Cost no object edition of DS DAC


#1

Dear Ted,

I am a happy owner of DS Jr. but, as a perfectionist and an audiophile, I like to day dream. I dream about DS Sr. and, as good Jr. already is, and an excellent value, after comparing both in the same very resolving system, I am in the process to make a switch.
Nearly every commercial piece of audio equipment is designed to a given price point.
If you would like to design a super version (say, cost no object) of already excellent DS DAC (Sr.), what would you improve on and in which sequence, having SQ as the only guidance?

Best, Plato


New high end PS DAC in the works
#2

He’s discussed this before…can’t wait to read what else he has to say…I know what I’d like to see in a SOTA DS DAC.


#3

By using a newer generation FPGA there would be more room for DSP, I’ve got a few ideas about things that wouldn’t fit in the DS/DS Jr. That’s where much of the improvement in the DS and DS Jr is from so I want to make sure that it can continue.

I’d continue trying to make cable quality irrelevant, in particular I’d try to directly address groundloop issues and lower the noise (especially from the digital part) that goes out (or in) on the cables (including making sure that less noise goes out (or in) the AC power cord.)

I’d use top of the line Jensen Transformers. I’d lower the analog output noise by doubling (again) the number of digital switches. I’d use parts with better specs where it makes sense.

I’d probably put the digital and analog into separate boxes connected by an optical link. I’d try to make sure that there was no digital hardware of any kind in the analog box (e.g. no processor (which means no display for the analog box), tho receiving a digital input signal means there’d be some kind of flip flops, etc. in there, but they don’t have to be CMOS or other noisy circuitry. (This also rules out any DSP based clock multipliers, jitter reducers, etc. that a lot of people are bragging about these days. but I never liked those anyway.)

I’d use more power supply filtering with many units in parallel to lessen the noise generated (including multiple AC transformers for the different functions.) I’d get power while staying away from the peaks of the input AC (which is where all of the typical noise generated by linear power supplies in most audio equipment is.) This will both lessen the noise introduced into the boxes but also lessen noise going out of the box when other linear equipment is most sensitive to noise.

Tho everyone wants to hook everything up to the net these days for updates, diagnostics, etc. I’d make sure that the people who don’t want any radios or 100MegHz or 1GigHz… generators (Ethernet) in their units don’t have to have them for normal operation and also that there’s the option of using simple IR in any remote.

I’d still continue to avoid things that are trendy but generate noise (e.g. RF remotes, live network connections, supercaps, clock receivers, synchronizers, PLLs (the analog box has to be the clock master.) To be clear I think there could be RF remotes, network connections, etc. but for those that don’t want to use them they have to be completely disableable when not being used and there has to be equivalent function provided without using them.

There are always points of diminishing returns, so even “cost no object” devices are built to some budget. Without a budget (and other constraints) you end up with the “everything including the kitchen sink” problem and you make the design time, etc. last “forever.”

Note that a few things wouldn’t cost much more, but no matter how one slices it I can’t think of ways to avoid significant cost for most of the items above (the most glaring thing being the output transformers.) Things like lowering noise by doubling (or tripling, etc) units obviously adds cost. Achieving the things that matter to me (like everything above) while not throwing people’s money away would take some serious design work.


New high end PS DAC in the works
New high end PS DAC in the works
#4
  1. Would you build a separate power supply box (eg the guts of a Stellar PP300 but with a DC output) and have a DC>DC link between the power supply box and DAC box? i.e separate chassis’ sitting atop each other, or side-by-side.

  2. Would you do a dual-mono design i.e. single channel DAC?

  3. Would you do a pure DAC with no volume control?

  4. Would you use Organic EL display instead of touchscreen?

  5. Would you at least make provision for external master clock sync signal (even though your thinking on that aspect is well known)? At least give customers the option.

These are all the things I’d like to see, plus more (of course).


#5
  1. I’d separate the digital and analog - that makes a much bigger difference than simply splitting off the power from the rest and allows the boxes to be connected optically rather than adding more ground loops to the whole system. It also allows the noisy digital inputs, (e.g. computers, streamers, USB, etc to be much better isolated from the analog. If there were a single external power supply box it would be for the analog box only but I don’t think an additional power supply box for the analog box is very cost effective and indeed since rejecting 60Hz (and it’s harmonics) is chickenfeed compared to cleaning up the high frequency garbage that comes with each wire from the outside world the analog box would require equivalent filtering of the “DC” inputs as just having the AC inputs. One of the biggest noise contributors of noise that isn’t handled by power supply filtering is the noise generated by the bridge diodes, by making the bridge diode switching as soft as possible the rest of the power supply is no different than you’d have with an external box…

