Review and Measurements of Benchmark DAC3

[John_Siau]

John -- Thanks for coming back to this thread! Though I have science and engineering experience myself, I'm certainly not an expert on high-end audio measurements. That said, your argument about noise influencing "linearity" at the low end makes sense to me. I have three remaining puzzles:

1) Amir's linearity measurements on the second (good) DAC3 unit show the unbalanced trace decreasing at the low end, not increasing as you state above.

2) Amir's presumably identical linearity test on the Topping D50, which has only RCA outputs, looks much better than the second DAC3 unbalanced. Yet his measurements of THD+N and SINAD are quite comparable between the D50 and the first (defective) DAC3. If these values improved significantly in the second unit (not measured by Amir), that would seem to make the paradox even worse, not so?

3) I don't think Amir has completely specified the filtering used in his linearity measurements. He said just above, "My tests include sharp filters on either side of the test tone so doesn't get corrupted by noise or distortion." Earlier he mentioned a figure of 50dB as the depth of the 200 Hz-wide bandpass filter. He has not, to my knowledge, stated if he's using a specific one of the built-in filters in the test unit, as you did in your post at https://www.audiosciencereview.com/...nts-of-benchmark-dac3.3545/page-15#post-90480.

Best Regards to All -- JClarkW

1) All bets are off when you are trying to measure something below the limits of your test equipment. I was never able to replicate Amir's results using the original DAC3 while testing it on one of my APx555b test systems. My conclusion was that the first DAC3 was not defective in any way. Amir's results for the second DAC3 were different than the first, but they measured the same here. These kinds of measurement anomalies are not uncommon when trying to measure beyond the limits of the test equipment.

2) Neither unit proved to be defective. The first unit tested perfectly here.

3) The low level extension of the linearity measurement is heavily influenced by the choice of filters. It is also very susceptible to interference from outside noise sources. Furthermore, the noise can cause the APx555 auto ranging to change at different parts of the measurement and this will produce a different curve shape at the extreme low level end of the measurement.

*** Bottom line, when you attempt to make measurements that exceed the capabilities of the test equipment, you will have some errors in your results. In the short term, these errors may be repeatable, but may not be repeatable on different day where temperatures and interference signals may be slightly different.

 

[John_Siau]

John,

As a daily user of a DAC3 in a professional mastering studio it's great to see you here and communicating technical issues with such clarity!

I used to work at PMC Speakers for many years and would occasionally drop by your booth at AES, and always enjoyed our chats and learned something every time.

There's an active system with ABH2 in my future, looking forward to it.

Cheers,
Ruairi

Interesting that you mention the PMC Speakers. I use a set of MB2S passive monitors in one of our listening rooms. I am driving each MB2S monitor with an AHB2 running in bridged mono. In the attached photo, you will see 4 AHB2 amplifiers, but 2 are reserved for driving other speakers when we bring them into the room. The PMCs have very low distortion, and this makes them a wonderful match for the AHB2.

 

[JClarkw]

1) All bets are off when you are trying to measure something below the limits of your test equipment. I was never able to replicate Amir's results using the original DAC3 while testing it on one of my APx555b test systems... Amir's results for the second DAC3 were different than the first, but they measured the same here...

*** Bottom line, when you attempt to make measurements that exceed the capabilities of the test equipment, you will have some errors in your results. In the short term, these errors may be repeatable, but may not be repeatable on different day where temperatures and interference signals may be slightly different.

Wow!! This is sobering food for thought! I don't know if Amir has ever remeasured equipment that he had evaluated here previously to verify reliability -- of the equipment or of the tests. (Obviously he cannot afford to keep all of this stuff around for long!)

It would be interesting to read Amir's his rebuttal to all of this...

 

[audiopile]

So this is a how many angels can dance a ballet on the head of a pin argument ? Is audibly significant because .........

 

[SoundGuy]

As owner of three generations of Benchmark DAC’s included the latest Benchmark DAC3. I am pleased to see that Benchmark is recommended. As a science based site this is how it should be. Since most users here are not making use of the high pro level XLR in the DAC3, I can see why RME is recommended as it measures superbly and is a cheaper option.

