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Old 1st April 2011, 04:56 PM   #1
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Default hafler dh 220 mono

HI, I have 4 hafler dh-220 amps that I want to make mono and see how to do it but the type and wattage of the 3000 ohm resistor is not clearly stated. does anyone know what I need for that part? Thanks! Tom
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Old 2nd April 2011, 01:01 AM   #2
sregor is offline sregor  United States
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I would use a 1 watt metal film. The resistance used is the same as the parallel combination of r25 and r26 (3.3k parallel to 33.3k) They use quarter watt for the 33.3k but 1 watt for the 3.3k . (they do it to make the DC resistance from output to - input 33k for low bias offset, but 3k for ac gain). Resistor for bridging should be same value as feedback resistor, and has to swing the same voltages. Good luck.
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Old 28th April 2013, 01:20 PM   #3
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Tube Tommy -

Did you ever convert your hafler 220 to mono? I am seeking to do the same and wanted to see how you fared.

Cheers.
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Old 28th April 2013, 09:45 PM   #4
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Default 220 mono

Hi, it worked out very well, no issues and the power in mono was able to dirve my soundlab m1 speakers pretty well. be sure to mark on the back what you did and how to connect it so the next owner will understand. I went and put a switch in it for easy stereo-mono. I also upped the main caps, bigger current bridge and a heavy duty power switch. I have done many of these this way since the first and all owners were very pleased. be sure to double check the dc off-set and bias when done. Good luck and enjoy!
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Old 29th April 2013, 01:18 AM   #5
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Thanks Tube Tommy -

I was wondering, did you use the Hafler bridging kit, or did you wire it yourself and add your own switch?

If you added your own switch, where did you source it or what kind of switch should I look for?

Thanks for your help!
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Old 29th April 2013, 01:38 AM   #6
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Sound lab speakers are very cool indeed.
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Old 29th April 2013, 03:43 PM   #7
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Default dh220 parts

Hi, if you have a kit , use it but I had a switch, DPDT, small "L" bracket from home depot to hold it, and a restistor. the wire is nothing special , I had some teflon coated I used and stayed to the color in the hafler schematic. Remember to tilt out the amp boards to get to the points to solder to. also be sure to drain the filter caps before going to work.
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