Preamp Problem


New member
Username: Ichbin

Post Number: 1
Registered: Dec-04
I have an AudioSource amp+preamp running a pair of Martin Logan Montage speakers. I have been very satisfied until the last few days, when I noticed that one side was louder than the other.

I poped in an audio test CD, and by various machinations (problem switches sides with output cables, goes away when inputs fed directly into amp), I was able to show that the problem is with the preamp. Correcting it required moving the balance knob about 90% to one side. I have two questions:

1. Anyone every enountered a problem like this before (preamp amplifies left and right differently)?

2. When I changed configurations from going through the preamp to going directly to the amp, not only did the difference go away, but the sound got much louder. With the volume knob at 20%, the preamp hadn't amplifed at all, it had suppressed. Is the the way preamps are supposed to work, or is this another sign that the device has problems?

Silver Member
Username: Edison

Glendale, CA US

Post Number: 593
Registered: Dec-03
Your pre needs work - might be cheaper to get a used one off ebay.

You can get old marantz receiver like 2230 for less than $100, and use it as a pre.

Since it's an old item, make sure all is working - ask the seller in advance - might want to get his/her phone no. and address, and talk to the seller before - gueranteeing not tobe damaged upon arrival - with return guerantee.

You might like the sound better, for not much money.

j. Vigne
Unregistered guest

Your pre amp does need servicing. You are probably looking at a fee around $100, if you can find a repair shop to work on it. Contact Audio Source for help in locating a service agent.
A pre amp is (usually) made up of gain stages, individual sections that amplify the signal in stages, and you have likely lost either an IC output or one of the components in front of the chip that feeds it the signal.
A pre amp is an attentuation device. The signal is fed into the pre amp which then does its work of stepping up the gain to the max level. The signal is then run through the volume control which is used to attentuate the signal to the desired level. All volume controls have a taper which determines the amount of attenuation at any one setting. As long as the voume control lets the pre amp reach full gain there is no problem.


Bronze Member
Username: Nuck

Parkhill, Ontario Canada

Post Number: 22
Registered: Dec-04
Your faulty knob is a pot, either 5 or 10 k , likely. You cn get one of these at ny radio shack or whatever, the pot is likely gone. Cheap and easy, just like all my friends, haha

Just add a new pot, 5$
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