How good and powerful is the internal headphone amp on Benchmark DAC1?
Oct 19, 2011 at 1:13 PM Thread Starter Post #1 of 32
cactus_farmer

cactus_farmer

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Can it;
 
A). Drive hard-to-power headphones like Audeze and Hifiman orthodynamics models to a good volume easily and without straining? And manage current-hungry models like the K702 as well?
 
B). Match upper-mid-range models such as the Graham Slee Solo, Lehmann Black Cube, Heed Canamp...etc... in quality? If not, how far off is it - and what is the general character of the amp (I'm guessing fairly neutral...?)?
 
Thanks in advance for responses!!
 
Oct 19, 2011 at 1:22 PM Post #2 of 32
The Benchmark's amp module will quite happily drive the K702s and I would be surprised if it struggled with at least the LCD2. Having trouble finding power output measurements for it...
 
As for the amplifier's sound, like the DAC it is designed entirely around measurable neutrality. It will produce its input signal, but louder, whilst not doing anything objectionable that could ever be considered audible.
 
Oct 20, 2011 at 1:32 PM Post #4 of 32
where's the content in that thread? - says nothing
 
 
people serious about their hobbies learn the basic numbers - for audio, headphone listening it is headphone impedance, sensitivity, and amplifier specs required to calculate the max SPL before clipping
 
as well as an appreciation for real world, recorded music dynamic range and safe listening levels
 
http://gilmore2.chem.northwestern.edu/articles/hearing_art.htm
 
 
recognizing Real information and using search can help - but an educated buying public is needed to demand amp manufacturers in particular put useful objective performance numbers where they can easily be found
 
 
Benchmark's data sheet is poor, uses pro dBu - not everyone can translate
 
http://www.benchmarkmedia.com/sites/default/files/documents/dac1-usb_spec_sheet_0.pdf
 
 
so look to reviews with tech data:
 
 
http://www.soundonsound.com/sos/jul05/articles/benchmark.htm
 
claims the DAC1 uses Benchmark's HPA2 headphone amp design - NE5534 with BUF634 buffer, internal analog supply is +/-18 V  - so no worry there
 
 
Stereophile does OK technical reviews, if a product has been reviewed there it is a good source of tech info
 
http://www.stereophile.com/digitalprocessors/108bench/
 
as a check, the specs page there gives 8.7 Vrms for the headphone output - lower than I'd expect if the 1st review above were correct about the +/- 18 V supply - so another lesson - crosscheck, get as many viewpoints as possible
 
 
the BUF634 is rated +/-250 mA which puts about 1.5 Wrms into 50 Ohms, for ~ +32 dB re 1mW
 
the 8.7 Vrms also give about the same 1.5 Wrms into 50 Ohms
 
 
LCD-2 sensitivity 91 dB SPL re 1 mW + 32 = 123 dB SPL - plenty of headroom
 
 
the 50 Ohm, same as LCD-2, HE-6 at 83 dB sensitivity still could be driven to 115 dB SPL - enough for most listening scenarios, your average SPL should be below 85 dB for all day use, very little music today is recorded with >20 dB peak-to-ave dynamic range
 
Oct 20, 2011 at 1:42 PM Post #5 of 32
Ah good, someone better than me has found the output figures! 1.5W? Unless you want serious hearing loss that should drive prettymuch any contemporary headphone! Obviously it will vary into different impedances, but that is really a lot of power to be getting on with.
 
Nov 1, 2011 at 2:07 PM Post #6 of 32
The headphone outs of the Benchmark are specified at
 
+21 dBu into 60 ohms, that's 1.26W and 8.7V
0.0005% THD+N at +18 dBu into 30 ohms, that's 6.15V and 1.26 W
0.11 ohms output impedance.
 
That's plenty of power, enough to drive any headphones up to the HE-6, and with very low distortion. Based on specs alone, the Benchmark headphone amp is state of the art with a lot of power behind it.
 
Edit: Full list of specs here: http://www.benchmarkmedia.com/sites/default/files/documents/DAC1%20HDR%20Manual%20RevG.pdf
 
Nov 6, 2011 at 10:21 AM Post #9 of 32
The HE-6 is rated at 83.5 dB/mW, it means that with 1 W of power the HE-6 will reach 113.5 dB.
The Benchmark can deliver 1.26W into 60 ohm, it very probably can deliver at least 1 W into 50 ohm.
 
