multipot kluge

[tedmich]

had occasion to want a LR 48db/octave low pass filter for my subwoofer and ran across a nice implementation with a single quad op amp. To give a variable freq. low pass I needed to vary 8 different resistances; two for each op amp section. Happens that West Florida Components has nice 8 section 20k Bourns pots for $2, so I made a toner transfer PCB that allows me to wire the 8 gang pot in series with 8 resistors.

I can flip the pot for either increase or decrease with clockwise rotation, and I now have a 42k-22k 8 section pot which sweeps my LR lowpass from 60 -120Hz.

Now to build my Linkwitz transform circuit so I can shred my 12" sub at 20Hz in a 1ft^3 enclosure!

[J M Fahey]

Nice.
Never thought you could actually buy one over the counter.

[tedmich]

just finished wiring up the +/-26VDC 20A power supply (Vicor/RO Associates DC/DC switcher) in the 1U case, but the LR wasn't work...the little Acopian op amp supply was putting out +1.5v/-5.2v... gotta put another in!