Big envelope filter fan here. I’ve updated my envelope filter reviews that I first put in a thread some time back on Talkbass.
Being a bit of a hoarder, I’ve still own all the pedals mentioned below with the exception of the Proton V.1, EBS BassIQ, and the Mantra (which I only borrowed for a short time)…
[b]Musitronics Mu-Tron III[/b] - The daddy of all envelope filters. Probably not the most extreme filter, and the always on slightly dirty gain may not be for everyone, but (to me at least) it is THE sound when you hear a 70’s funk record and that gritty dirty quack and squelch. It’s what Bootsy used on all those 70’s Parliament-Funkadelic, Bootsy’s Rubber Band records, what Stevie used on Clavinet for Higher Ground and of course Jerry Garcia and the Grateful Dead on guitar. IMO the Mu-Tron III is an awesome filter - 100% worth the hype, it’s the sound most other filters aspire to sound like yet still don’t quite manage. Easy to dial in: Low Pass, Gain around 4-5, Peak 8-maxed - and you can switch from low to high, up and down without changing the gain and peak controls. Downsides are primarily the large size and venerable age of the pedal. The likelihood is if you buy one it may need a service/calibration to bring it up to full spec. Another downside is the ‘unique’ power supply requirements (2x 9v batteries drain quickly and at different rates, whilst you can get costly dedicated power supplies from the likes of CAE Sound (which works great but have cost me a fortune) or Lingenburg sound). Lastly lack of true bypass is a big issue for some. I have two Mu-Tron’s - one is more ‘space-laser’ sounding than the other in high mode. Also playing them in tandem (one in up mode the other in down or one high the other low etc. makes for some fantastically stanky funk.
[b]Mu-FX Mu-Tron 3x[/b] ([b]Tru-Tron 3x)[/b] –Full of character, the 3x is a [u]very[/u] fat, warm, expressive and powerful filter, with a dedicated external 12v AC power supply seemingly giving the 3x that extra ‘Oomph’ over other filters. IMO, this absolutely nails the vintage Mu-Tron III sound, but in a modern pedal, and with a wider assortment of controls. In the ‘Mu’ setting if you roll back on the ‘Peak’ (Q) and the ‘Mu (Gain)’ controls then the filter can get really nasty, with a really nice gnarly growl & quack. Set the controls at higher levels to get the 3x bubbly and squelchy. On the ‘Mu’ setting the 3x can do everything the original Mu-Tron can do, but then there’s a lot more: the Peak and Gain settings go-up to ‘11’ (making the effect more extreme than the original Mu-Tron); you can really over-saturate the filter, [i]without[/i] the effect sounding bad. The ‘Pre’-setting engages a powerful built in pre-amp, giving you separate controls for envelope drive sensitivity and preamp (great if playing through a passive bass with low output pick-ups for example– the switchable Mu/Pre settings means the 3x sounds great with either passive and active basses). The new Mu also has a Mix-setting to mix in the dry tone of your bass with the filter. It also has the strongest, most chewy down-sweep I’ve yet come across in a filter. There’s also a filter range high/low switch (high is good for funk solos). The 3x is pretty easy to get to grips with and dial-in (it can do subtle too ☺). The only downsides with the Mu-Tron 3x are that now it’s discontinued it has become very expensive, and, given its large size and external power supply, is not particularly pedal board friendly. In comparison to the original it is hard to differentiate between the 3x and the Mu-Tron III - the gain on both my vintage units is slightly dirtier (in a good way) whilst the Tru Tron (in Mu mode) is ever so slightly cleaner. In Pre-(amp)-mode of the 3X, the sub-filter sounds are enormous (which the original can’t do - at least without a boost to the signal) and cranking up the controls means the 3x can get wilder and VERY LOUD.
The [b]Mu-FX Micro Tron III[/b] is likely to be the next filter to try on my shopping list but from the reviews that I’ve seen to date I can’t help thinking that being small form and 9v may mean the Micro-Tron may have sacrificed some of the ‘oomph’ that the originals and 3x have.
