Low Frequency boost-only Passive EQ ???

> Will this work?

No.

If the pot is at one end, or Bypass is engaged, you just short the input. Otherwise, you just load the input with a cap, with uncertain treble loss.

The original has a 10K+1K voltage divider to set an overall 20dB loss, and then monkeys that up or down to get more/less loss at certain frequency bands.

Near as I can tell without another coffee:

PRR beat me to the punch, but here's what I sketched:



The unmarked resistor is the load impedance, which is assumed to be high.

Looking at them both, PRR's configuration is better because it will give more of a subjective impression of a bass boost (as opposed to a treble cut) as it's switched in and out of bypass.

It's your final design, Dave? :wink:

Mine is constant-loss mid-treble, variable bass loss.

Yours is constant 20Hz loss, variable mid-treble.

Or maybe I should go for coffee.

Goddamnit, you guys are just too fast! :wink: I catch my error, edit my post and there are already two replies waiting for me

[quote author="PRR"]
....Yours is constant 20Hz loss....[/quote]

It's also 20Hz variable, IMO.

Well, I said I needed coffee.

The schematic seen this afternoon is wrong-wrong-wrong.

The version now visible may be right. The output has to come from the junction of the top 10K and the 1K. And after some thought, I decided that a boost-only rig did not need a 2-pole bypass switch. It is sufficient to short out the bottom 10K pot.

Pictures:



These runs were made with a (simulated) audio-taper pot wired as a rheostat. In terms of how a pot's pins are labeled: short In and Out together, use Gnd and In+Out as the two ends of the rheostat. If you use a linear pot, you basically have flat and big-boost, with little in between.