DAC Basics

[impala454]

So I keep hearing people talk about DACs, given my background I generally know what they are... Digital to Analog Converters. I deal with them on a daily basis in my line of work. But my question is more on the audiphile side of things. I see people hooking them up to their computers, CD players, and other sources and raving about the results. What confuses me is usually those sources all have their own built in DACs, so that leads me to a couple of questions:

1. How do you bypass an internal DAC on various sources, like a computer or CD player. Is it just a simple matter of a digital output? Or is it more complicated than that? Is the digital output on a computer or CD player truly bypassing any DACs inside that device?

2. Do people use them on multichannel setups, or is it mainly a stereo kinda thing?

3. What are the various types out there and what are some example setups? Are they all over the place in terms of price range, etc? I.e. XYZ Source -> BlahBlah Cable -> FillInTheBlank DAC

4. How would I determine which internal DAC a device has, and if/which DAC would be a worthy improvement? Are there some stats/numbers associated that are an indicator, like bit rates or frequency range or something? To get more specific, the Oppo BDP-83, and then roughly any built into motherboard sound card.

[stuofsci02]

All right.. I'll have a go at this:

1. Most sources (that are digital) have a DAC built in if there is analog outputs onboard. This could be RCA connections, mini stereo jack etc. A digital source without analog outputs is just a transport.

So to bypass the internal DAC/Analog circuitry you would have to use a digital output. These could be (but not limited to) USB, Optical, Digital Coax, HDMI.

2. For multichannel most people also need the CODECs (coder/decoder) for things like DTS and Dolby, so they will opt for a multichannel processor which will Decode and D->A in one box. For stereo setups and external DAC can be much better then the DAC inside a CD player or sound card etc. This is not just because of a better DAC chip, but also a better power supply and analog circuit design.

3. There are DACs all across the board in price range. From $200 to $5,000+. There are DACs that use tubes in the output stage and others that use transistors (just like you can get tube CD players and Transistor CD players). The better DACs will often have a reclocking circuit to eliminate digital jitter. This mean less emphasis is on the digital sources clock. Jitter does not sound good.

In general it is as you say.. XYZ source to DAC using some digital connection and then RCA or balanced outputs to your preamp.. From there treat it as any other analog input.

4. In general the DAC chip is not the be all and end all, although there are differences. A lot of the sound will come from the overall design including the analog circuit after the DAC chip.

The Oppo 83 is a decent player with an OK internal DAC. It would probably take a DAC in the $400+ range to beat it. Since the player is not much more then that new, it is good value.

But as a comparison the Oppo 83SE is the same player, but with an improved power supply, DAC chip and most important an upgraded analog output stage. As a result the Oppo 83SE is much harder to improve on with a DAC.

But if you got a good DAC to go with the Oppo 83 you could improve stereo output performance beyond the 83SE.

Also with the new Hi-Rez digital music 192khz/24bit a lot of the DACs can work with this also, making for big improvements.

I have found that a simple setup such as Squeezebox Touch + DAC can rival very expensive CD players, and can also play Hi-Rez formats.

As a result I have my Oppo 83SE for CD, DVD-A, SACD and Blu-Ray, but I use my Squeezebox Touch to DAC for all other digital music. All I need to do now is get a better DAC.

Cheers

Stuart

[impala454]

Awesome thanks for the well thought out answer. Lots of good info there. So are there some go to brands for these things? Also are there some kind of stats or specs to look for specifically?

i.e. looking at the specs on one particular one I saw this:

-Input digital signal format: 32-192 KHz, 16/24 Bit auto detection. (USB 2.0 supports up to 24Bit 96KHz)
-Output: DAC output, pre line output , tube buffer output.
-SNR: >120dB.
-Dynamic Range: 115dB.
-THD+N: <0.0008% at 20-20KHz (tube out :0.02%)

[madmac]

All right.. I'll have a go at this:

1. Most sources (that are digital) have a DAC built in if there is analog outputs onboard. This could be RCA connections, mini stereo jack etc. A digital source without analog outputs is just a transport.

So to bypass the internal DAC/Analog circuitry you would have to use a digital output. These could be (but not limited to) USB, Optical, Digital Coax, HDMI.

2. For multichannel most people also need the CODECs (coder/decoder) for things like DTS and Dolby, so they will opt for a multichannel processor which will Decode and D->A in one box. For stereo setups and external DAC can be much better then the DAC inside a CD player or sound card etc. This is not just because of a better DAC chip, but also a better power supply and analog circuit design.

3. There are DACs all across the board in price range. From $200 to $5,000+. There are DACs that use tubes in the output stage and others that use transistors (just like you can get tube CD players and Transistor CD players). The better DACs will often have a reclocking circuit to eliminate digital jitter. This mean less emphasis is on the digital sources clock. Jitter does not sound good.

