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Author Topic: 70 Volt amp question  (Read 3932 times)

Brian Heil

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70 Volt amp question
« on: May 19, 2010, 05:01:55 pm »

Currently I have a 70 volt system that I'm considering changing and I have a quick question I need answered.  The system consists of 10 speakers total - 1 in the main sanctuary, and 9 throughout the rest of the building.  This is driven by a Peavey PV900 amp in bridge mode (600 W RMS @8 Ohms). My goal is to send a different mix to the sanctuary speaker than is going out to the other rooms (I'd like to mic the congregation and choir for this mix and don't really want it in the sanctuary).  So my question is can I take the amp out of bridge mode and drive the sanctuary speaker on one channel and the other rooms on the other channel?  Since the amp is no longer in bridge mode, I suspect I'd need a couple of step up transformers.  If all of the speakers are using the 10 watt tap can I get by with a 200 watt transformer?  At 8 Ohms, this amp is rated at 180 watts per channel so it appears that 90 total watts (9 speakers) with the 200 watt transformer should work.
I'm an IT guy by day so I'm pretty comfortable with technical things, but I'm a little shaky on the specifics of 70 volt distribution. My research so far suggests what I've proposed above, I'm just looking for a little expert opinion! Hopefully I'm not too far off!
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Emil Barnabas

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Re: 70 Volt amp question
« Reply #1 on: May 23, 2010, 07:31:30 pm »

Is the amplifier directly feeding the 70V distributed speaker system, or is there a transformer connected to the speaker output that then drives the speaker system?

That amplifier is not rated to directly drive a 70V speaker system, though that might be what it is doing.

I would suggest disconnecting the sanctuary speaker form this system and connecting it to a new amplifier.

Radio Shack has a couple of amplifiers designed to push a 70V speaker for under $100.
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Brian Heil

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Re: 70 Volt amp question
« Reply #2 on: May 23, 2010, 11:39:09 pm »

This is a system I've inherited and I was a little concerned about the PV900 not supporting 70 volt distribution.  However I think I recall reading somewhere (possibly some Peavey brochures) that in bridge mode the amp does in fact support 70 volt directly from the speaker outputs. There is no transformer at the speaker outputs. The system has been working since 2007 so I hope there isn't any damage to the speakers we are using.
A little more explanation of the current system might be in order! There is a second amp driving 2 full range speakers in the sanctuary as well as the 70 volt amp/speaker.  I recognize this is not ideal and needs to be fixed, but our first priority right now was to expand the system to support a new praise band. We had 8 channels previously and have just spent the entire sound budget on a 32 channel mixer. My goal is to address the speaker issues in 1-2 years by hiring a professional. I know my limits!
Due to some financial and political issues I can't justify a new amp, however if the dual 70 volt transformers will allow me to drive the sanctuary speaker separately from the external rooms I can justify that expense (yep - doesn't make sense considering I'll probably pay more for the transformers but I'm not the guy holding the wallet!)
Will my plan (using something like this transformer on each channel) work?
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Arnold B. Krueger

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Re: 70 Volt amp question
« Reply #3 on: May 25, 2010, 09:19:53 am »

Brian Heil wrote on Wed, 19 May 2010 22:01

Currently I have a 70 volt system that I'm considering changing and I have a quick question I need answered.  The system consists of 10 speakers total - 1 in the main sanctuary, and 9 throughout the rest of the building.  This is driven by a Peavey PV900 amp in bridge mode (600 W RMS @8 Ohms). My goal is to send a different mix to the sanctuary speaker than is going out to the other rooms (I'd like to mic the congregation and choir for this mix and don't really want it in the sanctuary).  So my question is can I take the amp out of bridge mode and drive the sanctuary speaker on one channel and the other rooms on the other channel?  Since the amp is no longer in bridge mode, I suspect I'd need a couple of step up transformers.


It might be worth a try at driving the two systems directly from the amplifier channels. The cost is basically free except for your time, and the risk seems low enough.

Of course the Peavy amp is really only a 180 wpc amp. That means that its actual maximum output is only about 38 volts RMS. This is about 6 dB dB shy of 70 volts, but depending on the actual setup, it might be close enough to work very well.

If not, good quality 70 volt transformers rated at 200 watts should do the job.
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ProSoundWeb Community

Re: 70 Volt amp question
« Reply #3 on: May 25, 2010, 09:19:53 am »


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