The method Benchmark use to both reject jitter and adjust clock timing (less than 3Hz increments) is brilliant. Benchmark solution to inter-sample overs is simple but why does nobody else address this huge issue in rock/pop. The signal level in their pro XLR is a massive advantage over all other designs - even though most folks may not use it or appreciate how important gain staging is. Benchmark also recognize lazy filters, MQA and other distorting methodologies (like minimum phase) for what they are DISTORTION. This tells you something About their no compromise design philosophy. No DAC manufacturer making claims of high fidelity accuracy should honestly espouse faulty methodologies (even if these options come standard on a Sabre chip)

On a budget I would take the RME DAC for sure and be absolutely totally delighted with it (as close to perfection as it gets) however I feel the premium for Benchmark products is actually very easy to justify (and very much from a technical perspective)

two cents…

 

[JClarkw]

...Benchmark also recognize lazy filters, MQA and other distorting methodologies (like minimum phase) for what they are DISTORTION. This tells you something About their no compromise design philosophy. No DAC manufacturer making claims of high fidelity accuracy should honestly espouse faulty methodologies (even if these options come standard on a Sabre chip)...

Dear SoundGuy -- Just out of curiosity, to you know what kind of filter Benchmark uses in their DACs? They don't appear to say anything about this, only there is no filter selection setting that I can see on the device... -- JClarkW

 

[SoundGuy]

Dear SoundGuy -- Just out of curiosity, to you know what kind of filter Benchmark uses in their DACs? They don't appear to say anything about this, only there is no filter selection setting that I can see on the device... -- JClarkW

Fast roll off Linear phase (lowest pass band ripple) with some clever mathematics to trick the converter and ensure the entire filter transition is well outside the audible range. They up sample to 250 GHz mathematically and then down sample to 211KHz to feed the DA chip. The filters in the chip are effectively moved higher up as the chip operates at the higher sample rate ensuring the entire filter is outside audible range. This will preserve phase and amplitude within the audible range better than any other DAC that simply uses the chip as ESS intended. https://benchmarkmedia.com/blogs/application_notes/inside-the-dac2-part-2-digital-processing

 

[anmpr1]

... I feel the premium for Benchmark products is actually very easy to justify (and very much from a technical perspective)

I know what your are saying. But is it really a 'premium' charge. Or is it simply good value for the dollar? No one has ever picked up a Benchmark product (in spite of their smallish form factor) and commented about how it's not as solid as it could be, or that the fit and finish was less than first rate. No one ever said, "Man, this five year warranty is substandard. Who do these people think they are?" No one has ever said, "You know, if only the company could put some meat into their owner manuals--you know, give the end user something helpful, instead of this one page typewritten instruction sheet!"

Maybe some consider their prices 'premium'. Definitely more expensive than products stamped out in a factory on the other side of the globe. But if you desire a solid package, with first rate build quality, a long warranty, and no hassle's if you ever need to contact the company, then it's not a premium. Certainly within the scheme of over the top expensive boutique 'high-end'.

 

[RichB]

Dear SoundGuy -- Just out of curiosity, to you know what kind of filter Benchmark uses in their DACs? They don't appear to say anything about this, only there is no filter selection setting that I can see on the device... -- JClarkW

You can also read about the Benchmark Filters (also used in the DAC3) at HomeTheaterHifi:

Secrets Q&A with John Siau of Benchmark Media Systems - HomeTheaterHifi.com

Benchmark Media Systems is a small but accomplished audio manufacturer headquartered in Syracuse, New York.

hometheaterhifi.com

Q: ESS offers several oversampling filters on their DAC chips. Per the Secrets review, you expose one filter which is a “textbook Fast Roff-Off Linear Phase type with excellent attenuation of the first reconstruction tone”.

Was this choice driven by subjective and/or objective evaluation?


Digital Filter test result, Benchmark DAC3 B from Secrets review

Both.

Some engineers attempt to “improve” the time-domain response by relaxing the brick-wall filter. This appears to work when looking at the square wave response with an oscilloscope, but it changes the sound of the recording by causing phase and amplitude modulation of high-frequency signals. If you relax the response of the filter, transients move toward the nearest clock transition, damaging the time-domain response. Relaxed filters will sound different because they are changing the sound. You can cascade our A/D and D/A converters through many A/D – D/A cycles without causing a change in sound. Try the same thing with a relaxed filter response and it will not work!

