DIY DAC?

qtuner · 20th June 2005, 05:04 AM

I've been following the 192khz thread in the highend forum.

I'm wondering if it is possible to make a homebrew DAC? With the popularity of the seven circle audio mic pre's, has anyone attempted a DIY DAC?

here are some link to a couple reference designs: http://www.cirrus.com/en/products/pro/detail/P1024.html

I working with surface mount soic chips would be tough.

I found a the price for the new cirrus chip online to be 18$.

this is just a whim.

<update>

If I could build my own power supply and clock, I could get a reference board for ~$400. it is difinitely cost prohibitive to build you're own dac. If the chips were dip packages it might be easier, but there would probably be more noise.

The #1 problem I think would be minimizing noise to realize the full dynamic range of the chips.

</update

pendejo · 21st June 2005, 05:52 AM

I've been looking into this as well. The link you included was for an A/D converter.

Take a look at:

http://www.cirrus.com/en/products/pro/detail/P147.html

The D/A converter eval board ($400) includes a power supply. The onboard CS8414 chip provides a clock. SPDIF/AES-EBU input. Balanced XLR output. The only thing missing is a case :)

dasbin · 21st June 2005, 06:19 AM

Yup, these promo kits are great. Generally they are designed to utilize the full dynamic range and low noise and THD of the converter. Definitely wouldn't have to worry about noise except maybe in terms of providing a proper ground etc. I'm thinking of using the flagship Cirrus Logic A/D kit and putting something together, but the Newark website doesn't seem to be functioning properly so I can't really see what the deal is.

These kits usually use opamps with good specs but low musicality... often JRC. In other words, if you swap opamps for something more tasteful, like some TI stuff, you might end up with a more pleasing sound (although probably with a decrease in dynamic range, THD, noise performance). Power supply is probably well-designed. If they're putting DC-blocking caps in the analog signal path (not sure, haven't been able to look at the recent designs) then you may benefit from some better caps there, or just removing them altogether if your other equipment all already has some.

Jim Williams · 21st June 2005, 04:51 PM

Good ones are the Crystal CDB4398, BurrBrown DEMO PCM1792. The BurrBrown is the best but costs several hundred bucks. The Crystal 4398 is very good for sigma delta design. It has surface mount opamps of questionable quality, so rework is advised. It was just $150 a few months ago, but my promotion of it probably caused the price to go up. Just add a power supply and go.....

While at it, get a CBD 5381 A/D, the best A/D chip now out. It's $350 and just add a power supply. Surface mount analog should be changed. The surface mount blocking caps can be replaced, but avoid eliminating them as they block the 2.5 volt bias of the A/D's modulator.

Don't bother laying out a pcb or proto typing. The layouts are critical for proper operation and most pcb designers don't have a clue about doing it right, that's why the eval boards, they show proper layouts to achieve maximum performance.

Jim Williams
Audio Upgrades

qtuner · 22nd June 2005, 08:13 PM

So it is viable to go with a home brew solution based on eval boards?

Here's a really dumb question: What should I do for powersupply? Would wall warts work? Should I build my own?

What op amps would be a good for the analog section of both the cirrus logic eval boards?

I'm tempted to do it.

Jim Williams · 23rd June 2005, 03:32 PM

These require +- 12 volt analog and several +5 volt feeds for the digital. Get someone to make one for you if you don't know how to build linear power supplies.

These boards are supplied with either 5532 or 33078 opamps in surface mount. I would sub a Linear Tech LT1358 or National LM6172 for starters.

Jim Williams
Audio Upgrades

DrFrankencopter · 23rd June 2005, 04:09 PM

Where can you get the Cystal demo boards for a good price. Newark doesn't stock them, and quote a price of $420.

Thinking of getting one of these and putting a Forrsell JFET 992 output driver on the end.

Cheers,

Kris

rapfreak · 23rd June 2005, 04:22 PM

just get a power-one linear power supply from digikey (179-2070-ND). It gives 3A @5V and 1.25A @12V(adjustable). they run $62.75 and are easy to mount to a plate.

