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Using sound card to measure amps/preamps

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doors666

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anyone has done this? measure thd+n, phase etc. i will probably need some attenuator for use with amps. is isolation needed? what about impedances, this would act like a scope probe right? whats the best free software for this.
i guess odac wont do as it has no mic input. how good is the asus essence mic input.
 
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IndianEars

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May 18, 2008
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I have used a few .... including Virtins software.

There is lots of free ware available for signal generators, O'scopes and Spectrum analysers.

Yes, Ground isolation etc can be a Big issue. ... Must be careful. A laptop operating on battery is a good idea.

My experience is that Sound cards roll off VERY Sharply after 20 KHz. You will not be able to generate or view a 10KHz sq wave ( Critical for audio testing) via a sound card.

The sound card based soft instrumentation is a good thrill initially, but cant substitute a serious o'scope. Software is also great as a spectrum analyser, but the bandwidth restraints are very obvious.

Recently I discovered that Good Condition used Osciloscopes are available on OLX.in at Throw away prices ( Rs 4,500 upwards). A function generator for Rs 2,000 With Digital readout !

This is in the price range of a descent sound card !

If you want to go the whole Hog, a Brand new Tek Scope with FFT :


TEKTRONIX - TBS1042 - OSCILLOSCOPE, 2CH, 40MHZ, 500MSPS

scope for just Rs 23,413

TBS1042 - TEKTRONIX - OSCILLOSCOPE, 2CH, 40MHZ, 500MSPS | element14 India
 

doors666

Well-Known Member
Joined
Sep 15, 2008
Messages
1,837
Points
113
Location
bangalore
I have used a few .... including Virtins software.

There is lots of free ware available for signal generators, O'scopes and Spectrum analysers.

Yes, Ground isolation etc can be a Big issue. ... Must be careful. A laptop operating on battery is a good idea.

My experience is that Sound cards roll off VERY Sharply after 20 KHz. You will not be able to generate or view a 10KHz sq wave ( Critical for audio testing) via a sound card.

The sound card based soft instrumentation is a good thrill initially, but cant substitute a serious o'scope. Software is also great as a spectrum analyser, but the bandwidth restraints are very obvious.

Recently I discovered that Good Condition used Osciloscopes are available on OLX.in at Throw away prices ( Rs 4,500 upwards). A function generator for Rs 2,000 With Digital readout !

This is in the price range of a descent sound card !

If you want to go the whole Hog, a Brand new Tek Scope with FFT :


TEKTRONIX - TBS1042 - OSCILLOSCOPE, 2CH, 40MHZ, 500MSPS

scope for just Rs 23,413

TBS1042 - TEKTRONIX - OSCILLOSCOPE, 2CH, 40MHZ, 500MSPS | element14 India
I already have a much better scope, tek tds2024 4ch, 200mhz, 2gsps, 3 probes and a current probe. I also have a siggen but it only does pwm and sq wave. i was able to use odac (using audacity) to generate upto 20khz sinewave perfectly and i can see output on the scope. I use this to detect oscillations etc.
I cant do distortion analysis with this setup. it also doesnt have a usb interface, so i cant get the waveforms on to a pc. I am ok with just 1khz to get some idea of thd levels.
 

goldyrathore

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May 11, 2009
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I cant do distortion analysis with this setup. it also doesnt have a usb interface, so i cant get the waveforms on to a pc. I am ok with just 1khz to get some idea of thd levels.
Check out Right Mark Audio Analyzer along with Xonar DX/D2X sound card.
Thanks,
Goldy
 

IndianEars

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Joined
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Messages
692
Points
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Location
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Yes.

Right Mark Audio Analyser (RMAA) ... even their Freeware version is Excellent
 

goldyrathore

Active Member
Joined
May 11, 2009
Messages
160
Points
28
Location
Hyderabad
For a measurement setup, you should use line-out->amp->jig->line-in.
The jig is needed to protect the line-in from high voltages of the amp. Look at Figure 1.6 for the jig in Arta user manual.

Regards,
Goldy
 
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