Some measurements of the dam1021
Soekris DAM1021 R2R DAC Measurements | Audio Science Review (ASR) Forum
Soekris DAM1021 R2R DAC Measurements | Audio Science Review (ASR) Forum
I have a question for Soekris. Would it be technically be possible to extend the number of input bits from 24 bit to 28 bit or 32 bit on FPGA side of DAM1021? Reason I am asking this is that I use equalisation on PC side with a bit of headroom to prevent clipping. So effectively I could lose bits of precision while using 24 bit input material and applying a bit of attenuation and equalisation. If 32 bit could be used for communication to DAM, the equalized data could be upsampled in FPGA with less loss. What do you think about this?
Fedde
Fedde
Interesting, but I hate it when less knowledgeable post measurement using substandard equipment.... Just like other soekris dacs, the dam1021 is level linear all the way down to nothing, which his measurement equipment apparently isn't....
Could be done but too many things that need to be changed and tested.... Don't expect anything in this generation of DACs, although I'm considering more bits later on, not because I believe it will improve the sound, but just for the bragging rights....
Ok, I understand it is significant effort.
Alternatively I could do the equalisation on the DAM with the provided IIR filters (biquads). Here a bit more flexibility in usage would help. E.g. it would be great if IIR coefficients could be changed over the serial connection, either persistently (permanent storage. so restore after reboot) or non-persistently (for experiments). I would be willing to write a small PC app to provide GUI support for this serial functionality.
Fedde
Okey...
Some of the IMD measurements at SBAF actually look even worse. The "yikes messy" SMTP IMD corresponds to the 50+7000Hz dual tone at SBAF...
Really, they are not that different... check again!
Low level singel tone - jepp -> SOTA.
Maybe it's yours but it aint my favourite tune...
IMD is the most close to music that we measure.
//
Some of the IMD measurements at SBAF actually look even worse. The "yikes messy" SMTP IMD corresponds to the 50+7000Hz dual tone at SBAF...
Really, they are not that different... check again!
Low level singel tone - jepp -> SOTA.
Maybe it's yours but it aint my favourite tune...
IMD is the most close to music that we measure.
//
Okey...
Some of the IMD measurements at SBAF actually look even worse. The "yikes messy" SMTP IMD corresponds to the 50+7000Hz dual tone at SBAF...
Really, they are not that different... check again!
Low level singel tone - jepp -> SOTA.
Maybe it's yours but it aint my favourite tune...
IMD is the most close to music that we measure.
//
The thing that I complain about is not THD or IMD (which mostly are a result of THD), but the level linearity measurement. I know that the sign magnitude principle per definition is level linear down to the last bit, and SBAF could measure it. The reason why I focus on that is that it is one of the reason why my DACs sound so good. I'm also perfectly happy with the THD and IMD numbers, less than 0.01% on the lowest cost board, it look worse on the FFT because the noise level is so low....
SBAF could measure that because they used a Dscope III, that, like other real measurement equipment, change range as the signal goes down so the ADC converter stays in it's linear range. The QA401 don't do that, so instead it hit the limitation on measuring very low level signals as their ADC is simply not level linear that low....
How did you apply wax on the r-2r network?
First apply the wax pieces across the board, than use a hot-air rework station to melt wax and "push" wax all around. Take care to set your rework station to a low enough temperature and do not insist too much on a single spot.
Regards,
Tibi
Yeah, I know, I was just joking. There is a lot of bee wax around here, so, thanks again.
I have purchased over 6 Dam board till now infact I havent tried filter brewing. I have a doubt that I would like to change the filter by and external buttons either it could be using a micro controller or any other option is also fine. Can anyone tell me how to change the filters like take about 4 filters or 8 filters where it can changed externally? how its done?
Filter changing is well documented in the official docs and in this thread. Filter changing is done through the serial interface. I forget the exact specifics, but I think you can choose between four filters while the dam1021 is running. Or you can enter the uManager and upload new filters.
To use a physical button to change filters, you'd need to implement the serial commands in a microcontroller, or raspberry pi, or similar. If using a PC for serial connectivity (e.g. raspberry pi), then you can use the dam Python library, which implements all the dam controls into a simple API.
To use a physical button to change filters, you'd need to implement the serial commands in a microcontroller, or raspberry pi, or similar. If using a PC for serial connectivity (e.g. raspberry pi), then you can use the dam Python library, which implements all the dam controls into a simple API.