Implementing a true FIFO buffer with low phase noise clock on the Soekris DAM1021 DAC

TNT

Member
Joined 2003
Paid Member
No way the math is wrong, but you can get different results from a device to another because the error combination in the ladder is random.

When I will calibrate my DAM1021 I will publish the real accuracy.
I will measure each bit voltage with a 8 1/2 digit DMM to calculate the suitable digital correction.

The calibration process will be automated by a Windows application.
The application send a signal to the DAC (to the FIFO Lite) in order to measure each bit voltage and then it stores the measurement from the DMM.
Finally the correction digit for each bit will be calculated.

Will a user have to own a specific DMM to perform this procedure - I'm thinking of this potential board product + the Lite for DAM owners?

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Will a user have to own a specific DMM to perform this procedure - I'm thinking of this potential board product + the Lite for DAM owners?

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Yes, I will write the Windows application to interface my DMM via GPIB.

So if one would the DAM calibrated should send me the board for calibration.

At the beginning we thought to build a custom DMM using a precise ADC but the project is complex and the cost is high, and we haven't enough free time to design the instrument, so we moved to a commercial DMM.
 
Disabled Account
Joined 2019
After covid, we should have that listening session... in Belgium, or we come to France if you prefer. I'm really curious...
Edit: oops, sorry for the kind of off topic...


Or we will ask to Gentlevoice member to organise us a dac meeting in North Italy to met all each others and benchmark our ... tweaks and more (or less) clever designs :) ... I'm not sure to have better speakers than Dany's !
 

TNT

Member
Joined 2003
Paid Member
Yes, I will write the Windows application to interface my DMM via GPIB.

So if one would the DAM calibrated should send me the board for calibration.

At the beginning we thought to build a custom DMM using a precise ADC but the project is complex and the cost is high, and we haven't enough free time to design the instrument, so we moved to a commercial DMM.

OK! So you will use e.g. 0,1% resistors but with very good temp co and calibrate. Interesting approach. Nice to offer DAM calibration!

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Yes, in the DAC Lite we will use 0.1% resistors with 10 ppm temp co. or better.

The measurements and the correction algorithm implemented in the FIFO Lite allow a calibration to real 24 bit.

The same with the DAM1021, except for the thermal drift of the resistors used, I don't know what kind of resistors have been used.
 
I was wondering more about top DAC.

The top version of the DAC will keep long time development.

Substantially it's not only the DAC but the whole system including the front end (the top version of the FIFO).

The architecture is the same of the FIFO and DAC Lite, but with improved solutions in all the aspects.
For example we will use optic fiber cables to connect the dirty signals from the FIFO to the DAC, we will use different dividers for the LRCK, we will use different sine to square converters, the first 5 MSB of the DAC are thermometer decoded (instead of the first 3 MSB of the DAC Lite), and so on.

Maybe the main difference is that the FIFO Lite is a open system compliant with almost all DACs while the Top version is a closed system, the Top end of the FIFO works with the Top end DAC only, no way to use it with other DACs.
 
It could be useful if the designer told us what kind of resistors have been used in the DAM so we could take a look at the datasheet to know the thermal drift.

BTW, you can use wool for thermal stabilization of the resistors and also of the 595s, but I think a copper sheet will be better.