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Discussion Starter · #1 ·
For those of us that use the ECM8000 microphone and a Behringer mixer/mic preamp to drive it, I see that Behringer has added the XENYX 802 to their lineup (with a $20 price increase - although I see it lots of places for $59.99).

The difference between it and the EURORACK UB802 appears to be an FX Send control for each channel and assignable CD/tape inputs have been incorporated for routing flexibility. Something we surely don't care too much about when we only use them around here for the microphone preamp.

The specs are quite good on these mixers. In fact they are an amazing device for the price.

Here's a picture of my UB802 with my ECM8000 microphone plugged directly into it. If you were too cheap to buy an XLR cable and tripod for your microphone, you could get away with this as a mic cable and stand alternative.


UB802mic.jpg


The one thing I have been meaning to do with my UB802 is to do a frequency response check. The specs say <10HZ - 150KHz within 1dB. Holy ****, that's good. Since there are some wacky guys around here that seem to want to check their response to 5Hz, I decided I should at least feed their insanity with a spec on how much their UB802's were losing at 5Hz. I particularily wanted to ensure myself that the three equalizer controls were indeed defeated as advertised when in their middle detent positions.....

It's quite easy with REW to check the frequency response of any device (including checking cables for those who want to check the effect of a long cable for example).

To do a response check you require your soundcard calibration file loaded and C-weight compensation and microphone cal disabled. Then if you run a cable from LINE_IN to LINE_OUT and do a Measurement Sweep from 5Hz to 20000Hz, you should get a perfect flat-line response. (I'm using the new beta test version of REW, so I can go down to 5Hz).

If I then insert any device in that loop circuit and do a Measurement Sweep, it will plot its response. Easy stuff.

Here's a picture of the UB802 with the cable from my computer LINE_OUT and back to my LINE_IN......


UB802loop.jpg


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THE RESULTS


Here's a plot of :
(RED) the cable shorted together to produce a flat line response.
(GREEN) a plot of the UB802 inserted into the cable.

I'm using the normal vertical axis of 45dB to 105dB. **** good response from 5Hz to 20KHz.


ub802loop_response.jpg


Here I expand the vertical axis so I can take some readings. The results are well within the advertised spec to 10Hz within 1dB.



ub802loop_response_res.jpg


5Hz = -1.4dB
10Hz = -0.4dB
20Hz = -0.1dB
2KHz = +0.6dB

So, between 10Hz and 20KHz, for those with a UB802 preamp, you can safely ignore any response anomolies. For those that want to check down to 5Hz, you might add ~1.4dB to the microphone calibration file.......

brucek
 

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Hey Bruce,

Thanks for doing this, and for publishing the results. I had wondered about the EQ Myself when deciding between buying an 802 and a cheap sound card vs a soundcard with XLR and Phantom built in.

This definately could have saved me a few bucks!
 

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Hi Bruce and the gang ( sounds like a rock band eh?)

Was (re)learning the soundcard calibration technique today, and whilst on a roll thought I'd follow Bruce's lead and check out the response of the Behringer Xenyx 802 ( which is already quite hard to get here in Aus ), the replacement for the UB 802 as Bruce mentioned.

In good old 'monkey see-monkey do' fashion here we go


behringer xenyx 802 responses..jpg

The light blue line represents a successful test of the soundcard calibration file.

The green line represents my first measurement, with the eq buttons centered.

Then I got clever, and seeing as how I had two inputs thought I'd check the second one, and the dark blue line is the result.

Then I got really really clever, and noticing the two channels were different, suspected that maybe, even though the high eq button 'felt' centered, it might need a little tweak. The green line then became the red line.

So now we have both channels at least looking the same, but I leave it to better brains than mine to adjudicate on the quality of what we see here.

lots of love

terry
 

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Discussion Starter · #5 ·
Interesting.

So one of your channels has a detent that isn't perfect. I guess it pays not to draw conclusions on a sample of one. I assumed since my unit was flat, then they all would be.

Once your detent problem was 'calibrated', then the spec appears to remain within the 1dB claimed, but my unit appears to enjoy a slightly flatter response.

I suppose if anyone is using this preamp it only takes a second to do a response check, and perhaps it's worth it. You only do it once...

brucek
 

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Bruce, been pondering ( ponderously ) about your checking of the response of the 802, and the methodology.

What other types of equipmeny could conceivable have their response checked by such a method?? Amps, pres etc drivers.. just throwing anything that came up in there. Seems a powerful tool if it can be utilised.

Where did you get this type of knowledge???, electrical background, hobbyist....

lots of love

terry
 

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Discussion Starter · #7 ·
What other types of equipmeny could conceivable have their response checked by such a method?? Amps, pres etc drivers.. just throwing anything that came up in there. Seems a powerful tool if it can be utilised.
It would have to be limited to devices that were either passive or active devices with controllable unity gain that met certain impedance restrictions (such as line drivers, mixers, etc).
My experience comes from working in engineering as an electronics engineering technologist for over 32 years.... :)

brucek
 
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