Iso Cab Release Notes
Well, after three years and some change of development the Iso Cab is ready to meet the world. I’ll start off by trying to keep this brief, but for anyone who missed the technical Instragram videos I’m hoping this can be a great reference as to what the pedal does and how it came to be.
First off, let’s take a look at the artwork! This pedal comes in a 1590D enclosure, so there’s plenty room for art, and my friend and collaborator Tyler Blanchard (treemoss creates) did an absolute fantastic job here. I used AI to generate the face and get us in the retroactive wheelhouse for character development to match what Tyler has done with each of our other flagship pedals. Although Tyler didn’t use AI to generate the characters of the other pedals, I thought this was a good start to give him a template to work from. From there he did everything else from the half-tone facial features to creating the futuristic city-scape.
Original AI Artwork I created for reference
Iso Cab Art by Tyler Blanchard
Let’s talk about the circuit. Below is a basic block diagram of how the circuit works!
Iso Cab Block Diagram
Iso cab is an idea I had during the amp-in-a-box/pre-amp era around the time the Benson Preamp came out, along side the resurgence of the Peavey Decade amp and other pedals mimicking the Decade. Universal Audio came out with a great line of pedals recreating classic amps and companies are releasing pedals daily trying to recreate the sound of amps whether classic or niche - from twins to dumbles - marshalls to music man and sunns, the list continues to grow.
Enter my brain…. “how do I make an amp-in-a-box pedal that sounds like a cranked speaker being mic’d up” .. oh yeah you literally put an amp in a box and mic it. I’ll save the history lesson on 386 power amp chips (you can watch one of my recent reels that covers this in more detail and other pedals that use this chip without the speaker) but it’s a powerful chip that I’ve been obsessed with for a long time since I’ve started DIY pedal building. It sounds inherently bad in most applications, but with the right circuitry around it you can coax something decent which is why my three-year journey has led me down this rabbit hole.
Your guitar pickups enter a Tillman JFet preamp stage first, which then hits the 386 power-amp. You wouldn’t believe that an input preamp circuit so small (5 or 6 parts) would have as much impact on the power amp circuit as it does, but it does. It shapes your tone and boosts it ever so slightly and it really makes a difference. I assume an EQ pedal before this pedal would do sort of the same, but at this juncture I haven’t tried it… which now means I need to. Without the preamp stage this pedal sounds completely different, believe me after three years I’ve tried a lot of combinations and meticulously replaced part by part in the pre amp stage to get the perfect response.
Once the preamp hits the power-amp chip, the output has enough current to drive a speaker and sound literally comes out of the speaker inside of the pedal. (If you open it up and don’t plug anything into the output, you have yourself a small practice amp sort of). From there, I use a small condenser microphone to mic the speaker output. That goes into a small mic preamp booster where the first control comes into play .. the “Mic Volume”. This controls how much of the microphone/speaker output goes into the rest of the circuit.
That then hits a secondary gain stage amplifying it even more. You can control the gain of this stage with the “Post Gain” control. During development I found that using the power amp and speaker/mic circuit as a stand alone pedal didn’t sound that great. When I used it in my pedal chain with other dirt pedals after it I was able to finally understand its full potential so I knew I needed a secondary gain stage with EQ to bring out more from the power-amp chip. The Mic Vol and Post Gain work in tandem as sort of pre gain/post gain pair. If they’re both cranked the speaker will feed back. If the Mic Vol is more pronounced you’ll get more character from the speaker and mic combo, if the Post Gain is more prominent, then you’ll get more character from the back end of the circuit.
Lastly, there’s a three band EQ and a Master Volume. Not much to say there except that the eq is pretty powerful! You can coax out sounds ranging from a pretty decent sounding harmonic percolator (something about the crappy-ness of the 386 creates harmonic distortion - to my ears at least), Boss HM-2 doing the scooped mids things, and even a Big Muff if the bass is cranked.