Optimizing Digital Volume Control


First I would like to state that I am relatively new to audiophilia (sounds like a disease), however I have a relatively good engineering background.

Presently I am using a traditional CD->DAC->pre->power->speakers setup. I am using a Hegel HD20 DAC that has a digital volume control feature. I recently noticed that without the pre (ARC LS2) in the chain, using the DAC for volume control, I get better results.

Since the DAC is 24b, having a -140db noise floor (close to 144db theoretical limit) this makes sense to me. Since a CD, having 16bit resolution, supports a theoretical maximum of 96db (practical implementation are below 90db). So s properly designed digital attenuation of over 50db (probably in this case over 60db) should not degrade the sound.

Now to my question, assuming a computer as the source, followed by a 24b DAC that doesn't support volume control, one can in theory achieve the same results if the computer converts the 16b original data to 24b and then apply digital volume control. In this case the computer should output a 24b signal to the DAC.

Does anyone know if this is something that a JRiver or Foobar solution is capable of doing? or in general, does anyone know how volume control would work using JRiver or Foobar?

Thank you in advance for your attention.
That is how Jriver works. You can read up on this online.
Thank you. Just found the write up on this topic. Seems like they know what they are doing :-)

BTW, this leads me to believe that a preamp is practically no longer required. The best reference preamps at best can match a good 2K DAC. So most likely having a preamp in the chain simply degrades the result (unless of course you view the preamp as a filter that colors the sound to ones liking)
For someone who relatively new to the field you sound quite dogmatic. The subject of with/without preamp in digital systems is hotly debated. You should keep an open mind.
The fact is that no preamp will most of the time be better than using an active preamp. A transformer-based linestage (TVC) is one option. A DAC with really good volume technology (not like an active preamp) is another option. Both of these require that the DAC have a strong output buffer. Op-amps need not apply.

The best overall solution IME is to use a combination of volume control with a TVC or; DAC (with exceptional volume control technology) or discrete gain settings and a limited amount of digital volume control The ideal thing is to use up to -10dB of digital volume decrease and no more than that. This way the digital part can be the remote controlled part and the fixed volume can be manual.

So, there are these requirements:
1) sufficient drive from the DAC
2) Passive TVC or
3) DAC with discrete gain control or
4) DAC with reference voltage volume control

Steve N.
Empirical Audio
I was firmly into the no preamp camp (used the volume control of my msb dac) until I tried the arc ref5se. No comparison - preamp is back. Not cheap - extra set of interconnects, power cord - the works. Bottom line: forget theory and dogma and trust your ears. In my experience, only very high grade preamps will beat no preamp. But they do.
My DAC has a digital volume control and I've tried running it straight to my amp. It is very clean and musical, but lacks dynamics. When I put a pre amp back into the line, it was still clean and musical, but I got the dynamics back.
Let me qualify my comments by stating that my conclusions are a combination of about 6 months of listening and many years of engineering studies. I listen mostly to classical music, so this may be coloring my assessment. My speakers are Magnepan 3.6 and Willson CUB2s (I alternate between them).

During my brief journey so far I had the opportunity to work directly from the CD through an ARC LS2, Audible Illusions M3A, McCormak LD-2, and through the Hegel HD20 DAC (for the past 3 months). Today I can say with confidence that with the equipment I use, without the preamp, using digital volume control provides better result to my ears. I started with the expectation that a preamp is a good idea (based on the majority opinion), so my prejudice was to confirm that belief. But as I went through my music library I couldn’t ignore the fact that the sound without a preamp is better.
It so happened that this conclusion is aligned with sound engineering principles. The modern DACs are incredibly good. Their dynamic range and noise figures are amazing (to an engineer). This is a result of advances in semiconductor technology, which makes it practical to build such works of art at a low price. For example, Hegel just came out with a newer version of the HD20 that utilize a 32b DAC with a noise figure of -145db. With such a device I doubt an analog preamp (at least at the same price range) can compete, even up to a 50db volume range.

BTW, I contacted Hegel regarding this observation and Anders wrote me back the following: “At the top 50% it (the HD20) still outperforms our P4Amk2, that used to be our 4600 USD pre amplifer”.
Oferi, with all due respect, I came to the same conclusion with the caliber preamp you tried. You need to move way up the preamp foodchain to get an improvement over no preamp. So no preamp offers superior price/performance any day of the week, and will be the best architecture for the majority of systems.

However, in my experience, if you want the best of the best, you need to pull out the checkbook bigtime and get a VERY good pre. Nine out of ten "ultra high end" guys (six figure systems and up), will confirm this.
Like I said, the output of the DAC must be low-impedance with a lot of drive capability and then no preamp can beat it.

It just makes engineering sense. The more stages you add, the more noise, compression and distortion gets added. Less is more. If the output stage of the DAC is as good as any uber-expensive preamp (including power delivery), it will beat it.

