Using sound card to measure amps/preamps

[doors666]

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.

 

[IndianEars]

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]

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.

 

[IndianEars]

I Think the Tek TDS-2024 CAN Do FFT..... No sure but do check it out.

 

[goldyrathore]

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]

Yes.

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

 

[goldyrathore]

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