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Thread: What is the benefit of very expensive DACīs?

  1. #171
    Quote Originally Posted by Empirical Audio View Post
    Its not just a power supply. Because of inductance in the wiring and board, the power subsystem must be a distributed one, with some elements providing large currents and others providing high-frequency transient currents. All of this must work with multiple loads on the board demanding different power over time and not allow the voltage to droop, even a few fractions of a volt.

    When you have unregulated DC, there are roles for regulators, large electrolytics, smaller film caps, even smaller Teflon or similar caps and SMT ceramic caps of different types. Then there is the design of power cabling and the board power planes and grounds planes. All of this plays into the power delivery subsystem.

    Steve N.
    Empirical Audio
    Steve, are you progressing a new DAC design at the moment, or updating your existing OverDrive design? I am curious how far you have got with it, and if it is live and working (for review purposes?).

    Back to power supplies, as I understand it, a SHUNT power supply is possibly the best to use in a DAC or amplifier, as it can respond to sudden demands for extra power, which playing music requires. Sound silly as we are talking 2 volts line out, but the elements in a tube DAC or pre-amp need a lot of current and the bias circuits can run at 400V+ as I understand it. But aside from tube base designs and their 'unique' requirements, many solid state DACs and pre-amps still have very small (under sand low energy power supplies, and I wonder if those designs are being throttled of juice?

    On battery power supplies, there was a revered DIY DAC from Aussie that got good reviews and ran off a battery. But it was middle of the range, not really high end. I can't think off the top of my head any really high end DAC that uses a battery system. Any out there? My old Pink Triangle De-Capo 3 box DAC had one, and that was back in 1990. But it was a mixed bag, and had issues. Battery power is not as far as I understand it, (and read about) a perfect pure wave clean supply many may think. It has it's own problems that come with it.

    I am in the traditional camp of big power supply, well regulated and lots of storage capacity. It seems to me to make perfect sense. Dynamics and music flow surely depend on it?

    And then we have the mains supply before it even gets into the DAC itself. I am also convinced cleaning up your mains supply can benefit the whole hifi chain. I am only 500 metres from a large step-down transformer in the street, but I still see 2% line distortion. I use a PS Audio P10 to power / clean my supply. It works well, and really makes a difference, getting it down to 0.1% and rock solid 230v pure sine wave.

    So IMO clean supply in, big power supply in the DAC / preamp or Amp equates to a cleaner and more consistent / linear sound even at high levels. I don't hear those 'best moments' at 3 am in the morning anymore, it sounds the same (that good) 24/7 and some.
    Mac Mini Server with 12V DC Upton Audio MMK Mod and LPS feed , SSD and 16 GIG RAM, Audirvana V3 & Tital | Audio Note UK DAC 5 Special V2 (with Duelund Copper caps on line stage) | Passive pre-amplifier | Plinius SA-103 150W Class A / AB switchable | Zingali Client Name EVO 1.2 Horn Hybrids | Velodyne DD10 Sub | DIY KGSShv Carbon Electrostatic Headphone Amplifier | Stax SR-009 2016 | PS Audio P10 Power Regenerator | Dedicated Mains | AMR DP-777 DAC & Stax SR007A 2015 for second HP system.

  2. #172
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    Quote Originally Posted by astrostar59 View Post
    Steve, are you progressing a new DAC design at the moment, or updating your existing OverDrive design? I am curious how far you have got with it, and if it is live and working (for review purposes?).
    I have an updated Overdrive SX ready for review. First review is scheduled already. When I get it back, I'll look at additional reviews.

    Back to power supplies, as I understand it, a SHUNT power supply is possibly the best to use in a DAC or amplifier, as it can respond to sudden demands for extra power, which playing music requires. Sound silly as we are talking 2 volts line out, but the elements in a tube DAC or pre-amp need a lot of current and the bias circuits can run at 400V+ as I understand it. But aside from tube base designs and their 'unique' requirements, many solid state DACs and pre-amps still have very small (under sand low energy power supplies, and I wonder if those designs are being throttled of juice?
    They definitely are weak on the di/dt. I could name a few, (because I have either modded them or provided customers power systems for them), but I don't do that because I'm a manufacturer myself. Generally, the bigger the supply, the more di/dt you can get out of it, particularly with linears, but even switchers. Shunt is a good regulator, but burns a LOT of power, so thermal is a concern there. I typically already have so much heat due to class-A circuits and series regulators that I don't go there. Good passive series regulators usually require about 5 volts of headroom, so the voltage drop on the regulator is large and therefore it burns some watts. The problem with most regulators is the speed. It's difficult to make a fast responding regulator, so most linears do not do this well.

