Future of Dacs: Jitter being addressed, how about power and volume!

[[email protected]]

It's my impression that Jitter seems to be the big bad boogieman for dacs. And while i can't say i've heard an extremely low jitter set up (meridian 568 fed by a nordost optical cable from a RME card), i don't doubt that it can bring improvements.

 

However, in my own experience, it seems to me that power and volume are also 2 key issues that should be addressed.

 

Power:

From my own experience i know that power is a big deal. Adding a furutech fuse and a VH audio Airine power cable and plugging into my shunyata hydra 4 power conditioner, which itself uses a vh audio power cable, which is plugged into an Oyaide R1 outlet have raise my Meridian to another level. More detail, more separation, improved micro and macro dynamics, blacker blacks. I believe when the meridian was compared to a stock emm labs dcc2 it sounded more musical.. of course then subsequently when the Emm labs was given the same power treatments it blew away the meridian. But in retail prices, that's over $2000 of additional equipment. I know there are a few companies offering battery powered dacs (red wine, lessloss), but is it just a matter of time before everybody joins in? Is there a reason why you would't want to get off the grid?

 

Volume:

Computer-based audiophile systems are entering a new era. Most people only have 1 source and don't have the need for an actual separate preamp. And with this new paradigm, we now have a new option for volume control. Digital volume loses bits. Tradition analogue volume controls (passive and active) are expensive to get right, and can alter the signal. I've been reading about LessLoss and their solution that instead alters the output voltage itself (http://www.lessloss.com/page.html?id=36) and i'm thinking that's the future! Why doesn't everybody do this?

 

So does lessloss have it right? or are there holes in their approach?

 

Anways, that's just my thoughts. We're winning the war on jitter. How about power and volume?

 

[The Computer Audiophile]

I really like the topic of this thread, I think it's right on.

 

I agree that power is very important. One reason I think many manufacturers have stayed away from battery power is the perceived lack of convenience by consumers. Batteries go bad and batteries need to be charged. It seems like consumers want maintenance free and worry free components. I am sure there are many other reasons. I do think getting off the grid is nice and Red Wine Audio is a great example of well implemented battery powered components.

 

Volume control is a place where large gains and losses can be seen. No only in terms of volume level, but in quality. A well implemented digital volume control can surpass analog volume controlled preamps. For example, the Berkeley Audio Design Alpha DAC has an excellent volume control. Bypassing an extra set of interconnects and the filter of a preamp is a wonderful thing. In this discussion we must be certain to remember analog volume controls have their own problems and we shouldn't discount digital volume controls because they are digital.

 

As far as why doesn't everybody do this, I think manufactures will build whatever their customers want. It's that simple.

 

[tfarney]

Wouldn't the shortest, cleanest path be no power supply at all? To simply integrate the DAC into an existing component with an existing and already necessary PS? This whole thing of the DAC as a separate component, with it's own complex circuitry, ps, preamplification, etc., seems counter-productive to me. Isn't that which is inherently simpler inherently cleaner? What am I missing?

 

Tim

 

[audioengr]

These have all been addressed in my Overdrive DAC. see:

http://news.ecoustics.com/bbs/messages/10381/551392.html

 

The volume control is comparable to $10K+ preamps.

 

There is no power cord necessary, It is DC from the wall. Saves you $1-2K on power cord.

 

Using a power supply in another component is absoutely the wrong thing to do. These are sized for the load to begin-with. Secondly, the modulation of the power supply by the first component will affect the second component circuitry. It's called intermodulation distortion.

 

Steve N.

Empirical Audio

 

[audiozorro]

The biggest hole may be the statement that “most people only have 1 source”. Most of the audiophiles I know have several sources.

 

Typically a computer music server is the last source added to one’s audio system rather than the first or the sole source. A lot of folks have at least either a turntable, FM or satellite radio, or CD/SACD player as another source. A few folks are eager to add a Blu-ray player to their systems. And still a few others have powered speakers or other DACs with built-in volume controls. Finally, the audiophiles I know with only one source typically have a CD or Universal player.

 

So, why doesn’t everybody use the LessLoss approach? Mainly because everybody doesn’t want or need it. Is the LessLoss DAC 2004 with integrated volume control decent? Probably. Is it the best there is? Probably not.

 

I believe I may have offered the below link before that basically states that a direct connection is always the superior method of transmitting the signal, both in theory and in practice.

 

http://www.high-endaudio.com/RC-Linestages.html

 

 

 

[tfarney]

So this IM distortion exists, then, in cdps with DACs integrated into them? In integrated amps, for which the amplifier and preamp share a ps? in receivers in which DAC, preamp, tuner, power amps, etc, share a ps? When a DAC and preamp share a ps? And it is actually a more audible problem than is created by the introduction of an entirely separate circuit, ps, pre stage, volume control, two sets of interconnects, etc?