As a side note, we are not using the ESS filters, nor are we using the ESS DAC in a conventional manner.

Q: You mention in an article that you operate the DAC2 and DAC3 at a fixed 211 kHz sample rate. This is interesting in that fractional sample rate converters are often avoided. What was the reasoning behind this choice?

- Rich

 

[reddavin]

I’m a fan. Bluesound Node > Benchmark DAC3 > 2 Bridged Mono Benchmark AHB2 Amps > BMR Towers.

 

[JunkHippo]

I'm considering replacing my Funk preamp + Lake People DAC stack with a DAC3 HGC.
The only thing I'm worried about (except the hole in my wallet) is the high-pitched noise (coil whine presumably) when the DAC3 is in standby. It's been mentioned once in this thread and in a user review on a retailer's page.
Could owners of the DAC3 chime in: Is it an issue that affects all units? Maybe it's been fixed in production at some point?
It sounds like a petty detail, but I'm super sensitive to such noise and usually sit not far away from the electronics, in a fairly quiet room. So if the unit produces audible noise when switched off that's basically a deal breaker for me.

 

[reddavin]

My DAC3 HGC is dead quiet when turned on and not playing. It’s an older one. v1.1 that I upgraded to 2.1 (they have a chip for that!) input is Bluesound Node via coax. See pic 2 posts up. Everything is on triggers. Auto on / auto off. I wouldn’t want any kind of noise. That’s the point of Benchmark. (Excellent quality and craftsmanship)

 

[JunkHippo]

By "standby" I actually meant when the unit is switched off - that's when the noise occurs for some people.

 

[RichB]

I'm considering replacing my Funk preamp + Lake People DAC stack with a DAC3 HGC.
The only thing I'm worried about (except the hole in my wallet) is the high-pitched noise (coil whine presumably) when the DAC3 is in standby. It's been mentioned once in this thread and in a user review on a retailer's page.
Could owners of the DAC3 chime in: Is it an issue that affects all units? Maybe it's been fixed in production at some point?
It sounds like a petty detail, but I'm super sensitive to such noise and usually sit not far away from the electronics, in a fairly quiet room. So if the unit produces audible noise when switched off that's basically a deal breaker for me.

My DAC3 is also dead quiet. Have you contacted BenchMark or tried plugging it in elsewhere to see if there is noise on coming over the power line?

- Rich

 

[Martini]

I've got a DAC3b (no vol. control) which feeds a LA4 and it is dead silent when on and not playing and when off in "standby mode".

 

[reddavin]

No noise when switched off. (Standby)

 

[JunkHippo]

Thank you for your replies! Seems like it's not the standard behavior then.
@RichB I don't yet own a DAC3, I was just trying to find out about this potential aspect, after having read about it in two places.

 

[reddavin]

Thank you for your replies! Seems like it's not the standard behavior then.
@RichB I don't yet own a DAC3, I was just trying to find out about this potential aspect, after having read about it in two places.

If you are buying from Benchmark, I’m sure they could check it prior to shipping. Rory and the crew are extremely helpful.

 

[ex audiophile]

I've got a DAC3b (no vol. control) which feeds a LA4 and it is dead silent when on and not playing and when off in "standby mode".

I've often considered this a superb way to get your signal to your speakers (when using an AHB2 in the chain). Do you incorporate sub integration and/or DSP to correct for room modes? Would appreciate hearing your thoughts/experience.

 

[audiopile]

While I've had strange humm issues in the past from other equipment's transformers-have owned a Benchmark DAC-3HGC for 5? years or so and use it-dead silent on or off. Not sayin you couldn't figure out someplace or something (AC majic box of some sort?) to plug it into that causes this issue-but this is beyond weird given the number of this model sold by Benchmark. If you found two posts of this issue -what are the chances it's the same guy posting on two different forums ?If you buy from benchmark direct -I believe they have a return privledge for 30 days following purchase ? Might be worth calling Benchmark to see if they have any idea what would/could cause this ?