Below you see Sweef. It’s an embarrasingly simple attempt to build an inexpensive variable passive bandpass filter for my own live setup. It does a nice job on Ecco, and you can build it yourself, too.

Comments (at end of page) are appreciated.

sweef - by jayrope 2014

Sweef needs no power, can be bypassed and otherwise gets you almost any round sounding emphasis from sub bassy on the left side of the dial to almost ultra sounding on the right. I tend to use it on extreme settings, it doesn’t do much in the center, although kind of resembles a 1970s broadcast setting.
The filter sweep is very musical/smooth, without much noticeable filter resonation on the respective bandpass ends.

Schematic
sweef - by jayrope 2014

See part list at end of this article.
Values for the pot, C1 and C2 are mainly the result of experiments with spare parts (1k log pots with solder ends, a short dial and a small body size seem hard to get in Germany), mostly not calculation.

Precautions
1. Sweef has no flat frequency response other than bypassed,
2. If Sweef is on the overall signal level drops noticeably, well, it’s passive.

Other flaws (out of phase, impedance chaos etc.) are very possible.
I chose a pretty low impedance setting, for this wouldn’t steal too much audible level, when turned on.

Possible changes
1. If you don’t like the sudden drop towards the highest frequency level you can insert a 4.7 Ohms resistor (adjust to taste) before C1. This minimizes the range of the pot.
2. You’ll get even more bass by increasing the value of C2. But then you will probably also have to increase the value of C1, as otherwise there’ll be a significant level bump somewhere in the lower mids. See 1. for what happens then.
3. I might build an active version sometime. Don’t ask me when.

I am not a tech expert, i work by ear. If you’d like to give me audio expert tech advice regarding this, please comment.

Thank you and enjoy.

+++
Part list
Aluminium case type A – www.musikding.de – 4,50 €
Pot – www.conrad.de – 3,99 € (any is good as long as 5k log)
Cap MKP10 – www.sly.de – 1,09 €
Cap SHR – www.musikding.de – 0,40 €
Mono 1/4” sockets (2x) – www.musikding.de – 2,50 €

Addendum
Sweef is apparently an Africaans word, and it means “to float”. Hell yeah, it does.

Comment

Enter your comment below. Fields marked * are required. You must preview your comment before submitting it.