SPL Meters | Mic's | Calibration | Sound Cards

**JimP** · **06-23-07, 02:53 PM**

I have both the M-Audio AudioBuddy preamp and the Behringer 802 mixer and am trying to decide which to keep by doing sound card calibrations with each one.

In the attached jpgs, it seems that the AudioBuddy has a flatter response curve than the Behringer 802. At the same time, I'm questioning the impulse graph. In the help file, I get the impression that the Audio Buddy may have more distortion, but I'm not sure.

Would someone comment on these graphs as to how they relate to preamp performance.

I included a jpeg of the soundblaster usb soundcard as a reference.

**JimP** · **06-23-07, 02:58 PM**

Didn't know that I couldn't enter text between jpegs. oops

Anyway, the first two are from the audiobuddy, the second two are the Behringer 802 mixer and the last two are of just the soundcard

**brucek** · **06-23-07, 06:31 PM**

Well, that's the beauty of REW. You don't really care which preamp has the better response, because you simply include the inverse of the response in the soundcard.cal file. This makes the preamp perfect, just as it makes the soundcard perfect......

Personally I love the 802. Pretty useful if you ever need to mix some signals together too.....

brucek

**clubfoot** · **06-23-07, 10:11 PM**

For the price, lack of additional circuitry and for measurement I use the Audio Buddy.

**JimP** · **06-23-07, 10:25 PM**

Maybe running an actual test with both devices might shed some light on this. I know what I'll be doing tomorrow afternoon.

**brucek** · **06-24-07, 07:37 AM**

If you first create a soundcard.cal file with each preamp in the loop, then subsequent measurements taken will be identical - no test is really required....

brucek

**JimP** · **06-24-07, 08:09 AM**

bruceK,

I know in theory, that's how it should work.

Just seems that the audio buddy is a more elegant solution, but those impulse reading bother me. The 802 is large, but that might be the price for cleaner readings.

I don't know if it carries over to this software/hardware, but in the past I've found that the less you do to a signal, the better off you are. ...and there may be other things not readily apparant that will show up in a test comparing the two.

**JohnM** · **06-24-07, 05:42 PM**

Looks like the AudioBuddy is being overdriven or its gain is set too high resulting in severe clipping, hence the very high levels of distortion in the impulse plot, particularly the odd harmonics.

**clubfoot** · **06-24-07, 08:54 PM**

I have to agree with JohnM, my impulse response looks nothing like yours!

**JimP** · **06-24-07, 10:17 PM**

I've run additional sound card calibrations with the AudioBuddy in the circuit, varying the input levels to the point to where I was getting the "too low" message. Each time, I still get a impulse graph similar to what is shown above.

Which raises the question, does it really matter?

Here is a comparison of the Behringer 802 and the AudioBuddy using the respective sound card calibration and the Behringer ECM8000 microphone.

Although there is a slight difference in the frequency response curve, the impulse response graph appears very similar. Does this indicate that the distortion in the AudioBuddy is corrected in the calibration file?

The plots on the impulse graph were seperated to help in viewing. Otherwise, the red plot covered the blue one.

Although I prefer the size and simplicity of the AudioBuddy, I think I'll be taking it back tomorrow. I either have a defective unit or maybe I'm doing something wrong in calibration. Although, I used the same procedure with the Behringer 802 and didn't have the same distortion graph.

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