Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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Re: Help for Levinson JC2 (John Curl design) preamp

Posted by Elso Kwak on May 23, 2001 at 06:04:25

In Reply to: Re: Help for Levinson JC2 (John Curl design) preamp posted by cyclonic on May 22, 2001 at 23:57:18:

Hi cyclonic,
First of all are you sure both line modules are dead? Your problem sounds more like a bad powersupply as two dead modules at the same time is rather unlikely. Did you measure the supply voltages (+15V on the red wire and -15V on the yellow).? Did you check the offset voltage coming out the module? Set the DC/AC switch on the motherboard to DC and measure the offset at the main outputs. Bad modules usually have a large offset. Do you have a tape output coming from the phono playing a record?
Sorry to hear the Op-Amp book is sold out. But there is hope. You can also construct a line amplfier like the one in the Linear Technology Application Note High Speed Amplifier Techniques(#47) page 46. With a AD744 or 1/2 a AD823 as opamp. Do not forget the ferrite bad's! Only FET input type opamps work in the line amplifier of the ML-1, otherwise the input bias current cancellation scheme won't work.

I dot advice to run the ML-1 as a passive line amplfier. That will ruin the dynamics etc.

On the other possibility's, making a PCB, I will email you directly.
Good luck
ELSO

• http://www.linear.com

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