Benchmark DAC1 now available with USB

[EliasGwinn]

Originally Posted by s.a.b.

I have the DAC1 and k701 (as well as DT880 ('03) and DT990) and I wouldn't describe the reality as "brutal" at all.

I do have the ago old questions for Elias - at least when listening thru headphones, I (and even non-audiophile folks at my house) do hear a difference between transports and even digital cables. Any thoughts on this?

Thanks.

s.a.b.,

I'm not sure what is causing the differences you are hearing, but we have done extensive testing with different types of digital cables, and we have not been able to hear or measure any differences using various cables with the DAC1. Different analog cables can affect the output sound of the DAC1, but we have not been able to find any performance differences with different digital cables.

As Crowbar mentioned, sometimes its really difficult to hear differences between set-ups without a proper testing configuration. When conducting an A/B test, its very easy for even the most trained ear to lose their point of reference, making it very difficult to make accurate comparisons.

Thanks,
Elias

[StevieDvd]

Elias,

Thanks for the continued updates and persevering with the multiple and sometimes extensive questioning.

Can I just ask for suggestions/tips on using the DAC1 balanced xlr outs feeding into a balanced headphone amp? Any optimum or suggested settings?

Embarrasses me to admit I just left it at factory settings, all sounds well but it's be nice to know I'm not missing out for the sake of flipping a switch or jumper around.

My amp (Rudistor NX-33) volume control goes to about the 12 o'clock position before it gets too loud to use.

I read your position on using balanced headphones directly from the Dac1 but that's what I did initially before upgrading to balanced amp.

Have you opinions on balanced amps too?

Steve

[The Monkey]

Elias,

One design note for the good folks at Benchmark. The screws that need to be undone in order to get inside the unit could be improved. First, mine were screwed in so tight that it was almost impossible to remove them. Second, it is very easy to damage or "strip" the screw heads themselves. I'd love to see Benchmark go with hex socket head screws or thumb screws.

[EliasGwinn]

Steve,

The factory settings on the DAC1 are suited to fit most set-ups. How far are you turning the volume pot of the DAC1? If you are not able to get the volume knob past 10 o'clock or so, then you may want to change the output attenuators.

As for running balanced into an amp, that is the best way to interconnect the DAC1 and another device. Balanced headphones are a whole other subject...

On the subject of balanced headphones, we have found no evidence, documentation, or explanation to support the claims of performance advantages. For those familiar with bridged-mode power amplifiers, balanced headphones are a very similar topology....

Bridged-mode amplifying is used to increase power into a given load, while sacrificing performance (especially damping factor). This mode of operation is undesirable unless an increase in power is absolutely necessary.

From everything we have seen, balanced headphones suffer from the same symptoms, while not having any benefits to offer. The benefit of bridged-amping (additional power) is not needed in this case (the DAC1's headphone output has more then enough power for any headphones we have encountered). Therefore, we simply have no reason to believe there are any advantages.

Some people may enjoy this particular configuration, and we encourage those people to continue to enjoy it.

As a company and equipment designer, we choose to follow routes of technology which are founded in some sort of explainable / provable / understandable manner. Otherwise, we would be chasing every whim and trend that floated through the audiophile community (and, trust me, that could get very exhaustive ).

Thanks,
Elias

[EliasGwinn]

Originally Posted by The Monkey

Elias,

One design note for the good folks at Benchmark. The screws that need to be undone in order to get inside the unit could be improved. First, mine were screwed in so tight that it was almost impossible to remove them. Second, it is very easy to damage or "strip" the screw heads themselves. I'd love to see Benchmark go with hex socket head screws or thumb screws.

Monkey,

Thank you very much for this very valuable feedback. I will bring this up with our production team.

Thanks,
Elias

[music_man]

mr gwinn,

is the dac circuit connected to the headphone amp circuit balanced on the pcb? if not, why and how is it connected? edit: it appears that it is unbalanced?

also, what is the headphone amp using in place of an op-amp as the amplifier? a buffer ic? edit: wasn't it discussed that the headphone amp was discrete? there is mention of op-amps here.

edit: is there a pot on the pcb to adjust the headphone amps gain?

thanks,
music_man

[yourmando]

Originally Posted by Crowbar

What do you mean? No current DAC chip manages actual 24 bits resolution; about 21 is the highest I've seen...

