Harman Kardon 930 best way to reduce pre-amp gain

[Richie81]

Hi all,
this is my first post here so don't judge too harshly I'd like to reduce the audio amplification (gain) of Harman Kardon 930 pre-amp section for several reasons...

1) I don't need all the power with my rather sensitive speakers and that makes 930's volume knob somewhat uncomfortable (useful range is close to 0 volume and is toо sensitive to rotation).
2) Volume imbalance (left/right) is mostly pronounced near 0 position as you all know... And many HK930's are prone to this known problem. This effect should also be lowered when the pre-amp gain is reduced (thus moving the effective volume knob position further from zero).

The question is - how would you do that? Goal is - not to alter any other important parameters which might affect frequency response ("contour"/loudness section for instance).

 

[chazix]

how would you do that?

My thought would be to remove the pre/main jumpers and in their place, patch in a pair of RCA inline attenuators. No need to modify the internals of the HK (which might hurt its market value, if that's an issue) with this approach, and I think it will meet most of your goals.

The one caveat I can think of is that the loudness/contour effect will still be tied to the mechanical position of the volume control; so, you would expect its effect to be lessened because you're turning the volume control higher. Off hand, I can't think of any solution that will avoid this conundrum, since higher volume control position is in itself one of the goals.

 

[Richie81]

Thanks for idea Chazix. Really easy to implement I'm aware that due to the different volume/loudness pot position the "contour" rate will be lessen as well. Not a big deal because currently the effect is also more like "overkill". Lowering the "contour" effect would also be a positive bonus. Actually, the thing I wanted to avoid is to change some input/output signal chain resistance, which might affect frequency response (RC law) in that particular section, making it non-linear. Which is unacceptable of course. That's my only fear

 

[jheu02]

Does it have a Mute, -20dB switch, I can't remember? If so, run it with the muting switch On and see what range you now get for the volume knob.

Never mind...no mute circuit.

 

[billyz]

I made up a 100k stereo stepped attenuator to use between my cd player and pre amp. The cd player has enormous output compared to all the other inputs. Works fine. I can also insert it between the pre amp and power amp , as was suggested above. You could insert a stereo ( dual ganged) 100k pot between the pre and power amp. Set it where you like it. Measure the resistance on both sides of the wiper and make up a fixed Voltage divider , just two resistors each channel.