  2. Dual mono DAC isn’t well defined. And many of the possible interpretations are bad. To keep the sound stage stable I would share the digital input processing. The sound stage would suffer immensely without sample synchronized processing. The master clock needs to be shared , hopefully for obvious reasons. The digital switches need to be completely synchronized and have to share the clocking inputs (e.g. be in the same chip.) Since each channel already is on it’s own power supply I don’t know what the difference between that and “a single channel DAC” or “dual mono DACs.” In the DS the only thing common between the two output channels is the clock and reclocker as well. Going to a separate box after the reclocker is just a bad idea. Having each channel of the DAC on it’s own power supply (all the way to and including separate AC transformers) seems to be the way to go.

  3. A (properly implemented) digital volume control doesn’t affect sound quality in the least - one extra multiply after all of the multiplies in the upsampling filters, etc. isn’t a problem. I’m not sure of the goal of avoiding a volume control. a) if you don’t want to use it you leave it (or even lock it) at “100”, b) in an FPGA there’s no concept of saving work by skipping say, a multiply on special valued inputs, the multiply is always happening and all you’ve done is add more levels of gating to the signal. In the current implementation a final scaling multiply is required anyway and folding the volume control into that multiply is as close to free as you can get.

  4. I’m not as concerned about the exact screen type since it’s on the digital box. I’d like to have more resolution, and less “wavy lines” or fading than the current display (tho the longevity of the current DS screen is pretty darned good there are plenty that started out on PWD Mk I’s.) To be completely up front, I’m happy with whatever PS Audio wants there as long as it’s noticeably better than the current display.

  5. Options aren’t free (in sound quality or any other way) and in particular an optional input clock requires clock mux somewhere. Having it right before the reclockers is bad news for jitter. Being able to use an external or internal clock without a mux right before the reclockers will require a clock mux somewhere and then a jitter cleaner after it. The more jitter you want to get rid of the less accurately you are following an input clock, then what’s the purpose of a separate input clock? Also having two separate clocks in the same box in any way, shape or form, leads to beating problems, the closer to being sunk (but not being perfect in sync) multiple clocks are the more audible the interference.

To be able to accept any standard input (except USB) along with a separate external clock means that I’d have to have asynchronous sample rate conversion (a non-starter in my opinion.) Not accepting the standard (non-pro audio) digital input interfaces (AES3, S/PDIF, TOSLink, common implementation of I2S) for a feature that also compromises sound quality doesn’t seem like a good tradeoff.

Mentioning reclockers reminds me that I’d also be interested in having multiple reclockers in series, each with their own power supply regulators and power filters…

Mentioning multiple power supply regulators and power filters reminds me that I forgot to mention that I’d probably divide the circuitry into more sections each with it’s own power supply regulation (especially in the analog box.) Obviously dual mono analog output chains (like the DS and DS Jr), but also more separate pieces like each reclocker, the VCXO, the VCXO control, the optical receiver, optical transmitter, …


#6

Because:

  1. the volume won’t randomly go to 60 (or some other value) when you don’t want it to (happened to me frequently);
  2. the volume won’t go off the Richter scale and blow up your speakers when you accidentally sit on the remote control (happened to me), or when something goes whacky with network latency if there is an app controlling the volume (happened to me);
  3. presumably cheaper not putting in volume control bits and pieces, money which could be spent elsewhere;
  4. the vast majority of target owners of a cost no object DAC already have a pre-amp; and
  5. leverage sales opportunity for a BHK pre-amp for those who don’t already own a pre-amp.

#7

Dual mono-DAC i.e. one DAC sitting next to each mono power amp, with clocking of both sync’d to a master source (one or the other, or something else). The marketing leverage of doing something sort-of new that nobody else is doing. As far as I know the Esoteric D1 is the only dual-mono DAC in the consumer HiFi space.


#8

The volume control going to 60 is a bridge bug, I don’t think there will be a bridge in a cost-no-object-get-as-good-of-sound-quality-as-you-can-DAC - I’d recommend an external streamer (the upcoming PS Audio server or others)

There’s already an option (Since Huron?) to set the maximum volume and another to keep the 20dB attenuator from disabling, AFAIK nothing ever changed the volume to higher that that (well nothing except an update, dang it.)

There are no volume control bits and pieces: as I mentioned the volume is piggybacked on a multiply in the FPGA that needs to be done anyway.

I know that most customers of such a DAC would likely have a preamp as I do. Still the DS’s volume control (especially the knob on the Jr) is very convenient for me at times. Having better options for adjusting system gain levels is one of the things I didn’t explicitly mention above, but has always seemed like a good idea.


