Audio.TST Archive

By Bruce Hofer, Chairman & Co-Founder, Audio Precision

Hello Reader

As many of you know, on November 30, AP's President and CEO Alan Miksch passed away of complications from lymphoma. Al was passionately loyal to the company and all of its employees, sales partners and customers. Al's quickness to listen, smile, then lead in collaborative discussions and decisions were hallmarks of his special style of management. We at Audio Precision will miss him dearly.

Dave Schmoldt, AP's Vice President & CFO, has been serving as interim Chief Operating Officer of the company since September 2007. Earlier this week Recently, the AP 's Board of Directors voted to confirm Dave as our new President of Audio Precision. This decision was expected, and given Dave's six years with the company as Vice President, the transition has been very smooth.

I'll hand over next month's Notes from the Test Bench to Dave so he can introduce himself. In the meanwhile, I hope you enjoy the Christmas holiday; and if you knew Al, please join AP's employees to take a moment in your thoughts for him and his family.

Bruce.

APx500 v2.1 Beta v2 available

APx500 Measurement Software v2.1 is still on schedule for release January 15, 2008. First, thank you to customers who downloaded the first beta and sent in comments. A couple of bugs were found... and fixed.

APx500 v2.1 Beta v2 is now available. We have also updated the Visual Basic and LabVIEW sample tests to work with this second beta. Again, customers who do not own an APx can still download the software and play with it in demo mode.

For more information or a demonstration please contact your local AP sales partner or visit ap.com/products/apx.htm or read What's New in APx500 v2.1 .

Related downloads

• Download new beta and "What's New" PDF here: ap.com/beta

Measuring ADSR - Attack Decay Sustain Release

Applications Engineer Eric Schultheis looks at how to measure the ADSR of a compressor with a 2700 Series audio analyzer.

The ADSR measurement looks at the four segments of an envelope expressed as amplitude vs. time;

• Attack -- time for a signal to reach full amplitude.
• Decay -- time for the signal to drop from the initial attack level to the sustain level.
• Sustain -- time the signal remains at the constant amplitude.
• Release -- time for the signal to return to an off or zero amplitude condition.

ADSR measurements are typically used in characterizing dynamic altering devices such as compressors and/or limiters. For example, determining the accuracy or sensitivity of the compression ratio parameter.

In this example we'll be using the Burst option in the 2722 analog generator. Our DUT (Device Under Test) is a compressor. The DUT output(s) feed the analog analyzer which feeds the FFT spectrum analyzer.

Starting with the Analog Generator, select the normal burst waveform at 1 kHz. Set the burst on to 800 msec and the interval to 1 sec. I set the low level to -80 dB. Select the output configuration for your DUT.
In the Analog Analyzer panel I selected the unbalanced input and turned off auto ranging. I set the input range to 5 V, allowing plenty of headroom and signal level from my DUT. I left the bandwidth wide open (<10 Hz. to >500 kHz.)
On the Digital Analyzer panel select FFT spectrum analyzer, set the acquire to 72k and the display to Absolute Values. The triggering should be setup for at least 10 msec of pre trigger, so set the Delay to -10 msec and the source to Analog Gen.
On the Sweep panel select fft amplitude (Fft. Ch. 1 Ampl) for data 1 and enable Autoscale. Select fft time (Fft. FFT Time) for source 1. Set the start time to -50 msec. and the stop time to 1 sec.

Here is the ADSR envelope of my compressor (DUT.)

Related downloads

• You may download the AP2700 test file “ADSR.at27” here:
  ap.com/ap/downloads/ADSR.at27

AP Holiday Schedule
AP will be closed from Monday December, 24 through Tuesday, January 1, 2008.

• In case of emergency, Tech Support will be checking voicemail and email daily and they will respond as soon as possible. Please make it clear if this is an emergency and provide office and home numbers so they can reach you more easily.
• This applies only to the AP Factory in Beaverton; Sales Partners will have their own schedules. Please check with them individually for more information.

Events

• NAB Show 2008 | Las Vegas
  April 14-17
  Visit the show website

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