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Diagnosing noise problems with Yamaha FX550 effects box

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Visited Central London to spend the day with my client who was having problems with his Yamaha FX550s. Looked at the routing within his studio and tried to work out why he was getting terrible noise and distortion problems with the signal chain of guitar/bass to FX550 to UA710 preamp to Apogee Duet 3. After experimenting with all the different variables I could think of I eventually found the problem was an 11v power supply being using by the FX550. I discovered that with this particular model of effects box an 11v current will seemingly power the unit on but doesn’t deliver all the current needed around the circuit. The preamp feeding the analogue to digital converters were acting in a strange way and heavily distorting the signal at seemingly random intervals. Once we switched to a power supply with the correct voltage the problem was solved. We spent the remaining time testing the setup with his other guitars and basses and made videos to remind my client of the best settings to use on the equipment in various situations.

About the Author


I’m the owner and lead technician for Audio Support, a small company based in London, UK that connects remotely with clients worldwide to help them with their music technology issues. I’ve run Audio Support since 2005 and in that time I’ve seen and solved thousands of recording studio problems. 

Outside of Audio Support, I run music workshops at a local school, play bass in a 90s tribute function band and perform modular synth jams with friends on Twitch.

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