Hi All,
I've made a variant of the DDDAC (see e.g.:
http://www.diyaudio.com/forums/digi...pcm1794-waveio-usb-input-297.html#post4061924
http://www.diyaudio.com/forums/digi...-nos-192-24-dac-pcm1794-waveio-usb-input.html) )
... which instead of the capacitor coupled output uses a resistor combined with an emitter follower and a CCS.
I thought it could be interesting to measure how it actually performed at different sampling frequencies up to 384 kHz and so have made some measurements of various signals using the free "wavegene" wave generator which is capable of outputting 384 kHz sampling frequencies.
In case such measurements may also be of interest to others I've attached some of the measurements to this thread (the next two posts). Please note that since the DAC's output is ~ 0.3 Vpp this corresponds to app. -20.2 dBs on the ADC. In some cases this may also be a bit lower since when combining sine waves in Wavegene each of them have to be at less than 0 dB level to avoid output clipping.
The measurements are:
1. ADC noise level with input shorted (for reference, AD7760, battery PSU).
2. 1 kHz sine wave at 44.1 kHz sampling frequency (low ADC bandwidth).
3. 1 kHz sine wave at 44.1 kHz sampling frequency (wider ADC bandwidth).
4. 1 kHz + 1.1 kHz sine waves at 44.1 kHz sampling frequencies.
5. 1kHz + 1.1 kHz sine waves at 192 kHz sampling frequencies.
6. 1kHz + 1.1 kHz sine waves at 384 kHz sampling frequencies.
7. 9 kHz + 10.05 kHz + 20 kHz at 88.2 kHz sampling frequency (frequencies suggested by Bob Cordell on his homepage).
8. Ditto but at 384 kHz sampling frequency.
9. 1 kHz square wave at 44.1 kHz sampling frequency
10. 1 kHz square wave at 384 kHz sampling frequency.
... new post ...
1. 10 kHz square wave at 44.1 kHz sampling frequency
2. 10 kHz square wave at 384 kHz sampling frequency.
3. 49.05 kHz + 50 kHz sine wave at 384 kHz sampling frequency.
4. The DAC's noise level at no_data output (idle).
Cheers 😉
Jesper
I've made a variant of the DDDAC (see e.g.:
http://www.diyaudio.com/forums/digi...pcm1794-waveio-usb-input-297.html#post4061924
http://www.diyaudio.com/forums/digi...-nos-192-24-dac-pcm1794-waveio-usb-input.html) )
... which instead of the capacitor coupled output uses a resistor combined with an emitter follower and a CCS.
I thought it could be interesting to measure how it actually performed at different sampling frequencies up to 384 kHz and so have made some measurements of various signals using the free "wavegene" wave generator which is capable of outputting 384 kHz sampling frequencies.
In case such measurements may also be of interest to others I've attached some of the measurements to this thread (the next two posts). Please note that since the DAC's output is ~ 0.3 Vpp this corresponds to app. -20.2 dBs on the ADC. In some cases this may also be a bit lower since when combining sine waves in Wavegene each of them have to be at less than 0 dB level to avoid output clipping.
The measurements are:
1. ADC noise level with input shorted (for reference, AD7760, battery PSU).
2. 1 kHz sine wave at 44.1 kHz sampling frequency (low ADC bandwidth).
3. 1 kHz sine wave at 44.1 kHz sampling frequency (wider ADC bandwidth).
4. 1 kHz + 1.1 kHz sine waves at 44.1 kHz sampling frequencies.
5. 1kHz + 1.1 kHz sine waves at 192 kHz sampling frequencies.
6. 1kHz + 1.1 kHz sine waves at 384 kHz sampling frequencies.
7. 9 kHz + 10.05 kHz + 20 kHz at 88.2 kHz sampling frequency (frequencies suggested by Bob Cordell on his homepage).
8. Ditto but at 384 kHz sampling frequency.
9. 1 kHz square wave at 44.1 kHz sampling frequency
10. 1 kHz square wave at 384 kHz sampling frequency.
... new post ...
1. 10 kHz square wave at 44.1 kHz sampling frequency
2. 10 kHz square wave at 384 kHz sampling frequency.
3. 49.05 kHz + 50 kHz sine wave at 384 kHz sampling frequency.
4. The DAC's noise level at no_data output (idle).
Cheers 😉
Jesper
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