A friend loaned me his Levinson ML-1 (John Curl JC-2) that had been sitting in a closet for years.
I plugged it in and noticed a 60 Hz hum but gave it a listen.
Unfortunately, I'm falling in love with this pre-amp but it's freaking ancient! The soundstage & separation of instruments is fantastic😱. I didn't know my speakers were that good.
I studied ME in school, not EE, but I assume the hum is because of an old capacitor? Any help on finding the device(s) causing the hum would be appreciated.
I know the modules are non-serviceable & pricey to replace assuming you can find them - so if a bad module is the problem, I get it.
If anyone has any advice or experience in what I'm facing, I'd be grateful.
Thanks,
Kevin Looker
I plugged it in and noticed a 60 Hz hum but gave it a listen.
Unfortunately, I'm falling in love with this pre-amp but it's freaking ancient! The soundstage & separation of instruments is fantastic😱. I didn't know my speakers were that good.
I studied ME in school, not EE, but I assume the hum is because of an old capacitor? Any help on finding the device(s) causing the hum would be appreciated.
I know the modules are non-serviceable & pricey to replace assuming you can find them - so if a bad module is the problem, I get it.
If anyone has any advice or experience in what I'm facing, I'd be grateful.
Thanks,
Kevin Looker
Is the hum in both channels, and is it a low pitched tone, or a higher pitched buzzing?
Is it still there with shorting plugs in the input sockets? How is it affected by the volume control?
The problem could well be in the power supply, which is rather complex.
Is it still there with shorting plugs in the input sockets? How is it affected by the volume control?
The problem could well be in the power supply, which is rather complex.
I have attached the schematics. The ML-1 is class 1 with safety ground connected to the chassis which again is connected to audio ground. If e.g. your power amplifier does the same you get a ground loop. I would recommend to check this way: Connect only one source, which is class 2 (no safety earth) to the preamp. Most modern CD Players, DACs etc. are made this way. Check if the power amps signal ground is connected to safety earth. If yes, a "soft" connection via thermistor ar another kind of loop breaker will help like it is done in the various pass amps described in this forum.
It's in both channels. It sounds like 60 Hz - the same pitch I hear the transformer buzzing inside the power supply.
It's unaffected by volume setting or selected input.
I haven't tried shorting an input.
Kevin Looker