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BK Components Setting Bias and DC

Guide to Setting Bias and DC on BK Components Amplifiers

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BK Components Setting Bias and DC

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re: Setting Bias and DC

Setting bias and DC off set on B&K components,LTD.EX-4420 its same as EX-442 ?I have B&K EX-4420 ,can't found service manual for this amp.Only i see is available for EX-442.It's they are same ?

re: Setting Bias and DC

This is the only method that I have found to set DC offset and Bias for the ST 202+ and the EX 442. That I have found is the key sentence in this statement. I am sure that there are other ways but I personally have not found any other documentation (from sources besides this paperwork from B&K) that show how to do this or other ways to do this. I did read where one person said that the 100mV input or the dummy loads were not needed and to simply let the amp warm up and use the measurements across the -rail to set bias. This is what I did. The ST-202 + as I recall had no DC offset adjustment. The EX-442 did so I set DC offset to the lowest possible value. Hope this helps.

re: Setting Bias and DC

Hi,

One of the ways that I used to set bias when I didn't have manufacturer's documentation, was to monitor the ac current draw using a meter and adjust the bias pot until the current dropped to the lowest reading on the meter. Then slowly increase the bias until the current increased slightly. Do this for both channels. Then let the amp sit with no input and monitor the ac current and heat-sink temperature for 30 minutes. You want to make sure that you don't get the amp into a thermal runaway condition.

An alternate way with a distortion analyzer is to input a 10 khz signal at a low level and adjust the bias for minimum distortion and minimum power consumption.

Also remember that you do not set dc offset when the output of the amp is ac coupled. You set the dc balance by outputting a sine wave at maximum power output and adjust for symmetrical clipping on the top and bottom of the waveform.

-bob

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