-20dB audio cut

[SoundComposer]

Hi!

I have a field mixer which I have to syncronize with the gain in my camera, but the output on the mixer is to loud - so I need to dampen it by 10 or 20 dB before going into the camera. A technician guy at an audio department gave me a quick hand written diagram how to make a simple 20 dB CUT. It's supposed to go from one stereo-minijack to another stereo-minijack. But when I came home I saw the drawing lacks a connection from the third part of the minijack on the incoming signal...

Could someone please look at my drawing (I made it myself in photoshop so don't laugh...) and tell me where I should connect the third part of the minijack?

**broken link removed**

Also, if anyone could check that this is right. Or if you have a better solution please bid in!! The technician who made the drawing wasn't totally sure, if this was the way to go.

Thanks in advance!!

Toni

 

[OlPhart]

Perhaps an oversight, it's Ground/reference-. It goes to the same spot as where the 2 560 ohm resistors meet at the outer barrel of the connector. This is a simple voltage divider: 5600 / 560 = reduction of 10:1. I'm lousy at audio, but I think that's -20dB. <<<)))

 

[carbonzit]

Yes. What the audio guy meant was this:

**broken link removed**

Now, it'll work, but I think the resistors are a little on the low side and likely to overload the source (total impedance is ~6KΩ), so I'd probably use 8.2K and 820Ω instead.

But I'd probably just go ahead and make a variable attenuator out of a stereo potentiometer (20K or 50KΩ), like so:

**broken link removed**

That way you're not limited to a 20dB cut, unless you happen to need exactly that (you could actually determine the point equal to that, using an ohmmeter, and mark it on your dial). Using a miniature pot, the whole thing would fit nicely into an Altoids tin.

 

[SoundComposer]

Super!

Thanks!

 

[MrAl]

Hi,

Yes, sometimes impedance matching doesnt matter as much in audio like this, but you cant overload the source or else you'll loose more volume than you planned on.
I guess the source can be damaged too in some circumstances.
Just to note, some audio sources are only 600 ohms.

 

[carbonzit]

I guess the source can be damaged too in some circumstances.
Just to note, some audio sources are only 600 ohms.

No audio equipment is going to be damaged looking into a resistance of 6160Ω, which is what the O.P.'s suggested circuit has. Let's not needlessly frighten people.

 

[MrAl]

Hello again,

Well sometimes it matters and sometimes it doesnt. It's good to know when it does and when it doesnt, that's all.
Gee, i hope i didnt scare anybody too much it's not quite Halloween yet