This might work as your front end? TLV320AIC34 from TI, so you can TDM data out Harold Hallikainen wrote: > > Harold Hallikainen wrote: > >> I'm wondering if a multi-channel (perhaps 8 channels) audio level >> metering >> chip (VU meter) with an SPI interface exists. It would be great if the >> inputs were differential so they could be hung across a balanced audio >> line. A PIC will then pull this data and update a graphic display. Right >> now we're looking at individual balanced rectifier and filter circuits >> driving analog inputs on a PIC. LOTS of parts! It'd be great to just >> have >> one chip handle the whole thing. Another possibility would be run all >> this >> into a DSP and calculate the levels, but, if a chip is already out there >> that does this, it'd be great! >> >> Searching the usual suspects doesn't seem to turn up anyting. >> >> Ideas? > > Ummm, aren't you building this chip yourself? DSPIC with SPI interface, > and > 8 channels of A/D. Sample audio at 44khz, then rectify and filter > digitally. > You can put the needed prefilter into the differential to single > ended op amp circuit. > > Why would you use balanced rectifiers and filters? > Just do a balanced to single end conversion at the start and cut your > parts > count in half. > > Latest 'ideas for design in EDN mag) has a circuit for using a single > transistor > to do full wave rectification (just bias it right and use right gain set > resistors). > > Using software for the whole thing gives you the advantage of being able > to change the filtering, if needed. > > R > Thanks for the comments! I'm hoping to find a chip that already does the job, but can either do this in analog hardware or software. The balanced rectifier is an ideal rectifier circuit with a differential input. Our incoming audio is balanced, not single ended. I'd like a chip where I just feed it 8 balanced audio signals and all the VU levels show up on an SPI. I may end up doing it in DSP. I'd probably still need the differential amplifiers for each input. Thanks for the comments! Any more? Harold -- FCC Rules Updated Daily at http://www.hallikainen.com - Advertising opportunities available! -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --------------------------------- Fussy? Opinionated? Impossible to please? Perfect. Join Yahoo!'s user panel and lay it on us. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist