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Small, sweepable low pass filter?

ryognbass

ryognbass

Supporting Member
Nov 7, 2008
830
10
North NJ/Worcester MA
#1
Hi all,
Ive come to notice one of my most commonly used effects is a resonance filter on the ME50B in which sweeping the rocker pedal back cuts high frequencies much like a low pass filter. As far as LPFs go, I know of the Moog LPF but im turned off by its complexity and size. Im imagining a small enclosure (Roughly the size of an EHX nano) with a single knob to set the cutoff of the filter and the on/off footswitch, and an output for an expression pedal which could bypass the knob. Another option would be to forgo the separate enclosure and build all components into a wah housing such as the defunct shell of a Crybaby.

Im wondering if A) this is even feasible on a homemade scale and B) is there any interest elsewhere among bassists for a pedal such as this?

Thanks in advance for your help.
 
#4
Thanks for the link Jared! but that is a bit overkill for what i need. I'm just looking for a good sound in a stupid simple package.

and that is true about the Moog. I didn't mean to call it complex by any standards, just in comparison to a single knob option it is. Pardon the Misconception. :D
 
#10
You'll want a more complex filter circuit than that if you want that synthy squelchy resonance. Otherwise it'll just sound like a passive tone control, rolling off treble without the sharp resonant peak at the cutoff point. There is a 9v version of the Korg MS-20 filter circuit out there somewhere...
 
#11
Im not necessarily looking for the synth gulp, moreso a dubby, deep, yet punchy tone. i think my best option so far stands at the Moog LPF. i do like the idea of the ZCat though.

i would like to see this idea take shape one day as just a cheap, no frills LPF, almost like a passive tone knob but clear and deep. if only :ninja:
 
#12
I'm not sure what you mean by clear and deep, having never heard the pedals you're describing. IMO you need a boost of some sort to go along with the low pass. If you don't want a resonance peak, it'd probably have to be a boost in the lower mids or mids or an overall volume boost.
 
#13
Clear and deep sounds to me like a "butterworth" filter. No resonant peak, and you can build a 12db/octave one with some pretty simple parts (AFAIK):

RC12dBoctLPFNonInv.gif


I belive that you can replace the 10K resistors with a stereo (really just 2 stacked mono) potentiometer to change the cutoff freq, but don't quote me on that LOL

That circuit to a boost would provide some NICE times methinks.

Anyone know if you can get a stacked pot with like 4 levels? Then I think you could just run 2 (maybe make 1 switchable in/out) to get -24dB/oct....

EDIT: correct me if I'm wrong, but would replacing the 10K resistors with 250K pots allow a variable LPF from around 40Hz to totally open? (linked/stacked since I believe that both resistors must be equal in order to keep input and output in phase)
 
#14
ryognbass said:
Im not necessarily looking for the synth gulp, moreso a dubby, deep, yet punchy tone. i think my best option so far stands at the Moog LPF. i do like the idea of the ZCat though.

i would like to see this idea take shape one day as just a cheap, no frills LPF, almost like a passive tone knob but clear and deep. if only :ninja:
Click to expand...

For a focus on dubby sub-bass tones (vs modulation), the Moog LPF is your best option- wide resonant range that makes for huge round bass. Second best would be the MS-20 clones like the Brain Freeze and Photron; they have amazing clarity and a tighter resonant range, allowing more of the input signal's original tone to shine and can do some great punchy tones-- they also can do big fat bass, but I'd say its a little punchier and not quite as big and round as the MoogLPF, but either/or would do the job very well.

I think you might be overlooking the importance of the resonance control, even for static lowpass tones that do not include any filter movement (lfo, envelope, etc) and the associated 'synth slurp', but if not then another option that may suit your needs well would be the EHX Mole, or even just an EQ like the GEB-7... cut the highs, boost the lows-- a lowpass filter with no resonance! :smug: The DOD FX-25 might also be a good place to start your search, as they can be found for $30+ and do a nice fat and punchy bass tone when the sensitivity is set to 0, and they only have 3 knobs; if you spring for an original at about $60, you'll only have 2 knobs!
 
