[Frameworks] Sound ? from an Eikie

[Dave Tetzlaff]

Yes! That looks like EXACTLY what you need, and that's a good price for a readymade box.

Connecting a 16mm projector with only a speaker jack to an audio system usually requires TWO things, and the Rolls box offers both:

1. An attenuator circuit to drop the output level from the speaker and match the impedance of the audio system input.

2. An isolation transformer to eliminate ground-loop hum.

Some but not many projectors do have line level outputs, which don't require attenuation, but can still require isolation to prevent ground loop hum. You can usually get isolation cable with RCA jacks on each end at specialty car stereo stores.

I haven't used that Rolls direct box, but I like that it has a variable attenuation circuit. I've made some simple one-value attenuation circuits, but every two devices you connect are a bit different, and it's hard to find one perfect level that fits all.

Do note though, that the output of the Rolls box is a mono balanced line with an XLR connector – ideal for connection to an audio mixer, but to go directly into an equalizer you're probably looking at unbalanced stereo inputs (RCA jacks), so you'll probably need a custom cable for that. It should be a straight connection though — that is, you don't need another transformer to match the balanced out of the box to the higher-Z inputs of the equalizer.


> I would recommend an attenuation box to cool down the speaker level signal. 
> 
> This is a pretty cheap one that works: https://reverb.com/item/1133262-rolls-db25b-matchbox-direct-box-w-ground-lift-and-attenuator-switch?_aid=pla&currency=USD&pla=1&gclid=CPKBxcr278gCFdKGfgodVzYDuQ


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