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Old 23rd May 2012, 03:39 AM   #1
tttoan is offline tttoan  Viet Nam
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Default Audio generator question

Hi there,

I want to have an audio generator for THD measurement (require < 0.05%)

Has any one used this equipment for THD measurement?
BK Precision 3001 Audio Generator
bkprecision.com/products/signal-generators/3001-audio-generator.html
This one is brand new, the price is cheap but I am not sure it is ok for THD measurement < 0.05%.

And how about the Audio System One SYS-222A?
Does it have an low distortion Audio Signal generator that can adjust frequency (5Hz~20Khz) with amplitude 0~5V RMS?

There is another candidate is HP 8903A with many functions including analyzer.

Please advise advantages of each one if you know any of them.

Thanks,
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Old 23rd May 2012, 04:14 AM   #2
jcx is offline jcx  United States
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many/most portable media players, DAP, desktop CD, DVD players can do <0.05%

most classic audio testing today can be done with "prosumer" soundcards, maybe a few amplifier/filter/attenuator interface circuits to match levels to the common 2 Vrms 0 db full scale of most desktop consumer digital audio - some DAP may put out ~1 Vrms, a very few 500 mVrms
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Old 23rd May 2012, 06:11 AM   #3
tttoan is offline tttoan  Viet Nam
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Quote:
Originally Posted by jcx View Post
many/most portable media players, DAP, desktop CD, DVD players can do <0.05%
most classic audio testing today can be done with "prosumer" soundcards, maybe a few amplifier/filter/attenuator interface circuits to match levels to the common 2 Vrms 0 db full scale of most desktop consumer digital audio - some DAP may put out ~1 Vrms, a very few 500 mVrms
Thank you for reply.
Do you know where I can get a wave file to burn into a CD?
I want to see how low THD a desktop CD can create.
Thanks.
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Old 23rd May 2012, 06:50 AM   #4
jcx is offline jcx  United States
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quickest is to look up RMAA RightMark Audio Analyzer - the free version is often used to measure soundcards in loop-back

for other audio equipment performance tests there is a option for saving the test stimulus files for playback on other equipment with RMAA syncing up to the soundcard analog line level input - read the doc

other audio analyzer, sound editing, some math sw can manipulate .wav

Last edited by jcx; 23rd May 2012 at 06:53 AM.
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Old 23rd May 2012, 08:32 AM   #5
tttoan is offline tttoan  Viet Nam
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Join Date: May 2012
I used this software to create wave files then burn to a CD. then use a PC CD drive to play the disc:
"The Audio Test File Generator"
Frequency 100 Hz and 10 Khz, sample rate 44100, 16 bit.

And here is the bad THD result:
THD 0.4 % for 100 Hz
THD 1.8% for 10 Khz

The result is worse if measure from a sound card (on board sound card)
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Old 23rd May 2012, 07:33 PM   #6
jcx is offline jcx  United States
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I've seen much better:

Quote:
Originally Posted by jcx View Post
my $130 Juli@ does that good with much narrower noise skirt

here's one RMAA test: RightMark Audio Analyzer test : Juli@ loop
Quote:
Originally Posted by jcx View Post
just starting to play with the iPod shuffle I bought this week to test a 12 bit adc with - the shuffle output goes as low as you want - I've put 1 Hz sq, tri in r,l channels of a 16-bit 48K .wav file (created .wav in LtSpice bv source .wave cmd, load into iTunes>Shuffle) - no output coupling cap - no droop, just a few % gain loss when driving into 32 Ohms

for sine distortion I looked at a 800 Hz sine + dither .wav played back thru Shuffle into esi Juli@ soundcard set for 24 bit 192K gives -93 dB 2nd, -99 dB 3rd harmonics (10 sec record to reach below the noise)

refurb 1st gen iPod Shuffles are <US$40


for DAP, this compares Sansa Clip+ with an iPod, the Clip just hits your 0.05% spec

NwAvGuy: Sansa Clip+ Measured


I just tried to put RMAA on my desktop, won't install, doesn't like Vista?, I have it on an old XP computer around here somewhere...
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Old 12th June 2012, 12:01 AM   #7
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Send a message via MSN to Peavey MB1 MB-2
free AudioPrecision software APx test generator.
depends on DA converter.

Audio Precision : High Performance Audio Analyzer & Audio Test Instruments
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