[Ooztuncer]

Hello,
I am the new member to DAC1 family and i have two quick questions:

1) Is there a difference between January 2003 built DAC1 and the current version, except the USB input? I bought my DAC1 this morning from one of the recording studios and the owner remembers that it was updated at least once by Benchmark. Is there a way to learn what has changed/serviced? He thinks that the variable-level-pot was updated but he is not sure. I have the serial number but no build date sticker.

2) I am waiting to go home and put this puppy into action. I read somewhere in this thread that some people prefers to set XLR output attenuation jumper to 0db (rather than -20db by default). According to my manual it is already at 0db by factory default - am I wrong?

Thanks!
Onur

 

[EliasGwinn]

Quote:

Originally Posted by Ooztuncer /img/forum/go_quote.gif Hello, I am the new member to DAC1 family and i have two quick questions:

Hello Onur, welcome to the DAC1 Family!

Quote:

Originally Posted by Ooztuncer /img/forum/go_quote.gif Hello, 1) Is there a difference between January 2003 built DAC1 and the current version, except the USB input? I bought my DAC1 this morning from one of the recording studios and the owner remembers that it was updated at least once by Benchmark. Is there a way to learn what has changed/serviced? He thinks that the variable-level-pot was updated but he is not sure. I have the serial number but no built date sticker.

Since January 2003, there have been several revisions to the DAC1.

In May 2003, the XLR output attenuators were added.

In November 2004:
- the RCA output impedance was changed from 1.5 k-ohm to 30 ohms
- the optical input was upgraded to operate at 192 kHz
- the DC offset was reduced, and a detented volume control was used
- a trim-pot was added to properly balance between channels.

Quote:

Originally Posted by Ooztuncer /img/forum/go_quote.gif 2) I am waiting to go home and put this puppy into action. I read somewhere in this thread that some people prefers to set XLR output attenuation jumper to 0db (rather than -20db by default). According to my manual it is already at 0db by factory default - am I wrong?

I'm not totally sure if your DAC1 has output attenuators. Also, when you buy a DAC1 used, there is no way to know what the attenuators are set to without opening the chassis and looking (unless you want to measure the output voltage with a known digital input).

However, you can determine whether the attenuators are set properly for your system without opening the chassis. Here's how:

Before you turn your amplifier on, make sure the volume control of the DAC1 is all the way down, and make sure the DAC1 is in "Variable" mode (see the switch on the back panel). After you do this, turn on the amplifier and begin streaming digital music to the DAC1. Slowly bring up the volume until you reach a comfortable level. If this level is not achieved within the volume control range of 10 and 5 o'clock, the output attenuators should be adjusted.

To determine the how to correctly set your attenuators for optimum sonic quality, I suggest reading this article about setting the output attenuators.

Thanks,
Elias

 

[mofonyx]

I haved asked this before, but I would just like to make sure.

I know it's all right to leave the Benchmark DAC-1 turned on (because there is no "off" switch).

But is it okay to leave it on with the volume knob turned on to my listening level and with my headphones plugged in all the time? Or would it be better to turn the volume knob to minimum when I put my headphones down?

Also,
Quote:

Originally Posted by EliasGwinn The DC offset on the DAC1's output is +/- 5 mV, depending on gain setting.

What do you mean by "gain setting" - Is it Variable, Calibrated and Default? and how much will the DC offset vary with different gain settings?

Thanks again.

 

[EliasGwinn]

Quote:

Originally Posted by mofonyx /img/forum/go_quote.gif I know it's all right to leave the Benchmark DAC-1 turned on (because there is no "off" switch). But is it okay to leave it on with the volume knob turned on to my listening level and with my headphones plugged in all the time? Or would it be better to turn the volume knob to minimum when I put my headphones down?

It will not hurt the DAC1 at all. You may want to contact your headphone manufacturer if there are concerns about having constant audio through your headphones.

