Sony TA-343 Amplifier A/B Switching problem

[jakedavies8]

Hi all,

Firstly, i am very sorry for the upside down Images! I could not work out how to flip them!!!

I just purchased this Sony TA-343 Amplifier on eBay and received it in the post. I went to set it up with my two Wharfedale 9.0 bookshelf speakers and a KEF Q95c center speaker. Below is a photo of the rear channels with my two wharfedales plugged in across top the four slots and my center occupying the left hand two on the bottom.

Now when i got it i realised that it has an A/B switching system, i am not too familiar with this but the impression i get is that it allows you to run two separate sets of speakers on one receiver. Now, i want to run all three at the same time and i have tried many combinations of pressing the A/B buttons and here are the results.

A surpressed: both of the wharfedales work
A & B Surpressed: Left wharfedale and center work (Right wharfedale silent)
B surpressed: Only the center works

Now i dont know, but if i am wrong please correct me, when both A and B are surpressed, all speakers should work at the same time? If this is the case, am i right to assume that there is a problem with the amp itself and should consider returning it?

Any input would be welcomed as i really am stuck here!

Thanks, Jake

 

[vidjo]

Probably puts them in series when you have both sets switched to on. Therefore it need 4 speakers connected - then you can have set A, set B, or both A + B.

 

[jakedavies8]

Probably puts them in series when you have both sets switched to on. Therefore it need 4 speakers connected - then you can have set A, set B, or both A + B.

So if i attatch another speaker it should work fine?

 

[Philip4242]

Now when i got it i realised that it has an A/B switching system, i am not too familiar with this but the impression i get is that it allows you to run two separate sets of speakers on one receiver. Now, i want to run all three at the same time and i have tried many combinations of pressing the A/B buttons and here are the results.

A surpressed: both of the wharfedales work
A & B Surpressed: Left wharfedale and center work (Right wharfedale silent)
B surpressed: Only the center works

Firstly, this is a 2-channel, stereo amplifier; so there is no real facility for a centre channel, which is only associated with surround sound systems.

Secondly, the A/B/A+B speaker switching is for 2 PAIRS of speakers (usually in different rooms) and allows 1 PAIR of speakers; or the other PAIR; or both PAIRS; or neither PAIR (for listening on headphones only) to be selected.

(Note that there are limitations for minimum speaker impedance if A+B speakers are to be used, as the sets of speakers are then connected in parallel (NOT series, as suggested by another poster) - see the amplifier User Manual for details)

So with just your 'centre' speaker, connected as shown to the B Right channel amplifier, you'll only get the Right channel sound from it for whatever source you have connected.

And it's not simply a case of wiring the B Left and Right channels directly together (to get a mono signal), as this would also connect together the A Left and Right channels, if A+B is selected.

Given all that, the reason for the switches not working as expected may be down to them never having been used before, so the switch contacts might be just dirty.

Operating them both a few times (with the amplifier powered off, of course) may be sufficient; or you may need to take the top cover off (again, with the amplifier powered off) and squirt some aerosol contact cleaner into the switches.

If it still doesn't work correctly then, it will need further investigation (or just forget about using any B speakers).

 

[jakedavies8]

I have just plugged in another speaker and now sound comes out of every speaker when A + B are suppressed, is this problem solved?

 

[Philip4242]

Probably puts them in series when you have both sets switched to on. Therefore it need 4 speakers connected - then you can have set A, set B, or both A + B.

If that were the case, assuming that both sets of speakers in their different rooms have the same impedance, switching from (say) A to A+B would reduce the voltage on the A speakers to 1/2 what it was before, so the sound volume will reduce to 1/4 of what it was before in that room.

If the volume control is then operated to restore the volume to what it was before, when the switch is eventually moved back to A, the sound level would suddenly jump up to 4 times what it was - This could be considered undesirable !

Putting a set of speakers in parallel does not alter the volume at all on the original speakers, but simply increases the power that the amplifier needs to produce - hence the limitation I referred to in my response to the OP.

 

[jakedavies8]

Hi,

I'm a little list, what is the difference between parallel and series, and how do I put them into parallel?

Thanks

 

[Philip4242]

I have just plugged in another speaker and now sound comes out of every speaker when A + B are suppressed, is this problem solved?

Well, while I stand by all I've said in my previous posts, the OPs confirmation that connecting a full B speaker pair has led me to search for the User Manual for this amplifier - but I've been unable to find it - even on the Sony website.

I HAVE found a Circuit Diagram however, and can see from that that selecting speakers A+B does indeed connect the A and B speakers in SERIES, which I have never seen or heard of before !!!

I can see nothing on the circuit diagram which connects a compensating series resistor when just the A or B speakers are selected, so, perhaps the OP could comment on whether the volume on the A speakers decreases or increases markedly when going to/from A+B (as I am sure it must for a series connection) ?

 

[Philip4242]

Hi,

I'm a little list, what is the difference between parallel and series, and how do I put them into parallel?

Thanks

Sorry to confuse you, Jake, but you don't need to do anything more, now you've got 2 PAIRS of speakers connected..

What I'm talking about is the way that the amplifier's internal A/B/A+B switching works - which seems to be to make a series connection on this amplifier; whereas all the others I've ever known have made a parallel connection.

Do a Google search for 'series/parallel wiring' if you're still interested in the difference.

 

[jakedavies8]

Sorry to confuse you, Jake, but you don't need to do anything more, now you've got 2 PAIRS of speakers connected..

What I'm talking about is the way that the amplifier's internal A/B/A+B switching works - which seems to be to make a series connection on this amplifier; whereas all the others I ever known have made a parallel connection.

Do a Google search for 'series/parallel wiring' if you're still interested in the difference.

Awesome Philip, thanks for all your help, it is much appreciated!