Jim Williams · 23rd June 2005, 05:06 PM

Quote:

Originally Posted by DrFrankencopter

Where can you get the Cystal demo boards for a good price. Newark doesn't stock them, and quote a price of $420.

Thinking of getting one of these and putting a Forrsell JFET 992 output driver on the end.

Cheers,

Kris

Insight Electronics is the distributor. Local offices are in your area.

Forget the 990 style opamps, these are fitted with SURFACE MOUNT opamps, very small footprints, besides the functions are a 2 pole low pass filter. You will have to redesign one and still fit that discrete monster on a board laid out for a 1/4" square opamp. Won't happen, besides there are better opamp choices with higher loop gain for higher performance. Remember, this is a converter, not a preamp or compressor. Leave the colors out unless you want the converter to mask things. This is the one device that should reveal colors, not create them.

Jim Williams
Audio Upgrades

DrFrankencopter · 23rd June 2005, 05:43 PM

Yeah, I realized the board was surface mount, but figured that a daugter board could be made to perform the analog functions.

I didn't realize that the output stage was a filter...I must admit I didn't check the schematic, as it was just a passing thought (I have about 6 other projects to finish first). If this is the last stage that the audio goes through before getting to the outside world though, you'll want some drive capability....especially if you're going to use your DAC to connect to old 600 ohm gear for some outside of the box FX (less of a big deal if it'll just be connected to a monitor controller).

At $400+ my time to fabricate a box, PS, upgrade op-amps/caps/etc I don't think I'll bother with this project...Benchmarks DACs are around $1K and have good resale.

Now, at $150.....different story!

Cheers,

Kris

PS: I've found the 992 to be a very clean op-amp...doesn't spec as well as modern IC's, but does sound clean.

Marik · 27th June 2005, 05:43 PM

Check out Kevin Carter's kit. At $249 starter price it has a great value:

http://www.kandkaudio.com/digitalaudio.html

dasbin · 27th June 2005, 06:26 PM

Not so much great value. You also need to add on the $79 power supply and at least the $279 passive output stage kit. In terms of value I think you're better off with one of the better manufacturer eval boards. Frankly I think these guys should at least be offering a $50 opamp output stage. I doubt it would really lack performance as compared to the transformers if well designed and used good chips. But I guess that's why they don't offer it...

dasbin · 29th June 2005, 02:54 AM

Quote:

Originally Posted by Jim Williams

4398 is very good for sigma delta design. It has surface mount opamps of questionable quality, so rework is advised. It was just $150 a few months ago, but my promotion of it probably caused the price to go up. Just add a power supply and go.....

There is a very decently-designed soundcard for $150-200 on the market currently using the 4398.. The EMU 1212m. Good clock and digital sections, even a decent stereo A/D included... opamps are surface mount JRC 2068 and could use changing based on taste (I changed mine to LT1364's, though the difference is very slight), decoupling caps should be changed. But I just thought I'd throw this out there because it's a nearly-effortless 4394 solution with a lot more features at a lower price than DIY.

Quote:

While at it, get a CBD 5381 A/D, the best A/D chip now out. It's $350 and just add a power supply. Surface mount analog should be changed.

I'm thinking about going this route. Looking for a sort of "gold channel"ADC on the cheap. What do you like in terms of input opamps?

Quote:

These boards are supplied with either 5532 or 33078 opamps in surface mount. I would sub a Linear Tech LT1358 or National LM6172 for starters.

5532's are used in some nice sounding high-end designs... Benchmark DAC-1 comes to mind. If implimented well I'm not sure any real benefit besides a different flavour would come from swapping those out in particular. They sure measure well anyway and apparently have a very clean sound.
Anyway do you like the LT for AD input section too, or just as output? I've heard good things about Analog Devices AD8022. And do you prefer biasing to Class-A?

Washington · 7th April 2008, 06:02 PM

Speaking of 4938, I've just found this (below) and ordered one. It hasn't arrived yet.