In general it is as you say.. XYZ source to DAC using some digital connection and then RCA or balanced outputs to your preamp.. From there treat it as any other analog input.

4. In general the DAC chip is not the be all and end all, although there are differences. A lot of the sound will come from the overall design including the analog circuit after the DAC chip.

The Oppo 83 is a decent player with an OK internal DAC. It would probably take a DAC in the $400+ range to beat it. Since the player is not much more then that new, it is good value.

But as a comparison the Oppo 83SE is the same player, but with an improved power supply, DAC chip and most important an upgraded analog output stage. As a result the Oppo 83SE is much harder to improve on with a DAC.

But if you got a good DAC to go with the Oppo 83 you could improve stereo output performance beyond the 83SE.

Also with the new Hi-Rez digital music 192khz/24bit a lot of the DACs can work with this also, making for big improvements.

I have found that a simple setup such as Squeezebox Touch + DAC can rival very expensive CD players, and can also play Hi-Rez formats.

As a result I have my Oppo 83SE for CD, DVD-A, SACD and Blu-Ray, but I use my Squeezebox Touch to DAC for all other digital music. All I need to do now is get a better DAC.

Cheers

Stuart

Perfectly explained Stuart... :T

[wkhanna]

Perfectly explained Stuart... :T

Agreed! Excellent explanation!

One detail mentioned is the fact that implementation (the circuit design) is often overlooked and too much emphasis is placed on the DAC IC chip alone.

Some of this misunderstanding is likely due to manufacture's marketing departments stressing the use of the 'flavor of the day' popular chips. Simply putting a Ferrari engine in a Fiat does not guarantee a great car.

As always, JMHO, YMMV

[Hdale85]

The DAC chip in and of it self isn't the only factor of the performance of the over-all DAC. The implementation and design of the circuit can effect a lot as well, just like amps and what not.

[JonMarsh]

Yeah, a complete discussion of this topic would be VERY long-

Other pertinent issues are how the digital receiver is configured, (very critical), whether is uses high stability local clocks, or locks a local clock with PLL to the incoming S/PDIF close, or whether it just uses SRC (Sample Rate Conversion) to take anything incoming and upsample to some specific rate for the main DAC IC. In more pro oriented gear, the possibility of using external clock sources arises, both for synchronization and to get ultra low jitter (ever heard dual Zodiac Gold DAC's driven from a Brainstorm DCD-8 with an external Rubidium ultra low jitter crystal clock?)

Another critical facet is the digital filters used after conversion (or before!) and the interface to analog- a big part of some companies "secret sauce" is using custom PLD's or DSP to implement their own filters and disable ones built in to the chips.

Everything counts, from the input receiver to the power supply to the analog output stage. Only in the last few years has D/A under $10K really gotten fairly good.

Awesome thanks for the well thought out answer. Lots of good info there. So are there some go to brands for these things? Also are there some kind of stats or specs to look for specifically?

i.e. looking at the specs on one particular one I saw this:

-Input digital signal format: 32-192 KHz, 16/24 Bit auto detection. (USB 2.0 supports up to 24Bit 96KHz)
-Output: DAC output, pre line output , tube buffer output.
-SNR: >120dB.
-Dynamic Range: 115dB.
-THD+N: <0.0008% at 20-20KHz (tube out :0.02%)

With regards to Impala454's questions, it looks like you're looking at a DAC that has "standard" USB Class 2 Audio support (on PC, which only goes to 96 kHz), with both a solid state and tube output stage, with fairly typical THD specs for FS input at 24 bit depth (THD <0.0008% 20 Hz - 20 kHz). SNR is fairly high relative to FS (full scale) output; this may be measured with a silent input track, which for many CD players engages muting, so it may or may not be handling signal.

If you're curious about DAC's and differences and what tech specs have some bearing, I'd suggest reading some of the reviews on Stereophile magazine, because they have both subjective comments and some in depth measurements by John Atkinson. The latter will give you a realistic view of achievable performance with 16 bit and 24 bit sources, and some of the issues around dynamic performance, including jitter and multi-tone HF IM.

Still, in the end, you need to listen to the component in your system, or in a very similar configuration to your own. Listen to music that matters to you, not just audiophile tracks, but be realistic - thrash metal will probably never sound pristine! But there are high energy rock, jazz, and classical recordings that can be quite demonstrative of definition, imaging, and articulation, and also any tendency towards sonic fatigue.

Also, I'd recommend listening first to some gear that's absolutely top flight, with recordings you have some familiarity. Though that may not be what you'll purchase, you can use that to help "grade" the performance and qualify what's most important to you in the range you're willing to spend on.