 

Tim

 

 

 

 

 

[audiozorro]

SteveN, thanks for the info on your OverDrive DAC. Your discussion below was interesting and I would love to hear more.

 

[steveN post]

 

Certainly there are a lot of other sources for jitter. Just measuring it properly is a major challenge, and accurate correlation to audibility does not exist yet either. The two clocks that I use the most, my standard monolithic oscillator and the Superclock4 both have 2psec of RMS jitter, but they sound radically different. All of the studies that I have read would have you believe that less than 10nsec is inaudible. Pure poppycock.

 

Quote

2) With those limitations in mind, what do you see as the next significant improvement the overall digital playback chain?

 

By order of importance, I believe the problems are:

 

1) Jitter

2) D/A distortion and noise (particularly digital filter response)

3) preamp noise and dynamic response

 

My Overdrive DAC tries to address all of these.

 

Certainly better clocks will help with jitter in playback, but the problem now is the recording itself. Studios need to do more IMO to improve the quality of the recording and the A/D jitter.

 

I have plans to design my own clocks in the future. Getting the studios to acknowledge that they have hardware limitations is difficult. They often rely heavily on measurements rather than listening tests I have found. Measurements to fully characterize recording equipment as well as playback equipment dont exist IMO.

 

Steve N.

 

[audioengr]

"So this IM distortion exists, then, in cdps with DACs integrated into them? "

 

Yes, if they share resources, such as a transformer, power regulation or even ground return paths through the board or cables.

 

"In integrated amps, for which the amplifier and preamp share a ps? "

 

You bet.

 

"in receivers in which DAC, preamp, tuner, power amps, etc, share a ps? "

 

Why do you think these sound so poor compared to good separates?

 

"When a DAC and preamp share a ps? "

 

Yep. The difference with the preamp in my DAC is that it is not a preamp at all in conventional sense. There are no components to be powered or send the analog signal through.

 

"And it is actually a more audible problem than is created by the introduction of an entirely separate circuit, ps, pre stage, volume control, two sets of interconnects, etc?"

 

Yes, in general. Why do you think so many high-end companies create "dual-mono" power amps instead of stereo? It's to separate the power systems.

 

You can certainly do a poor job of designing any component by adding too many stages or poor circuit or power delivery design, which can add more distortion and noise than the integrated version of the same thing done by a more competent designer, but this is not a problem for good designers. Separates are always better. Cables that are virtually transparent (not the brand) can easily be obtained now, without spending thousands.

 

Steve N.

 

[tfarney]

"Yes, in general. Why do you think so many high-end companies create "dual-mono" power amps instead of stereo? It's to separate the power systems."

 

I've never been quite sure. I have an old Harman Kardon that is designed that way. It is pretty quiet. No quieter, though than the AV receiver that sits next to it. Not as quiet as the cheap Yamaha cdp I have that integrates cdp, DAC and headphone amp with volume control all into one box with one power supply. I can find the noise floor with very sensitive phones, no music playing, and an open volume control. I think there may be noisier fish to fry.

 

Tim

 

[audioengr]

Tim - when you start comparing Esoteric, Cary and BAT, then we are on the same page. The things you are talking about are mass-produced mid-fi equipment. Not in the same league. Sorry if I damaged your ego...

 

There are some crossover companies, like the Odyssey power amps, McCormack, CIAudio and the like, that are slightly more expensive than mass-produced consumer gear, but deliver the high-end sound quality.

 

BTW, You can get good used gear on Audiogon.com for about the same price as mid-fi gear that you find at Best Buy.

 

Steve N.

 

[tfarney]

Sorry. I thought we were talking about intermodulation distortion, not brands or price points. And my ego is safe. I understand that the equipment I'm talking about is not the absolute pinnacle of audio reproduction. I've heard true high-end (and a lot of crap impersonating it) and I understand there is a gap. I'm not sure many audiophiles understand how narrow it is, though.

 

Cary doesn't publish IM figures for their quite complex A/V processors, probably because it is a non-issue. Yamaha doesn't publish them either, if they both did, we would understand how wide the gap is if we found one at all.

 

Tim

 

[PeterSt]

Leaving out the preamp is the single most important SQ improving phenomenon thinkable.

 

In order to do that, that DAC must be "the best" or otherwise you'll end up with worse (there's so much more dynamics, that even the slightest harshness comes throug as rough sound). A "not so good further chain" may flatten that out though.

 

Analogue volumes of any kind are no good because of the inherent principle (and I'm not talking about the non linearity of the volume means itself; what I'm referring to counts for any analogue volume means).

 

Digital volume of any kind that I know of is not right, except my own which is propriatary.

 

This is merely a teaser than that I'm ready to discuss it. It is practice though, and I have it all running here.

