Benchmark DAC1 now available with USB

[TreAdidas]

Quote:

Originally Posted by schaqfu /img/forum/go_quote.gif Since the balanced XLR outputs have been substantially improved in the DAC1 USB, and "can now drive... low-impedance loads... without any loss in THD+D performance," this raises the question: will balanced headphones, HD 650s in particular, now play even better directly out of the balanced outputs? At 300 ohms they certainly qualify as low-impedance loads. Will the relatively minor distortion reported by current users playing their HD 650s out of the DAC1 balanced outputs be reduced? Any other benefits we can anticipate?

I did not see an answer to this. I'm wildly interested in a response to this as well.

 

[schaqfu]

Quote:

Originally Posted by TreAdidas /img/forum/go_quote.gif I did not see an answer to this. I'm wildly interested in a response to this as well.

x2

 

[audioengr]

Quote:

Originally Posted by choariwap /img/forum/go_quote.gif so maudio's drivers dont do bit perfect? even in ASIO? wow... i'm really itching to get a dac1 usb, but the closest i can get one is in hong kong. curses! soonest i can go is june-ish... sigh

They do, but it depends on the ASIO that you use. I actually prefer the sound of one that is probably not bit-perfect. Much more natural vocals.

 

[EliasGwinn]

Quote:

Originally Posted by TreAdidas /img/forum/go_quote.gif I did not see an answer to this. I'm wildly interested in a response to this as well.

The XLR outputs on the DAC1 USB are not designed for driving headphones because they have a 30 ohm resistor in series. For a headphone amp, ideally, you would want 0 ohms output impedance, which is how the HPA2 is designed (the HPA2 is Benchmark's signature headphone amplifier which is featured in the DAC1 and other products.)

With that said, if one was to try driving balanced headphones from the XLR outputs, the DAC1 USB is much better suited for that then the DAC1. The DAC1 USB would be able to drive 300 ohm headphones to 28 dBu, but we have not tried nor measured the performance of such a setup. Therefore, we offer no claims or guarantees about the performance of this setup.

Thanks,
Elias

 

[EliasGwinn]

Please let me know if anyone tries the balanced headphones from the XLR outputs of the DAC1. I'm very curious as to how it performs.

A question for you all: how are you building your balanced headphone cables? What type of wiring configuration are you using?

Thanks,
Elias

 

[granodemostasa]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif Please let me know if anyone tries the balanced headphones from the XLR outputs of the DAC1. I'm very curious as to how it performs. A question for you all: how are you building your balanced headphone cables? What type of wiring configuration are you using? Thanks, Elias

sadly, right now just about all headphone balenced cables are just standard cables with XLR termination. there has been talk of a cable that would have the ground separated but no one has built it yet.

 

[kool bubba ice]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif Please let me know if anyone tries the balanced headphones from the XLR outputs of the DAC1. I'm very curious as to how it performs. A question for you all: how are you building your balanced headphone cables? What type of wiring configuration are you using? Thanks, Elias

They sound great.. I'm using my Balanced SA5000/650's with my DAC1 from the XRL outputs.. My Sony 5000 are 70 ohm, & theres no distortion or hiss, even on the highest volume setting (Variable). I needed to Change the ATT to 0DB though.. Cause at -20DB the volume was set to low. My balanced cables were made by Alex.. apuresound.com. Not sure what type of wiring con fig was used..

I think you would be impressed how headphones sound balanced through your DAC1x especially the 650s.. Awesome synergy.. In scale terms, If I rated the DAC1 headphone amp, I'd give it a 6.. Through balanced I'd rate it a 9...

 

[kool bubba ice]

I'm using the non USB version by the way..

 

[TreAdidas]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif Please let me know if anyone tries the balanced headphones from the XLR outputs of the DAC1. I'm very curious as to how it performs. A question for you all: how are you building your balanced headphone cables? What type of wiring configuration are you using? Thanks, Elias

I'm not really electronics savvy so, I was looking to buy some. I'm considering Zu Cable's Mobius V2, Moon Audio's Silver Dragon V2, and the Cardas Balanced headphone cable.

www.zucable.com (note the V2 is not yet on their website but it is being talked about here: http://www.head-fi.org/forums/showthread.php?t=233917 )

www.moon-audio.com

I'm very interested in more information on this. Note the Sennheiser 650's nominal impedance is 300 OHM's

 

[kool bubba ice]

Gwinn,
I have pics of my balanced cables in my sig, if that will give you any idea..

 

[EliasGwinn]

It seems (from the things I have read) that a balanced headphone configuration consists of driving the positive and negative terminal of the drivers with the positive and negative versions of the audio (respectively). In other words, the two terminals get the same active (with opposite polarity) signals.