#9

I addressed that: it’s a bad idea from the standpoint of sound quality. Just having separate reclocking chips in the Jr compared to a shared one in the DS is a noticeable compromise in soundstage stability. (Except for the clock, reclockers, top level transformer and bridge, etc. both the DS and the Jr are dual mono design.) Having two separate low jitter clocks would not be a step up from dual mono with a shared clock.


#10

Yes, I get that. I like the volume control function on DSJ. Much better than touchscreen, and much much better than eLyric driving my DS Snr all the way vol+ and blowing up my Accuton mid-driver. That was pre volume limiter days of course. If you could do digital volume control in a SOTA DAC that matches performance of analog preamp I’m in favor of that. But you’d need an analog input on the DAC before I could retire the preamp, and that would probably get a bit messy and be outside the scope of the project.


#11

I always talk about digital volume control and avoid the word preamp when talking about the DS or DS Jr.

I definitely agree that having an SOTA preamp in a SOTA DAC for near the money of just the SOTA DAC is not going to happen. In an earlier version of the DS, I designed one in and it more than doubled the parts count and the cost of the analog board (and IMO wouldn’t have been good for sound quality of the DAC.) If preamps were free, well they’d be free :slight_smile:


#12

I think people conflate volume control and preamp (it’s understandable since the number of volume controls without a preamp function and the number of preamps without volume controls is very small (at least excluding phono preamps.))

But a different way of looking it is that a properly implemented digital volume control is absolutely better sound quality than the analog volume control in a preamp. The real question is whether you can make a DAC whose output never sounds better when using the non-volume control part of a preamp in any system than when not using a preamp. I know that doing system wide gain matching without a preamp isn’t going to happen much of the time and that since a preamp is needed most of the time I certainly don’t begrudge someone using it’s volume control :slight_smile: I certainly don’t want a system without a good preamp (with a volume control.)


#13

If there is no downside to digital volume control in a SOTA DAC then there can be no argument against putting one in it. I did find the volume control in DSJ useful on occasion in my system that already has a very good pre-amp in it. Just as long as there is no wriggle room in the software that makes the digital volume work for bugs to creep in that might give rise to undesirable consequences, like unintended volume changes, and sound artifacts like the snap/crackle/pop noises that get reported by some DS system owners, whatever those causes happen to be.

About the dual-mono DAC concept, Esoteric got it working, it’s their top model at $40k/pair.

http://www.esoteric.jp/products/esoteric/p1d1/indexe.html

I plan on buying what replaces it later this year. However if there is any prospect that Ted Smith will be given a blank sheet to build the best DAC he knows how to build I might hold off on that Esoteric purchase for the time being.


#14

https://forum.psaudio.com/t/new-high-end-ps-dac-in-the-works


#15

Thank you Ted and Brodic for your replies, comments and links. A lot of ideas to think about for a notorious modder :slight_smile: My approach to computer audio is simple in concept and old-fashioned, like playing vinyl or reel-to-reel tapes old days; no streaming, no wi-fi, just wired connections only. Mac to dac to amps to speakers, insisting on top SQ and musicality via clever audio design and best quality components available. I understand, that the reported issues with volume control in a full version of DS DAC are things of the past. I observed none of the kind in my Jr implementation.


#16

Oh, I hadn’t seen that. Not many topics escape my attention here but that one did.


#17

may I kindly ask for the link to the right topic on this forum (or elsewhere), comparing comprehensively the differences between DS and DS Jr?

Thank you,

plato


#18

Comprehensively? Probably not. I’m assuming you’re wondering how the hardware differs given your statements above.

The single largest difference is only one digital switch per channel instead of four, that saves a bunch. That also makes a 6dB difference in S/N. The Jr uses active opamp based filtering and output drivers instead of a passive filtering with a transformer. Some components are “little brothers” to the ones used in the DS. The whole Jr is on one board instead of the four in the DS. The display and knob are different, the Jr only has 1 I2S input. The Jr has built-in support for a Bridge II module. Otherwise just simpler implementations of the same features possibly with fewer components. I tried to keep as much quality as possible and only economize on things that wouldn’t directly affect sound quality (with the exception of fewer digital switches, which was required by price point considerations.)


#19

TED, how much does a digital switch cost?


#20

Depends on the version :slight_smile: In the Jr $3.50 each (at build quantities) but the real cost comes from the current they take and hence the larger power supplies which ripples all the way to needing a bigger power transformer. And to a lesser extent, the surrounding support components.