Just wanna know of a good design for bass, or at least mods for good response with bass. Thanks a lot!
All IMHO of course:
a) EH BassBalls - take the filter tune trimmers out to the front panel, also add in a pot to adjust the volume of the fuzz fed through the filters when 'fuzz' mode is engaged (otherwise the volume of the fuzz is proportional to the sensitivity control, which unless you are lucky means the engaged / bypass volumes are markedly different)
b) MutronIII - can adjust the range of the hi/low switch by changing the pairs of associated caps (the 'hi' range isn't so useful for bass); add in a clean / effect blend control; separate the sensitivity and gain controls .... all these mods I've done on the rubber fetish (MutronIII clone I make) and will be up in the not too distant future for DIY purposes.
For bass the MAIN thing is to be able to blend in some clean signal so you don't lose the bottom end / tone ... I think Moosapotamus has a bass mixing design up on his website also....
Mike
Be sure to search here for lots of general envelope filter info, a lot of it from resident expert Mark Hammer. Also check the *Technology of* article at geofex by M. Hammer. I wish I had a bass rig, as I LOVE the sound of EF on bass.
Kerry M
I just built my own version of the Neutron at GEO. It ended up more like the Meatball.....
There you have two different animals, which work almost the same. You can basically take parts from both and combine them as you want, as long as you understand how they work. There are a couple of things you might want to try:
1. A blend knob, for blending wet and dry. That's fairly simple to do. Check the McMeat
2. The feedback capacitor values. Try everything. I built the Neutron with leds and LDRs and ended up puting in something completely different, because the LDRs were VERY sensetive. (I also ended up putting a 10k resistor in series, to stop it from distorting oddly...) For a ballsy wah you would like big values, and for more of an harmonics colourer you would like smaller values. And, if you use distortion, you can get a great growl with smaller values.
3. Input and output caps. At higher settings you'll want them as big as possible (like 2,2u or something...). At lower settings you might find the boominess annoying. I have't made any high-pass filtering after it, but I probably will some day...
These were mainly for low-pass filtering. High-pass is something completely different... With distortion, a slow attack and decay you can get cool synth sounds... But twiddling the knobs is an art of it's own. I wont get into that now.
Good luck with the build!!! :D
There are really only 3 things you need to keep in mind about an env fil for bass:
1) That the type or sweep of the filter not be such that one loses the "foundation" that bass provides. This can be via using a lowpass filter mode, rather than bandpass, or by being able to blend in full-bandwidth straight signal with a bandpass signal. In most instances, I imagine the designer/s have tried to retain full bandwidth at the input and output, by using suitably large DC-blocking caps, but occasionally you can profit by increasing them a bit to keep more bottom (e.g., if the low-end rolloff is around 60hz, given the input cap, doubling that cap value may be helpful).
2) That the filter range be suited to the harmonics that matter for bass. Most envelope filter pedals are made for guitar, with some lip service to bass. Generally speaking, the filter-cap values can be doubled to lower the filter range by an octave, which can still work a bit for guitar but improves things for bass.
3) That the envelope follower response be appropriate to the instrument. This actually has a few sub-factors:
a) Many basses put out more substantial signal levels than do guitars, simply because of what a string that thick does to your average pickup coil. In some instances, this may mean that only a small portion of the Sensitivity/Sweep-Amount pot's rotation is usable to you, which makes it harder to dial in the sound you may want. There are a few fixes. One is to simply reduce the gain of the envelope follower section by reducing a feedback resistor. Another is to stick a fixed resistor in series with the input of the Sensitivity pot, so that it mimics a higher-value pot turned part way down (this will let you use a larger part of the pot's rotation).
b) Envelope followers also have to see only AC, which means there will be a DC-blocking cap en route to the follower, which in turnmeans that some vital low end may be inadvertently shaved off from what gets fed to the follower. You may, or may not need to increase cap value here too. Alternatively, you can shape what part of the note range the pedal responds to most by changes to the cap value - including making it smaller/lower.
c) Envelope-ripple is a constant plague of envelope filters, but is a bigger problem with basses because lower notes (and especially single notes) mean big gaps between the peaks of a rectified signal. You will definitely want a filter with a full-wave rectified envelope follower, like the Mutron and some others. You can certainly get nifty sounds out of a DR.Q or Baseballs, but you will never get anything that will sound pristine after the initial attack of the note - the ripple will bug you. The LDRs used in the Mutron/Q-Tron also further smooth out the ripple.
d) Time constants. You can get around the ripple issue on any env filter by having a longer decay, but longer decay times mean you need to wait longer between notes to get a nice pronounced attack on the sweep of the next note you pick/whack, so too much decay ends up being a cure that causes problems. Strummed chords on guitars can sound nice with long decay, but I suspect in many instances it is kind of a hindrance to moving on for bass players. Better to start with a FWR envelope so that you have more room to play with decay time (i.e., shorter decay-times will be more tolerable). Variable attack time is probably important for matching effect to song "feel" for all instruments but moreso for bass. "Dreamy" bass drones for slower ballad things are virtually impossible if the attack time is permanently whip-fast. So, either buy/build something with a variable attack, or do the mod. Most folks here will confirm that it dramatically ups the odds that any given envelope filter can be a successful match to any gven song.
well thanks you guys!!. what about the bifilter follower?.
The BFF is a terrific and truly underrated unit. Although in some respects it would seem to be the same thing as a Baseballs (dual staggered bandpass filters), there are a few things noteworthy about it.
1) It is bipolar powered, which makes for awkward use of wallwarts, but yields more headroom and has no specific op-amp requirements at all. Use the best that your pocket allows.
2) It is cleaner-sounding than the BB.
3) The filters are bandpass but of a different type. As JC Maillet wisely noted, the location of the LDRs in the bandpass filters transforms the unit into something that *feels* very different to the user. Normally, the centre frequency of that type of bandpass filter can be tuned by means of a resistance to ground. The LDR half of the CLM6000 provides that resistance to ground. Of course, such filters are typically used as fixed devices, so although that resistance to ground has an impact on signal *level* no one really makes a big deal of it. When JC was over at my place last summer and tried out my BFF, his ears detected something I hand't really noticed before, and that was a certain compression. Looking over schematic, he realized that the input resistor in the filter, and the optoisolator, formed a voltage divider, such that as the centre-frequency swept upwards, this voltage divider attenuated the input signal much like a compressor would. The result is a much smoother sound than you get out of the Baseballs.
Both the Baseballs and BFF are quite mod-friendly and I've modded each and been very pleased with the possibilities provided. The BB will sweep a little faster than the BFF, because the control element is a transistor rather than an LDR. As for a clean sound like you'd want for bass, though, the BFF wins hands down. The headroom, better op-amps, inherent compression, and greater ripple-rejection of the LDRs gives a much smoother tone.