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Help with 4 Speakers connection

I have a Tecstar mini Hi Fi stereo Amp, model TAA-33 . Its sound is very nice to me. Im using a pair of Technics bookshelf speakers, but I would like to add another pair and use them at the same time.
The amp has got A and B speakers output. When I select A and B, both, the signal is between B ground and A positive!
Is it possible that these could not be used at the same time?

May be, this is normal on 70s - 80s amplifiers....

Re: Help with 4 Speakers connection

I don't know the amp, but normally if there are two switches, one or A and one for B, they will both work when depressed.

Internally it is common for both A and B speaker terminals to be joined to the same output so electrically it's the same as connecting both speakers to one set of terminals. With this circuit when both A and B switches are depressed there should be a signal between all positives and the shared ground.

Re: Help with 4 Speakers connection

Well finally I understood how does it works. I leave it posted in this picture for further users. It has a 4 to 16 ohms output. In A+B it use a serial connection.

Thanks JaS for reply!

Re: Help with 4 Speakers connection

Sorry but I don't agree with this. Each speaker should be connected to their own terminals. Placing them in serial will make one speaker influence the other speaker. As speakers do not have a linear load (impedance), the way you connected them could work with 4 similar speakers. Otherwise the sound will be severely compromised if 2 dissimilar speakers are placed in serial.
Therefore, I believe with the speaker buttons you should be able to drive either set A, set B or both.
I tried to find an owners manual on line without succes.
Therefore I suggest you look in the owners manual to find the allowed speaker impedance and verify with the impedance of the speakers. The amp. might switch off to protect itself from driving a too low impedance when both speakers are connected.