JAN6418 pre-amp advise

[briansune]

I brought a pair of JAN6418 which i found some schematic. I found something strange, it seems to be a stereo amp from the schematic. But after the first trial . the amp only takes the left side of the input and return both L&R output have the same sound. Could any one tell me what's wrong?

 

[JonSnell Electronic]

Make sure the ground point between R14 and R18 is good.If that is floating, that is your cause.

 

[briansune]

Hi JonSnell R14 & R18 is good, will this cause by two pentode are config in series?

 

[JonSnell Electronic]

It has to be something common to both sides. Because both signals are mixing together. All I would do is run through the board with an oscilloscope and measure until I found the point at which it wasn't mixed. After that point is where the issue lies.
Start from the output and work backwards.