# Art USB dual pre calibration



## Luca61 (Feb 16, 2012)

I swear I searched the forum, but could not find an answer. :innocent: I believe I am close, just need a little nudge in the right direction. 

I have an Art USB dual pre connected to a laptop (windows 7 ult. x64). The Art pre is powered by a 9v battery (no AC adapter was included), which prompts my first question: is this OK or I need a power adapter?

I am trying to calibrate the sound card. Upon connecting the art pre to the laptop via the USB cable, drivers got automatically installed, no problem there.

I looped the left output to the left input using a mono 1/4" jack both ends (male-male) cable.
These are the setting on the pre:

- none of the 2 on/off switches are pressed, though the left switch lights up upon connecting the USB cable
- the Left 'monitor' knob is turned all the way towards 'computer'; the Right knob set to to 0
- the Left input knob is what I am using to set the cal. level; Right input knob set to 0

Windows sounds setting:

- Default playback device is set to USB codec (speakers), sampling 16bit/48k, level 100%
- Default recording device is set to USB codec microphone, sampling 16bit/48k, level 100%
- 'Enhancements' are disabled for both playback and mic

REW settings:

Java drivers. 48k. sweep level -12dB. Output USB codec (speakers). Input USB codec (mic). Imput channel Left

I thenb click 'calibrate', next, next - 1KHz tone starts:

The *Out* REW bar gets to -12dB
The *In* bar gets to -30db at most (left gain turned all the way up). If I raise both the output volume and the input volume to 1, I gain a few more dB, but still a long way from getting with 6db of the output level.

Now the strange part. If I turn the Right 'monitor' knob even a tiny bit up, all of a sudden plenty of signal shows on the 'In' bar, but the resulting generated measurement is noisy.

I don't understand what's going on. Why does the position of the Right monitor knob affect the signal, and why the signal level is too low in the first place?

I am sure I am doing something silly... Are my connection correct? Do I need to connect the mic during calibration?


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## JohnM (Apr 11, 2006)

This post may help: http://www.hometheatershack.com/forums/rew-forum/56379-getting-started-art-usb-dual-pre.html


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## Luca61 (Feb 16, 2012)

JohnM said:


> This post may help: http://www.hometheatershack.com/forums/rew-forum/56379-getting-started-art-usb-dual-pre.html


Hi John, thanks for replying. From the post you linked, I think I was using the wrong cable for the loop. The recommended cable is this:

http://www.monoprice.com/products/p...=10244&cs_id=1024402&p_id=4759&seq=1&format=2 

The 1/4 inch TRS connector looks like stereo one, while I was using a mono 1/4 inch cable. Is this it? Would a 1/4 TRS 'stereo' at both ends work (in case I can't find the TRS to XLR cable locally)?

Luca


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## EarlK (Jan 1, 2010)

Luca61 said:


> <<<<<snip>>>>>Now the strange part. If I turn the Right 'monitor' knob even a tiny bit up, all of a sudden plenty of signal shows on the 'In' bar, but the resulting generated measurement is noisy.
> 
> I don't understand what's going on. Why does the position of the Right monitor knob affect the signal, and why the signal level is too low in the first place?
> 
> I am sure I am doing something silly... Are my connection correct? Do I need to connect the mic during calibration?


I'm guessing that your Win7 sound control panel is still set to "Factory Default";

- Meaning, Win7 ships setup to record in mono ( from the left channel input & that signal is then sent to both channels ) . 
- "Listen to this device" must remain also unchecked .
- With "Listen to this device" still checked ( & an out of phase loopback cable ), turning that right knob might just explain those bizarre symptoms ( by unbalancing an inherently unstable situation due to the addition of in-phase noise through cross-talk ) .


















Make sure your loopback cable isn't somehow contructed wrong ( look at the color coding of the wires by screwing off the covers & determine it's consistent between the two ends / or use a multimeter if you have one ) .

If none of this applies , then it's a mystery to me what your problem is .:scratch:





> Would a 1/4 TRS 'stereo' at both ends work (in case I can't find the TRS to XLR cable locally)?


Yes, that'll work .

:sn:

PS : that soundcard should work just fine powered off the USB buss ( to check, simply remove the battery ) .


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## Luca61 (Feb 16, 2012)

EarlK said:


> I'm guessing that your Win7 sound control panel is still set to "Factory Default";
> 
> - Meaning, Win7 ships setup to record in mono ( from the left channel input & that signal is then sent to both channels ) .
> - "Listen to this device" must remain also unchecked .
> ...


Earl, thanks for your detailed reply. I went out and bought the 'proper' TRS to XLR (male) cable, but it did not make any difference in what I was seeing before. The win 7 settings are as you posted: the mic is setup for TWO channels 16bit/48000 (though I admit I tried 1 channel as well), speakers at 16bit/48000. "Listen to this device" checkbox was always UNchecked.

May I have damaged the USB dual pre by using the wrong cable? Or I guess this could have been a defective unit all along... 

I am almost ready to give up. I am going to test it on my desktop, which has a decent separate sound card (asus xonar dsx), to see try to rule out the laptop as a possible cause.

[...]

Done. Same behavior with the soundcard connected to my desktop. With the left gain knob all the way up I get ~-32dB (20dB lower than out). If I turn even slightly the Right "monitor" knob, plenty of signal, but the result is too noisy (best I got was +/-7dB). I can even turn the Left gain knob to 0 and get plenty of signal just by turning the Right "monitor" knob.... :coocoo:

And you were right on the battery, I removed it (not easy, the receptacle is way too small) and did not make any difference: USB seems to be providing all the power needed. The cables _seem_ to be oof the hook to me, as I get the very same behavior with two different cables.

All this seems to point to a problem with my USB dual pre...? Is there a good, reliable external sound card I can get to replace it? It will need to have phantom power for my EMM-6 mic.

Luca


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## EarlK (Jan 1, 2010)

There's always the possibilty that you might have a bad soundcard ( hard to know due to your overall inexperience with these things ) .

If you need to replace it, this one gets good reviews around here ;



:sn:


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## Luca61 (Feb 16, 2012)

This morning I decided to give the Art dual pre a last shot. All I did was connecting the loop on the right channel, instead of the left one I was using before. 

Right away I was able to obtain a useful measurement (+0.2/-0.7dB). I repeated calibration with slightly different speakers and mic levels, same result: =0.2/-0.7dB. REW thinks this is sufficient to generate a calibration file.

All the controls on the USB dual pre were turned down, except for the "monitor" knob, which was used to match the out/in level.

As an aside, with the right channel connected, turning the "preamp/computer" knob had an effect on the Out level (it didn't before). During calibration, this knob was turned all the way towards "computer" (as before). On the windows and REW side, the only change was to switch the "input channel" to right channel.

The soundcard measurements looks OK, what do you think? Any idea about what was going on? :huh: 

Luca


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## EarlK (Jan 1, 2010)

Luca61 said:


> <<<<<<SNIP>>>>>>
> 
> The soundcard measurements looks OK, what do you think? Any idea about what was going on? :huh:
> 
> Luca


Glad it seems to be working now ! :clap:

Yep, that trace looks OK . :T

I really have no idea why this fumbled previously ( it's usually a case of "noobness" of some type , either a lack of familiarity with ones own hardware or the new software being presented ) . 

Sometimes hardware really is broken .:huh:

I don't really want to guess . :rubeyes:

:sn:


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