Re: Codec & ADC's
¿ªÔÆÌåÓýYou probably know this but there have been several papers written on the weak signal performance of A/D and D/A converters being a function of the quality of the voltage reference quality.? Noise at the reference (the reference is generated internally with the PCM1808) that comes in via the Vcc power supply line sets the zero signal bit range of the device. ?That does beg the question of how clean the power is that was used in the experiment (to correlate to the zero ¡°shorted¡± signal level).? I¡¯ll have to try this myself to see because ¡®ve been looking at some new low noise VRs for this very reason. ? ? Dr. William J. Schmidt - K9HZ J62K(J68HZ) 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ? From: [email protected] <[email protected]> On Behalf Of Bob Larkin
Sent: Saturday, May 3, 2025 5:40 PM To: [email protected] Subject: [SoftwareControlledHamRadio] Codec & ADC's ? I recently did some ADC measurements in preparation for an update to my Audio VNA.? I mention it here as I think it has some stuff of interest to the T41 project.? The measurements are on-going, but as of now included the SGTL5000 (ADC side)and the PCM1808.? I believe it was the T41 use of the PCM1808 that got me to look at that part---thanks.? The web page for the study is ? For this group, one interesting element that came out is that the PCM1808 produces 24-bit output data, but this is lost back to 16 if you input I2S via the Teensy AudioInputI2S followed by a Q15 to F32 conversion.? If you do the input via AudioInputI2S_F32 of the , it will include all 24-bits automatically, as well as saving a conversion. ? ?Questions, comments and corrections are all appreciated.? Bob? W7PUA |
K9HZ