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Hum on FPIII - A Definitive Troubleshooting Checklist

Good day, Bottleheads. I purchased and built a complete Bottlehead system last year (Paramounts, FPIII and Seduction). Awesome experience and really nice sound.

I recently moved from Florida to North Carolina. After hooking up my components, I am getting hum through my Pi Two DIY speakers. Using the search function, I have read tons of posts from 2000 to the present on hum and buzz troubleshooting, but have not found a definitive troubleshooting guide to hunt down these problems, identify the difference between hum and buzz, what to look for when the problem increases and decreases with changes with volume changes of the FPIII and a comprehensive list of possible corrections to hum and buzz. I suppose I am begging for a repository of knowledge in a single thread or on the Bottlehead site to help us less knowledgeable folks troubleshoot our systems.

My FPIII has hum, and that hum increases and decreases with the volume control. Since I can only hear sound when the FPIII is connected to the Paramount amps, I assume the hum source is the FPIII. While this is not normally a problem when the music level is high, it is apparent during quiet musical passages or when there is no music playing.

When I choose the input to the FPIII which is connected to a DAC and Squeezebox unit, the hum is very minimal when the DAC is turned on. When I click to my Seduction input or the unused third input on the FPIII, the hum is very pronounced. from my reading about these issues, grounding is something I should suspect. Considering the FPIII is built stock, it seems I have to look to grounding the phono inputs to a single point on the chassis and put some sort of resisotr in-line to filter out the noise. I have no clue if this is the path I need to follow or how to figure what resistance would be needed.

Things I have tried to reduce the noise is to connect all devices to a different electrical outlet, switch tubes from L to R, remove all inputs to the FPIII to see if there is a difference between inputs, and moving the Paramounts and FPII away from the audio rack while listening for reduction in noise.

Anyone willing to help out fellow Bottleheads woudl be appreciated. Thanks for reading through my diatribe.


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Topic - Hum on FPIII - A Definitive Troubleshooting Checklist - breakfastchef 14:21:28 09/21/09 (5)

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