How good and powerful is the internal headphone amp on Benchmark DAC1?

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.

Check this thread:

http://www.head-fi.org/t/265737/headphone-amp-for-benchmark-dac1

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

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.

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

I am Benchmark's applications engineer.  Let me know if I can answer any questions.

Best,

Elias

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

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

Why would you think the amp would damage itself driving low impedance loads?

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.