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Harman Kardon HK775 mono
Harman Kardon HK775 mono
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Old 27th February 2012, 02:53 PM   #1
Ann4 is offline Ann4
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Join Date: Feb 2012
Default Harman Kardon HK775 mono

I bypassed the filter board on one of my hk mono blocks so that the signal goes from input straight to the pre-driver board with no ill effects so far. I was warned by an electrical engineer friend that the move was risky, but there have been no ill effects so far. The speaker driver is in the same position when the amp is powered on and off. And I inadvertantly powered the amp on and off with upstream components powered on. Nothing blew up. And the sound quality is significantly improved. Has anyone ever bypassed the filter board on these amps or have an opinion on whether I should go ahead with the other amp and make this modification permanent?

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Old 27th February 2012, 03:29 PM   #2
sgrossklass is offline sgrossklass  Germany
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Join Date: Nov 2004
Location: Germany
Looking at the schematic, I am not sure where any significant improvements in sound would be coming from. Are you sure that the effect is real? If anything, you could have cleaned the subsonic and ultrasonic filter switches and possibly replaced the two series-connected 100/16 caps with a new 47-100 bipolar with the same result.
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Old 27th February 2012, 03:50 PM   #3
Ann4 is offline Ann4
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Join Date: Feb 2012
OK. I should have explained that one of these amps started dying and that working the subsonic filter switch caused it to work intermittently. I attempted the bypass in the interest of straight-wire-and-gain. Years ago a high qualified tech bypassed all the switches except balance on the companion preamp with a dramatic improvement in clarity. Thanks. Ann
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