Which means that the you can play music with up to 113.5 dB peaks with the Benchmark + HE-6 combination. So theoretically, it is plenty powerful enough
 
Nov 23, 2011 at 3:22 PM Post #10 of 32
Sorry I haven't responded sooner! Somehow I didn't get a notification of your posts.
 
khaos974's math is correct; the HPA2 (Benchmark's headphone amp circuit that's in several of our products) will have plenty of power to drive the HE-6's, according to their spec.
 
Keep in mind, we offer a 30-day trial when you buy directly from us.  So if you find it lacking in any way, you can simply return it for a full refund.
 
Best,
Elias
 
Jan 22, 2012 at 10:43 AM Post #11 of 32
Is the DAC1 OK to use with headphones lower than 60ohm impedance. I hooked up a (38ohm) Audio Technica M50 to it and wondered if that pairing would cause any damage to either the headphones or the headphone amp of the DAC1 (assuming average listening volumes of course).
 
Jan 22, 2012 at 11:36 AM Post #12 of 32
Why would you think the amp would damage itself driving low impedance loads?
 
Jan 22, 2012 at 11:47 AM Post #13 of 32


Quote:
eliasgwinn said:
Sorry I haven't responded sooner! Somehow I didn't get a notification of your posts.
 
khaos974's math is correct; the HPA2 (Benchmark's headphone amp circuit that's in several of our products) will have plenty of power to drive the HE-6's, according to their spec.
 
Keep in mind, we offer a 30-day trial when you buy directly from us.  So if you find it lacking in any way, you can simply return it for a full refund.
 
Best,
Elias
Click to expand...


Hi Elias,
 
I saw some people post in these forums that in order to drive the Hifiman HE-6 orthodynamic headphones, the internal jumpers of the headphone amp section need to be set to '0' attenuation (instead of -10 or -20).
 
Those people must have a newer version of the DAC1 (DAC1 HDR?), because I have the original DAC1 which doesn't have any decibel attenuation settings for the headphone amp section. There are internal jumpers relating to the XLR output attenuation, but not the headphone amp section.
 
Therefore, can the original DAC1 that I have put 1W per channel into 50ohm from the headphone output and drive the HE-6?
 
If so, what settings need I change from the default (if any?) for optimum performance?
 
Thanks for your time
 
Jan 23, 2012 at 6:24 PM Post #14 of 32
According to the documentation, the original DAC1 uses the HPA2 headphone amp (power specs should be the same as the HDR, which also uses the HPA2), and the fact that you have no jumpers simply means you're locked at the maximum gain setting (already set to 0 attenuation). According to this documentation, the HPA2 can deliver 1.26W @ 30 ohms, so it should have no problem delivering 1W @ 50 ohms.
 
Jan 24, 2012 at 2:35 AM Post #15 of 32
Hi, just asked Benchmark, this is what they said;
 
[size=11pt]The DAC1 should have absolutely no trouble driving the HE-6. It does not have the jumper settings of the HDR model and is equivalent to the HDR at '0dB". [/size]
[size=11pt] [/size][size=11pt]The HE-6 is 50 Ohms.  [/size][size=11pt] [/size]
[size=11pt]The HPA2 (in the DAC1) current limits at 0.8 A.  The maximum peak current that could be delivered to a 50-Ohm headphone given our 18 volt rails is about 15V/50Ohms = 0.3 Amps.[/size]
[size=11pt]Into a 50-Ohm load we can deliver more than 20 Vrms.  At 20 Vrms, the output level of the HE-6 will be an ear-splitting  122 dB on musical peaks.[/size]
 
[size=11pt]I hope this helps.[/size]
 
[size=11pt]Best regards,[/size]
 
[size=x-small]Rory Rall[/size]
[size=x-small]Sales Mgr.[/size]
[size=x-small]Benchmark Media Systems, Inc.[/size]
[size=x-small]203 E. Hampton Place, Ste 2[/size]
[size=x-small]Syracuse, NY 13206[/size]
[size=x-small]http://www.benchmarkmedia.com[/size]
[size=x-small]800-262-4675[/size]
[size=x-small]fax 315-437-8119[/size]
 
[size=x-small]Does their math seem to add up?[/size]
 
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