The Mod

If you just want to skip to the fix, head to this section.

At the advice of Brian Wampler, I caved and bought a minty used Boss GE-7. Imagine my surprise after moving any of the EQ sliders introduced very noticeable noise! How could you, Boss? Apparently, when the GE-7 was first designed, battery life and price point were more important considerations than audio fidelity. As a result, any GE-7s made from 1981 to 2017 use the TL022 dual op-amp chips. These outdated chips are surpassed in every aspect of audio performance by the more recent NE5532 dual op-amps, despite drawing more current. (38 mA vs 6 mA in output short-circuit condition. This is a good read if you need a refresher on op-amp datasheet deciphering).

Boss also used cheapo-ceramic capacitors in the signal path of the GE-7. Ceramics can be microphonic due to the piezoelectric effect: this is possibly the worst type of non-ideality an audio component can have. Subsitituting these for film capacitors would drastically improve audio fidelity. Since my pedal was an older model, I decided to replace all of the electrolytic capacitors as well. These caps have most likely dried out after 40+ years of use.

Not in the mood to source parts for myself in the middle of a rabid chip market (Even through-hole parts are getting hard to find!), I opted for the Fromel mod kit.

This pedal was made back when manufacturers cared about repairability, and it shows. The GE-7 was very easy to disassemble. After socketing and soldering the new op-amps, I tried to fire the pedal up. There was no sound.

The Problem

The broken pedal behaved as follows:

• If the switch was held down, the clean (bypass) signal could be heard clearly
• If the switch wasn’t held down, an extremely loud buzzing could be heard
• The wet (equalized) signal could not be heard, regardless of switch position
• The LED never turned on

The buzzing noise sounded a bit like a ground loop, which is often caused by grounding issues. Using a continuity checker, I discovered that the switch ground wasn’t connected to the power jack’s ground. But the pedal worked before I took it apart: what could have changed??

The Fix

Taking a closer look at the switch grounding revealed all! See how the switch’s ground (black wire) is attached to the output jack, and nothing else? The switch will only be grounded if output jack is attached to the enclosure. The enclosure itself needs to be grounded as well: The ground output from the 9v input connection to the input jack handles this. All this means that the pedal will only switch properly if the input and output jacks are electrically connected to (or screwed into) the enclosure! After alligator-clipping the switch ground and power jack ground together, and plugging my guitar in, it worked like a charm!

If you’ve been having this issue, check 2 things:

• Use a continuity checker (most multimeters should have one) to see if all of the grounds are connected
• Make sure a 1/4" cable is plugged into the pedal’s input jack. If nothing is plugged in, the pedal won’t activate.

The Takeaway

While I’ve been told to always ground the enclosure, this is the first time I’ve seen an entire pedal’s functionality rely on this rule of thumb. Doing so saves exactly two, but those are two wires to potentially break, and two wires to pay for. But there’s a pretty cool reason behind all of this. In 1981, Boss couldn’t rest on the laurels of being a legendary effects manufacturer: it had to build a reputation, which it did by offering invincible pedals at an unbeatable price point. Even using the enclosure as a ground plane speaks to the dual priorities of build quality and cost that continue to make Boss pedals so ubiquitous, even today.