TFM-45 Bridged Mono Buzz

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UncleMeat
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TFM-45 Bridged Mono Buzz

Post by UncleMeat » Tue Oct 13, 2015 10:56 pm

I was trying to run my TFM-45 as a bridged mono amp, but when I turned it on I noticed that it was not sounding right; there was a buzz coming out of the speaker, not super loud but definitely not faint or below the threshold of hearing. I connected the speaker and pre-amp to the amp per the instructions in the manual, and double checked my connections after hearing it buzz. Any idea what the problem could be? It does not buzz on either channel in stereo mode.

elgrau
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Re: TFM-45 Bridged Mono Buzz

Post by elgrau » Sat Oct 17, 2015 1:13 am

De-oxit the mono/stereo mode switch? Long shot, but worth a shot...
FR: 400 disk changer with PS Audio Digital Link III DAC; Technics SL-1100A TT. QED Quenx1 IC's from DAC & TT to Adcom GTP-602 preamp/Tuner. AudioQuest King Cobra IC's from preamp to M1.0t mk-II opt2. QED Silver Spirals 4M wires to EPI 1000’s.
LR: AudioEngine wireless link from family room preamp to Barcus-Berry 2002R Sonic Maximizer to GlowPower Zyxt IC's to Sunfire 300x2 to Nordost 6M bi-source wires to AOS 28" MDF spherical speakers using six 6.5" woofers and eight 1" dome tweeters symm. arranged around the surface.
SS system: CX-995V DVD to AV-634x 3-4 channel amp (center/rears) & M1.0t mk-II opt2(fronts).
Garage: 300 disk changer to Entech 202.5 DAC to MXR150 Receiver (pre) to TFM-42 to EPI 400 speakers.

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UncleMeat
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Re: TFM-45 Bridged Mono Buzz

Post by UncleMeat » Tue Oct 20, 2015 3:11 am

It turns out that the TFM-45 needs dual mono input, both channels need the same mono signal. There is an addendum to the manual that says you need to split the single channel signal into dual mono signals and then connect to both L and R inputs on the amp. When I followed the directions in the manual on the page that describes bridged-mono operation it said to connect the mono channel to the Left input, and that resulted in a buzz. When mono signal was connected to both inputs the buzz went away. WRF over on C! helped me on this by finding the addendum page in the manual (thanks Wayne).

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radioeng2
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Re: TFM-45 Bridged Mono Buzz

Post by radioeng2 » Tue Oct 20, 2015 3:19 am

Glad you got the answer. Sounds like it saw the other open input and it picked up noise. Feeding it with the same signal means no open. Wonder if a resistive 10K load would also be a "fix"?

Thanks for sharing the story.

Mark
I was there "At the Fest!" Hope you were too!

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