't be a problem, as relays could be used to swap inputs. I think I want to use the CS8414, as they are selling on eBay pre-soldered to an adapter, so it would obviously make it easier to experiment with.

abraxalito, I know you said you would post a few schematics in the next few days, but I have still been looking on the net for various designs.

I visited a site I have used in the past..... Elliot Sound Projects website:

S/PDIF Digital to Analogue Converter

This seems a pretty simple design, although the PSU could be better. I see that it uses a CS4334 DAC chip which is I2S format, so if I want to use a TDA1545A, I would have to wire the receiver chip to a different mode.

I notice he mentions a 'reset circuit', do all receiver chips need this?