Passive Mixer with "Thru"s for In-Ear Mix

[mattmayfield]

Hope this isn't too offtopic. I also posted this on another forum, so if there are any Logic Studio users on here, this post might look familiar. :-D

I'm looking to build a device to help me with my in-ear mix that includes a guitar amp simulator and a keyboard. I am using an unbalanced mono 1/4" line output from each instrument. I want to obtain three signals from those two:

1. Mono keyboard signal alone (goes to DI to PA)
2. Mono guitar signal alone (goes to DI to PA)
3. Mono mix of both (goes to my headphone amp for in-ears)

I also want the design to be completely passive, i.e. no power required. Several dB of signal attenuation is OK, and I plan to adjust the balance using the volume controls on the keyboard/amp sim.

Attached is a basic block diagram of the circuit I want to build. Will someone please give me some ideas on how to build this, or point me to some useful resources? Are there any important things I'm not taking into consideration?

Thanks,

Matt

Image at:
www.flickr.com/photos/21800184@N02/3326752362/

[ashcatlt]

I'm not going to ask why you want to do this, but if you want to relate the story, feel free.

I don't believe this is going to happen in a purely passive manner as you've described it. I think we might be able to work something if you could swing balanced inputs, depending on how those signals get balanced. It would be relatively easy to do this well with an active circuit.

[mattmayfield]

Thanks for the reply!

So I take it this will have problems with distortion, crosstalk, levels, or some such? Maybe no signal will get to the monitor mix because it's following the path of least resistance?



The reason for all this is that I want to use in-ears with nothing but my own mic, keyboard, and guitar in the mix. (I can hear everyone else clearly through their stage monitors, even wearing in-ears.) I'd rather have the controls onstage with me than with the sound guy; plus, not everyone we work with is equipped for in-ears.

I have a Rolls Personal Monitor box that has a mic thru and a 1/4" input for a monitor mix.

I thought about using a simple passive mixer to combine the R outputs of the keyboard and Pod into the 1/4" monitor mix input on the Rolls - while putting the L outputs into a DI box and giving them to the sound engineer. Trouble with that is, we run mono, and some of my patches are stereo. The devices only mix down to mono when there is a plug in the L jack but not the R jack.

Hence, the requirement to use the mono outs using basically a Y-connector type circuit to send each of them to both the monitor mix and the DI box.

Am I going way overboard? Should I just approach this whole situation differently?

[ashcatlt]

The signal will take every path it can. There will be some attenuation through the mixer, but I would expect the crosstalk to be unacceptable. Also "all grounds tied together" could cause some ground loop issues.

Is there a specific reason you want to keep this passive?

[mattmayfield]

Hmmm...

Thanks again for your replies. In fact, it doesn't have to be passive, but you've made me realize I need to explore other solutions. Taking a step back, here's what I'm trying to achieve:

• mix of my mic, keyboard, and Pod in my in-ear monitors, controlled from onstage.
• uses the mono outputs of the keys and guitar.
• gives the sound guy his usual 3 separate signals of mic, keyboard, and Pod.
• as inexpensively as possible.
• use as little additional equipment as possible.
• Neat & tidy stage setup.
• No batteries.
• AC adapter/power cord OK.

Resources I have to achieve this:

• $50-100 budget
• Soldering skills
• Rolls Personal Monitor amp (in-ear output, stereo 1/4" input, XLR passthrough, mix controls)
• Behringer UB802 mixer

....

Uh, I guess I just solved my problem. I'm going to use the mixer's FX sends for the instrument headphone mix, pan the channels and use the mixer's L and R main outs for the signals to the sound system, then use the XLR passthrough on the headphone amp for vocals.

Thanks anyway. ;D

[ashcatlt]

Having done a quick google search, it seems the easiest solution would be to buy a pair of Y-cords for the keyboard and pod, and a dual mono > TRS stereo 1/4" cable (sometimes labeled as an Insert Cable), and flip the switch on your Rolls amp to Mono.

[mattmayfield]

Mar 5, 2009 23:28:53 GMT -5 ashcatlt said:

Having done a quick google search, it seems the easiest solution would be to buy a pair of Y-cords for the keyboard and pod, and a dual mono > TRS stereo 1/4" cable (sometimes labeled as an Insert Cable), and flip the switch on your Rolls amp to Mono.

I can't believe i didn't think of that.

Thanks.

[ashcatlt]

considering that most DI boxes have parallel jacks on them for splitting the signal to an amp, you don't really even need the y-cables.

Glad I could help/