Help with 70 volt system - AVS Forum
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post #1 of 8 Old 03-11-2013, 12:05 PM - Thread Starter
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We just bought a house with a 70 volt speaker system upstairs and although I am somewhat familiar with surround sound systems, I am largely unfamiliar with 70 volt systems. I would like to get a system of preamp+amp or integrated amp that will do AM/FM, CD, and MP3 (iPod) without breaking the bank (less than $1,000). I want a decent system that will last, but won't cost me an arm and a leg for something that I won't be using all the time. Does anybody have any suggestions on a good fairly inexpensive setup?
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post #2 of 8 Old 03-11-2013, 02:13 PM
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70 volt systems were/are used to overcome the line losses in long runs, smaller gauge wire and multiple speakers, much like the electric company uses high voltage lines that are converted to lower voltage by transformers on poles near your house.
The amplifier would have a 70 volt output transformer and there would be a reciprocal transformer at each speaker to convert back to the normal speaker impedance, 4, 8, 16 or etc ohms. A 70 volt transformer could probably be added to most amplifier outputs.
Ok for background music but not for critical listening.
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post #3 of 8 Old 03-12-2013, 08:39 AM - Thread Starter
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Thanks for the info. about 70 volt systems. Our system is already in place (put in by the home builder in a now 2 year old house), however I was wondering if anyone had suggestions on the type of amp + preamp or combo thereof that is good for a home. I see a lot of commercial grade systems with unnecessary features that I won't use. I just want a decent system that can do AM/FM radio, play CD's, and has a hook up for iPod/mp3 player.
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post #4 of 8 Old 03-12-2013, 08:58 AM
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Quote:
Originally Posted by harve007 View Post

Thanks for the info. about 70 volt systems. Our system is already in place (put in by the home builder in a now 2 year old house), however I was wondering if anyone had suggestions on the type of amp + preamp or combo thereof that is good for a home. I see a lot of commercial grade systems with unnecessary features that I won't use. I just want a decent system that can do AM/FM radio, play CD's, and has a hook up for iPod/mp3 player.

Usually 70 volt systems are for background music or voice announcements, and are thus mono.

Do you know for sure that your system is mono or stereo?


In principle, a standard amplifier can be adapted for 70 volt use with just a step-up transformer. Does your system already have one>

While in principle just the transformer is needed, in practice some power amps aren't happy driving them.
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post #5 of 8 Old 03-13-2013, 01:32 PM
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Quote:
Originally Posted by arnyk View Post

Usually 70 volt systems are for background music or voice announcements, and are thus mono.

As well as limited frequency response - 100hz to 10khz is common. This is due to the low cost transformers often used.

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post #6 of 8 Old 03-14-2013, 04:54 PM
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Your best bet might be to ebay a TOA 70-volt amp. One amp would probably do the whole house, but if your system is set up as stereo, it would require two amplifiers. I’m sure there are stereo 70-volt amps out there, but most I’ve seen are mono.

Regards,
Wayne A. Pflughaupt



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post #7 of 8 Old 03-22-2013, 06:54 PM
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Late to the thread, but.

Rane Corp. has a paper on:

Constant-Voltage Audio Distribution Systems: 25, 70.7 & 100 Volts

http://www.rane.com/pdf/ranenotes/Constant_Voltage_Audio_Distribution_Systems.pdf


Also the parts-express catalog has a 8 page section:

Pro Audio 70V Commercial

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post #8 of 8 Old 03-26-2013, 12:49 PM
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Quote:
Originally Posted by Speedskater View Post

Late to the thread, but.

Rane Corp. has a paper on:

Constant-Voltage Audio Distribution Systems: 25, 70.7 & 100 Volts

http://www.rane.com/pdf/ranenotes/Constant_Voltage_Audio_Distribution_Systems.pdf


Also the parts-express catalog has a 8 page section:

Pro Audio 70V Commercial

Yes, that's a good resource.

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