Ferbose
Headphoneus Supremus
- Joined
- Jun 27, 2004
- Posts
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Some head-fiers have reported that Benchmark DAC1's balanced (XLR) out can drive Senn 580/600/650 series headphones very well (DAC1 has preamp function so the volume knob controls XLR output level). I have to thank Neilpeart for discussions about using the XLR out as a headphone amp instead of the built-in headphone amp in DAC1.
DAC1 has one internal headphone amp driving two headphone jacks on the front panel. It uses NE5532 opamps to drive BUF634 output buffers. This is a very high current headphone amp capable of driving even the monstrous K1000 to a usable level. Neilpeart has commented that its quality is roughly equivalent to a basic PIMETA, which I have not heard personally.
The first question that comes to my mind of using XLR to drive headphones is whether it has enough current output. HD650 (300 ohm, 97 dB/mW) is a hard-to-drive headphone, but XLR drives it well. K501 (120 ohm, 94 dB/mW) is even harder to drive, current-wise. The XLR can output >20 dBu voltage, so the high voltage demand of high impedance phones is not a problem. The question is the current demand. Surprisingly, XLR also drives K501 very well, without signs of weak bass, compressed dynamics or clipping.
The second question is the damping factor. XLR output, when bridged to unbalanced mode, has 30 ohm impedance. For a 120 ohm load, the damping factor is only 4. After I look up the impedance curve of K501 on headroom.com, a simple calculation showed that the impedance bump of K501 is not large enough to alter the frequency response curve to any appreciable amount. In fact , XLR produces better bass response on K501 than the zero ohm headphone jack.
Based on these technical considerations and listening tests, I conclude that XLR out of DAC1 can drive almost all headphones satisfactorily except for the "super low efficiency" studio headphones. In fact, few headphones have higher current demands than K501. As for lower impedance (<120 ohm) phones like HD280, DT250, RS-1, ER-4P, CD3000 and SR-60, they all have pretty flat impedance curves so that low dmaping factor is not an issue. Taken together, I believe DAC1's XLR out will drive most of the high-end headphones commonly discussed here.
Next question is: how to drive headphones using XLR output?
IMO the easiest solution is to get these two adapters:
http://www.sweetwater.com/store/detail/GXF132/
http://www.sweetwater.com/store/detail/YMR197/
The first one is XLR to RCA adapter (pin2 to hot; pin1 and pin3 to ground). Neilpeart and I both connect the XLR pins to RCA this way and it seems to work fine, although another option is to leave pin3 floating.
The second adapter truns L/R RCA signal to a female 1/8 plug, making L/R channles share a common ground.
Sweetwater.com offers free shipping, so for $23 you can start using any headphone with a 1/8 plug with DAC1's XLR put.
So far I have established that most headphones out there can be easily used with XLR out of DAC1, what about the sonic benefits?
Neilpart and other Senn 6xx users have already said that DAC1's XLR sounds even better than its headphone jack. Is this a special case or a general rule?
After testing with K501 I would say that it is a general rule that XLR sounds better than headphone out on DAC1.
The sonic benefits of using the XLR reminds me very much of going from CD to SACD. The improvements are smoother highs with more airiness, more rounded transients with better rhythm, and stronger bass with less booming. In instrument terms this translates to a fuller and more resonant violin sound, a crisper piano sound with a more natural decay, and a faster drum sound with more impact. The difference is not huge, but quite noticeable. Going from headphone jack to XLR offers about 50% improvement compared to going from CD to SACD on my Sony player. I would personally call that s significant improvement.
Incidentally, Neilpeart and I both feel that lifting the safety ground prong of DAC1's powercord makes it sound better. I don't know if this becuase the safety ground of my house is not clean or something.
In conclusion, I think DAC1's XLR output drives headphones better than its headphone amp. Its headphone amp by itself is not bad either, but XLR is just a step up. Connecting DAC1 to Sonic Impact T-amp and speakers, I also feel XLR also sounds better than RCA out. Since XLR-to-RCA adapters are inexpensive, DAC owners ought to give it a shot.
DAC1 has one internal headphone amp driving two headphone jacks on the front panel. It uses NE5532 opamps to drive BUF634 output buffers. This is a very high current headphone amp capable of driving even the monstrous K1000 to a usable level. Neilpeart has commented that its quality is roughly equivalent to a basic PIMETA, which I have not heard personally.
The first question that comes to my mind of using XLR to drive headphones is whether it has enough current output. HD650 (300 ohm, 97 dB/mW) is a hard-to-drive headphone, but XLR drives it well. K501 (120 ohm, 94 dB/mW) is even harder to drive, current-wise. The XLR can output >20 dBu voltage, so the high voltage demand of high impedance phones is not a problem. The question is the current demand. Surprisingly, XLR also drives K501 very well, without signs of weak bass, compressed dynamics or clipping.
The second question is the damping factor. XLR output, when bridged to unbalanced mode, has 30 ohm impedance. For a 120 ohm load, the damping factor is only 4. After I look up the impedance curve of K501 on headroom.com, a simple calculation showed that the impedance bump of K501 is not large enough to alter the frequency response curve to any appreciable amount. In fact , XLR produces better bass response on K501 than the zero ohm headphone jack.
Based on these technical considerations and listening tests, I conclude that XLR out of DAC1 can drive almost all headphones satisfactorily except for the "super low efficiency" studio headphones. In fact, few headphones have higher current demands than K501. As for lower impedance (<120 ohm) phones like HD280, DT250, RS-1, ER-4P, CD3000 and SR-60, they all have pretty flat impedance curves so that low dmaping factor is not an issue. Taken together, I believe DAC1's XLR out will drive most of the high-end headphones commonly discussed here.
Next question is: how to drive headphones using XLR output?
IMO the easiest solution is to get these two adapters:
http://www.sweetwater.com/store/detail/GXF132/
http://www.sweetwater.com/store/detail/YMR197/
The first one is XLR to RCA adapter (pin2 to hot; pin1 and pin3 to ground). Neilpeart and I both connect the XLR pins to RCA this way and it seems to work fine, although another option is to leave pin3 floating.
The second adapter truns L/R RCA signal to a female 1/8 plug, making L/R channles share a common ground.
Sweetwater.com offers free shipping, so for $23 you can start using any headphone with a 1/8 plug with DAC1's XLR put.
So far I have established that most headphones out there can be easily used with XLR out of DAC1, what about the sonic benefits?
Neilpart and other Senn 6xx users have already said that DAC1's XLR sounds even better than its headphone jack. Is this a special case or a general rule?
After testing with K501 I would say that it is a general rule that XLR sounds better than headphone out on DAC1.
The sonic benefits of using the XLR reminds me very much of going from CD to SACD. The improvements are smoother highs with more airiness, more rounded transients with better rhythm, and stronger bass with less booming. In instrument terms this translates to a fuller and more resonant violin sound, a crisper piano sound with a more natural decay, and a faster drum sound with more impact. The difference is not huge, but quite noticeable. Going from headphone jack to XLR offers about 50% improvement compared to going from CD to SACD on my Sony player. I would personally call that s significant improvement.
Incidentally, Neilpeart and I both feel that lifting the safety ground prong of DAC1's powercord makes it sound better. I don't know if this becuase the safety ground of my house is not clean or something.
In conclusion, I think DAC1's XLR output drives headphones better than its headphone amp. Its headphone amp by itself is not bad either, but XLR is just a step up. Connecting DAC1 to Sonic Impact T-amp and speakers, I also feel XLR also sounds better than RCA out. Since XLR-to-RCA adapters are inexpensive, DAC owners ought to give it a shot.