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View Full Version : How do you adjust the balance on the Hafler DH-120? (Schematic included)


Andy
August 4th 03, 08:37 PM
Schematic is here (warning, ~2mb file..)

http://www.hafler.com/techsupport/pdf/DH-120_amp_man.pdf

The instruction is given for the bias, but not for the balance.
How do I adjust the balance? Is this a good amp?

Thanks
Andy

Browntimdc
August 4th 03, 09:21 PM
(Andy) wrote in news:aed59298.0308041137.122690e5
@posting.google.com:

> Schematic is here (warning, ~2mb file..)
>
> http://www.hafler.com/techsupport/pdf/DH-120_amp_man.pdf
>
> The instruction is given for the bias, but not for the balance.
> How do I adjust the balance? Is this a good amp?
>
> Thanks
> Andy
>

According to the manual balance is adjusted for minimum distortion. You
need a low distortion sine wave generator, distortion analyzer and
presumably an 8 ohm load resistor. You also need to know what signal
level and frequency to use. I'm guessing 1 kHZ and 10% of full output
would do the trick.

Have you changed transistors or have some other reason to beleive the amp
needs adjusting?

Tim

Kevin McMurtrie
August 5th 03, 04:03 AM
In article >,
(Andy) wrote:

>Schematic is here (warning, ~2mb file..)
>
>http://www.hafler.com/techsupport/pdf/DH-120_amp_man.pdf
>
> The instruction is given for the bias, but not for the balance.
>How do I adjust the balance? Is this a good amp?
>
>Thanks
>Andy

It appears that the balance control adjusts the uncompensated slew rate
balance between positive and negative swings. A high frequency square
wave of moderate amplitude might help you. Adjust it so that that an
oscilloscope shows a symmetrical output waveform.

Or it might not work. Mark where the pot is before you turn it :)

Kevin McMurtrie
August 5th 03, 08:43 AM
In article >,
(Andy) wrote:

>Schematic is here (warning, ~2mb file..)
>
>http://www.hafler.com/techsupport/pdf/DH-120_amp_man.pdf
>
> The instruction is given for the bias, but not for the balance.
>How do I adjust the balance? Is this a good amp?
>
>Thanks
>Andy

It appears that the balance control adjusts the open loop slew rate
balance between positive and negative swings. A high frequency square
wave of moderate amplitude might help you. Adjust it so that that an
oscilloscope shows a symmetrical output waveform.

Or it might not work. Mark where the pot is before you turn it :)