Latest Thread Images

Featured Sponsor Listings

Benchmark DAC1 now available with USB

Apr 3, 2007 at 7:27 PM Post #257 of 3,058
Elias, I've been using my DAC1-USB for a while now. It's great. I must be using really efficient headphones, though, because with the unit in its stock state and Itunes volume turned to max as recommended, I can only have the volume control to about the 4th detent, 3d detent with louder CDs. This is with Shure E500 'phones. When I use the DAC1 as a pre-amp for the stereo, I get the normal position of around 11 o'clock. Which makes me wonder what I'm doing to the E500s when I forget to unplug them...
 
Apr 3, 2007 at 7:35 PM Post #258 of 3,058
Elias's computer must be in some sort of loop! A quadruple so far.
wink.gif
 
Apr 3, 2007 at 9:44 PM Post #260 of 3,058
Elias,

Well, this thread got me -- just ordered the USB DAC1 from Benchmark.

Two questions. Can you suggest settings for J River Media Center? This is my playback software of choice.

Also, what is the max safe distance for a USB cable run?
 
Apr 4, 2007 at 5:21 AM Post #262 of 3,058
I just got my DAC1 USB delivered today. Sounds great -- I'm burning it in as we speak.

I'd just like to say how silly I think it is that the DAC1 USB is limited to the USB 1.1 spec. What person connects a $1300 device to a computer that is so old it doesn't have USB 2.0? And even assuming a pre-2003 computer, it's cheap and easy to add USB 2.0 to it, and it's backwards compatible anyway, so they could always use it at 1.1 speeds which supports 96/24 processing. Who in the world processes 192/24 audio on a PC without USB 2.0 capability? Unless there is a technical reason I'm not aware of, this was a silly design decision -- fortunately one of extremely few on this miraculous device! The explanation on Benchmark's website simply makes reference to the wide adoption of USB 1.1 computers. This is not compelling. The DAC is capable of 192/24 resolution, yet we're only hampered when using the one connection that is unique to this updated -- and more expensive -- device. Not good.

I'm very curious to know why.
 
Apr 4, 2007 at 3:20 PM Post #263 of 3,058
Quote:

Originally Posted by schaqfu
...how silly I think it is that the DAC1 USB is limited to the USB 1.1 spec.

What person connects a $1300 device to a computer that is so old it doesn't have USB 2.0?

The DAC is capable of 192/24 resolution, yet we're only hampered when using the one connection that is unique to this updated -- and more expensive -- device.

I'm very curious to know why?


This occurred to me as well. The beauty of this DAC is the ability to transparently stream our lossless music files via USB sans custom driver, one of a kind. I also can't imagine anyone who would buy this device for this specific purpose would have only USB 1.1. Certainly the folks who will use this in the studio will not. Heck, my PC is from 2000 (yeah I know, but I'm on a budget) and yet I put a USB 2.0 PCI card into it. In fact, if I were to purchase this DAC, it's primary use would be via USB. It would be great (OK, WAY beyond great) if we could utilize the full 24/192 capabilities via USB (hint, hint,
wink.gif
)

<dream sequence starting>
Ahhh! Lossless FLAC files streaming via USB 2.0 to my DAC 1 USB and then out to my new active studio monitors (else insert favorite headphones +/- headphone amp here) in full 24/192! Nirvana found?
<dream sequence ending>

1. Curious as to whether the PCB and other circuitry would allow for easy upgrade to 2.0?

2. If the 2.0 upgrade is possible, would it still require no custom drivers?

Thanks! Hope you feel well rested after the dream sequence, now BACK TO WORK!
 
Apr 4, 2007 at 4:16 PM Post #265 of 3,058
A couple of things worth mentioning...

1) The DAC1 resamples to 110 KHz. Even though it accepts 192 KHz music, it still resamples it to 110 KHz.

2) There are cheap USB audio ICs available at the moment that just happen to support 24/96. One of these is probably being used for USB input in the new DAC1. Using one of these ICs (integrated circuits) takes a lot of work and hassle out of designing the USB audio input. It is possible to make it support 24/192 over USB 2.0 but this will require a lot more effort and the learning curve is steeper.

If there was a USB 2.0 audio chip available that supported 24/192, then benchmark would probably have used that one instead. But I'm guessing that the benchmark engineers don't know how to implement a USB 2.0 solution. Unless they are just trying to save money which is ok.




Information about the sample rate converter in the DAC1 is HERE.
Quote:

At the heart of the DAC1 are Analog Devices AD1853 DACs operating at a sampling rate of 110kHz. I talked to Allen H. Burdick, president of Benchmark Media, about the internal operation of the DAC1 and the decision to settle on the 110kHz sampling rate. According to Burdick, all incoming signals are brought to that sampling rate by using an Analog Devices AD1896 sample-rate converter. He says that operating at that rate offers a "20dB filter-performance improvement" with the AD1853 DAC chip over a higher sampling rate such as 192kHz. The tradeoff, he says, is reduced analog bandwidth -- down to 55kHz versus 96kHz. However, he feels that very little musical information resides that high anyway, and the improved filter performance achieved offsets that 41kHz loss in bandwidth. The DAC1 can accept digital input of signals up to 24 bits and 192kHz sampling rate.


 
Apr 4, 2007 at 4:17 PM Post #266 of 3,058
Quote:

Originally Posted by Jetlag /img/forum/go_quote.gif
This is probably a stupid question, but, the DAC 1 USB does 192/24 via the three other inputs (SPDIF/AES, AES, Toslink) and is only limited to 96/24 via USB, correct? This limit is due to the USB 1.1 specification, also correct?

Thanks


This is correct.