I didn't mean to quibble with any specific points, but thought you might be interested to know that the DAC1 jitter immunity is more than just attenuation from an ASRC. Yes, I did mention that the effective number of bits of any DAC has not hit 24 bits (And this is probably not possible with current technology because of the thermal noise floor at room temp). My original point is that the DAC1 represents the current state of the art in terms of measurable performance over a wide range of real world operating conditions.

For a third party look with Audio Precision measurements of the non-usb DAC1:
http://theaudiocritic.com/blog/index...Id=10&blogId=1

I can't say it better than that! The USB version has more features (beyond USB) and a wider range of operating conditions.

Armando

[Crowbar]

Well, specific points are what makes a discussion concrete, and I wouldn't call it quibbling. Looking at the linearity graph in your link, it's linear to about -115 dB. I don't know what DA chip is used in the DAC1, but AD1955 datasheet shows linearity down to -125 dB, and that's a 5 year old IC. The PCM1794A has similar performance. Both are cheap. My other two points are not discussed at the site you linked to. The dither test is nice, showing the ~18.5 bit effective resolution. Still, I'd still like to see the high frequency jitter test I mentioned above, and especially the thermal memory measurement. I would guess the DAC1 would do fine in the former, but I have my doubts about the latter due to the use of opamps.

[yourmando]

Originally Posted by Crowbar

That's an unwarranted statement. The ITU recommends double-blind triple-stimulus with hidden reference testing; I'll believe it when I see the results.

There are many other things wrong with sound reproduction besides the electronics, such as that all speakers and headphones have tremendous distortion...

I would also love to see more double blind tests! In absence of this, I will pick the product with the best and most extensive measurements (and useful features), even if I feel it is probably overkill. That we are "probably" well past the audibility threshold is a sufficiently hedged comment. I, too, love to learn about the limits of perception, the design gear, etc. Like you, I believe that transducers--loudspeakers and their interaction with the room, headphones--are by far the limiting factor; The speakers are the sole determinant on the reproduction side of the width, height, and depth of the sound stage and size of virtual images (aside from intentional or unintentional distortion/processing in the electronic signal path).

Let me put it this way, if a friend wanted a recommendation on the best near-field audio reproduction electronics components, I would recommend a computer or bit-perfect streamer as the source (not a cd player that I have to feed!), and a Benchmark DAC1 USB as the DAC/preamp/headphone amp with the volume control kept within arms length, because I know of no other combination with this level of end to end distortion and noise with real resistive loads. (This doesn’t include multiple channel and DRM restricted audio, which would require another setup.)

Cheers,
Armando

[yourmando]

Originally Posted by Crowbar

Well, specific points are what makes a discussion concrete, and I wouldn't call it quibbling. Looking at the linearity graph in your link, it's linear to about -115 dB. I don't know what DA chip is used in the DAC1, but AD1955 datasheet shows linearity down to -125 dB, and that's a 5 year old IC. The PCM1794A has similar performance. Both are cheap. My other two points are not discussed at the site you linked to. The dither test is nice, showing the ~18.5 bit effective resolution. Still, I'd still like to see the high frequency jitter test I mentioned above, and especially the thermal memory measurement. I would guess the DAC1 would do fine in the former, but I have my doubts about the latter due to the use of opamps.

You are certainly the tough critic! “The” Audio Critic, champion of mesurement-driven and DBT evaluation was much “softer” than you:

The cloud-cuckoo-land high-end DACs at ten times and fifteen times the Benchmark’s price are no better and in most cases not as good...

Why can I confidently make that statement? Because I measured the DAC1 up and down and sideways with the Audio Precision SYS-2722, possibly the most sensitive and accurate audio-test instrument in the world, and found it to be as nearly perfect as a digital-to-analog converter can get at the present state of the art. Totally perfect 24-bit converters, with the theoretical noise floor of –146.24 dBFS and a perfect monotonicity “staircase” waveform at the ten lowest LSBs, do not yet exist, at any price, and probably never will. Still, the DAC1 yielded the best measurement figures that I have ever obtained out of a digital processor on my test bench, nor have I ever seen better measurements on other units in other publications...

...I’ll take electronic perfection, any day of the week, if it costs $975 instead of $17,500.

We have about 20 pages in the DAC1 manual of Audio Precision graphs and specs, seven more independent graphs in the article linked above, and I’m sure there are plenty more out there. Your drive to know more amazes me. Good luck in your search, and please do let me know if you find some more data, or another unit with a comparable set of measurements showing better performance all the way to headphone amp stage with at least the same range of operating conditions!

Armando