#15
Not to be an ***-HOLE or anything, but my experiences with the rudimentary LPF/HPF on the EQ of the GT-10B say different.

An EQ with at most be +/- a certain # of dB. With a high shelving EQ set to say 100Hz and -20dB, everything above 100Hz (approximately) will be @ -20dB. 200Hz=-20dB, 400Hz=-20dB, 800Hz=-20dB, 1600Hz=-20dB, etc....

With a LPF or HPF the dB cut (what we're looking for in this case) keeps getting greater the farther from the knee frequency you get. Say you go for an LPF at the same 100Hz, -12dB/octave. 100Hz would be around -6dB (soft knee freq stuff), 200Hz=-12dB, 400Hz=-24dB, 800Hz=-36dB, 1600Hz=-48dB, etc.... To compare apples with apples, how about a -20db/octave LPF @ 100Hz? --> 100Hz=-10dB, 200Hz=-20db, 400Hz=-40dB, 800Hz=-60dB, 1600Hz=-80dB...

not really the same, depending on what kind of signal you're running before each one. An octave up+dry mix comes to mind. With the right LPF you can boost like crazy and still not have any harshness from the octave.
 
#16
Nyarlathotep said:
Not to be an ***-HOLE or anything, but my experiences with the rudimentary LPF/HPF on the EQ of the GT-10B say different.
Click to expand...

Im not 100% sure what you're responding to, but I'll go out on a limb and assume it to be this:

then another option that may suit your needs well would be the EHX Mole, or even just an EQ like the GEB-7... cut the highs, boost the lows-- a lowpass filter with no resonance! :smug:
Click to expand...

-Note the ":smug:" and think about my suggestions relative to his application, not an 'octave up+dry mix" ;)

Going by my experience with a long list of lowpass filters and a GEB7 which I currently use, I'd say that any of my suggestions will produce a "dubby, deep, punchy, clear" tone he seeks. I still say a lowpass would probably be best, though his description is vague and leaves lots of room for interpretation, therefor I tried to give as comprehensive of an answer as possible.

rygonbass - could you post some clips of the kinds of tones you're looking to make?
 
#17
its not a very specific sound, but its similar to the sweep found in the synth line of pink floyd's breathe at 5:18.

if i can figure out how to post a recorded clip i can give the exact sound im prettymuch after. its the "resonance" filter on the expression pedal of an ME50B though if that helps. when back, its deep, cuts highs and masks distortion, and opens up the tone full when rocked forward. thanks for the conjecture though. its very interesting to get in on the jargon:smug:
 
#19
fightthepower said:
-Note the ":smug:" and think about my suggestions relative to his application, not an 'octave up+dry mix" ;)

Going by my experience with a long list of lowpass filters and a GEB7 which I currently use, I'd say that any of my suggestions will produce a "dubby, deep, punchy, clear" tone he seeks. I still say a lowpass would probably be best, though his description is vague and leaves lots of room for interpretation, therefor I tried to give as comprehensive of an answer as possible.
Click to expand...

True, I guess. Anything EQish, set right, would work for dubby stuff :D Our very own BurningSkies gave me that advice once, and its damned good advice. Actually, now that I think about it, an EQ might work out better depending on how and where on the neck you play (especially if you're cutting out stuff up from a very low freq) since the attenuation of the higher notes on the bass would be cut equally instead of getting less and less audible as you go up the neck.

If all you play is anything below the E on the A string, or if your bass has a lot of high end, ya, an LPF would prolly work better.

Jazz Ad said:
Sweepable hi and low pass filter.
Click to expand...

the LPF (hi-cut) only goes down to 1000Hz tho. The moog (and brain freeze, IIRC) go MUCH lower. Also, the HPF (low cut) only goes as low as 80Hz. It would still kill (or sufficiently maim) most of the notes on my bass, tho not as many on a standard tuned 4 banger I guess.

Interesting that I missed looking at anything "lo-fi sim" when seeing if anything could do the low set HPF thing that I have my GT-10Bs EQ set to. Works out great after some fuzz to create some nice fakitar sounds.
 

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