    On battery power supplies, there was a revered DIY DAC from Aussie that got good reviews and ran off a battery. But it was middle of the range, not really high end. I can't think off the top of my head any really high end DAC that uses a battery system. Any out there? My old Pink Triangle De-Capo 3 box DAC had one, and that was back in 1990. But it was a mixed bag, and had issues. Battery power is not as far as I understand it, (and read about) a perfect pure wave clean supply many may think. It has it's own problems that come with it.
    The former Red-Wine audio DAC was quite good and ran on batteries, but he has abandanded that now and renamed his products Vinnie Rossi.

    I am in the traditional camp of big power supply, well regulated and lots of storage capacity. It seems to me to make perfect sense. Dynamics and music flow surely depend on it?
    Yes, however the design of the supply and the parts chosen make all the difference in the transient response. It's much easier to get a fast reacting switcher than the same in a linear.

    And then we have the mains supply before it even gets into the DAC itself. I am also convinced cleaning up your mains supply can benefit the whole hifi chain. I am only 500 metres from a large step-down transformer in the street, but I still see 2% line distortion. I use a PS Audio P10 to power / clean my supply. It works well, and really makes a difference, getting it down to 0.1% and rock solid 230v pure sine wave.
    Regenerators and AC regulators are goodness. I use a Plasmatron for digital myself. I have not found anything for amps that I like yet.

    The other thing to note about power supplies is that the di/dt must also be supported by using the right decoupling caps on the boards. The optimum values in the optimum locations. It's a puzzle that must be resolved by the designer and they usually get it wrong. This is one of the reasons I had such a lucrative modding business from 1990-2009. I don't mod anymore BTW.

    Steve N.
    Empirical Audio

  3. #173
    Good info there Steve, thanks for that work.

    I dunno about SMPS though, the ones I have heard or experienced have been hideous. BUT I see Chord has managed to use them in their power amps and DACs. But aren't they switchers by nature, so generate lots of noise and digital hates ANY noise as we know.

    Yes heat with a SHUNT maybe an issue in some cases. Your Overdrive is a compact chassis so probably a moot point. Going bigger chassis can avoid it I would have though, and improve cooling?

    Vinnie Rossi, I forgot the name. But I can't think of any other DAC, certainly a high end DAC that has battery power. Saying that I think there is a version of the Nagra HD DAC that has one, and can run for 2 hours (clarification required).

    Here is a good article about the pros and cons of Battery power, SMPS and LPS. It doesn't include tube regulated PS or SHUNT.

    Note: A version of this article was originally written and published on Larry Ho’s personal blog on December 1, 2014.
    There’s a common assumption that battery power supplies are much less noisy than switched-mode, or even linear, power supplies.

    I think the most likely reason that people make this assumption is because, they believe, pure DC power doesn’t have any AC noise on it. But let’s take a closer look at this and see if I can help you decide which method for powering your audio gear is best.

    The way a battery produces power
    Batteries produce and deliver power through a chemical reaction. Every type of battery will use a different chemical mixture to generate power. Lithium Ion and Sealed Lead Acid are two of the most popular (of the more than 150 types of) batteries. For your reference, Wikipedia has a nice long list of battery technologies here: http://en.wikipedia.org/wiki/List_of_battery_types

    As a battery drains, the amount of chemical compound available to produce electricity is reduced. That means there’s an exponential decay on the amount of power a battery can produce. So a battery with a 100% charge will have far more capability of producing fast transients than a battery that isn’t fully charged, especially if that charge is below 50% of its capacity. Depending on the battery’s manufacturing process and the stage of its life cycle, the problem of power delivery speed is compounded. This is the reason some people note that a new battery sounds better than an older battery.

    With this information, it behooves users to replace batteries often and keep them charged to capacity as much as possible. This, of course, means that larger budgets must be set aside for batteries as frequent charging leads to shorter battery life.