One last point to keep in mind, there are many newer DACs which can operate as a digital control/preamp center, with high resolution volume controls and strong line drivers built in (like the NAD M51 I've been commenting on lately, or the Berkeley Alpha DAC, or Metric Halo ULN-2 and ULN-8, or the Benchmark DAC1 HDR. These may enable you to spend more on the DAC versus the rest of your system, a choice that can be beneficial.

[wettou]

Very interesting, also I saw this on a couple of other sites,

http://audiophilereview.com/cd-dac-digital/audiophile-reviews-top-five-dacs-under-1000.html

http://www.computeraudiophile.com/content/Best-DAC-ever-heard

[kvardas]

Buffalo III DAC with Tube Output Build

See link below.

http://www.twistedpearaudio.com/digital/buffalo.aspx

Getting ready to build one that will use John Broskie's Unbalancer as an output stage. See link below for the tube output stage.

http://www.tubecad.com/2011/03/blog0203.htm

Regards

Kris

[Hdale85]

I have the Opus DAC, been thinking about selling it for a while to get the Buffalo. The Opus is quite good though I do like it but it hasn't been used in quite some time.

[wkhanna]

I’ve been reading John Broskie’s web site for years. IMHO, one of best resources for analog DYI’ers out there.

This guy happily shares everything he knows, and he knows a lot. Sort of in the same way Nelson Pass does everything except build it for you. If you’re interested in tubes you should check this out.

Tube CAD Journal

[impala454]

Very good info, thanks a lot guys. I have a lot to chew on for a while!

[madmac]

Yeah, a complete discussion of this topic would be VERY long-

Other pertinent issues are how the digital receiver is configured, (very critical), whether is uses high stability local clocks, or locks a local clock with PLL to the incoming S/PDIF close, or whether it just uses SRC (Sample Rate Conversion) to take anything incoming and upsample to some specific rate for the main DAC IC. In more pro oriented gear, the possibility of using external clock sources arises, both for synchronization and to get ultra low jitter (ever heard dual Zodiac Gold DAC's driven from a Brainstorm DCD-8 with an external Rubidium ultra low jitter crystal clock?)

Another critical facet is the digital filters used after conversion (or before!) and the interface to analog- a big part of some companies "secret sauce" is using custom PLD's or DSP to implement their own filters and disable ones built in to the chips.

Everything counts, from the input receiver to the power supply to the analog output stage. Only in the last few years has D/A under $10K really gotten fairly good.



With regards to Impala454's questions, it looks like you're looking at a DAC that has "standard" USB Class 2 Audio support (on PC, which only goes to 96 kHz), with both a solid state and tube output stage, with fairly typical THD specs for FS input at 24 bit depth (THD <0.0008% 20 Hz - 20 kHz). SNR is fairly high relative to FS (full scale) output; this may be measured with a silent input track, which for many CD players engages muting, so it may or may not be handling signal.

If you're curious about DAC's and differences and what tech specs have some bearing, I'd suggest reading some of the reviews on Stereophile magazine, because they have both subjective comments and some in depth measurements by John Atkinson. The latter will give you a realistic view of achievable performance with 16 bit and 24 bit sources, and some of the issues around dynamic performance, including jitter and multi-tone HF IM.

Still, in the end, you need to listen to the component in your system, or in a very similar configuration to your own. Listen to music that matters to you, not just audiophile tracks, but be realistic - thrash metal will probably never sound pristine! But there are high energy rock, jazz, and classical recordings that can be quite demonstrative of definition, imaging, and articulation, and also any tendency towards sonic fatigue.

Also, I'd recommend listening first to some gear that's absolutely top flight, with recordings you have some familiarity. Though that may not be what you'll purchase, you can use that to help "grade" the performance and qualify what's most important to you in the range you're willing to spend on.

One last point to keep in mind, there are many newer DACs which can operate as a digital control/preamp center, with high resolution volume controls and strong line drivers built in (like the NAD M51 I've been commenting on lately, or the Berkeley Alpha DAC, or Metric Halo ULN-2 and ULN-8, or the Benchmark DAC1 HDR. These may enable you to spend more on the DAC versus the rest of your system, a choice that can be beneficial.

Wow!!!!..............who did you say was on first base??? :lol:

[impala454]

He tried to nail me with the

(ever heard dual Zodiac Gold DAC's driven from a Brainstorm DCD-8 with an external Rubidium ultra low jitter crystal clock?)

But other than the brand names I definitely understand crystals and clocks

[JeremyG]

Who doesn't use a rubidium oscillator for their audio needs??? :rofl:

[cbark]

Rubidium oscillator....I think I got that from an ex-girlfriend once....

[Chris D]

Oh, man... you didn't use a mylar sheath on your cables?

[madmac]

I still like the idea of "wobulation" being introduced into audio. It's catchy and I think people could be bought into it (Or deeked into it anyway!!!)