Trap Door Electronic’s Active Acid is essentially a Prophet 5 SSM filter in a guitar pedal format. But the mono effects unit definitely has a few tricks up its sleeve that we were able to uncover in this long-term review. We employed five different evaluators: two guitarists, one keyboard player, one sound designer and a live ambient music performer, who kept the pedal for six weeks (Don’t think we’ll be getting that back anytime soon. —Ed.) The evaluator’s impressions are in quotes below.
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Trap Door Electronics is essentially Travis Johnson who started his adventures in guitar pedals working for Death By Audio and is also a member of the band Activity. According to legend, Johnson was intrigued by the possibilities of Death By Audio’s Exit Index pedal, “but didn’t [they] quite pulled it off, so [he] rebuilt it and did some stuff to get the sound [he] wanted.”
For a pedal that’s all about the filter, “Trap Door definitely delivered.”
One of the benefits of having your own boutique pedal company is that you can make changes to the design even after production has started, which is what happened to the Active Acid midway through our review process. One of members of the band Tortoise asked Johnson to make some mods to his pedal and he liked the results so much, he decided to implement those features in each pedal going forward. No worries. Johnson swapped out our pedal and we started the evaluation process all over. There are just two changes, but both are significant. First, Active Acid’s LFO can now go four times slower than the previous version – from 0.2 Hz down to 0.5 Hz. He also changed the sensitivity of the envelope to allow higher volumes to occur before “the filter bottoms out.”
The pedal has eight knobs, Volume, Drive, Frequency, Resonance, Follow, Depth, Rate and Wave; three toggles: Envelope Follow on/off, Sidechain or Internal Trigger, and Envelope Response Type, Harsh or Smooth, denoted by a Diamond and Circle icon respectively. There are two footswitches: one for tapping the tempo manually and another to turn the effects on or off. On the rear we have a 1/4″ Input (mono), a 1/4″ Sidechain Input, a 1/4″ Expression Pedal Input and a 1/4″ Output (mono).
The four-pole analog filter is “much more subtle than you would anticipate” and “sometimes takes quite a bit of coaxing” to get the “sonic experience you’re looking for,” according to one of our reviewers. For a pedal that touts itself as a great choice for “acid house/techno, psych, and otherworldly ambient,” Active Acid does not have MIDI implementation or CV/Gate action. We asked Travis Johnson about this specifically since three of our evaluators noted this in their evaluations and he had this to say: “since I make electronic music in my band and use MIDI a lot, this was the saddest thing to not be able to include. But I realized at some point not having MIDI didn’t get in the way – between the tap tempo and the envelope that responds to the rhythm of the input (or a Sidechain) I was able to get all the sounds I wanted while still keeping the footprint and price down.” Our keyboardist and ambient musician concurred and got around this limitation by utilizing the Sidechain input with an individual drum machine output and a semimodular Trigger output respectively. Our guitarists couldn’t care less about MIDI and both were dependent on the envelope being triggered successfully by the volume of the input.
Active Acid does have an Overdrive function that affects the signal pre-filter. It’s not nearly the riff-maker that can be achieved with Eventide’s Knife Drop, but if “you’re looking for some additional texture and volume, it does the trick.” The LFO has eight different shapes: Upramp, Downramp, Square, Upside Down Triangle, Sine, Scoop, Sample and Hold, and Random. Plenty of options here and you can morph from one shape into the by simply turning the knob. The Resonance can self-oscillate, but “it’s smooth and musical” and “works quite well to create acid sounds without being brittle.”
Active Acid’s Sidechain Input
For a pedal that’s all about the filter, “Trap Door definitely delivered.” The “glass-like” filter is “smooth and planted” with “no stepping” or “any sort of artifacts that betray the signal.” With that as the foundation, Johnson provides the user with several different ways to control the filter, and even better, many of these can control the filter simultaneously for true sonic mayhem. Of course the envelope follower can control the filter, as well as the LFO, but you can also have an expression pedal work its manual magic. And get this, you can use all three at once. The downside is that this flexibility can also make finding the exact tone you desire much more difficult with complex signals such as synthesizers. In fact, guitars and drum machines seem to fare better in when ganging the filter modulators together. Well, it is a guitar pedal.
