Originally Posted by audioengr /img/forum/go_quote.gif If you come to the Head-Fi meet in San Jose you can hear for yourself. I can give you technical explanations about the improvements in person and you can listen to the modded DAC-1. You can hear my new headphone amp mod for it.
I am too far away (other side of the world) to take up the Empirical audio offer of listening to the modded DAC1 - I would be interested in what people think though. Again, blind tests are a must. It is pretty easy to hear a qualitative difference when someone is standing there coaching you to hear it (by this I mean we tend to 'hear' differences that are not there). The other thing you need to do to convince is run the stats: get 10 to 20 people to do a double blind AB comparison with the same music and see if we get something significantly (in probability) different from a 50-50 split. I would almost bet a body part that this is not going to happen though.
Suggested experimental design:
Because we are in Headphones the 'double' part of the blind is easily cheated - just get the listener to face away from the source controller.
Switch between sources in some non-standard way. For example start with A for 3 minutes then reset the track and hit them with A again. Restart the track then hit em with B. Continue like this so that over 6 or eight changes there is 3 of each source: eg AABABB. The listener is simply asked to state whether the source he/she hears after the breaks (when we reset the track) is an improvement on the previous source. This will provide clear and convincing data.
If any doubt arises from the results it could be repeated with different music etc..
Originally Posted by boggle /img/forum/go_quote.gif I am too far away (other side of the world) to take up the Empirical audio offer of listening to the modded DAC1 - I would be interested in what people think though. Again, blind tests are a must. It is pretty easy to hear a qualitative difference when someone is standing there coaching you to hear it (by this I mean we tend to 'hear' differences that are not there). The other thing you need to do to convince is run the stats: get 10 to 20 people to do a double blind AB comparison with the same music and see if we get something significantly (in probability) different from a 50-50 split. I would almost bet a body part that this is not going to happen though.
Suggested experimental design:
Because we are in Headphones the 'double' part of the blind is easily cheated - just get the listener to face away from the source controller.
Switch between sources in some non-standard way. For example start with A for 3 minutes then reset the track and hit them with A again. Restart the track then hit em with B. Continue like this so that over 6 or eight changes there is 3 of each source: eg AABABB. The listener is simply asked to state whether the source he/she hears after the breaks (when we reset the track) is an improvement on the previous source. This will provide clear and convincing data.
If any doubt arises from the results it could be repeated with different music etc..
I'd like to compare the Stock/modded DAC1 with my DVD player & songs I know inside & out..Yes, I need a better CD player..
Originally Posted by EliasGwinn /img/forum/go_quote.gif OPA627 vs. NE5532:
The OPA627 will offer no advantage over the NE5532 in this application. High-frequency THD+N may actually be slightly higher with the OPA627. We are using the new LM4562A in the DAC1 USB. The LM4562A is pin-compatible with the NE5532, but you can't just drop it in and get all of the advantages of the DAC1 USB. We changed all of the resistors in the XLR output pads to take advantage of the high drive capability of the LM4562A."
Pay particular attention to items B and D in the list above. The modified units we have seen have incorrect capacitor values substituted for the original parts. Substituting incorrect capacitor values will result in serious deficiencies in sound field accuracy and also freq response accuracy.
Thanks,
Elias
Well shucks.....I've been completely satisfied with my stock DAC1 (it's great as it is, so why mess with perfection?). But now I'm wondering what the sonic differences are between the original DAC1 and DAC1 USB, if you guys changed op amps and redesigned the outputs. I don't use a computer as transport, so I didn't even think about considering the DAC1 USB. If it also offers improved audio for the digital audio inputs, I might just have to keep my eye on this
Originally Posted by Davesrose /img/forum/go_quote.gif Well shucks.....I've been completely satisfied with my stock DAC1 (it's great as it is, so why mess with perfection?). But now I'm wondering what the sonic differences are between the original DAC1 and DAC1 USB, if you guys changed op amps and redesigned the outputs. I don't use a computer as transport, so I didn't even think about considering the DAC1 USB. If it also offers improved audio for the digital audio inputs, I might just have to keep my eye on this
Originally Posted by EliasGwinn /img/forum/go_quote.gif We are using the new LM4562A in the DAC1 USB. The LM4562A is pin-compatible with the NE5532, but you can't just drop it in and get all of the advantages of the DAC1 USB. We changed all of the resistors in the XLR output pads to take advantage of the high drive capability of the LM4562A."
THAT IMO is huge news. LM4562 is capable of 45 mA current output and is National's newest breed of op-amps vs. NE5532, which is an ancient standard in comparison.
