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[Gary Fitzpatrick]

Hi,

So I have a few projects coming up where I need to get an audio feed into a camera. The easiest and shortest cable run would have me connecting into the 100v speaker lines going to the speakers in the church. Is it okay to use a standard 100v 8/16 ohm transformer to drop the signal down?
 


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[John Roberts {JR}]

Hi,

So I have a few projects coming up where I need to get an audio feed into a camera. The easiest and shortest cable run would have me connecting into the 100v speaker lines going to the speakers in the church. Is it okay to use a standard 100v 8/16 ohm transformer to drop the signal down?
 

It might still be a little hot depending on how many watts it is tapped to deliver (less watts is better).
 
JR

[Gary Fitzpatrick]

It might still be a little hot depending on how many watts it is tapped to deliver (less watts is better).
 
JR

Thanks For the reply JR. what would you recommend for dropping it down? I see quite a few of these systems coming on board (it is for streaming church services) so I wouldn’t mind doing it “right”

Gary


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[Geoff Doane]

1W into 8Ω is about 2.8 Vrms.  If you allow 6 or 7 dB for the crest factor of the signal, that takes you down to an average level of just about +4 dBu.  Chances are the crest factor is higher than that (average level is lower), but it looks like you'd be in the right ballpark, using the 1W tap on a transformer designed for an 8Ω speaker.

GTD

[Gary Fitzpatrick]

That’s great...thanks for the advice.

Gary


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[John Roberts {JR}]

Cheapest and easiest is a resistor pad, but a transformer will give you isolation which could be useful.

Try it and see... A wrong size (too hot) transformer can still be combined with a resistor pad to dial it in, while keeping the transformer isolation.

JR

[Gary Fitzpatrick]

Cheapest and easiest is a resistor pad, but a transformer will give you isolation which could be useful.

Try it and see... A wrong size (too hot) transformer can still be combined with a resistor pad to dial it in, while keeping the transformer isolation.

JR

Do you mean like a 100v rotary attenuators? Like this one?

http://cpc.farnell.com/unbranded/p605d/line-attenuator-switch-12w/dp/AR71993

Gary


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[John Roberts {JR}]

Do you mean like a 100v rotary attenuators? Like this one?

http://cpc.farnell.com/unbranded/p605d/line-attenuator-switch-12w/dp/AR71993

Gary


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no.. don't know what that does.

JR

[TJ (Tom) Cornish]

Hi,

So I have a few projects coming up where I need to get an audio feed into a camera. The easiest and shortest cable run would have me connecting into the 100v speaker lines going to the speakers in the church. Is it okay to use a standard 100v 8/16 ohm transformer to drop the signal down?
 


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100v systems are only 100v at full-tilt boogie; in practice you're probably a lot less than that.  Even if you are operating around 100v, that's still not a particularly big deal.  A isolation transformer box or DI box with a 20dB pad would get you from 100v at clipping down to around 6 volts at clipping, which should be well within the capabilities of a professional-level line-level input.  If you need to drop it for a consumer-level input, you might need more gain reduction, but there are DIs that have larger pads than that.  The Rolls Matchbox DB25 comes to mind, and has a selectable 20dB and 40dB pad.

[John Roberts {JR}]

100v systems are only 100v at full-tilt boogie; in practice you're probably a lot less than that.  Even if you are operating around 100v, that's still not a particularly big deal.  A isolation transformer box or DI box with a 20dB pad would get you from 100v at clipping down to around 6 volts at clipping, which should be well within the capabilities of a professional-level line-level input.  If you need to drop it for a consumer-level input, you might need more gain reduction, but there are DIs that have larger pads than that.  The Rolls Matchbox DB25 comes to mind, and has a selectable 20dB and 40dB pad.

Check with the DI mfr before putting 100V into a DI.

I am not very confident about doing that.

JR

[David Sturzenbecher]

this was made for doing exactly what you want...
http://www.rdlnet.com/product.php?page=162

[Kevin Graf]

Another solution might be:
A small speaker transformer and an old Radio Shack auto radio Line-out Converter #12-1238.

[Hal Bissinger/COMSYSTEC]

I second the RDL TX70A. In lieu of that a 100v line transformer with a 1/8W tap.

Do you mean like a 100v rotary attenuators? Like this one?

Doesn't anybody know how to wire a simple pot like 100K off the transformer secondary for a level control?

-Hal

[Nathan Riddle]

The cheapest way: http://www.epanorama.net/circuits/speaker_to_line.html/ (what JR was saying to do).

There's this: https://www.rapcohorizon.com/product/233/db-1sl-direct-box
Unknown what the voltage is. (400w @ 8ohm is 56v)

Or this:
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/direct-boxes/director
100v -30dB = 3.16V = 12.2 dBu (+22dBu line level max, most mixers)