Hello World,
I'm a EE student at George Washington U and I'm working on putting
together a 90dB SNR amplifier. I'm starting with first trying to get a
90dB pure tone at 1khz. Ofcourse, it wasnt as easy as I expected, the
school's gear had 60Hz hum at -60dBFS. I tried to use my firewire audio
interface as a signal generator and that was slightly better at -80dBFS
60Hz hum.
Ofcourse, you should be asking what is 0dBFS? Well, that would be my
`spectrum analyzer'. Which is really a Texas Instruments evaluation
module for the ADS 1672 ADC. It has an SNR around -110dB.
Well, the cleanest signal I was able to get is by generating a 1khz
sinusoid using my ADI 21369 EZ Kit. However, I see some nasty stuff
somewhere in the 8 - 10kHz range. Anyone know what is the source of this
noise? It seems to be somewhat present in my audio interface output.
Note that I am using unbalanced output from my audio interface and from
my EZKIT (AD1835). I am then using a 9v battery hooked up to an LM 317
regulator set at 2.5vdc.
http://ottomansignalprocessing.com/EZKit.png << ADSP 21369 EZKit
(tested in my lab)
http://ottomansignalprocessing.com/Fireface.png << my audio interface
(tested in my lab)
http://ottomansignalprocessing.com/TektronixAFG3021B.png << the school's
newly acquired arbitrary waveform generator (tested at school)
Tips? Tricks?
Mucho gracias,
Omer Osman
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