Pre out attenuation

kb1uab · 15th March 2011, 02:46 PM

I recently resurrected a Teledyne Acoustic Research GCS 80/40. My problem is that it has no gain controls on it. I'm feeding it with a Pioneer AVH-P6500 DVD head unit, 4V preouts. The problem is when I come off of 0 on the volume the gain is so high it starts to hiss, by 20 (max of 62) its screaming (sounds good too I might add). Can anyone suggest a attenuation circuit that might be commonly used in these situations? I don't want to go back in the amp or build a box with a pair of pots.

AndrewT · 15th March 2011, 07:32 PM

"head unit"?
Is this car audio?

firechief · 15th March 2011, 10:05 PM

I suggest that you make some fixed resistor attenuators to go inline with the wires between the head unit and the amp. See Pi Attenuator calculator
Try mabe 6db of attenuation and I would guess at an impeadance of 600 ohm. If it is too much you can just re-calculate and adjust. These resistors can be built into the wire and heat shrinked to protect.
Andrew - is this reasonable?
Bob

15th March 2011, 02:46 PM	#1
kb1uab diyAudio Member Join Date: Mar 2011	Pre out attenuation I recently resurrected a Teledyne Acoustic Research GCS 80/40. My problem is that it has no gain controls on it. I'm feeding it with a Pioneer AVH-P6500 DVD head unit, 4V preouts. The problem is when I come off of 0 on the volume the gain is so high it starts to hiss, by 20 (max of 62) its screaming (sounds good too I might add). Can anyone suggest a attenuation circuit that might be commonly used in these situations? I don't want to go back in the amp or build a box with a pair of pots.

15th March 2011, 07:32 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	"head unit"? Is this car audio? __________________ regards Andrew T.

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15th March 2011, 10:05 PM	#3
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	I suggest that you make some fixed resistor attenuators to go inline with the wires between the head unit and the amp. See Pi Attenuator calculator Try mabe 6db of attenuation and I would guess at an impeadance of 600 ohm. If it is too much you can just re-calculate and adjust. These resistors can be built into the wire and heat shrinked to protect. Andrew - is this reasonable? Bob

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