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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
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Old 14th February 2018, 12:42 AM   #7081
soekris is offline soekris  Denmark
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Quote:
Originally Posted by matthiasw View Post
Looking at the 1321 circuit board I see neither TP1 nor TP2.

Please, can you shed some light on this?

Thanks

Matt
Look closely, the two holes, larger than vias, at the end of the R-2R network (closest to the outputs).
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Old 14th February 2018, 06:24 AM   #7082
TNT is offline TNT  Sweden
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These? TP6=ground?

//
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File Type: png tp.png (799.5 KB, 360 views)
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Old 14th February 2018, 10:16 AM   #7083
soekris is offline soekris  Denmark
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Quote:
Originally Posted by TNT View Post
These? TP6=ground?

//
Yes, looks like the text has disappeared from the PCBs, and TP6 is GND.
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Old 14th February 2018, 10:30 AM   #7084
matthiasw is offline matthiasw  Germany
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Quote:
Originally Posted by soekris View Post
Yes, looks like the text has disappeared from the PCBs, and TP6 is GND.
Thanks,
@soekris and @TNT

Matt
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Old 14th February 2018, 02:44 PM   #7085
zfe is offline zfe
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Quote:
Originally Posted by TNT View Post
Intriguing... you dont happen to have an s/pdif inlet?

//
Here the picture from S/PDIF. The signal (fs=48kHz) comes from the optical out of a Mac Book Pro. The wandering signal is here in the 800Hz area.
DAM 48 SPDIF.jpg

I now have an idea what is going on. Hint by the observation that the level of the wandering peak does not increase when I increase the gain of the buffers of the ADC, I think what we are seeing is the clock of the DAM itself, aliased back in the audio band.

Then the peak (mean) frequency is explained by the slight difference of the clock frequencies of the ADC clock and the Amanereo clock, resp. the Mac Book clock in the S/PDIF case.

The ADC is 32x oversampling at 192kHz, so the aliases are in the passband of its digital low pass filter for +-96kHz + multiples of 6,144MHz. This fits well as the DAM clock should also be operating at some 2-power multiple of 48kHz.

As the input buffer of the ADC is not made for that high frequencies there is no effect of the gain setting - the signal gets trough only strongly attenuated.

So Soren is right - I need to push some wires around in my DAM

But first I would like to see the peak at its original frequency somehow.
Soren, could you please tell me at which nominal frequency the DAM clock is running with an fs=48kHz Input signal?

Last edited by zfe; 14th February 2018 at 02:50 PM.
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Old 14th February 2018, 02:47 PM   #7086
matthiasw is offline matthiasw  Germany
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@soekris:

In a set-up WITHOUT headphones comparing dac1101 to dac1321:

Which one sounds better?

Thanks

Matt
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Old 14th February 2018, 03:48 PM   #7087
soekris is offline soekris  Denmark
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Quote:
Originally Posted by zfe View Post

As the input buffer of the ADC is not made for that high frequencies there is no effect of the gain setting - the signal gets trough only strongly attenuated.

So Soren is right - I need to push some wires around in my DAM

But first I would like to see the peak at its original frequency somehow.
Soren, could you please tell me at which nominal frequency the DAM clock is running with an fs=48kHz Input signal?
44.1K / 48K * 1024 = 45.1584 Mhz / 49.152 Mhz Oscillator Clock.
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Old 14th February 2018, 03:49 PM   #7088
soekris is offline soekris  Denmark
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Quote:
Originally Posted by matthiasw View Post
@soekris:

In a set-up WITHOUT headphones comparing dac1101 to dac1321:

Which one sounds better?

Thanks

Matt
They use the same R-2R core, but in principle the dac1321 is a little more refined, like better power supplies and better output buffers, so the dac1321 will be a little better.
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Old 15th February 2018, 07:30 PM   #7089
sfox7076 is offline sfox7076  United States
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I went to buy the board today. The shipping cost to US is $65 US. Is that correct?
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Old 15th February 2018, 07:34 PM   #7090
wcwc is online now wcwc  United States
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Yes, that is about what I paid last year. You can add a few more boards and it doesn't change the shipping any. This is one reason we have been bugging Soren about a US based store.
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