 

Second most important, I think, is the power supply section of the DAC and the output stage without any opamps, transformers or capacitors in the signal path.

 

Jitter may be third.

 

The DAC's filtering is hard to give a place. I mention it as the last, but has top priority in my book. It is the most complex thing when it is to be done right. Working on it ...

 

Peter

 

[glt]

I tend to believe that PS noise is no mystery to the engineering departments in large consumer electronic companies. There are ways to filter, attenuate and eliminate the types that matter. There is psrr in the 100 db range withing the audible range in modern electronics. There are well known methods for circuit layout and capacitor bypass to create low impedance filters for high frequency noise, etc.

 

This is another practical test I do: If I play a silent track through the entire chain, and crank up the volume to its max and still hear silence, then there is no noise in (my) audible range.

 

[glt]

I believe a simple resistor voltage divider can't really introduce any artifacts into the sound. Prior to that, the sound must have traveled many more resistors and capacitors. The only thing to be careful about are the RC filtering introduced by the cables.

 

for Digital Volume, I plan on utilizing the one built into the current state of the art DACs.

 

And I don't understand why opamps are " bad". Because of intrinsic non-linearity in the Silicon, the only way to get high performance and high psrr and cmrr is to build them in the same neighborhood in the silicon with well known layout techniques, plus the fact that with smaller feature size, you can remove a lot of the parasitic capacitance and leakage current that will kill your performance.

 

[Ashley James]

It's good to see that someone understands the theory.

 

Ash

 

[[email protected]]

Hi Chris,

 

You wrote: "A well implemented digital volume control can surpass analog volume controlled preamps. "

 

I think this is really dependant on if the output voltage of the dac is similar to the input sensitivty of the Amp. In my case it's not. I have to set my dac volume well below unity gain to obtain a comfortable listening level. I'd suspect that most dac & amp combinations have this issue. In my research of the weiss dac2 i read from the manual that they recommend to have the volume near max, and i suspect max volume on the weiss would be way too loud for my system. SteveN also agrees about degradation when turning the volume too lows:

 

"Because all 16-bit 44.1kHz sampled files (native CD sample-rate) that are streamed using the USB interface are converted to 24-bit 44.1kHz sample-rate (bit-perfect data), this provides 8 bits or 30% digital volume control before the data bits are affected."

 

As well, i'm hearing a lot of conflicting things about digital volume. There are some who suggest that upsampling does not give you extra bits to throw away when lowering digital volume. This is way beyond my understanding, but it makes sense to me.

 

[PeterSt]

It is most certainly true that the output of the DAC must match the gain of the amplifier. When you play at maximum SPL to your likings, the digital attenuation must be 0dB. Anything less degrades unnecessary.

 

But :

 

I usually play in between -36 and -18dB, and when 16 bit material is played onto a 24 bit DAC you'd still loose NOTHING. Only at -54dB you would, but when playing at -54dB when -18dB is an acceptable level just as well, there hardly is sound anymore and there is no way you will be hearing that missing bit.

But as I said earlier : this only applies with the good digital volume, and I don't know those (yeah, well :-).

 

Peter

 

PS: I tried to get your last remark into my brain, but failed on it.

 

[[email protected]]

Hi Steve, you wrote:

"These have all been addressed in my Overdrive DAC. see:

http://news.ecoustics.com/bbs/messages/10381/551392.html

 

The volume control is comparable to $10K+ preamps.

There is no power cord necessary, It is DC from the wall. Saves you $1-2K on power cord."

 

I'm very curious about your approches...

 

Power

I see that you'll have a battery option later, but as for now i have to say i don't understand how your approach addresses power at all. As i understand it, you are replacing the power supply in the dac with a wall wort. I can see possible benifits moving magnetic inteference, but see a lot of pits fall too.

 

Do you make the wall wort? - If not, how can you be sure that the component inside would be superior to a power supply solution?

 

Does the wall wort's cord have some sort of shielding? - If not, how do you prevent the cord from acting like a big antenna, which is one the things a 1-2k power cord often addresses.

 

What's the wall wort's plug made out of? Gold, rhodium, berylium have very different sounds.

 

Does your wall wort filter power? If not , your solution would still require a power filter of some sort.

 

Without the future battery option, it appears to me that you approach is taking a step backward. Please point out where i'm wrong.

 

Volume:

"Volume control is accomplished without any added parts to the line-output signal path. It is not an entirely digital or entirely analog volume control. It is a little of each actually. The volume is adjusted by changing the behavior of the D/A conversion. It does NOT adjust attenuation of a resistor divider, change the gain of an amplifier stage or truncate bits in the digital data. All of these would add noise and/or distortion to the signal. "

 

You tell us what it's not, but you don't seem to tell us what it is. I'm curious about what your solution is...