Steve N.
Empirical Audio
This seem to be a popular topic nowadays since quality of DACs keeps getting better.
I can agree with Edorr and I can agree with Oferi. In my case and in my system where I run esoteric K-01 direct to Krell 302E, the use of ARC 5se did not bring the desired results to justify its price with extra ICs and power cord, the esoteric direct to amp sounded more refined with equally great dynamics and timbers. But I may agree that using ultra high end pre-amp ( tube or solid state) can result to the better sound. But in case of my system I will need to spend another $20K to achieve this. Instead, I can spent around $5k on a great ICs that will highly improve quality of the sound when running direct.
The important factor to the whole approach ( NO Pre-amp) is to have high quality DAC were its output impendence will match input impendence of the amplifier.
Steve, this is the theory. As I mentioned, nine out of ten of the guys on whatsbestforum with six figure systems end up adding a preamp to their DAC. They can't be all tone deaf and/or suckers. As Denon mentioned, you need to spend $20K (and up) to get the desired result, which they do.
Regarding preamp drive or DAC drive, the argument that the upstream component driving the amp should have a "low impedance with a lot of drive capability" while technically correct, in practice should be a non issue for any reasonable designed component. The input impedance of most power amps is 50K or higher (I know some are down to 10K), and with current state of electronics it is trivial to design an output stage with 200 ohm or less impedance. In fact if you look at reference preamps schematics they typically have a resistor in series at the output of roughly 200 ohm.I am guessing this is for protection against shorts. Regardless this tells me that reference level designers are not too concerned with having a very low output impedance. Otherwise removing that resistor would be the first thing an audiophile should do to get the best sound. I know that some of you may say that this has to do with impedance matching. Unfortunately physics tells us that for up to 20KHz bandwidth with short distances there is practically no impedance matching involved (unlike in the case of microwave or RF where the wavelength are on the order of the interconnect length or smaller). I believe the critical functionality for a preamp is minimizing noise and distortion that may be introduced due to attenuation or amplification, while presenting a high impedance to the source and reasonably low impedance to the load. I suspect that this is what differentiate a good (line stage) preamp from an average one.
Ed - 99.9% of iPod users use the stock earphones too. Means nothing. Means that they are just uninformed.

Steve N.
Empirical Audio
Oferi - The input impedance of an amp has nothing to do with the dynamic response to an input current and voltage signal. It's usually only a resistor to ground.

Just put a resistive passive linestage to an amp and you will typically experience a loss in dynamics.

Steve N.
Empirical Audio
Steve, bad analogy. iPod users use the stock earphones because they sound "good enough" and they don't feel the need to spend the money to get better sound.

Uber-audiophiles have exactly the opposite motivation; no preamp does NOT sound enough, and they are willing to spend the price of a mid size sedan to get better sound.

This is typically a highly informed decision, based on extensive auditioning of gear. I personally went through a few preamps that did not make the cut, a digital and analog volume control on a DAC and ended up settling for the arc ref5SE with transparent reference ICs and shunyata python zitron powercable (I threw in three stillpoint ultra's under the preamp for good measure as well).

I bought the preamp used with the intent of immediately reselling it if it did not improve SQ over the analog VC of my DAC (like I did with the Pass Labs XP-10 and the EMM Labs Switchman - resold within 48hours). If someone expertly "informed" me I was in fact getting worse sound because of some engineering principle, I would have still trusted my ears and kept the preamp.
Audioengr, I agree that the input impedance of a power amp is probably slightly frequency dependent, and hopefully not amplitude dependent. So I agree that a low impedance source is a good idea. My point is only in regards to how low is good enough. A 200 ohm source into a typical amp would be plenty good (as evident by the design of reference preamps having a 200 ohm or bigger series resistor at the output). On the other hand a passive (pot) would probably degrade the quality if its impedance is on the order of the amp input impedance.

BTW, a passive volume control with a 20K ohm into a 100K good amp seems to do an excellent job (but not as good as the best preamps).
"07-10-13: Edorr
Steve, this is the theory. As I mentioned, nine out of ten of the guys on whatsbestforum with six figure systems end up adding a preamp to their DAC. They can't be all tone deaf and/or suckers. As Denon mentioned, you need to spend $20K (and up) to get the desired result, which they do."

I agree overall, but you don't have to spend 20k. If you match your components well, you can get away for less.

You can also get great sound without a preamp. In both cases, it comes down to good system matching and what you like.


For someone with 6 months experience in audio, you seem to have your mind made up about a lot of things. Nothing wrong with that. I won't tell you how to think. You did ask for advice, though. You appear to have a good start on the technical aspects of audio. I would now balance that with some listening experience. Not everything in audio can be measured. If you don't accept that and find a way to blend your listening experience with the tech aspect, this will not be a fun hobby for you.
Oferi - I have had he opportunity to compare good active preamps with passive resisive, passive transformer and DACs with good drive. Comparing some of the best of each I conclude that resistive passive is the worst. Transformer and a good DAC are the best.

Output impedance in the 20 ohm range is much too high. Needs to be in the 10 ohm range. Has nothing to do with the terminating resistor in the amp.

Steve N.
Empirical Audio
@ Audioengr , You mean above 200 ohms on the digital source is to high and 100 ohms is Ideal!, I agree!, cheers.
I have a Burmester 980 DAC, I used to run direct to the amps ( gryphon ref 1) but I wasn't satisfied with digital volume control so I tried a TVC and it was worst, finally I bought a gryphon sonata and boy that make a difference.
I fully agree with Edorr good high end preamp improve the dynamic.
Even 100 ohms is too high IMO. The lower the better. This alone does not guarantee that the output driver is a good one though. It also requires good circuit design and parts choices as well as good power delivery infrastructure.

Steve N.
Empirical Audio