Quest for a Portable Amp and Pedalboard
Tags: Guitar, Guitar Pedals, Music

There’s a few additions such as extra footswitches for the Boss GT-1, the Digitech Trio+, a mixer and a PolyTune 2 mini.

But mainly, there were a few issues with the previous setup that needed to be addressed while keeping everything battery powered.

Ground Noise

The first issue was that there was tons of resting noise in the previous system.

http://www.pedalsnake.com/blog/category/the-noise-manual was a pretty neat resource for debugging the noise source.

There was no AC anywhere in the system since it was all on a USB battery pack but there’s still likely a ground-loop-like hum causing issue.

All these pedals filter their own output signals but likely don’t filter noise they generate back into the DC. This causes voltage fluctuations across other devices that are all powered by the same battery and draws or pushes against their output signals All the 9v pedals are powered by a daisy chain from a 5v->9v step-up converter which apparently is a bad decision regardless of the power source.

The solution was luckily fairly simple. I swapped out the daisy chain with:

A USB->9v power supply with 4 parallel regulated outputs for 24$. The difference was night and day. With the isolated outputs, high gain amp settings are completely silent at rest.

I kept the adapter underneath the pedalboard to keep everything clean and out of sight

Mixer

The previous setup also had 2 other issues:

There was no bluetooth which was super annoying and inconvenient for playing along with YouTube etc. Adding one more bluetooth receiver adds just one more device (and friction point) to connect and to turn on and off each time I want to play. The BeatBuddy Mini doesn’t list its detailed specs like output impedance but the full sized BeatBuddy is 26Ω which is a weird number that ends up strangely amplified with a poor SNR when plugging directly into the GT-1’s aux in. The DigiTech Trio+ will end up needing a mixer but we’ll get into it later.

The challenge is that most mixers have their own AC adapter plug that neither uses the 5.5mm/2.1mm pedal plug or are 12v or 5v. Mixers also tend to waste one of the channels being optimized for microphone levels and impedance.

Luckily, I found an uncommon mixer but a huge gem.

The Pyle Bluetooth 3-Channel Mixer:

Is fully powered by USB (which also acts as an audio interface both in and out) Has an adaptive channel 1 combo XLR/TS 1/4" that changes impedance Has bluetooth built-in!!!

And all that for 53$ which is about the same price as the Behringer Xenyx 302USB but is way better built with a full metal construction and has bluetoot.

Looping

Since the objective is still playing for fun at home, looping makes the sound way fuller and more fun.

The GT-1 has pretty much all types of effect pedals from octaver to wah to looping included. But using the GT-1’s looper turned out to be less practical. Since, as mentioned in the previous article, the GT-1 is missing a drum machine that makes it way more fun to play by myself. And without MIDI sync on neither the BeatBuddy Mini and GT-1, timing the external drum machine and the looper is basically impossible.

Even if you played a loop and pressed the start/stop almost absolutely perfectly with the drum loop from the BeatBuddy, a 1ms deviation will accumulate to a point where everything’s a mess after a couple of measures.

So I turned to the DigiTech Trio+ which had the drums and looper together (and self synchronized). It also has the bonus of having an interpreted bass player and is also a fairly bit easier to control than the GT-1’s looper which needs to be turned into looping mode first.

One challenge with it though is that it’s so geared towards a conventional amp with a separate pedal chain that it’s hard to figure out how to even wire the thing.

The DigiTech Trio+ has 5 I/O connections.

Guitar In needs a clean input signal so that’s easy to figure out. The wireless Line 6 G10 receiver goes through the PolyTune then into it directly.

Mixer outputs the drums and bass sound so that one’s easy too. Good thing we have a mixer already :) There’s an option to use just the Amp Out or the Mixer connection but both are very suboptimal.

Amp Out outputs both what you’re playing live and and the recorded guitar loop after going through the Fx Send and Fx Return loop which is pretty awkward instead of sending the recorded loop to Mixer instead.

Fx Send is meant to go to your pedals before coming back into the loop and out to Amp Out

Fx Return is the return signal from your pedals.

All of this works well if you had a single amp and make the assumption that the effect pedals change while playing but the amp is mostly static. But the amp in this case is the same unit as the effect pedals and we wouldn’t want to put the GT-1 after the Amp Out because if you change your GT-1 settings after looping, the looped recording gets altered.

Luckily, the looped recording saves everything that went through the Fx Send and Return loop as is so we can wire this as:

G10 wireless receiver -> PolyTune -> DigiTech Trio+ Guitar In -> Fx Send -> Boss GT-1 -> Fx Return.

Then send both the Trio+’s Amp Out and Mixer to 2 different channels on the Pyle Mixer.

This deviates from DigiTech’s canonical usage of letting the guitar’s pre-amp and cabinet simulation be inside the Fx loop instead of being after the Amp Out connection but since it records Fx Return and sends it out to Amp Out verbatim, it doesn’t really matter.

Summary

In total, this portable setup is still powered by a single USB powerbank.

The whole package can be picked up and played anywhere.

It consumes 1A from the G10 wireless system and 500mA from the mixer at 5v.

It consumes 100mA from the PolyTune, 200mA from Boss GT-1 (😱 so surprisingly low), 800mA from DigiTech Trio+ (I don’t know what it does with so much power) and an unknown but <500mA from the BeatBuddy Mini at 9v.

It comes to ~4A at 5v which is about 1 hour from a 5000mAh battery. All probably want something like

this 185Wh portable power block for longer sessions that will put me back to ~9h per charge.