For testing my various diy dacs I have used CD test discs in the past.
Ideally an audio to I2S interface would bypass this and allow direct audio from a sig gen to the dacs I2S (PCM)
i found this one:-
https://www.audiophonics.fr/en/devi...onverter-wm8782-i2s-24bit-192khz-p-13351.html
or this one maybe a better choice:
https://www.audiophonics.fr/en/devi...dc-board-wm8782-i2s-24bit-192khz-p-14897.html
Any views?
Ideally an audio to I2S interface would bypass this and allow direct audio from a sig gen to the dacs I2S (PCM)
i found this one:-
https://www.audiophonics.fr/en/devi...onverter-wm8782-i2s-24bit-192khz-p-13351.html
or this one maybe a better choice:
https://www.audiophonics.fr/en/devi...dc-board-wm8782-i2s-24bit-192khz-p-14897.html
Any views?
Sure, these will work but why involve an analogue signal generator at all? Everyone has a few USB/i2s boards anyway. Add something like Wavegene and you get a lot more control upon the quality of your test generator. Various sampling rates too.
Thanks, a good idea, especially since the French seller of the ADC boards have a minimum order of 160euros.
The normal approach for testing dacs is to use measurement software (E.g. REW, Arta), some USB-I2S board and an ADC for sending dac output back to SW. So the chain is like this:
host SW -> USB-I2S -> DAC -> ADC -> I2S-USB -> host SW
Typically the "ADC -> I2S-USB" part is an external USB-based soundcard (e.g. Focusrite).
host SW -> USB-I2S -> DAC -> ADC -> I2S-USB -> host SW
Typically the "ADC -> I2S-USB" part is an external USB-based soundcard (e.g. Focusrite).
Yes, I have a USB to I2S board and REW etc so don't know why i didn't think of doing it this way. I prefer to use Picoscope for the measurements.
Thanks.
check this - I am using it since first version, well made and good product. Have various output formats, you can test everything with it http://www.jlsounds.com/i2soverusb.html
It couldn't complete the purchase so have messaged them. (I did select UPS shipping)
NO! They will not ship any order to the UK unless the total is over 161euros, even though they do not have to charge vat on exports. I've never come across such a stupid policy and their claims this is due to Brexit is nonsense. UK customs will collect UK vat if it is due (not normally on low value (<£39) items)
I have bought this item instead -it uses a PCM1802 ADC and costs £5.40 inc postage from China.
https://www.ebay.co.uk/itm/193744231145
https://www.ebay.co.uk/itm/193744231145
No. All Brexit problems ended months ago but maybe they are out of touch. i send and receive items from all over the world and only Portugal still cause delays but no customs problems.
Anyway I have ordered the above ADC and a 11.289Mhz TCXO to provide the master clock for it.
Its to inject audio from my battery signal generator (or Picoscope's AWG) by converting it to I2S for testing and measurements.
As others have suggested, i could have used a USB to I2S adapter and software.
That ADC is probably too high in distortion to be very good for instrumentation purposes. Also, with an 11Mhz audio clock it would be limited to 44.1kHz sample rate...
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Why?
Its a PCM1802 clocked with a 0.1ppm 11.2896TCXO and fed from a LT3042 low noise regulator..
The sig gen will be the limiting factor but I am really more interested in comparing the three nos dacs, than aiming for technical perfectionism.
It must be better than using an audio test cd.
Datasheet gives the specs: https://www.ti.com/cn/lit/ds/symlink/pcm1802.pdf?ts=1664288508909 ...and that probably assumes good layout and good quality support circuitry.
Also, 0.1ppm TCXO means almost nothing for audio. Long term frequency stability is not the issue. Its jitter and close-in phase noise specs that are more important.
Also, 0.1ppm TCXO means almost nothing for audio. Long term frequency stability is not the issue. Its jitter and close-in phase noise specs that are more important.
It might be better to use the everyday digital feed you will use for the DAC anyway, so the usual operating conditions eg the usual jitter is included? Its simpler too. That helps standardise the measurements and reduce spurious errors creeping in.
It super great you are testing your DAC objectively. Thanks very much for all your effort.
I am doing what I'd do if I was testing an amp - analogue audio in from sig gen and scope (freq sweep) / spectrum analyser on the output.