I finished testing and finally boxed up the Larsen Expressive Feedback Loop this morning. It’s good to have it done.
It’s more of a prototype than a finished product; while the circuit itself is really solid and I’m proud of its design, learning to work with wah enclosures was a giant pain and I had to jerry-rig several things with the hardware to get it to work.
Bit of a mess inside, but it’s loud and weird and fun.
The feedback potentiometer (what the foot treadle controls) is pretty sensitive; most of the play is toward the heel-down position of the treadle. If I were doing it again, I’d experiment with making a super-anti-log taper pot out of a linear pot and a resistor. Or, maybe I’ll upgrade this one with that in the future.
If I ever get around to making one of the doom records I’ve been writing, this thing will be all. over. it!
This week I ran across an email from July 30, telling Drew and Cory I’d started messing with a feedback loop circuit on my breadboard. It’s taken until this weekend to get it soldered up.
Feedback loops can be simple and fun, but simple ones have a lot of limitations. Two big ones are that many pedals do nothing in them (because the pedals flip the signal’s polarity, so feeding them back just results in a quieter sound due to phase cancellation), and that they can get excruciatingly loud, fast, if the rest of your signal chain has enough headroom for it (like if your amp is running pretty clean).
I fixed those issues with a polarity inverter and limiting/hard clipping in the feedback loop. I also added expression via treadle control of the feedback amount, and two modes for the loop: always-on (regardless of feedback on or off) and only-on-when-the-feedback-is-also-on. (Mode names need work.)
Most pedals have one input, one output, and the circuit itself in a sort of loop within the pedal. A feedback loop effectively has three inputs (main input, loop return, feedback circuit output) and three outputs (main output, loop send, feedback circuit input). I hadn’t thought about all of that when I jumped into designing one, and all those signals crashing into each other results in a lot of parallel impedances and switching headaches I didn’t anticipate. Given the challenges, I’m pretty happy with the performance of the design.
It’s not quite finished yet because I seem to have burned one of the footswitch connections, so I’m waiting for a replacement part to arrive. I’ll do a video once it’s done.
That’s a lot of tech talk, but it’s pretty intuitive once it’s plugged in, I think; when you roll your heel back, you get more feedback. It’s super-fun to play and useful for anything from freak-out noise to gentle washes of added delay or reverb.
I’ve finished my DS-1 lab experiments (previously discussed here and here) and boxed it up. The full report is over on Mr. Furious Audio.
Booking: marslightsnoise (at) gmail (dot) com
Some of us spend a good amount of time and energy on gear; searching, shopping, watching demos, even fixing, designing, and building new stuff.
Why not spend it on making music?
(I ask myself this, as the months pile up without a release… )
Making music is exploring, in many ways. Exploring new techniques, more advanced skills, different performances, writing unique material, and new gear. Gear is on the same spectrum. Different areas of exploration speak to different musicians, and gear is one that seems to speak to me.
Gear can be inspiring. For example, as I was finishing design work on my DS-1 lab yesterday, two new riffs popped out as I was fooling around and testing sounds. They emerged out of my interaction with the pedal; they wouldn’t have occurred otherwise.
That validates the gear quest, for me, in principle.
Whatever keeps you exploring; do that.
Finished a couple of small soldering jobs this weekend.
The DS-1 (orange guy) is my very first pedal. Cole had added the Casper Electronics gated feedback mod a year or two ago; I swapped in a different transistor, changed the switching to a different leg of the transistor for quieter operation when the feedback is off, and added a “chaos” control (the knob on the side of the pedal) that can tame the feedback a little when it’s on. This transistor oscillates with the distortion all the way up; rolling back the chaos control can change the pitch of or eliminate the oscillation.
The Korg 301dl just had a broken pot; simple, though it was kind of a bear to replace. I couldn’t find a replacement pot with the same shaft as the original to accommodate the original knob so it got that clear one, which turned out to be easier to use anyway.
The DS-1 will go onto my Mars Lights board for the time being, until I finish the super ultimate modded DS-1 that’s currently in pieces.
The Korg will just hang around at home, which will be handy for times when my big board is at Drew’s. It has a cool feature set including two presets, separate high and low frequency damping on the repeats, a hi-fi / lo-fi blend, and a weird ducking control.
What’s strange is that the ducking isn’t very interactive with the input signal; it’s more like another kind of pre-delay and the control sets the amount of time it takes the delay signal to come up to its full level. That means that with the ducking maximized, if you hit a staccato note, you hear a bit of silence and then the delay fades in. The ducking I’m used to from recording and the TimeFactor is more like a compression ratio, and would fade the echo in immediately as the the input signal dropped on a staccato note.
It doesn’t self-oscillate at maximum feedback level, which is OK – I have the DE7 for that – and can make for nice ambient pad sounds.
I’d like this pedal a lot more if the delays spilled over from one preset to the other. It could actually back up my TimeFactor in a limited way if it did that, but we have songs – Nein, Stangray, Radio Edit – where I need an echo with a lot of feedback that spills over on bypass or when the preset changes.
I guess with the A/B box I plan to build and any two delays (like the DE7 and 301dl) I could back up the TimeFactor somewhat. Maybe I need two A/B boxes?