On May 18, 10:50*am, "Michael A. Terrell"
wrote:
klem kedidelhopper wrote:

I need to install a 60 Watt paging amplifier on a job. The maximum
load at this time is 42 Watts, however we need to have a slight amount
of room to move in the future. So I felt that 60W unit would be a good
cushion. I currently have in the shop a nice Technics 100 Watt mono
amp that I rebuilt and have no plans for. I would really like to sell
this to the customer to use for this application. The problem is
though it does not have the 70V output that I need. So I had two
thoughts. The first is can I buy a transformer that will have a
primary of 4, 8, or 16 ohms and a secondary which will provide the 70V
output that I need, and handle at least 60 Watts RMS? * The second
thought is this: I have a number of 60Watt amplifiers in the scrap
pile with good transformers I'm sure. The schematics show these
transformers hung on the outputs as though they were a speaker load. I
have no idea what the primary impedance could be though on any of
these transformers, but I was wondering if it is anything close to
typical speaker impedance? *If it was then perhaps I could pull one of
these from a junker, hang the primary across the Technics amplifier
output, (which I think is 8.0 ohms} and then have my 70V output? Has
anyone ever done anything like this? Of course I would do a load test
on the amp/transformer combination before selling it. Thanks for your
thoughts on this. Lenny

* *Lenny, the biggest difference in the amplifers is that a PA amp is
designed to be used 24/7/365.25. *The transformer adds isolation from
the amplifer, as well. *I see no problem, as long as you're willing to
stand behind what you sell and tell them that the transformer was added
to match the speaker wiring. *MCM sells transformers for this
application. *We did it back in the '70s to clean up installations done
by knowitalls, and their victims didn't want to pay for another
amplifier.

* *As far as matching constant voltage speaker system impedance, keep
these numbers in mind:

70V = 5000/W *which means your 100 W amp would be 50.00 Ohms.

25V = *625/W *which means your 100 W amp would be *6.25 Ohms.

* *100W is in the ballpark of what I beleive that there will be more speakers installed at later date.
It could drive up to 120W load, in most installations with no problems.

--
You can't have a sense of humor, if you have no sense.

Well as it turns out, (and Phil was correct), so call me an oxygen
thief, ****wit or whatever else suits your fancy Phil, in that the amp
is not a mono amp but a 100 Watt per channel stereo amp. So now I
don't want to use this amp for this application. This has all been an
interesting exercise but unfortunately I have now run out of amps so I
may very well have to buy a 60watt paging amp. Lenny