 

[[email protected]]

Peter wrote: "When you play at maximum SPL to your likings, the digital attenuation must be 0dB. Anything less degrades unnecessary.

But :

I usually play in between -36 and -18dB, and when 16 bit material is played onto a 24 bit DAC you'd still loose NOTHING. Only at -54dB you would"

 

These 2 comments seem to be contradictory? You say anything less than 0db degrades unnecessarily, but also say you can got to -54db without losing any resolution. So if you don't lose resolution, why the degradation?

 

ALso, where do you get 54db from? 54db = 9 bits, but there's only 8 bit between 16 and 24.

 

In any case, does anyone have any links to any material that has a definitive answer about digital volume?

 

BTW, i do agree with you that bypassing the preamp and power trump jitter control. I may not have the lowest jitter system but when i went from a generic optical class cable to the nordost optical cable it was a appreciable jump which i assume comes from having less jitter. However, it was nowhere near the jump of i got when bypassing my preamp or improving my power.

 

[audioengr]

"I tend to believe that PS noise is no mystery to the engineering departments in large consumer electronic companies."

 

Well, you would be wrong. At Intel for instance, there were a handful of doctorate-level guys that dealt with power delivery to uProcessors. I worked with them and knew them all.

 

It is non-trivial to deliver clean, dynamic power to any device, analog or digital devices.

 

Steve N.

Empirical Audio

 

[audioengr]

"I believe a simple resistor voltage divider can't really introduce any artifacts into the sound. Prior to that, the sound must have traveled many more resistors and capacitors."

 

Resistors create thermal noise. The more of them in the signal path, the more noise. My DAC has only 37 ohms of resistance in the signal path. This is one of the reasons why it is so quiet.

 

"And I don't understand why opamps are " bad". Because of intrinsic non-linearity in the Silicon, the only way to get high performance and high psrr and cmrr is to build them in the same neighborhood in the silicon with well known layout techniques, plus the fact that with smaller feature size, you can remove a lot of the parasitic capacitance and leakage current that will kill your performance."

 

Op-amps are not as perfect or ideal as we have been taught in school. They vary widely in performance, mostly due to on-die power delivery, but there are other issues as well.

 

There are however some very musical op-amps available now. The designer must understand the idiosyncrasies of the op-amps in order to design around these in order to achieve the same performance possible with discretes. One undeniable advantage of op-amps is their size, which improves the chances of delivering dynamic power to them as needed.

 

Steve N.

Empirical Audio

 

 

[audioengr]

"As well, i'm hearing a lot of conflicting things about digital volume. There are some who suggest that upsampling does not give you extra bits to throw away when lowering digital volume."

 

Upsampling does not give you bits to throw away, but padding from 16-bits to 24-bits does. This is not upsampling. The data is not touched.

 

Steve N.

 

[audioengr]

"SteveN also agrees about degradation when turning the volume too low"

 

I do, but for a different reason. It is because of the way that my unique volume control system works. It is not because of gain changes or resistance changes in the signal path.

 

In most typical volume control circuits, the gain is changed or the resistance or load in the signal path is changed.

 

I believe the best scenerio is to get as much gain as possible in the first stage and then very little after that. This way, the noise created by the following circuits is not amplified.

 

If you believe this, then gain-controlled volume cicrcuits should sound better with the volume very low. Depends on the source gain/amplitude however.

 

Steve N.

 

[audioengr]

"Do you make the wall wort? - If not, how can you be sure that the component inside would be superior to a power supply solution?"

 

What is inside the wall-wart is essentially the same circuit that would be inside the DAC. It's a very large wall-wart, and high-quality.

 

"Does the wall wort's cord have some sort of shielding? - If not, how do you prevent the cord from acting like a big antenna, which is one the things a 1-2k power cord often addresses."

 

The DC power cable from the wall-wart is shielded, but it really does not need to be.

 

"What's the wall wort's plug made out of? Gold, rhodium, berylium have very different sounds."

 

Nothing interesting. The fact that it is not connected to a power cable however makes this less important. Even adding 3 feet of typical AC power cable makes a huge detriment. I have tried it.

 

"Does your wall wort filter power? If not , your solution would still require a power filter of some sort."

 

I have my own filtering in the DAC. I dont trust outboard filters or power "conditioners". They usually impact dynamics adversly.

 

"Without the future battery option, it appears to me that you approach is taking a step backward. Please point out where i'm wrong."

 

Read the reviews. It crushes DACs costing upwards of $35K. Leaves everything in its price-range in the dust.

 

Steve N.

Emprirical Audio

 

 

 

[audioengr]

"You tell us what it's not, but you don't seem to tell us what it is. I'm curious about what your solution is..."

 

The volume control changes the behaviour of the D/A conversion without changing the data.

 

Steve N.