Question about 70V transformers

[Old Guy]

Originally posted by CONVERGENCE:
There's Edcor Electronics. They have different
wattage transformers.You might want to chek them out.

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<font size="2" face="Verdana, Helvetica, sans-serif">Edcor is very well thought of...no personal experience but too many people I know say they are good- I have no idea how pricing compares..

[valhallax]

i had some 409-b's with transformers on them, i assumme 70 v..when bypassed the speaker was much louder. perhaps we should expand this post abit to explain to the ignorant umongst us, namely me..just what a 70 volt transformer is used for? i kinda knew it was for like a paging system..to ditribute the limited available power for many speakers? im more than likely wrong here but a little schooling in this area would be much appreciated

[Old Guy]

Essentially, the power is stepped up to run long distances, just like high tension lines, then stepped down at the speaker, just like the pole transformer outside your house.

Less power loss at high voltages.

By hooking up the transformer, you were stepping down your amp with out ever having stepped it up.

Make sense? Only use the transformer when connecting to a constant voltage line.

This is over simplified, the analogy between a high voltage 70/100 volt system and high tension lines only goes so far, but I hope it gets the idea across.

[katzenandguthrie]

Wow great info! I checked out the QSC and the Peavey and they both look like what I'm after but the Edcor TA-100-8-70 seems to be dead on and the price is something like $34.00 each. I think at that price I should just pick some up, run the same test, and see what happens. That Altec 15524A, man, now that's a nice transformer! It's the reference standard I'll use to judge the others with.

[Old Guy]

Originally posted by Mark Guthrie:
Wow great info! I checked out the QSC and the Peavey and they both look like what I'm after but the Edcor TA-100-8-70 seems to be dead on and the price is something like $34.00 each. I think at that price I should just pick some up, run the same test, and see what happens. That Altec 15524A, man, now that's a nice transformer! It's the reference standard I'll use to judge the others with.

<font size="2" face="Verdana, Helvetica, sans-serif">You do of course realize the $34 Edcor you mentioned is a 100 watt transformer and the $63 Peavey is a 400 watt?


Just wanting to make sure it's apples to apples...of course if 100 watt is adequate for your needs- I can't remember the last time I used a 100 watt amp....I don't even have that small an amp on my stereo...so I may have tried to over sell you. That's what I get for not asking enough questions...just give me a pointed hat.

[LICORNE]

There is one rule for installation.

Q: How many loudspeakers can I hook up to my 70 volt amplifier?

A: All you need to remember is to not exceed your power amplifier wattage rating by the total sum of the transformer power taps that are used by each loudspeaker. We recommend you also allow a 25% safety margin for losses in the transformers and wiring


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[valhallax]

old guy..well put! i completely get it now! i do have some long runs here at home, it all seems to be working fine. makes sense when explained by a technician with yrs of feild service, and priceless experience actually using the gear we all love! truely a resource we can rely on.

[Old Guy]

Originally posted by CONVERGENCE:
There is one rule for installation.

Q: How many loudspeakers can I hook up to my 70 volt amplifier?

A: All you need to remember is to not exceed your power amplifier wattage rating by the total sum of the transformer power taps that are used by each loudspeaker. We recommend you also allow a 25% safety margin for losses in the transformers and wiring


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<font size="2" face="Verdana, Helvetica, sans-serif">Agreed except-one big but- bigger even than J Lo's...

His amplifier is drect coupled. He needs one BIG transformer to step up to the high voltage line...it has to handle ALL the power the amp puts out, and then some. That's why I posted the caution- the one transformer has to be as heavy duty as all the others COMBINED.

[katzenandguthrie]

I'm with you on all your points and yes, a 100w should work just fine. (good call about the Peavey being higher wattage than the Edcor, I didn't catch that)But the part I'm could use a little help on is when to use 70v vs 25v.

[LICORNE]

If the taps on your speakers are 70v then you must use 70V on the amp. If your taps were say 25
V then you you would need 25V. Your carrying the signal on a 70 volt line "careful for shocs".
or 125 volts. The sender transformer has to be the same as the receiver transformer.

Then you must match the wattage of each speaker taps to the wattage of your amp. It should never exceed the output of your amp. As a matter of fact
you should give yoursel 25% of headroom.

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