Mini HiFi audio PC USB SPDIF 24bit 192K D/A converter - eBay (item 170208692886 end time Apr-14-08 03:17:15 PDT)

I wonder how it compares to the (more or less) Benchmark equivalent DAC-1. I'm currently working with a Lynx Aurora 16, and I must say it makes a BIG difference with the AD/DA stage of a Motu Traveller I used until then. That's why I jumped on this eBay deal, 4938 being the Lynx usual DA if I am not mistaken.

Mr Williams (or anybody), at that price, I agree there must be a catch. What do you think it would be? Circuitry? Amp stage? Fake chip? Who knows? Who cares?

Thanx in advance and have a good one.

Washington · 17th April 2008, 10:56 AM

If anyone cares, I'm VERY glad to report that the above mentioned DA gives excellent results.

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17th April 2008, 10:56 AM	#15
Washington Gear Head Join Date: Mar 2008 Posts: 73	If anyone cares, I'm VERY glad to report that the above mentioned DA gives excellent results. __________________ ... and for a bit of true wisdom: "I was under medication at the time I decided NOT to burn the tapes" - Richard Nixon

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20th June 2005, 05:04 AM	#1
qtuner Gear addict Join Date: May 2005 Posts: 302	DIY DAC? I've been following the 192khz thread in the highend forum. I'm wondering if it is possible to make a homebrew DAC? With the popularity of the seven circle audio mic pre's, has anyone attempted a DIY DAC? here are some link to a couple reference designs: http://www.cirrus.com/en/products/pro/detail/P1024.html I working with surface mount soic chips would be tough. I found a the price for the new cirrus chip online to be 18$. this is just a whim. <update> If I could build my own power supply and clock, I could get a reference board for ~$400. it is difinitely cost prohibitive to build you're own dac. If the chips were dip packages it might be easier, but there would probably be more noise. The #1 problem I think would be minimizing noise to realize the full dynamic range of the chips. </update

21st June 2005, 05:52 AM	#2
pendejo Gear nut Join Date: Sep 2004 Location: Kalifornia Posts: 119	I've been looking into this as well. The link you included was for an A/D converter. Take a look at: http://www.cirrus.com/en/products/pro/detail/P147.html The D/A converter eval board ($400) includes a power supply. The onboard CS8414 chip provides a clock. SPDIF/AES-EBU input. Balanced XLR output. The only thing missing is a case :)

21st June 2005, 06:19 AM	#3
dasbin Gear addict Join Date: Jun 2004 Location: Vancouver Posts: 412	Yup, these promo kits are great. Generally they are designed to utilize the full dynamic range and low noise and THD of the converter. Definitely wouldn't have to worry about noise except maybe in terms of providing a proper ground etc. I'm thinking of using the flagship Cirrus Logic A/D kit and putting something together, but the Newark website doesn't seem to be functioning properly so I can't really see what the deal is. These kits usually use opamps with good specs but low musicality... often JRC. In other words, if you swap opamps for something more tasteful, like some TI stuff, you might end up with a more pleasing sound (although probably with a decrease in dynamic range, THD, noise performance). Power supply is probably well-designed. If they're putting DC-blocking caps in the analog signal path (not sure, haven't been able to look at the recent designs) then you may benefit from some better caps there, or just removing them altogether if your other equipment all already has some.

21st June 2005, 04:51 PM	#4
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 4,503	Good ones are the Crystal CDB4398, BurrBrown DEMO PCM1792. The BurrBrown is the best but costs several hundred bucks. The Crystal 4398 is very good for sigma delta design. It has surface mount opamps of questionable quality, so rework is advised. It was just $150 a few months ago, but my promotion of it probably caused the price to go up. Just add a power supply and go..... While at it, get a CBD 5381 A/D, the best A/D chip now out. It's $350 and just add a power supply. Surface mount analog should be changed. The surface mount blocking caps can be replaced, but avoid eliminating them as they block the 2.5 volt bias of the A/D's modulator. Don't bother laying out a pcb or proto typing. The layouts are critical for proper operation and most pcb designers don't have a clue about doing it right, that's why the eval boards, they show proper layouts to achieve maximum performance. Jim Williams Audio Upgrades

22nd June 2005, 08:13 PM	#5
qtuner Gear addict Join Date: May 2005 Posts: 302	So it is viable to go with a home brew solution based on eval boards? Here's a really dumb question: What should I do for powersupply? Would wall warts work? Should I build my own? What op amps would be a good for the analog section of both the cirrus logic eval boards? I'm tempted to do it.

