Right Channel A dropping when B Channel on

[M.O. Deloofs]

Greetings Kenwood crew. I recently bought a stack of Kenwood components and have been enjoying getting things running and starting my hi fi audio journey. Here are my components:

KA-127 Stereo Integrated Amp
- 125 watt peak output
- 8 to 16 ohms
- A and B channels with L and R each for total four outputs
Two JL-870 Tower Speakers
- 180 watt max input power
- 8 ohms each
One Jl-W970 Subwoofer
- 140 watt max input power
- This one subwoofer has two speakers with separate terminals so it's more like two speakers in one box
- 8 ohms
12 AWG speaker wire (brand is Gear IT)


I'm having a problem where one side of the A channel drops out entirely and the A channel volume overall drops considerably when I engage the B channel. The A channel sounds excellent with the B channel disengaged. I have tried several different speaker wires for the subwoofer wiring and the subwoofer seems to be working. It is difficult to tell if both the subwoofer speakers are working because of the enclosure. I reversed the L and R terminals on the sub and the dead A channel switched sides as well.

I did some research and found some threads about other Kenwood amps saying that the channel switches are wired in series and that there are frequently problems with the switch needing cleaning. The symptoms described in those threads were different than mine so I wanted to ask about my problem specifically.

Does anyone have any insight or suggestion for where to start troubleshooting?

 

[rschweitzer]

Typically speakers are wired in series, but not always. Most of the Kenwood receivers I have, are in series. Thus, an 8 ohm speaker in series becomes 16 ohm and the volume will drop. I forget the math on exactly how many decibels?

As for your issue, I suspect the switch, but let's try the process of elimination.

I assume both sets of speakers are working.

Remove the subwoofer and put the JBLs in series on the left channel. Set the the switch to A and then B and then to A+B. Then do the same for the right channel. I expect the volume to drop overall in a A+B arrangement. Sound quality should be the same. What do you get?

If that works, then do the same with the sub. You should be able to hear low frequencies, but drop overall in the A+B arrangement.

 

[M.O. Deloofs]

Remove the subwoofer and put the JBLs in series on the left channel. Set the the switch to A and then B and then to A+B. Then do the same for the right channel. I expect the volume to drop overall in a A+B arrangement. Sound quality should be the same. What do you get?

If that works, then do the same with the sub. You should be able to hear low frequencies, but drop overall in the A+B arrangement.

Thanks for the suggestion. I'll try it and get back to you!

 

[M.O. Deloofs]

I ended up just plugging the working tower speakers into the B channel and they worked fine so I'm assuming my problem is with the subwoofer. Thanks for the help!