    Battery noise generation
    The assumption that batteries aren’t noisy is flawed because batteries have a substantial amount of high frequency ripple. Meaning that there’s a large amount of high frequency AC noise that rides on top of the DC output voltage. Different batteries using different chemical reactions will generate different types and frequencies of noise. And, as the chemical reaction changes as the battery drains, the spectrum of noise changes as well. Also, as discussed above, as the battery discharges, the output voltage and current destabilizes, causing a slower transient response.

    Ultimately, batteries provide a non-constant power source that produces a variable spectrum noise that users are trying to get rid of by switching to batteries in the first place.

    Introducing Noise as Batteries Recharge
    As mentioned above, in order to get the most out of your batteries, they need to be as close to 100% charged as you can get them. One way to keep your batteries charged is to use an automatic trickle charger. This device detects when voltage from the battery is below a pre-determined threshold. When the threshold is reached, it begins to recharge your batteries. In this scenario, the AC recharge injects noise into the battery’s path, when means your system has to include a filter to address both battery noise and AC noise.

    The other option is to manually recharge batteries when the system isn’t in use. This is a much better option when it comes to noise, but it’s inconvenient to users. Who wants to stop in the middle of a listening session so you can manually recharge your batteries?

    Grounding
    By using a batteries, you aren’t connected to ground in the same way. The connected device is either isolated from an earth ground altogether or it’s directly connected, depending on the battery powered device’s connections to other devices, such as a computer. This means that shields can become noise cages. In addition, it’s easy to end up with a ground loop along your system’s cables as the system tries to find an alternative path to ground. When this happens, it’s not easy to find the cultrip for the loop.

    Batteries vs a Switched-Mode Power Supply (SMPS)
    Noise generated by batteries is usually very high frequency noise, well into the MHz or even GHz range. This noise is very difficult to filter and is exactly the kind of noise we hate the most because of the artifacts it sends down into the audible range. Still, this noise is less than that which is generated by a switched-mode power supply. In comparison, batteries are the better choice, but still not a great choice.

    Linear Power Supply (LPS) with a Super-Quiet DC Circuit

    A linear power supply can be designed with a much wider bandwidth, a super-stabilized voltage and current capacity, a considerably lower noise floor, and much more power than a battery power supply. It does come with trade-offs, though.

    A good LPS is usually very heavy due to the amount of metal needed in its transformers and the size of its capacitors. The more wattage you need, the heavier it is. Nobody in the last 30 years has been able to solve the issue of weight.

    A good LPS is not inexpensive. Again, because of the components that are needed, cost is a major contributing factor into why users elect against an LPS.

    Conclusion
    There’s no perfect solution for noise-free power. Each one we’ve discussed (battery, SMPS, & LPS) come with their own pros and cons. In my opinion, based on how I use my audio system, I rank these solutions as #1: linear power supply, #2: battery power supply, and #3: switched-mode power supply. The beauty of this hobby, though, is that everyone gets to make their own decision. Hopefully now you have more considerations as you decide which method you like most.
    Mac Mini Server with 12V DC Upton Audio MMK Mod and LPS feed , SSD and 16 GIG RAM, Audirvana V3 & Tital | Audio Note UK DAC 5 Special V2 (with Duelund Copper caps on line stage) | Passive pre-amplifier | Plinius SA-103 150W Class A / AB switchable | Zingali Client Name EVO 1.2 Horn Hybrids | Velodyne DD10 Sub | DIY KGSShv Carbon Electrostatic Headphone Amplifier | Stax SR-009 2016 | PS Audio P10 Power Regenerator | Dedicated Mains | AMR DP-777 DAC & Stax SR007A 2015 for second HP system.

  4. #174
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    Excellent article and I agree with all of it. Switchers are like LPS in one way: the devil is in the details. They are not all alike. Different switching frequencies, different output inductors etc.. If you put a good linear regulator after a switcher that rejects the noise from the switcher, it can every bit as good as a much larger, less efficient LPS. This is why I do this in my Overdrive power supplies. Even the smps get quite warm. To replicate what I do with smps would fill the top of a desk if it were LPS.

    I didn't abandon batteries because of noise, I abandoned them because the di/dt was improved using LPS and switchers. Transient audio response was improved.

    Steve N.
    Empirical Audio

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