Audio Systems: medical office setup, rca cables, stereo amps

Question
QUESTION: Hi

Thanks for your help. I have connected all 12 speakers in a 70V system. Each speaker has its own step down transformer. I am using a standard 5.1ch receiver - Kenwood VR-407 (100W per RMS). I am connecting the receiver to an external 70V 200w step up transformer. My questions are:

1) How do I connect the receiver and the step up transformer i.e. should I connect to either the L or R channel? Anyway to combine both L and R channel into mono?

2) I am thinking of connecting the Ipod via RCA cables to L and R aux. Should the signal be combined before the amp? If so how is that done?

Thanks

ANSWER: Yes, you can connect the 70v transformer to either/any channel.  

1)No, you cannot combine the amps unless they are specified as bridgeable and I don't think that is possible.

You can, however, use two 70v step up transformers and have half the speakers on one amp and the other half on another amp.

2)  You are best to have the signal "monotized" before feeding the amplifier.  I am looking at the specifications of the Yamaha receiver as writing this reply and I don't see either a provision for bridging the stereo amps OR a stereo to mono switch.  Thus you have two options; leave it in stereo and hope that nobody notices they are listening to only one channel of a stereo recording!  Or, you can use a connecting cable that goes stereo to mono by combining the channels together in the cable. You should be able to find the right jacks/cables here:

http://www.audiogear.com/Audio-Adapters-Miniplug.html

Most of these are also found at Radio Shack or any good audio shop.

Hope this helps.




---------- FOLLOW-UP ----------

QUESTION: Thank you so much. Just to be clear, are we combining stereo to mono before the receiver ie when I connect the ipod to the receiver. If so am I still using the same channel as out. In other words I connect the ipod using the Y cable to either L or R input on the receiver and using the SAME L or R as output?

Answer
Yes, but you can combine the channels at any point. The object is to have mono sound in all the speakers.  Most music you will be feeding is in stereo.  The ipod output is stereo - I don't think it has  a mono setting - if it does, you are in luck.

Most older receivers have a mono switch, but newer ones do not, unfortunately.  However, the modification to combine the channels internally inside the receiver is a simple job for someone who knows audio circuits  (for example, coupling the top of the volume controls together will combine the two channels together but I don't recommend doing it until a tech has looked at the circuit to make sure it does not cause loading of the preamp inside the receiver.)

Yes, to your last sentence; once the audio is combined into mono the L and R are the same identical signal.