Tinkering with my stereo

[Electric-T]

Hey guys long time no talk. So ive been tinkering with my stereo. I have a bunch of speakers ive salvaged from storage and i think i have a good set now.
The stereo has an A channel, a B channel, an A+B channel and OFF.
A sounds great, my treble section of speakers. B sounds pretty good too, the deeper bass section. Only heres the thing, A+B sounds terrible and quiet. Ive tinkered with it for weeks and ive found out the some ports on the back are "dead" when on A+B channel.
Ive had it apart and i found the component responsible for "distribution" of sound as i understand it. (Where all the speaker wires plug into)
Im thinking I just need to replace this component, but i wanted to see if anyone else had any other ideas before i went and started ordering parts.

 

[ramussons]

Model?
Schematic?
Photos?
....
would be highly welcome for suggestions from members...

 

[Electric-T]

Model?
Schematic?
Photos?
....
would be highly welcome for suggestions from members...

Ill see if i can look up a schematic. Pictures and info when i get a chance later today

 

[Electric-T]

Sony STR-D715
couldnt find a schematic

A channel is too much trebble
B is all bass
AB is just out of balance somehow

Any ideas?

 

[Tha fios agaibh]

Try posting a few clear photos of the components on the back side of the speaker jacks and the A/B switch. Perhaps that will lend some clues.
All the A/B switch should do is reroute the signal to the corresponding speaker jacks without altering the audio.
Perhaps a shorted cap is taking out your high frequencies? Crossover problem?

I trust you've tried moving the known "great" sounding speaker to both A and B sides? Also try just one speaker without one hooked to the other channel. Then swap. Does it sound the same?

 

[Electric-T]

Heres some pictures of the components
The last one is the best shot i could get of the board sending the signal out to the speakers

 

[Electric-T]

This is the channel switch itself

 

[Tha fios agaibh]

I can't quite tell from pics.

I have seen where strands of speaker wire will break off and get into the Jack's and short to ground. You might want to remove the board along speaker jacks to look at the underside. Maybe yank out the A/B switch also. Its a strong suspect, although I would expect signal loss, not high/low frequency problems.

 

[Electric-T]

Thanks. It does need a good cleaning. Im also starting to suspect the speakers themselves. It might just be that the subwoofers really just drown the trebble out. I was hoping for a nice blended sound but it may be the nature of the beast

 

[Tha fios agaibh]

Im also starting to suspect the speakers themselves.

That's why I suggested moving same speaker to different outputs.
Also try it with a mono input so the output will be the same.