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GB for Virtins MI Pro for RTX6001 autoranging/autoscaling & for soundcard end users
GB for Virtins MI Pro for RTX6001 autoranging/autoscaling & for soundcard end users
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Old 12th August 2018, 05:29 PM   #301
etlasr is offline etlasr
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Join Date: Jun 2012
Getting two error messages 'fail to start DAQ' and 'fail to start DAO'. Thought I would ask in case there is an obvious answer before i investigate further. Using trial version until dongle arrives, installed ASIO drivers and selected the RTX with ASIO. RTX shows as under remote control.
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Old 12th August 2018, 08:41 PM   #302
etlasr is offline etlasr
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ignore last post from ETLASR. Very basic mistake, I forgot I'm now using a new laptop and hadn't installed the RTX application!!
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Old Yesterday, 06:15 AM   #303
acg is offline acg  Australia
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Join Date: Oct 2013
Location: Sunshine State
Default RIAA Testing

Virtins,

With MI Pro and RTX6001, is it possible to test the frequency response of a RIAA Phonostage without building an inverse RIAA filter from caps and resistors, attaching it to the DUT and running frequency sweeps? It would be lovely if it was possible to sweep the Phonostage directly (no inverse RIAA filter) and correlate the resulting frequency response to the RIAA curve in software. Is this possible in MI Pro?

Cheers,

Anthony

Last edited by acg; Yesterday at 06:15 AM. Reason: Spelling
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Old Yesterday, 07:37 PM   #304
VIRTINS is offline VIRTINS  Singapore
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GB for Virtins MI Pro for RTX6001 autoranging/autoscaling & for soundcard end users
Default RIAA

Thank you for your questions.

Yes, it is possible. There are three methods:

Method 1. Apply Recording RIAA IIR filter in time domain (Oscilloscope)

Right click anywhere within the oscilloscope window and select [Oscilloscope Processing]>”Digital Filtering”>”Arbitrary”>”IIR Coefficients” and then load a preconfigured Recording RIAA IIR coefficient file, e.g.:

(1) RecordingRIAA_SR44100Hz_IIR_Order2.iir
(2) RecordingRIAA_SR48000Hz_IIR_Order2.iir
(3) RecordingRIAA_SR88200Hz_IIR_Order2.iir

Note that the sampling rate of the IIR coefficient file must match the sampling rate of the oscilloscope.

In MI, generally the acquired signal will be processed in time domain (Oscilloscope) first and then flows to frequency domain (Spectrum Analyzer). Please refer to Section 1.6 Signal Flow Block Diagram of the software for details if you want to configure your own DSP processing and analysis algorithm.

After the above Recording RIAA filtering in time domain, if the frequency response of the DUT follows Reproducing RIAA exactly, then the measured magnitude frequency response in the Spectrum Analyzer should be a flat horizontal line.


Method 2. Apply Recording RIAA frequency compensation in frequency domain (Spectrum Analyzer)

Right click anywhere within the spectrum analyzer window and select [Spectrum Analyzer Processing]>”Intra-Frame Processing” > ”Compensation1” and then load the frequency compensation file: RecordingRIAA.fcf.

If the frequency response of the DUT follows Reproducing RIAA exactly, then the measured magnitude frequency response in the Spectrum Analyzer should be a flat horizontal line.

Note that the time domain waveform will not be affected by this method, unlike the previous one.


Method 3. Check the measured magnitude frequency response directly against the Reproducing RIAA reference curve

To load the reference curve, right click anywhere within the spectrum analyzer window and select [Spectrum Analyzer Reference] and then load ReproducingRIAA.ref. It is advisable to load this reference curve in a channel different than the channel where the measured frequency response curve resides, so that you can adjust the vertical offset between the two curves for easier comparison. To hide the real-time spectrum in the reference channel, set its color to the background color.

The following are two examples using white noise as stimulus through software loopback (iA=oA, iB=oB). White noise spectrum is flat.

(1) A ReproducingRIAA IIR filter is applied in the oscilloscope. The measured spectrum matches the Reproducing RIAA reference curve.

(2) A ReproducingRIAA frequency compensation file is configured in the spectrum analyzer. The measured spectrum matches the Reproducing RIAA reference curve.
Attached Images
File Type: png RIAA_IIR_filterAppliedInTimeDomain.png (150.0 KB, 39 views)
File Type: png RIAAcompensationInFrequencyDomainOnly.png (150.0 KB, 40 views)
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Last edited by VIRTINS; Yesterday at 07:42 PM. Reason: previous attachment wrong
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Old Yesterday, 09:18 PM   #305
acg is offline acg  Australia
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Join Date: Oct 2013
Location: Sunshine State
Excellent! Thank-you for your detailed reply. I'm glad I signed up for this software: it seems very useful and I eagerly await the dongle to turn up in the mail.
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Old Yesterday, 09:20 PM   #306
PH104 is offline PH104  United States
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GB for Virtins MI Pro for RTX6001 autoranging/autoscaling & for soundcard end users
Looks like my USB is at the postoffice waiting for my signature. Thanks again to the team who made this all possible.

(edit - and happy to see the above 2 posts, that will be helpful.)

Phil
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