[b]Emma DiscumBOBulator[/b] –I’ve really grown to love this pedal. IMO it’s a milder filter than the Mu-Tron, but more characterful than the [b]3Leaf Proton[/b] for example. Warm, quacky, not too wet, very organic and easy on the ear. Although there is no blend control, it retains the natural tone of your bass with the envelope effect. It’s definitely not as resonant nor peaky a filter as a Q-Tron or a Mu-Tron. I’d describe the ‘DiscoBob’ is more punchy than fat & is very simple to use & dial in. Roll back on the ‘Sensitivity’ knob and it can also sound quite gnarly. There’s no discernable volume boost either when engaged. I really like the DiscoBob, but, if you are looking for more squelchy funky extremes; then this is [u]not[/u] the filter you are looking for. Kind of Mu-Tron-lite, if you get what I mean. The down-sweep too is more subtle in comparison to the ‘Tron’s’ unless you max out all the settings. On a passive bass I find combining a boost pedal with it, makes the filter sound really filthy, adds more snap & crunch & really brings out the funky best in the DiscoBob. It sounds great with a bit of distortion in front of the DiscoBob too. Takes a standard 9v Boss style adapter or 9v batter to power it. Same small size enclosure as the Micro-Q-Tron. From the clips I’ve heard, the new [b]DiscumBOBulator V.2 [/b]sounds pretty much identical to the V.1 but is meant to have more sensitivity range and triple the headroom (as well as a boost [i]after[/i] the filter) which should make it better suited to cope with all types of basses. The V.2 is on my short list to try soon.
[b]MXR M82 Bass Envelope Filter[/b] –Easy to dial in, having the separate ‘Dry’ and ‘FX’ knob’s is a really great idea. It gives you a lot of control & easily gives you as much (or as little) of your natural sounding bass, or filter effect, as you need. (You could effectively leave this as an ‘always on’ pedal if you dial in more of your dry sound for a more subtle effect). This is a band pass filter & so it sounds quite different to the Mu-Tron’s and Q-Tron’s of this world. As a result, the MXR is not as fat or peaky sounding as some other filters, but has a very analogue, liquid, percolating bubble gum pop sound to it & can get quite synthy. The Decay knob surprisingly seems to control the depth of the filter sweep (lower decay settings can make the filter sweep very low if you hold the note). The Q control adjusts the width of the frequency sweep, & sensitivity as expected determines the level that the filter is engaged. On subtler settings I think the MXR sounds very similar to the DiscoBob, but the MXR can get much more gooey & synthy if you want it to, sounding not dissimilar to a Chunk 00Funk. I think I prefer playing the MXR through a passive bass, however, you’ll likely need to crank up the sensitivity to really open up the filter. Given its tiny form factor, ease of use, & can be powered with a standard 9v power supply (or 9v battery), this is a fantastic choice for a small form mid-priced envelope filter, (oh and did I mention it has a purple sparkle finish! ☺ ). The only real caveat being the lack of a down sweep. Possibly also the best sounding filter for slap…not that I’m any good at slapping!
[b]Chunk Systems Agent 00Funk [/b]– Still the synthiest, slurpiest, sloppiest, gloopiest filter I’ve tried. The 00Funk can definitely get Mu-Tron-a-like, (if you set all four dials to around the 12:00 mark), but the 00Funk is a lot more wet and synth orientated. It’s been said previously on Talkbass that the 00Funk is hard to dial in the sounds that you want, but I found the trick to controlling the 00Funk is to keep the “Sweep” around the 12:00 mark and then adjust the ‘”Pitch”, “Smoothness” and “Squelch” to your liking. Want ‘wacky 70’s space laser’ sounds? then the 00Funk is definitely for you.. The 00Funk even has a ‘mayhem’ setting on the squelch knob. If you partner the 00Funk with a [b][i]Chunk Systems Brown Dog[/i][/b] gated fuzz you get some incredibly funky, chunky, synth sounds. The 00Funk also sounds very funky indeed with an OC-2 or Octron, or the like. The 00Funk can be powered by a standard 9vdc Boss style power supply or has a handy slide out tray for 9v battery. The downsides of the 00Funk: the control knobs are [u]very[/u] sensitive, change a setting just slightly and you get a completely different sounding effect. Whilst powerful, I also found the down-sweep to be a bit noisy (the filter is wide open) and it’s not as simple to dial the down sweep compared to the Mu-Tron 3x or big box Q-Tron. Watch your speakers on the down-sweep setting too. Sadly, Chunk pedals are currently out of production. The [b]Iron Ether Xerograph Deluxe[/b] and [b]Moog MF-101 LPF[/b] are the most similar sounding to the 00Funk but I’ve yet to try either of these first hand…one day maybe.