Quote:

Originally Posted by mofonyx /img/forum/go_quote.gif What do you mean by "gain setting" - Is it Variable, Calibrated and Default? and how much will the DC offset vary with different gain settings?

In other words, the DC offset will vary based on the gain settings of the volume control, trim-pots and/or attenuators. The higher the gain setting, the higher the DC offset. It will vary no more then 8mV.

Thanks,
Elias

 

[mofonyx]

Thanks for the quick reply Elias..

 

[little-endian]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif The dynamic range of the DAC1 is 116 dB.

Interesting. So the dynamic range equals the signal to noise ratio. Because in most other systems, these two values often differ a bit.

Actually, I always thought that the noise would limit the dynamic range per se but according to Bob Katz, the dynamic range can be even higher than the signal to noise ratio in dithered systems (~ 115 dB dynamic range while < 91 dB SNR on a properly dithered audio-cd for instance).

At least, there seems to be no DAC available at all which would reach the theoretical limit of 144 dB for 24-bit-audio. I'm very sure that even the dynamic range of 16-bit-audio is enough in most listening situations but a bit funny if one recognizes all the "24 bit" here and there advertisement if even the finest equipment seems to not be able to catch up.

 

[mofonyx]

Quote:

Originally Posted by little-endian /img/forum/go_quote.gif Interesting. So the dynamic range equals the signal to noise ratio. Because in most other systems, these two values often differ a bit.

I believe that's just a coincidence.

 

[xenithon]

Hi all. I have a quick question regarding the XLR output attenuation jumpers...

...the DAC1 will be used with output set to "calibrated" and directly feeding an amplifier. I read that the default/factory setting is -20dB for the XLR output; adjustable via the jumpers. I have read though that the performance/quality is much better when these jumpers are set to 0dB (in the manual it says 0dB = attenuator disabled).

Has anyone tried this? Would you agree? Is there anything wrong or potentially harmful about using it like this? Everything else would be left at stock/factory settings.

EDIT: just to add, it would be feeding a Stax SRM-717 energizer. Not sure if, or which specs would affect this, but what I know off hand is
- Gain :60dB
- Rated Input Level :100mV (with 100V output)
- Input Impedance :50Kohm (RCA), 50kohm x 2 (XLR)

 

[EliasGwinn]

Quote:

Originally Posted by little-endian /img/forum/go_quote.gif Interesting. So the dynamic range equals the signal to noise ratio. Because in most other systems, these two values often differ a bit.... ...

The dynamic range and signal-to-noise ratio of the DAC1 are both determined by the D/A chip used (AD1853).

Thanks,
Elias

 

[EliasGwinn]

Quote:

Originally Posted by xenithon /img/forum/go_quote.gif Hi all. I have a quick question regarding the XLR output attenuation jumpers... ...the DAC1 will be used with output set to "calibrated" and directly feeding an amplifier. I read that the default/factory setting is -20dB for the XLR output; adjustable via the jumpers. I have read though that the performance/quality is much better when these jumpers are set to 0dB (in the manual it says 0dB = attenuator disabled). Has anyone tried this? Would you agree? Is there anything wrong or potentially harmful about using it like this? Everything else would be left at stock/factory settings. EDIT: just to add, it would be feeding a Stax SRM-717 energizer. Not sure if, or which specs would affect this, but what I know off hand is - Gain :60dB - Rated Input Level :100mV (with 100V output) - Input Impedance :50Kohm (RCA), 50kohm x 2 (XLR)

xenithon,

The October edition of our "Feedback Newsletter" had a detailed article about the optimal attenuator settings for a system.

From the spec's that you've listed, you will get significant clipping if you operate in Calibrated mode with 0 dB attenuation. The average level from the DAC1 with those settings is 1.22 Vrms, or about 12x the rated input level of the Stax.

If you read the article in that link, you'll know everything you need to know to properly configure your system. And if you have any questions, please feel free to ask!!

