One of the N-audio clients, Dirk Baranowski from GittarSchool in Germany, had a noise issue when using a Korg rackmount tuner with his 4X4 amp switcher. Others have also asked why the tuner output works only when the switcher is muted. That inspired me to write this blog post and share a few helpful tips for using a stage tuner connected to your N-audio amp switcher.
When the tuner out is active?
When I designed the N-audio amp switcher, one of my top priorities was to keep the guitar tone as pure as possible. In my experience, any extra circuitry or load can slightly alter the tone. That’s why I used only relays between the guitar and the amplifiers. It’s the best way to keep the tone intact!
Guitar tuners vary in their input schematics design. Some can affect your tone. To avoid this, the amp switcher routes the guitar signal to the tuner only when it’s in mute mode. Just like most pedal tuners, it mutes the amp while tuning.
If you want to see your tuner while playing, plug your guitar to the tuner, then connect the tuner’s output to the amp switcher. In this setup, the tuner is always active and buffers the signal. Whether that’s a good or nor depends on your gear, your ears, and what you personally prefer.
The High-Pitched Noise Issue
The problem with switch-mode adapters is that their output is floating and often noisy due to high-frequency switching. In most rack setups, this isn’t a problem. Once the tuner connects to grounded gear like your amplifier, the noise disappears.
But when used with an amp switcher, the tuner ground remains floating while the tuner isn’t active. This is intentional to avoid ground loops with tuners that use 3-pin IEC power connectors. However, it can cause high-pitched noise to leak into the signal through capacitive coupling inside the amp switcher.
Rotating the power adapter 180 degrees in the mains outlet may reduce the noise slightly, but won’t eliminate it! It depends on the position of the internal Y2 safety capacitor inside the adapter.
The good news: There’s a simple and effective 5-minute life-saving hack 🙂
Tuners like Korg have an output jack on the back side. Its ground shares the same potential as the input. If you plug a short patch cable between that rear output and the Slave input on your N-audio 8X7 or 4X4 amp switcher, the noisy tuner ground will be pulled down to the amp switcher’s signal ground. This will eliminate the noise!
The Slave input on the back of the switcher is automatically disabled when you use the front panel input. So this grounding trick won’t interfere with normal operation.
This method solves the issue entirely, and it only applies to tuners powered by external switch-mode power supply adapters.
Niki Hristov