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Johnson’s decision to slow down the LFO even more was received very positively by our sound designer and ambient musician. Both loved how your could get the Active Acid to “just breath – in and out” in ways that “showed off the filter’s creamy nature.” For even more sound design tricks, manually manipulating the filter to adjust to the incoming signal allowed them to create “other worldly soundscapes” and to turn samples and other commercial sound libraries into something uniquely their own.
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Trap Door Active Acid Specifications:
- Dimensions: 5.875” x 4.75” x 2.375” (including knobs/jacks)
- Weight: 18.5 oz
- Power: 9V DC 2.1mm, positive ring, negative tip jack. Current draw: 88mA
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Conclusion
Trap Door Electronics’ Active Acid has a lot to offer to a select niche of the market. The build quality is outstanding, the filter sounds amazing and the different ways you can modulate the filter certainly sets it apart. For our evaluators, we asked them if they would buy an Active Acid for themselves. The result? One guitarist and the ambient musician were a definite yes, the other guitarist and keyboard player were a no and the sound designer was on the fence, since he had other gear that could get the job done. Thus, the Active Acid could be a wonderful solution for your rig, or it could be one of those pedals that doesn’t get much use after the initial infatuation. That said, we think it’s a standout among filter pedals in this price range. Highly Recommended.
Trap Door Electronics Active Acid Review Rating 86%
Cheers:
+ Build Quality
+ Sound Quality
+ Glorious Filter
+ Envelope Manipulation
Jeers:
– No MIDI
– Mono
Trap Door Electronics Active Acid costs $295 and is available now.
The Future: We expect that Travis Johnson will continue to tweak the Active Acid for the benefit of all, but we’d love to see the pedal go full stereo with the ability to sweep the filter throughout the spectrum. It would be great to have the ability to put the overdrive before or after the filter. We did mention MIDI above, but we have to make that request again, especially since it would be great to control all parameters with CC.
Future Music: What was the impetus for developing the Active Acid pedal?
Travis Johnson: There’s the practical impetus and the musical/sonic one.
The practical one is that I had a filter pedal that I used a lot, but it was massive, took up way too much space, and I only used the low-pass setting with an expression pedal and none of the other features. So I wanted a filter in a smaller footprint that did what I wanted.
The musical/sonic one is music I love. Firstly, acid house/techno. Secondly, I’ve always wanted to be able to make certain sounds that I heard on Tortoise’s TNT that were the motion created by an envelope filter on guitar and bass. Since I was a teenager I’ve been enamored with that sound and I simply wanted to do my take on it. It’s such an expressive thing that I find really addictive to play into. So I set about trying to make it work for both the Tortoise thing and the acid house thing.
Future Music: What was your biggest challenge in bringing this to market?
Travis Johnson: There were times where it was an issue to decide on what features to have, and what parameters those features would go to on the high and low side of a sweep. I wanted it to be as compact as possible and not ridiculously expensive so not everything could happen while keeping it analog. There were so many possibilities and I tinkered a lot, had people that I trust play around with it, went back to the drawing board a few times. There were several absolutely crazy features that I had to jettison because, interesting as they were, they weren’t very usable for most people and got away from what I really wanted the pedal to do.
Future Music: Was it your intention to only create a mono pedal, or did you consider a stereo output?
Travis Johnson: This might make me sound really limited in a number of ways, but I simply don’t use stereo features with pedals. I never have. I know for some people it’s a big plus, but, related to previous questions, nothing eats up space on a pedal like jacks and getting the pedal to do what it currently does in the footprint it does it in was the top priority.
Future Music: What Activity songs feature the Active Acid?
Travis Johnson: I think virtually all of the album that we recorded last year (which will be getting announced soon) has it on there in some capacity. It wasn’t on previous albums because I hadn’t designed it yet. On the new one, my guitar was going through it almost constantly, with maybe a subtle resonance at a subtle cutoff, or with the envelope, or with the expression pedal, or the LFO. Synths and drum machines for sure too. We also used it in some pretty insane ways. I came in one day and Jeff Berner, our producer, had overnight used the Active Acid to sidechain the room mic on one song to the busy drum buss on another song, creating this beautiful rhythmic sucking sound. Amazing. It’s such a versatile pedal that you could spend all day processing sounds you already recorded in new ways.
Future Music: What’s next for Trap Door?
Travis Johnson: Currently working on what might sound kinda boring, a big nasty fuzz, but that I think is really interesting and addictive and responsive. I let a friend play it and he said it made him want to develop a new way of playing guitar just to see what all would happen. Hoping to do something cool in the phaser world soon too.