USB or not, it seems I need to do some comparisons between DAC-1 and DAC-1 USB
Originally Posted by Jon L /img/forum/go_quote.gif THAT IMO is huge news. LM4562 is capable of 45 mA current output and is National's newest breed of op-amps vs. NE5532, which is an ancient standard in comparison.
USB or not, it seems I need to do some comparisons between DAC-1 and DAC-1 USB
So it sounds like the DAC1 USB might perform better when used as a balanced headphone amp, as compared to the standard DAC1...
Originally Posted by EliasGwinn /img/forum/go_quote.gif If you are considering having your DAC1 modified, please read Benchmark's official statement regarding modifications to Benchmark products (copied directly from Benchmark DAC1 USB manual, page 2 - http://www.benchmarkmedia.com/manual...USB_Manual.pdf ):
Benchmark’s official statement regarding modifications:
"CAUTION: DO NOT SUBSTITUTE PARTS OR MAKE ANY MODIFICATIONS WITHOUT THE WRITTEN APPROVAL OF BENCHMARK MEDIA SYSTEMS, INC. MODIFICATION MAY CREATE SAFETY HAZARDS AND VOID THE WARRANTY.
NOTICE: CHANGES OR MODIFICATIONS NOT EXPRESSLY APPROVED BY BENCHMARK MEDIA SYSTEMS COULD VOID THE USER'S AUTHORITY TO OPERATE THE EQUIPMENT UNDER FCC REGULATIONS."
John Siau, the director of engineering, and chief designer of the DAC1, has addressed this, so I will copy his response here.
John Siau: "I have not seen, measured, or listened to a modification that I would recommend. Modified units usually perform more poorly. We have measured modified units and have found the following problems:
a) Distortion due to opamp substitutions
b) Phase errors between channels due to capacitor changes
c) UltraLock(tm) rendered non-functional due to IC change
d) Frequency response problems due to substitution of incorrect capacitor values.
We have fixed several modified units at customer expense after they failed. This has given us the opportunity to measure the performance and inspect the workmanship. In all cases the performance was degraded. In all of these RMA cases, the modifications caused failure of the product. I do not recommend the services of modifiers. We had good reasons for using the parts that we used. Our reasons had everything to do with performance and nothing to do with cost.
OPA627 vs. NE5532:
The OPA627 will offer no advantage over the NE5532 in this application. High-frequency THD+N may actually be slightly higher with the OPA627. We are using the new LM4562A in the DAC1 USB. The LM4562A is pin-compatible with the NE5532, but you can't just drop it in and get all of the advantages of the DAC1 USB. We changed all of the resistors in the XLR output pads to take advantage of the high drive capability of the LM4562A."
Pay particular attention to items B and D in the list above. The modified units we have seen have incorrect capacitor values substituted for the original parts. Substituting incorrect capacitor values will result in serious deficiencies in sound field accuracy and also freq response accuracy.
Thanks,
Elias
To my knowledge, an Empirical Audio modded DAC-1 has never been repaired by anyone but Empirical Audio. The only record I have of ANY repair is one where the customer twisted some heavy IC's on and off, breaking the ground connection to the circuit-board at the RCA jacks.
The mods that we do here at Empirical Audio attempt to put the DAC-1 at the top of the price-performance curve knee, competing with DAC's in the $10-15K range. The stock DAC-1 is an excellent value IMO, and as I have heard the USB version in my reference system as well, I feel that it is definitely better than the non-USB version. It is one DAC that I can listen-to, even unmodded.
Steve, maybe you should send one of your modded units to Elias and John Siau
I've been following this thread with great interest. Some of the more technical stuff is beyond me, but interesting to read nonetheless. I wouldn't mind having brushed metal silver DAC1 USB on my desk... Ah, the limitations of student life
Originally Posted by kool bubba ice /img/forum/go_quote.gif Yeah.. I'd love to see how far 500 could take me with your mods..
I guarantee it'll make your wallet lighter by $500 dollars. If it ain't broke, don't break it. Just put it through an amp of choice and leave the DAC1 pristine for the day when you want to go back to hear what accuracy sounds like.
Originally Posted by lowmagnet /img/forum/go_quote.gif I guarantee it'll make your wallet lighter by $500 dollars. If it ain't broke, don't break it. Just put it through an amp of choice and leave the DAC1 pristine for the day when you want to go back to hear what accuracy sounds like.
I feel you..I'm just never satisfied..I have yet to reach the point where my ears tell me, ok, this is when I stop..Ofcourse, I'm not made out of money either.. The search is on a budget.. I'd like to get as close as possible..
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