The No.1 Website for Pro Audio
 Search This Thread  Search This Forum  Search Reviews  Search Gear Database  Search Gear for sale  Search Gearslutz Go Advanced
70 volt system questions
Old 17th September 2011
  #1
Lives for gear
 
johndykstra's Avatar
 

70 volt system questions

Hey guys.

I'm assisting a friend who needs an amplifier to drive what appears to be an existing 70volt system. There are 12 speakers with in wall attenuators already in place. I've pulled down a speaker and found that they have transformers installed. The speakers are 25watt rated.

Before calling me, the guy attempted to simply connect the run to the output of a home receiver. He was able to pass audio, but his volume was cranked to get barely anything... This is when he called me.

I'm wondering if I can simply connect a bridged amp with adequate wattage to drive this system, or is there another transformer required at the front end? To that end, if it is just as simple as a bridged amp with nothing else, I'm not sure what ohm load the amp will be operating on.
Old 17th September 2011
  #2
Lives for gear
 
KRStudio's Avatar
 

If I'm not mistaken, you need a 70volt amp. Bogen among other used to make these. Look around ebay for a cheap one.
Old 17th September 2011
  #3
Lives for gear
Or a step-up transformer at the output of your 8 ohm amp.

QSC OT300A
Old 17th September 2011
  #4
Lives for gear
 
johndykstra's Avatar
 

Thanks guys. Looks like the dedicated 70 volt amp is the way to go as it has all the inputs/mixer built in.
Old 17th September 2011
  #5
Lives for gear
 
djmukilteo's Avatar
Quote:
Originally Posted by johndykstra View Post
Hey guys.

I'm assisting a friend who needs an amplifier to drive what appears to be an existing 70volt system. There are 12 speakers with in wall attenuators already in place. I've pulled down a speaker and found that they have transformers installed. The speakers are 25watt rated.

Before calling me, the guy attempted to simply connect the run to the output of a home receiver. He was able to pass audio, but his volume was cranked to get barely anything... This is when he called me.

I'm wondering if I can simply connect a bridged amp with adequate wattage to drive this system, or is there another transformer required at the front end? To that end, if it is just as simple as a bridged amp with nothing else, I'm not sure what ohm load the amp will be operating on.
You should take a look at the transformers mounted on each of the 12 speakers and find out what they are tapped at. Typically they are 1/2W, 1W, 5W, 10W etc. If they are actually tapped at 25W you would need at least a 300W power amp to drive those. Add up the total wattage of the tapped speakers to get the correct power amp needed. There are many brands of 70V PA distribution amps out there pretty cheap. Bogen, TOA, Rauland etc.
Old 17th September 2011
  #6
Lives for gear
 

Quote:
Originally Posted by johndykstra View Post
Hey guys.

I'm assisting a friend who needs an amplifier to drive what appears to be an existing 70volt system. There are 12 speakers with in wall attenuators already in place. I've pulled down a speaker and found that they have transformers installed. The speakers are 25watt rated.

Before calling me, the guy attempted to simply connect the run to the output of a home receiver. He was able to pass audio, but his volume was cranked to get barely anything... This is when he called me.

I'm wondering if I can simply connect a bridged amp with adequate wattage to drive this system, or is there another transformer required at the front end? To that end, if it is just as simple as a bridged amp with nothing else, I'm not sure what ohm load the amp will be operating on.
you need a bigger amp
and an output that drives a 70.7volt line

would hve to review my old notes
but i think this is a voltage issue not an impedance matching one.
Old 17th September 2011
  #7
do the speakers have different watt settings with the transformer? You're going to want to not exceed the rating of the 70 volt amp when you add all the wattage up.
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump