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Old 29th April 2012, 07:19 PM   #1
ziranos is offline ziranos  Spain
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Smile Connect an Audio Precision to an Amplifier.

I recently purchased a AP Sys-1, (Model: 22A with IMD) and I am investigating the possibilities of this equipment. My question is, To perform a basic measure of an amplifier żof the XLR connector (both generator and analyzer) which connections should I use 1, 2 or 3?
The input of the amplifier I'm testing, it is unbalanced (two connections, signal and ground), the output is also unbalanced (two connections, signal and ground).
How should I configure the Analog Generator?

I tried:
Unbal-Float
Unbal-Gnd
CMTST

For each configuration, I get somewhat different results. Clearly I have no terminal I use, and exactly how to configure the Analog Generator for this amplifier.

Thank.
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Old 1st May 2012, 03:11 PM   #2
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Unfortunately AP obsoleted the Sys1, the Sys 2 is close (better specs). Go to Audio Precision : High Performance Audio Analyzer & Audio Test Instruments and find Audio.TST under Service & Support.
Good Luck! E
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Old 1st May 2012, 10:39 PM   #3
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Quote:
Originally Posted by ziranos View Post
I tried:
Unbal-Float
Unbal-Gnd
CMTST

For each configuration, I get somewhat different results. Clearly I have no terminal I use, and exactly how to configure the Analog Generator for this amplifier.

Thank.
Now you know that grounding makes a difference!

There is a book on the AP site, Audio Measurement Handbook by Metzler. Download it, it will answer most of your questions.
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Old 2nd May 2012, 08:09 AM   #4
ziranos is offline ziranos  Spain
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In a video tutorial found on the website of AP that more or less tells me as I make the connection.

I have not done any testing in light of this video tutorial, when I have banana plugs, I will make some tests to see what I get.

Bob Metzler's book is very good, but there are things that speaks very generically.

Thank you very much.
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Old 2nd May 2012, 08:58 AM   #5
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Quote:
Originally Posted by ziranos View Post
I recently purchased a AP Sys-1, (Model: 22A with IMD) and I am investigating the possibilities of this equipment. My question is, To perform a basic measure of an amplifier żof the XLR connector (both generator and analyzer) which connections should I use 1, 2 or 3?
The input of the amplifier I'm testing, it is unbalanced (two connections, signal and ground), the output is also unbalanced (two connections, signal and ground).
How should I configure the Analog Generator?

I tried:
Unbal-Float
Unbal-Gnd
CMTST

For each configuration, I get somewhat different results. Clearly I have no terminal I use, and exactly how to configure the Analog Generator for this amplifier.

Thank.
Obviously you would used the unbalanced connection. You can try float or unfloat to see which has highest S/N.
The connections on the XLR are standardised and available on the 'net.
In such situations, I also have used BNC-to-banana adapters into the S1 front panel banana jacks.

jan didden
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Old 2nd May 2012, 08:23 PM   #6
ziranos is offline ziranos  Spain
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So far, I've been doing is using the XLR. But I have as I make clear the terminal configuration and I use the XLR connector.

I've done several tests to the same amplifier, using different connections and XLR configurations, but I get different results, and I'm a bit lost, since it is not exactly all the testing I've done, what is the more correct or true. Of all the graphics that I have obtained, which does not correspond to the actual characteristics of the amplifier under test.

Is it possible to buy or ride any amplifier (which is cheap or easy to assemble), and compare the measurements made ​​to this amp with my instrument measurements obtained with AP-1 Sys?. This test would be ideal for clearing Any doubt.

My instrument Sys AP-1 passes all tests the manufacturer is more, the graphs obtained match perfectly to provide the manufacturer's procedure or self-check test.

Thank you.
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Old 9th May 2012, 09:24 PM   #7
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If you do the distortion vs power level graphs, look at the level where the distortion starts to rise, typically around 1 Watt (but could be lower). That's where noise starts to dominate. You want the lowest noise

Here's a thread where I show my setup: Audio Precision System One woes

Last edited by Loudthud; 9th May 2012 at 09:29 PM.
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Old 13th May 2012, 11:54 AM   #8
ziranos is offline ziranos  Spain
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I found the information he sought. It is in great detail in the following document "8211_1_.0029_P1_PA_Users_Manual.pdf" and also in "AUDIO PRECISION Portable One Plus Access User.pdf" is basically the same document.
The information appears on pages 6-8 to 6-11, and is perfectly explained.

Another thing,
The manufacturer Texas Instruments has test plates, and mounted amplifier, to which has already tested, which are published in the document "sloa068.pdf". Post testing to integrated amplifiers TPA731, TPA2000D1, and TPA711 TPA0211. Testing is done with Audio Precision SYS 2.
It can be a good idea to have a board test these amplifiers to contrast the information from which I can get with my Audio Precision System.

Does anyone have a better idea?

thank.
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