I've also heard of balanced headphones as being a positive signal lead and an isolated return path (sig ref). In other words, it would be similar to a regular headphone setup, but each headphone driver would have its own isolated return path (instead of sharing one).

Thanks,
Elias

 

[choariwap]

Quote:

Originally Posted by granodemostasa /img/forum/go_quote.gif sadly, right now just about all headphone balenced cables are just standard cables with XLR termination. there has been talk of a cable that would have the ground separated but no one has built it yet.

i think you're mistaken here.. balanced headphone cable terminate in TWO xlr plugs. the ground is separated in this case, actually there is no ground connection.

the driver is hooked up to the + and - signal of one xlr, with the third xlr pin unused. same for the other driver/

 

[choariwap]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif It seems (from the things I have read) that a balanced headphone configuration consists of driving the positive and negative terminal of the drivers with the positive and negative versions of the audio (respectively). In other words, the two terminals get the same active (with opposite polarity) signals.

thats correct.

 

[EliasGwinn]

I'd be interested in hearing the dual-active configuration, but I can't see how it would make a difference aside from having a signal with twice the magnitude.

Plus, they would have to be driven from a source with very low (near zero) output impedance.

The problem with using the DAC1 for such an application is the output drivers are designed to drive a line input device, hence the 60-ohm output impedance. With headphones, this output impedance will cause the damping factor to drop significantly, causing ringing, overshoot, and all sorts of distortion based on driver resonances. Let me elaborate on this further...

Damping factor is a ratio of [load impedance vs. source impedance]. In the case of the HPA2, the output (source) impedance is less then 0.11 ohms. Therefore, the damping factor with 300-ohm headphones will be near 3000.

The damping factor with a 30-ohm output impedance and 300-ohm headphones will be 10. The damping factor with 60-ohm outputs and 300-ohm headphones will be near 5.

As you can see, we lose the tight control over the drivers which is essential for the reactive load which a speaker presents.

Another problem with a significant (>1-ohm) source impedance: the headphones have frequency-dependant resistance. Therefore, the voltage divider that is created between the source impedance and the load impedance is now a frequency-dependent voltage divider. This means the frequency response is going to be anything but flat.

I would be hesitant to use this type of configuration. In fact, I don't recommend driving headphones with any source with an output impedance >1 ohm to drive headphones at all.

With that being said, it will not hurt the DAC1 to do this, so feel free to experiment with this setup without worrying about causing any damage. My philosophy is...if it sounds good to you...go for it!

However, don't evaluate the quality of the DAC1 based on driving headphones with the XLR outputs.

Thanks,
Elias

 

[kool bubba ice]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif I'd be interested in hearing the dual-active configuration, but I can't see how it would make a difference aside from having a signal with twice the magnitude. Plus, they would have to be driven from a source with very low (near zero) output impedance. The problem with using the DAC1 for such an application is the output drivers are designed to drive a line input device, hence the 60-ohm output impedance. With headphones, this output impedance will cause the damping factor to drop significantly, causing ringing, overshoot, and all sorts of distortion based on driver resonances. Let me elaborate on this further... Damping factor is a ratio of [load impedance vs. source impedance]. In the case of the HPA2, the output (source) impedance is less then 0.11 ohms. Therefore, the damping factor with 300-ohm headphones will be near 3000. The damping factor with a 30-ohm output impedance and 300-ohm headphones will be 10. The damping factor with 60-ohm outputs and 300-ohm headphones will be near 5. As you can see, we lose the tight control over the drivers which is essential for the reactive load which a speaker presents. Another problem with a significant (>1-ohm) source impedance: the headphones have frequency-dependant resistance. Therefore, the voltage divider that is created between the source impedance and the load impedance is now a frequency-dependent voltage divider. This means the frequency response is going to be anything but flat. I would be hesitant to use this type of configuration. In fact, I don't recommend driving headphones with any source with an output impedance >1 ohm to drive headphones at all. With that being said, it will not hurt the DAC1 to do this, so feel free to experiment with this setup without worrying about causing any damage. My philosophy is...if it sounds good to you...go for it! However, don't evaluate the quality of the DAC1 based on driving headphones with the XLR outputs. Thanks, Elias

With all due respect, driving my headphones out of the DAC1 XLR output is a much more enjoyable listening experience then using the single ended HPA2. You should try it for yourself. I'm sure you will be surprised by the results. If going balanced with the DAC1 was a bad experience I doubt headfiers would be using the DAC1 as a balanced set up.. I'm sure amps that are made for balanced headphones will sound better cause they are tailor made for that purpose.. But the DAC1 does more then a decent job IMO..