preamp for Behringer mic comparison--which should I keep???

**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.

**JohnM** · **06-25-07, 02:54 AM**

Those latest plots look fine. When calibrating with the AudioBuddy in circuit what input on the AudioBuddy were you using? Trying to drive the mic-level input of the AudioBuddy with the line output of the soundcard might account for the severe clipping...

**JimP** · **06-25-07, 03:12 AM**

Channel 1 with XLR input and 1/4" output.

I lowered the input level on the soundcard calibration screen (in REW) which also lowers the output (they seem to be linked) and still got the distortion.

What I am curious about is about it really mattering as the actual plots relative to the 802 are similar enough. Is the software correcting for the distortion?

**brucek** · **06-25-07, 08:18 AM**

Quote:

I lowered the input level on the soundcard calibration screen (in REW) which also lowers the output (they seem to be linked) and still got the distortion.

Input Level? There is no control called Input Level....... Do you meant Input Volume or Sweep Level? ...because Sweep Level is an output control....

brucek

**JimP** · **06-25-07, 08:50 AM**

Input volume, sweep level, wave volume on the soundcard calibration screen and also adjusted the gain on the Audiobuddy....in numerous test with adjustments to all of them in various combination and still had the distortion.

I'd really like the AudioBuddy to work out, so I'm going to pull it out of the box (have it ready to go back to the store) and give it another try.

One thing that the 802 has a leg up on the AudioBuddy is that the gain control on the AudioBuddy is borderline oversensitive and is harder to dial in your setting. Tends to overshoot slight adjustments. The 802 gain and trim controls are less sensitive allowing quicker calibration. Now I do have to say that the power cable connection for the 802 is some screwy non standard type that won't handle a lot of plugging/unplugging. Probably a good idea to leave it in and add some hot glue for additional stability. The power adapter on the 802 otherwise uses heavier wire than the AudioBuddy. Warranty wise, the AudioBuddy's covered as long as you own it. You do pay for shipping and handling charges (might be a concern) if it goes bad.

**JimP** · **06-25-07, 12:00 PM**

Reran the soundcard calibration with the AudioBuddy in place to verify my earlier findings. It measured the same on the impulse graph. Ran two test and then ran two more on channel 2 in case the noise was confined to channel 1. Channel 2 was the same.

Back to the store with it.

**JohnM** · **06-25-07, 04:36 PM**

Quote:

JimP wrote:

What I am curious about is about it really mattering as the actual plots relative to the 802 are similar enough. Is the software correcting for the distortion?

The log sweep measurement technique is very tolerant of distortion, the elements of the response which do not correspond linearly to the sweep end up in the region before time=0 on the impulse response and are excluded from the frequency response by the impulse response window, so only the linear part of the response gets displayed.

**clubfoot** · **06-25-07, 05:07 PM**

Quote:

JimP wrote:

Channel 1 with XLR input and 1/4" output.

I lowered the input level on the soundcard calibration screen (in REW) which also lowers the output (they seem to be linked) and still got the distortion.

What I am curious about is about it really mattering as the actual plots relative to the 802 are similar enough. Is the software correcting for the distortion?

I used mini stereo to 1/4 input and 1/4 to mini stereo output to and from the sound card. My M-Audio Revolution 7.1 sound card shows <0.001% second and third. The Audio Buddy and Revolution show 0.005% and <0.001% distortion numbers combined. Furthermore the Hz is .2db to .1db from 20Hz to 20KHZ with both units in the chain!
I think you're splitting hairs here.

**JimP** · **06-25-07, 05:55 PM**

Clubfoot,

Frankly, I don't enough about this stuff (yet) to know what you're saying. The impression I'm getting is that the distortion is small enough to be negligable.

In any case, the AudioBuddy has been returned and I'll be keeping the 802.

**clubfoot** · **06-25-07, 06:01 PM**

Sorry if I came over badly, I meant either unit's contribution to the measurements would be negligible, especially if you create your .cal file with the sound card and mic pre amp in the same loop.

**JimP** · **06-25-07, 06:52 PM**

Not a problem.

This hometheater thing is a hobbie (out of control that it is) and I enjoy getting to know everyone here and learning what I can.

Take care

**Sonnie** · **06-25-07, 09:24 PM**

Hey Jim... it appears my wife will actually be driving to Montgomery to pick up that part. If you want, I can mail that mic to you. You should have my email... just shoot me your address once again. I know how to get there, but the address escapes me...

.. other than Wetumpka, AL.

**JimP** · **06-26-07, 10:46 AM**

Email sent to your snapbug address.

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