best diy envelope filter for bass

[axr]

a friend of mine asked about building a envelope filter for his bass (passive pickups), any recommendations, thanks.

[mikeb]

MutronIII or clone, but check in a clean blend control (easy to do)....

Mike

[Bent Penguin]

Hi Mike, do you have a particular blend circuit in mind. I have a Neutron build in progress (for my bass) and would be interested if you have any specifics or success stories. Thanks.

[niftydog]

define "best"!

Simplest?

Most flexible?

Cheapest?

Most tricked out?


For cheap and simple, you can't go past a Bassballs.

For tricked-outedness, a Rubberfetish.

For flexibility, there's a DIY version of the Meatballs.

For classic sounds, Mutron like Mike said.

Anyone seen/heard the MXR Bass Auto Q?


But boy do I love my new BassIQ... thanks again Mike! (PS: some goodies in your inbox!)

[Mark Hammer]

It would depend on the style of music he plays.  Many of the envelope-controlled filters tend to have longer decay times.  These are helpful for minimizing envelope-ripple** and nice feelwise for rhythm guitar, but take too long to resettle for the purposes of bass playing a lot of the time.

The decay time and "resettling" issue is mediated by a few other things.  One of them is the type of filter and how much bass is preserved throughout the sweep.  Some of the most familiar ECFs use a bandpass filter.  While this does a nice job at emulating an automated wah, as it sweeps upward, you lose the bass for a moment, and that can be annoying.  One way around this is to use an ECF which has a lowpass setting.  I suspect this is part of what made the Mutron so desirable, historically.  Being able to retain the bass but create the illusion of a swept bandpass with the resonance cranked, would prevent losing the "solid foundation" aspects that people expect from a bass.  So that's solution/recommendation #1: opt for an ECF that has a lowpass filter setting.

Of course, that's not the only way to get bass content in there.  Another way is to use a blend circuit, such as is found in the Meatball, but which can be added in a variety of other designs.  Here, a mixer stage is used at the output (could be passive or active), and a bit of the straight signal is blended in with the filtered signal.  It makes the filtering seem less obvious, but for bass that works out nicely.  There's solution/recommendation #2.

The third way to keep the bottom is to use the traditional swept bandpass filter, but shift the filter range downward, and keep the resonance modest.  So, when it sweeps, it will start from way down, and not sweep too far out of the bass range, returning to it in reasonable haste.  A reduced Q means that it will not place too much emphasis on a highly select band and draw attention away from the bass frequencies.

Last year, I made a modded Doctor Quack for a bass-playing buddy who uses it in his studio.  I doubled the values of the range-setting caps (from 4n7 to 10 or 12nf. to move the range of sweep down an octave from stock, and stuck in a passive blend control to mix what comes out of the buffer stage (Q1) with what comes out of the filter, prior to overall output.  Sounds great and he likes it.

I might point out that when you retain the bass, the longer decay times needed to minimize objectionable envelope ripple aren't themselves quite as objectionable.  If you had to wait for a Dr Q/Quack to resettle before you heard bass again, it'd drive you nuts.  With a bit of clean bass always mixed in, the resettling isn't as UNsettling.

(**"Envelope ripple" is the result of imperfect detection of the instrument envelope, usually through half-wave rectification.  The small variations in envelope signal make their way to the component being controlled by the envelope, and "wiggle it just a bit, mostly during the much slower decay phase.  Many musicians hear this as a kind of annoying trill or distortion.  The simple mods that can be done to reduce or smooth out such ripple also result in having longer decay times.  All other things being equal, LDR-based filters tend to have less noticeable envelope ripple that FET, transistor, or OTA-based filters.  Of course, it is always possible to improve envelope detection/rectification and make a filter unit with no discernible ripple using ANY technology.)

[Connoisseur of Distortion]

Build the Fuzzy Balls by Marjan Systems!! (link to marjan available in schematic section of aron's page...) With a dozen pots and a dozen switches, he's bound to be able to find a nice sound  

[niftydog]

Yeah, that's on my list. That is the clone of the meatballs, BTW!