[b]Chunk Systems OS [/b]– ostensibly the same analogue filter circuit as the Agent 00Funk but throw in a mix of Octaver, Gated Fuzz (from the Brown Dog), LFO, ADSR, etc., and you have an incredible range of analogue synth and fuzz-filter & filter-fuzz effects and the like out of this little red funk-box. Throw in the ability to build your own patches from scratch with up to 50 savable presets, so you can create and save exactly the effect that you want and go straight to it time and time again. The default thirty firmware presets are generally out of this world too. The downside? the UI is not particularly user friendly to say the least – it’s a very complicated interface, with no save/upload error messages! The Chunk OS is a pedal you really need to invest a lot of time (and patience) with, but it’s well worth it: Once you get ‘that’ sound lock it in as a preset, or save it to the memory card, and funk away to your heart’s content. The OS can also be powered by a standard Boss style 9vdc supply or 9v (slide drawer entry) battery (although I found the OS drains batteries quite quickly). Also out of production currently.
[b]EHX Q-Tron (original) [/b]– This is the old wood boxed trapezoid Q-Tron’s (I’ve not tried the newer XO series, or the Q-Tron+ which has an added effects loop and a fast/slow response switch). In comparison to the Mini or Micro Q-Tron, the original Q-Tron is a bit harder to dial-in, & needs some adjustment to trigger the filter across different basses; (to start with you need to set the gain (sensitivity) low, and the peak (Q) high and then slowly adjust the gain up & peak down). Once you get there though, it sounds absolutely fantastic. On low range, the big box Q-Tron can get [i]really[/i] very quacky, and on high range it can get pretty squelchy, (though not as wet as the 3x, Chunk, or as bubbly as the Enigma or MXR). A VERY Mu-tron III-esque filter: If you over-saturate the filter I think it adds a nice distortion too. Additionally, there’s a lovely staccato ‘bwap-bwap’ down-sweep that gets really chewy especially on Mix or BP settings. Sounds great too with a Boss OC-2 and/or a bit of dirt in front in it. Added features of the big box Q-Tron in comparison to the Mini/Micro Q are: down-sweep, bass boost, mix and range controls. It’s a ridiculously retro chunky-sized pedal however, can be overly peaky if you don’t set it right (ice pick like!), and needs its own dedicated 24v power supply, so is not at all pedal board friendly.
[b]EHX Mini Q-Tron[/b] –The Mini Q-Tron is positively dripping with old school Bootsified funk: warm, deep sounding, very fat, greasy, & squelchy. I’m amazed that these don’t sell for a lot more second hand as they are as good as , if not [i]better[/i] than many other ‘higher-end’ filters (IMO fatter sounding than a [b]3Leaf Proton[/b], or [b]EBS BassIQ[/b] - both of which I owned and sold soon after as they sounded a bit “meh” and muddy sounding respectively to me in direct comparison). Easier to dial-in than the original Big Box Q-Tron. With the Mini it’s pretty much put it on ‘low pass’ set Q and Drive anywhere between 11-3 o’clock and funk away! The Mini-Q gets close to an original Mu-Tron but also has its own character. I can get it sounding like some of those old 70’s Parliament records. I managed to get one with the original wooden box (these wood boxes officially help keep the funk in when it’s not in use! ☺). Downsides are there’s a definite volume boost when you engage the pedal, the BP and HP settings lose all bottom end on bass, and the Mini really isn’t very ‘mini’ at all – it’s only slightly smaller than the original big box version! The Mini Q also needs a special 9vdc 1o0mA (thin pin) adaptor if you want to power this from the mains (or use a 9v battery).
[b]EHX Micro Q-Tron[/b] – My first ever filter purchase. EHX swear that these are the same circuit as the Mini-Q-Tron just in a smaller enclosure, but I’ve A/B'ed the Mini and Micro Q side-by-side and to my ears the older Mini Q [i][u]is[/u][/i] more organic & juicier sounding than the Micro Q-Tron. The Micro Q-Tron can be just a bit abrasive in comparison to the other Q-Tron models, with harsher peaks. However, by adjusting the internal trimpot to around the 5 o’clock mark, then the Micro gets to sound real close to the Mini Q-Tron: fat, warm & squelchy, but not [i]quite[/i] with the same mojo as the Mini Q (which I do prefer). IMO, the Micro Q has this slightly "metallic" sounding edge in comparison to the Mini. The trimpot adjustment does tame that Q-Tron volume boost (slightly). Like the Mini Q, only the Low Pass setting is useable on bass. For the money though, the Micro Q –Tron is a good value budget filter, has plenty of quack and squelch, and [i]is[/i] pedal board friendly (smallish form factor and is powered by standard Boss style 9vdc supply or battery).