All digital inputs can handle sample-rates up to 195 kHz, except the USB input, which can handle sample-rates up to 96 kHz. This is a limitation imposed by the USB 1.1 specification.

Thanks,
Elias
 
Apr 4, 2007 at 4:57 PM Post #267 of 3,058
Quote:

Originally Posted by Lord Chaos /img/forum/go_quote.gif
Elias, I've been using my DAC1-USB for a while now. It's great. I must be using really efficient headphones, though, because with the unit in its stock state and Itunes volume turned to max as recommended, I can only have the volume control to about the 4th detent, 3d detent with louder CDs. This is with Shure E500 'phones. When I use the DAC1 as a pre-amp for the stereo, I get the normal position of around 11 o'clock. Which makes me wonder what I'm doing to the E500s when I forget to unplug them...


If you use the headphone input to the left (the one closest to the input switch and LED's; furthest from the volume knob), the rear outputs will be muted until you remove the headphone plug. This will remind you to remove the headphones when you're using the main outputs.

There is also a 10 dB pad for the headphones so that you can turn the volume knob up further. It should have shipped with these pad's inserted, but you can open the DAC1 USB's chassis to check. If you want to do this, I can step through it with you.

Thanks,
Elias
 
Apr 4, 2007 at 5:15 PM Post #268 of 3,058
Quote:

Originally Posted by gregeas /img/forum/go_quote.gif
Elias,

Well, this thread got me -- just ordered the USB DAC1 from Benchmark.

Two questions. Can you suggest settings for J River Media Center? This is my playback software of choice.

Also, what is the max safe distance for a USB cable run?


Gregeas,

I'm glad I could help you in your decision. Keep in touch...let me know what you think of it.

As for J River, I have not tested it yet (or even used it at all). I will try to do it soon so that I can help you, but there are a few things that are generally a good idea with any media player.

1. If there is a setting for sample-rate, be sure it matches the sample-rate of the audio you are playing.

2. If there is a 'word-length' setting (aka 'bit-depth', aka 'size'), it should be set to 24-bit, regardless of the word-length of the audio you are playing

3. Keep all audio processors off, where possible. This includes any EQ's, 'Sound Enhancers', Surround processors, Bass Boost, etc.

4. Keep volume at 100%. Some players have better volume controls then others. As I haven't tested J River, I would recommend keeping the volume at 100%. In fact, the only player I've found to have a properly-designed volume control is Windows Media Player. Also, the Windows Volume Mixer (the system control, unrelated to a specific player) is a properly-designed volume control. Therefore, if you need PC control of volume, I recommend using this.

As for USB cable length, Wikipedia says the max length is 5 meters.

Thanks,
Elias
 
Apr 4, 2007 at 5:48 PM Post #269 of 3,058
Quote:

Originally Posted by schaqfu /img/forum/go_quote.gif
I just got my DAC1 USB delivered today. Sounds great -- I'm burning it in as we speak.

I'd just like to say how silly I think it is that the DAC1 USB is limited to the USB 1.1 spec. What person connects a $1300 device to a computer that is so old it doesn't have USB 2.0? And even assuming a pre-2003 computer, it's cheap and easy to add USB 2.0 to it, and it's backwards compatible anyway, so they could always use it at 1.1 speeds which supports 96/24 processing. Who in the world processes 192/24 audio on a PC without USB 2.0 capability? Unless there is a technical reason I'm not aware of, this was a silly design decision -- fortunately one of extremely few on this miraculous device! The explanation on Benchmark's website simply makes reference to the wide adoption of USB 1.1 computers. This is not compelling. The DAC is capable of 192/24 resolution, yet we're only hampered when using the one connection that is unique to this updated -- and more expensive -- device. Not good.

I'm very curious to know why.


You're argument is valid. It is something we considered, and it was not an easy decision. We appreciate your input, however.

Thanks,
Elias
 
Apr 4, 2007 at 6:17 PM Post #270 of 3,058
Quote:

Originally Posted by Dave_M /img/forum/go_quote.gif
2) There are cheap USB audio ICs available at the moment that just happen to support 24/96. One of these is probably being used for USB input in the new DAC1. Using one of these ICs (integrated circuits) takes a lot of work and hassle out of designing the USB audio input. It is possible to make it support 24/192 over USB 2.0 but this will require a lot more effort and the learning curve is steeper.

If there was a USB 2.0 audio chip available that supported 24/192, then benchmark would probably have used that one instead. But I'm guessing that the benchmark engineers don't know how to implement a USB 2.0 solution. Unless they are just trying to save money which is ok.


This is partly accurate. Let me clarify...

The price of USB 2.0 chips was not a factor. However, there are no USB 2.0 chips available that support native USB audio. So, one of the trade-off's of using USB 2.0 is the necessity of a custom driver. As I've elaborated before, we tested several other (3rd party) USB audio devices that use custom drivers, and the results were not positive. In fact, throughout our testing, the only devices that achieved bit-transparency were native devices (devices which do not need custom drivers).

Also, custom drivers often cause conflicts with other drivers. Even if the driver is designed well, another driver may not 'get along' with it. Using the native drivers (which are inherently installed with the operating system) gives you the guarantee that, if a 3rd party driver ever worked on these computers, they will work with the DAC1 USB running.

Another point you made is accurate, and partly affected our decision. That is, it would have taken longer to develop a USB 2.0 device. This wasn't an issue about saving money as much as getting the product to market as soon as possible. If the other factors weren't already weighing against a USB 2.0 solution, we may have decided it was worth waiting to release this product until a USB 2.0 solution was developed.

However, the decision was primarily based on the design goal of a native, bit-transparent USB audio solution.
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 2 (members: 0, guests: 2)
Back
Top