Thanks,
Elias

 

[xenithon]

Hi Elias. Thanks for the link and the info about the average output level. I will certainly follow that procedure in the newsletter to try and find the optimal attenuator settings.

What I am a little confused about though is that my previous DAC, the Musical Fidelity X-DAC V3, has a rated output of 2.2VRMS, and worked fine with the SRM-717 with no clipping.

Admittedly though, perhaps all the exact specs would explain why this was so:
- Output at 0dB level: 2.2VRMS at 1kHz nominal
- Output impedance: 50 Ohms

Looking purely at the specs as per the newsletter, is there an attenuation setting which appears to be - at least on paper - ideal to match the Stax's specs?

Thanks and have a great new year Elias!
X

 

[kool bubba ice]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif Terje, The DAC1 is compatible with any 2-channel PCM data. Therefore, if a DVD video (or DVD audio or BlueRay or HD-DVD) is formated with 2-channel PCM audio, the DAC1 will convert it properly. Also, even if the audio on a disc is not PCM format, many DVD players will convert the audio to PCM. Thanks, Elias

So The DAC1 can support 2 channel Uncompressed PCM to take advantage of Blu Rays audio? Or Dolby HD? Or would I need a HDMI device, as I been told, next gen audio HD/BR needs more bandwidth that optical/coaxial doesn't have..

 

[infinitesymphony]

Quote:

Originally Posted by kool bubba ice /img/forum/go_quote.gif So The DAC1 can support 2 channel Uncompressed PCM to take advantage of Blu Rays audio? Or Dolby HD? Or would I need a HDMI device, as I been told, next gen audio HD/BR needs more bandwidth that optical/coaxial doesn't have..

Coaxial can support up to 24-bit/192 kHz two-channel audio (and some people have found optical to work at that rate, too). However, transmitting 5.1+ channels of uncompressed 24/192 content requires a higher bandwidth than S/PDIF. But, as long as the player can downmix to two-channel, or the media you're using has a stereo track, you can use it with a stereo DAC like the DAC1.

Edit: Except with the new HD formats, there are restrictions that prevent the signal from being digitally output over S/PDIF. So, the DAC1 can play 24/192 uncompressed PCM, but it will be almost impossible to find a player capable of outputting that information.

 

[riverlethe]

Elias,
I noticed the new DAC1/HD650 package and I'm curious as to why the HD650 was chosen. Have you performed any frequency response tests with various headphones?

 

[EliasGwinn]

Quote:

Originally Posted by xenithon /img/forum/go_quote.gif Hi Elias. Thanks for the link and the info about the average output level. I will certainly follow that procedure in the newsletter to try and find the optimal attenuator settings. What I am a little confused about though is that my previous DAC, the Musical Fidelity X-DAC V3, has a rated output of 2.2VRMS, and worked fine with the SRM-717 with no clipping. Admittedly though, perhaps all the exact specs would explain why this was so: - Output at 0dB level: 2.2VRMS at 1kHz nominal - Output impedance: 50 Ohms Looking purely at the specs as per the newsletter, is there an attenuation setting which appears to be - at least on paper - ideal to match the Stax's specs? Thanks and have a great new year Elias! X

Hello X,

What makes this assessment difficult is that different manufacturers use different methods for listing specs. When the amp says "Rated Input Level", does that mean it is the input level at which the THD+N spec was measured? Or is it the highest input level before the THD+N rises above a certain threshold?

You will probably want to contact the manufacturers to find out what the maximum input level is. But, at the end of the day, you will want to feed your amp only as much as needed to create the volume output desired for comfortable listening levels. That's what we are talking about in the article from the newsletter. The important thing is to make sure the volume control of the DAC1 is in its optimal range, and then you will get the best results.

Thanks,
Elias

ps. sorry it has taken so long to respond....we're preparing for T.H.E. and NAMM and its C.R.A.Z.Y. around here!!