building direct outs on behringer mixer

[jkvd]

Dear Gearslutz,

This is my first post on gearslutz.com!

I have a problem,,, I'm trying to build a few directs out on my behringer UB1202 mixer. Just 4 rca connectors for the 4 mic channels. post preamp and pre the rest.



That will give me 4 mic preamps for the recording device and the rest of the mixer for monitoring. It's all on a budget, but it's good to start with junk i.m.o.

Anyway, I just looked at the channelstrip and tried to find a soldering on the PCB that gave a good signal testing a loud bleep. Now I noticed that it hardly gives any output when I hook on a mic. So, I must have placed the connection before the gain stage. Testing again with a bleep I found out that input gain had no effect on the direct out volume.


sorry for the crap picture, it's done with my phone.

Where on the PCB should I look for the right direct out?

[gyraf]

You will need to consult a schematic to find the right point. There's no "empirical" way of finding this in any sensible way.

Jakob E.

[Scott003]

I've been looking at putting direct outs on a Sony MX-P21. I've got the schems, and found a point post-fader to send the signal from. Can I wire the 8 sends straight to a DB25? Douglas Self wrote that unbalanced outputs will still have the CMRR of a balanced connection when wired to a properly balanced input, so supposedly I could wire hot-hot and ground-neutral. Would this work, and would it stand up to a hostile, noisy environment?



thanks,
Scott

[Matt Syson]

Hi
The psudo balanced out uses same value resistors (say 47 Ohm) in both the signal and 'cold' path.
You should use a rsistor on the 'hot' anyway as a small source of short circuit protection and to 'isolate' the capacitance of your cables which may otherwise encourage the amplifiers to oscillate.
Use as short an interconnecting cable as possible to your gear and you should be OK.
Remember that wherever you are sending the signal from was not specifically designed for extra loading so be as 'gentle' as you can.
Matt S

[Scott003]

cool, makes sense. I definitely want to make the outs post-fader. I'm looking at the schems, should the hot output be after a 33 uF cap directly after the fader, and the cold output on common after a 100k resistor joining hot and common?

[Matt Syson]

Hi
The output should be taken from the output of an opamp not the fader wiper.
You should use a resistor, say 47 Ohms, and a capacitor (to block any DC there may be on the op amp output) and another 47 Ohm resistor in your 'cold' feed.
Taking signal from a fader wiper will ruin any quality as the impedance it too high to 'drive' the capacitance of a cable.
Post a chunk of schematic if you want better info.
Matt S