Clarion APA4400G: poor channel separation

[miniman82]

Channels 3 & 4 are bleeding over to each other, channels 1 & 2 work the way they should. Thinking the STK350-000 is the issue, only because I had one of those go bad on an MC431 a while ago (there’s no heat sink on them). The channels themselves are clear and strong like they should be, just poor separation. Thoughts?

 

[Perry Babin]

Have you swapping the STK ICs between 1/2 and 3/4 to see if the problem follows the IC?

 

[miniman82]

If I unsolder it I’m just gonna go ahead and replace it since past experience tells me it’s likely the guilty party, just making sure the diagnosis makes sense before doing so.

 

[Perry Babin]

At this point in time. a great number of the STK ICs are counterfeit. It would be better (in my opinion) to determine whether the IC is defective or not.

 

[miniman82]

They sure are! lol

But when one goes bad like it did on my MC431, I didn’t have a choice. Would it be advisable to open up one input or output of the STK from the rest of the circuit, to see if the separation issue goes away?

 

[Perry Babin]

I don't know how the IC will behave with un-connected pins.

You don't know for certain that this one is defective. Swapping them around will tell you definitively. If it's not defective, you can continue troubleshooting.

 

[miniman82]

Swapped STK's, problem remains. Gotta be something with an OPAMP, or possibly the channel summing circuitry. This is a 4-channel unit, but the preouts are only 2 channel meaning 1&3/2&4 are summed.


Any ideas?