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Testing your Metric Halo hardware [message #86132] Thu, 04 September 2014 01:19 Go to next message
rabyn is currently offline  rabyn
Messages: 27
Registered: July 2014
Location: Planet Earth
Junior Member
I have purchased a number of brand new Metric Halo products but I have also purchased a few used over the years on EBAY. I recently purchased a 2882 that appeared to be in great shape. Before I left positive feedback, I went about checking each input and output with a set of headphones and a microphone. Interestingly I discovered an issue with some of the mic preamps.

My first test was to patch a condenser mic into each mic pre with the 48v turned on and listen to my voice. Seems simple enough. I immediately discovered that mic pre 3 was noisier than the other mic preamps even with modest gain. Unplugging the mic (no load) didn't change the noise. Using a different type and brand of mic also didn't change the noise.

I would of used the Transfer Function to compare different mic preamps but in this situation, that wasn't possible. Patching a 2882 output into an input set up for MIC / 48v ON would likely fry the unit. DO NOT DO IT!

Since the noise was audible and consistent, I used the Spectragram and took screen shots to share with Jon Stern.

I also used the RP to record the noise.

Here are some screenshots taken using the Spectragram instrument. The first photo is mic pre 3. The second photo is mic pre 4. Same channel settings and no load.

index.php?t=getfile&id=68&private=0

index.php?t=getfile&id=69&private=0

Notice the lines? Notice how much more prevalent they are on the mic pre 3 measurement.

After providing some details to Jon Stern @ MH and verifying the issue would require a visit to Metric Halo for repair, I decided to request a refund and return the device to the seller. I did receive a refund and I ended up shipping the device to Metric Halo on behalf of the seller.

Going through the process, I learned some information that might help others.

In a follow up post, I'll provide details about how to test your gear to verify it's working properly.

ra byn (robin)


ra byn (robin)

[Updated on: Thu, 04 September 2014 01:22]

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Re: Testing your Metric Halo hardware [message #86135 is a reply to message #86132] Thu, 04 September 2014 17:45 Go to previous messageGo to next message
rabyn is currently offline  rabyn
Messages: 27
Registered: July 2014
Location: Planet Earth
Junior Member
Here is an email from Jon Stern providing directions for testing the unit.

Hi Ra Byn,

Please make a test recording.

Play a 1kHZ sine tone at -6dBFS out of one of the
outputs of the 2882.

Set the output to +4 with 0dB of trim in the I/O Control
pane. Loop a cable from the output on the back to the input in question set to
Line +4 and 0dB of trim.

You can use the tone generator in an app like Logic or Spectrafoo, or just play the
attached file out of iTunes with the volume slider all the way up and with Sound
Enhancer (in Preferences) and Equalizer (in the Window menu) turned off.

Confirm that while you are playing the tone out via DAW 1/2, you have the input you are
recording on muted within the mixer (for example, input 5).

This will ensure that you do not create a feedback loop.

Use the Record Panel and record a 5 second .aiff file and send it to me at
jon (at) mhsecure (dot) com

We can take a look at how the captured result may differ from the factory spec. If
you are getting tones around 9 kHz, there may be a resistor we might need to change
on the 2d Card. The test recording may say more.


ra byn (robin)
Re: Testing your Metric Halo hardware [message #86136 is a reply to message #86135] Thu, 04 September 2014 17:47 Go to previous messageGo to next message
rabyn is currently offline  rabyn
Messages: 27
Registered: July 2014
Location: Planet Earth
Junior Member
Here is a follow up email from Jon Stern:

"You can set the input to Mic, but keep phantom power turned off and start with no
gain added (the channel will likely clip otherwise),

Don't do a loopback with phantom power at any point, but you could also try playing
a tone out that is attenuated enough so that the input doesn't clip when you turn up
the gain to see if that makes a difference. Try input 3 and another known good
input and we can compare results. Please make a recording."


ra byn (robin)
Re: Testing your Metric Halo hardware [message #86137 is a reply to message #86136] Thu, 04 September 2014 17:48 Go to previous message
rabyn is currently offline  rabyn
Messages: 27
Registered: July 2014
Location: Planet Earth
Junior Member
Here is a follow up email from Jon Stern:

"There are a lot of procedures we do in house during the build process. If the goal
is to verify the integrity of the analog path, the starting point in our approach is
the loopback procedure I described.

That ring is not expected or desired, and actually it appears to be present on input
4 as well as input 3 (albeit at a much lower level). If you can reproduce this with
other microphones we probably need to have a look at the box. Please confirm the
serial number if you'd like to proceed and we can confirm that it's registered and
generate an RMA number for you. For something like this, it's unlikely we can know
more or do anything further to test until we see it here."


ra byn (robin)
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