23rd June 2005, 03:32 PM	#6
Jim Williams Lives for gear Join Date: Feb 2004 Location: beautiful Carlsbad, CA Posts: 4,503	These require +- 12 volt analog and several +5 volt feeds for the digital. Get someone to make one for you if you don't know how to build linear power supplies. These boards are supplied with either 5532 or 33078 opamps in surface mount. I would sub a Linear Tech LT1358 or National LM6172 for starters. Jim Williams Audio Upgrades

23rd June 2005, 04:09 PM	#7
DrFrankencopter Gear nut Join Date: Sep 2003 Location: Ottawa Posts: 138	Where can you get the Cystal demo boards for a good price. Newark doesn't stock them, and quote a price of $420. Thinking of getting one of these and putting a Forrsell JFET 992 output driver on the end. Cheers, Kris

23rd June 2005, 04:22 PM	#8
rapfreak Lives for gear Join Date: Jun 2005 Location: Columbus, Ohio Posts: 1,055	just get a power-one linear power supply from digikey (179-2070-ND). It gives 3A @5V and 1.25A @12V(adjustable). they run $62.75 and are easy to mount to a plate.

23rd June 2005, 05:43 PM	#10
DrFrankencopter Gear nut Join Date: Sep 2003 Location: Ottawa Posts: 138	Yeah, I realized the board was surface mount, but figured that a daugter board could be made to perform the analog functions. I didn't realize that the output stage was a filter...I must admit I didn't check the schematic, as it was just a passing thought (I have about 6 other projects to finish first). If this is the last stage that the audio goes through before getting to the outside world though, you'll want some drive capability....especially if you're going to use your DAC to connect to old 600 ohm gear for some outside of the box FX (less of a big deal if it'll just be connected to a monitor controller). At $400+ my time to fabricate a box, PS, upgrade op-amps/caps/etc I don't think I'll bother with this project...Benchmarks DACs are around $1K and have good resale. Now, at $150.....different story! Cheers, Kris PS: I've found the 992 to be a very clean op-amp...doesn't spec as well as modern IC's, but does sound clean.

27th June 2005, 05:43 PM	#11
Marik Gear nut Join Date: Feb 2004 Location: SLC Posts: 80	Check out Kevin Carter's kit. At $249 starter price it has a great value: http://www.kandkaudio.com/digitalaudio.html

27th June 2005, 06:26 PM	#12
dasbin Gear addict Join Date: Jun 2004 Location: Vancouver Posts: 412	Not so much great value. You also need to add on the $79 power supply and at least the $279 passive output stage kit. In terms of value I think you're better off with one of the better manufacturer eval boards. Frankly I think these guys should at least be offering a $50 opamp output stage. I doubt it would really lack performance as compared to the transformers if well designed and used good chips. But I guess that's why they don't offer it...

7th April 2008, 06:02 PM	#14
Washington Gear Head Join Date: Mar 2008 Posts: 73	Speaking of 4938, I've just found this (below) and ordered one. It hasn't arrived yet. Mini HiFi audio PC USB SPDIF 24bit 192K D/A converter - eBay (item 170208692886 end time Apr-14-08 03:17:15 PDT) I wonder how it compares to the (more or less) Benchmark equivalent DAC-1. I'm currently working with a Lynx Aurora 16, and I must say it makes a BIG difference with the AD/DA stage of a Motu Traveller I used until then. That's why I jumped on this eBay deal, 4938 being the Lynx usual DA if I am not mistaken. Mr Williams (or anybody), at that price, I agree there must be a catch. What do you think it would be? Circuitry? Amp stage? Fake chip? Who knows? Who cares? Thanx in advance and have a good one.