[b]EHX Enigma Q-Balls[/b] –This is a very flexible filter, with a steeper initial learning curve than other filters, but don’t let that put you off. The Enigma has a kind of Mu-ton/Q-tron vibe; very Bootsy, (really bubbly, gurgly & quacky), but with more controls & therefore a lot more flexibility & range than most other filters, especially with the versatile downsweeps. I really like that ability to control the blend between the clean tone of your bass and the effect in a single control. This also makes the BP (and HP) settings far more useful than they are on a Mini or Micro Q-Tron. The start & stop frequency controls are intuitive with a wide range, and very interactive with the sensitivity, Q, attack and decay settings. The Enigma can be both subtle or can get pretty extreme, especially with the blend, Q and Sensitivity turned fully clockwise, whilst the reverse sweep at its most extreme can get very ‘whompy’. The switchable distortion is also very useful for making lovely thick old school analogue synth sounds, (but the distortion itself is not adjustable, unless you count the internal trimpot level control). The Enigma can get very loud with the Q and Sensitivity maxed out, and, when you engage the distortion, but have found this is controllable somewhat by using the Q and the Blend. It’s a knob twiddler’s delight of a filter, and really rewards spending lots of time understanding how the controls interact with each other.The Enigma can be powered with a standard Boss style 9vdc adapter (doesn’t take batteries though). I do really wish the Enigma had presets though, I find myself drawing diagrams to remember my favourite settings! All that can mean it is not an easy pedal to gig with.
[b]EHX Sovtek Russian Bassballs[/b] – A vocal sounding dual band filter. Extremely simple to use; one knob, with a switchable on/off distortion. The Bassballs is a bit of a one-trick pony, (and definitely not Mu-Tron/ Q-Tron a-like at all – it doesn’t quack or squelch), but what it does it does very well. Mine’s an ancient pedal and the sputtery (almost dying out) distortion gives the Bassballs real depth and character. Without the distortion on, I prefer the ‘Sensitivity’ at quite a low setting to bring out the ‘burbling,’ ‘burping’ best in this filter. On higher settings you can really hear the sweep of the filter. Like a lot of the EHX filters, The Bassballs also has an internal trim-pot apparently, but I’ve never messed with it. No idea if the Russian version sounds any different from the NYC version though! The Sovtek version needs a special 9vdc 1o0mA (thin pin) adaptor if you want to power this from the mains (or use a 9v battery). The NYC version takes a standard 9v Boss style adapter or 9v battery, and the Nano is a lot smaller than the industrial looking Sovtek version.
[b]EHX Stereo Talking Machine[/b] –The STM is a formant filter, shaping vowel type sounds replicating the human vocal system through (I think) multiple filters. The STM, therefore, sounds unlike any other filter I’ve come across. The STM speaks to you (almost literally): it’s the closest thing you can get to a talk-box on your bass. It comes with 9 editable/savable presets, and the default presets are really strong. The (+/-) sensitivity sweep gives you double the fun as you can control the direction of the sweep of each effect. The Blend, Attack and Decay controls really add to the STM’s flexibility. The STM also can be used with an expression pedal too, and has built in (& programmable) fuzz and LFO modulation. Downsides - to my ears, the Bassballs effect on the STM sounds more digital than the standalone Bassballs, (the STM [i]is[/i] digital not analogue). It’s a lot of fun though I don’t know if you’d use some of the more wacky effects in a live scenario (having said that I only noodle about at home). It’s also another pedal (much like the Enigma) where you need to spend some real time with it in order to get the most out of the range of effects available. You also need a spare pair of hands for adjusting the auxiliary fuzz and LFO functions, whilst trying to play & hear what they sound like ☺ Can be powered with a standard Boss style 9vdc adapter only (doesn’t take batteries).
[b][u]My Disclaimer [/u][/b][b][u]☺[/u][/b][b][u]:[/u][/b] Envelope Filters are [i]the[/i] most subjective of effects. Filters react differently on your playing style, your tone & equaliser settings on both your bass & your amp. The strength of your signal to the filter is also very important, and also the type of bass you’re playing may make a big difference; a hot-active bass can be too much for some filters (& you may have to dial back on your volume or the Q and Drive/Sensitivity controls of the filter); whilst a passive bass with lower output pick-ups may benefit from a signal boost, which on a passive bass really helps to open-up and trigger the envelope and make the filter effect come alive. From my own experience I think I prefer analogue filters. The EHX Talking Machine and [b]Source Audio Manta[/b] sound digital to me (perhaps because they are ☺). The Manta that I tried out had some great synthy sounds in it, but I couldn’t get it quacking like an old school Mu-Tron. Maybe I needed to spend some more time with it.