New FAQ article about envelope filters and auto-wahs.

[bongomania]

http://www.ovnilab.com/articles/filter.shtml

As with all of my articles, it's a work in progress, so please give me feedback on anything that needs correction, clarification, more in-depth discussion, or is missing altogether. I don't intend this article to go into much technical detail, or to name or compare all the popular models out there--just to correctly answer the basic question of "what is it" in a way any noob can understand. Whatcha think?

[fightthepower]

One thing that I would potentially add is something along the lines of 'LFO', or 'ie LFO, low frequency oscillator' after the bolded 'oscillator' quoted below, since 'LFO' is sometimes used in a pedals description, and its connection to 'oscillators' might not be made by the uninitiated.

The term "auto-wah" is used by different companies to mean two different things: either an envelope filter, or a filter that constantly opens and closes in a repeating cycle (controlled by an oscillator). So be aware of that double meaning when asking about auto-wahs, or when reading the label on a pedal. A "touch wah" is just an envelope filter.

The only other thing that stood out to me was the potential lowend loss during the 'more closed parts of the sweep'-- I tend to think of the loss occurring when the filter is more open rather than closed, but might just be my interpretation of what I hear, just thought I'd put that out there.

--It is a bandpass filter, so you may need to adjust your signal path, or use a parallel blender, to retain your low end during the more "closed" parts of the filter sweep.

All in all, its a great introduction to the nature of filters and written in a way that should be easy to understand for those not familiar with filters, and the sometimes ambiguous terms used to describe/market them. Thanks for the contribution!

[bongomania]

Thanks--I made a couple of changes there. The open vs. closed question is an interesting one, because technically the bandpass allows a wider range of frequencies through when it is open, not closed; however in this particular case the massive resonant peak normally heard in the lows when the filter is closed gets moved up to a much higher frequency when the filter opens, so the lows do in fact drop in level at that time, as they are no longer resonating.

[cheapbasslovin]

Attack and decay time, up or down sweep (or start/ stop frequencies), multiple filters (like the bassballs) are not mentioned in the write-up. One other question I've had about filters is the movement of the filter. If my ears treat me right I hear some filters with a great amount of movement (the FX25 among them) and others with less movement but more resonance (Qtron). I feel like all of these should at least have a mention, if only as a 'what affects the sounds of a filter pedal' section of the article.

[dannybuoy]

Also might be worth mentioning that some filters tend to invert phase which is something to bear in mind when using in a blend loop.

[Joe Gress]

Filters with fx loops: The shizz!

[warwick.hoy]

The term "auto-wah" is used by different companies to mean two different things: either an envelope filter, or a filter that constantly opens and closes in a repeating cycle (controlled by an "LFO", a low-frequency oscillator). So be aware of that double meaning when asking about auto-wahs, or when reading the label on a pedal. A "touch wah" is just an envelope filter.

You might cite some examples as to which Auto Wahs are envelope filters and which are oscillator based.

[bongomania]

OK, I added some stuff about attack, release, and sensitivity. I'll have to think a while about the phase inversion question, as that's a tough one to put in simple terms. I'd like to get some more input from you on the ideas of "movement" (cheapbasslovin) and pedals with loops (Joe Gress). I tend to think the question of "movement" is answered by discussion of the envelope--let me know if that's not quite what you meant. Most pedals with built-in fx loops that I've used just have the loop in series with the effect input or output, making it no different than putting the other pedal before or after the one with the loop--except that you can dis/engage them both with one footswitch. Is the footswitching the big shizz, or are there filters with loops that have more interesting location/function?

[dannybuoy]

With a loop, the filter usually goes after the fx loop but the envelope is triggered by the clean signal. It lets you get more precise control when filtering a fuzz for example.

[OhulahanBass]

I'm glad you mentioned Bootsy and the Mutron. I love my Mutron, for me it's the one pedal worth any compromise. Was the Mutron the first? First envelope filter pedal that is?

