I was wondering, how do you calculate the values for a JG style filter? I haven't seen many RLC passive low pass filters, are the resistors to improve stability? Or some sort of neat impedance matching for the L?

Hey All. JL can have boards produced in ~15 days. A couple of questions for all of you; would you like 1) bare boards, 2) boards with SMD assembled, or 3) boards full assembled and tuned for JL DACs & 2nd order?

Whoops, managed to miss a bunch of replies with that sticky on the top!

Looks like I was following the wrong schematic- R1 is either 470R or 18.9K here. I'd be very interested to see your schematic (especially the new approximation you're working on) if you can post it!

Very neat to see the source resistance and capacitance being used to form another filter pole. I hadn't accounted for this and that would explain why my sims were so ringy. You mention the FR changes depending on the filter order; is that a symptom of instability, or just a slower rolloff associated to the lower filter order? I've had issues with variable order filters going unstable when you'd just remove a pole in passive implementations.

No boards for me since I don't have any Vout DACs, but I'm with Hroð. Sorted transistors would be awesome, but nothing soldered in case we want to tweak. Since it's just a ladder filter and a JFET buffer you could easily make it into an awesome universal discrete DAC filter that way.

Thanks mates; I'll pass that information on to the JLSound team. Here's a schematic of the a JLFilter build tuned for 3rd order. For second order, drop C3, change L1 to 18mH, and change C4 to 100p. This schematic is for 1 channel, so 2x for the build: