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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