[BobaMosfett]

Originally Posted by dannybuoy

With a loop, the filter usually goes after the fx loop but the envelope is triggered by the clean signal. It lets you get more precise control when filtering a fuzz for example.

Yup, this is the case with my Groove Regulator. I put my fuzz in the loop, and the difference is remarkable!

[cheapbasslovin]

I actually kind of worked through the movement question as I was typing the response; but yes, a mention of the filter movement vs. resonance as part of the filter tone should be in the discussion.

Regarding FX loops; they are triggered by the input but only effect the return signal. Using an attack delay in the loop makes for a striking effect as the filter has already peaked when the audible signal comes up. Bass player had a demo using a drum machine into the input of a Groove Regulator while the bass input went to the return. You'd lay down a chord and get a varying rhythmic filter effect on it. The sonic possibilities with a filter effects loop are great.

[kenstee]

Originally Posted by bongomania

http://www.ovnilab.com/articles/filter.shtml

As with all of my articles, it's a work in progress, so please give me feedback on anything that needs correction, clarification, more in-depth discussion, or is missing altogether. I don't intend this article to go into much technical detail, or to name or compare all the popular models out there--just to correctly answer the basic question of "what is it" in a way any noob can understand. Whatcha think?

Nicely done Bongo! Great point-of-departure for noobs (and oldbees)

[bongomania]

Originally Posted by cheapbasslovin

I actually kind of worked through the movement question as I was typing the response; but yes, a mention of the filter movement vs. resonance as part of the filter tone should be in the discussion.

Sorry, but I still don't know what you mean. Can you tell me what you mean by movement, and how it differs from envelope?

[cheapbasslovin]

The movement across the frequency spectrum versus the resonance peak. To my ears a FX-25 has a greater movement across the frequency spectrum than a Qtron, but the Qtron has a greater resonant peak. This is what I hear, but a scope may prove my ears incorrect.

[bongomania]

I just added a section about loops--thanks for all the input on those.

Seems like I should be saying a little more about wah pedals. What is some important quality or interesting fact/feature of wah pedals that I have not mentioned?

[bongomania]

Originally Posted by cheapbasslovin

The movement across the frequency spectrum versus the resonance peak. To my ears a FX-25 has a greater movement across the frequency spectrum than a Qtron, but the Qtron has a greater resonant peak. This is what I hear, but a scope may prove my ears incorrect.

To be sure I understand, are you talking about the resonant peak either being fixed at one frequency versus changing across a range of peak frequencies?

[OhulahanBass]

Originally Posted by BobaMosfett

Yup, this is the case with my Groove Regulator. I put my fuzz in the loop, and the difference is remarkable!

I tried the drum machine in the input and bass in the FX return thing, very cool effect with the correct settings. I'd like to filter my drummer and my bass through it in the future. Spencer's Groove Regulator is a pretty cool filter. Anyone know how to bring a drum mic output to a level ideal for driving such a filter as the GR?

[cheapbasslovin]

Originally Posted by bongomania

To be sure I understand, are you talking about the resonant peak either being fixed at one frequency versus changing across a range of peak frequencies?

Not necessarily. I think the Enigma is the only mass produced filter that can do a fixed peak, so a fixed peak may not merit a mention. I was just referring to the freq. sweep vs. Q in regard to the sound. I may have already taken this too far.

With the FX25 I hear a BP filter that starts very low and broad but moves considerably higher as it approaches peak resonance. With the Q-tron I hear a BP filter (when that switch is chosen) that starts a little higher and narrower, has a shorter frequency sweep than the DOD, but greater peak resonance. At the right settings they sound similar, so based on a sound clip somebody may think that they are interchangable when they really are different beasts.

(/ramble)

I guess the short version is that at some point a mention that, "different filters will different frequency ranges, different filters will have different peak resonances. These will all sound different and your preference will be a personal choice." Or something more eloquent than that.

[OhulahanBass]

Bongo:

Are you thinking about adding envelope filter reviews or are you mentioning them since they are often used with limiters?

I would personally enjoy such reviews as there are so many options out there, I'm sure many I haven't even heard of yet.