Building a mixer for live vocal FX

Reknes

Member
2020-03-01 10:09 pm
Hi!

I have been thinking about learning electronics the last year, but today I really got a kick to start learning.

My girlfriend and producer/bandmate is a singer and has been using guitar pedals and kaoss pads live for vocal processing. Today we talked about that it really doesn't exist a mixer that suits her needs.

I'm a 25 year old musician with medium+ soldiering experience and I'm pretty confident that I can learn what I want to learn (in life). But, I need some thoughts about my dream to build the complete vocal FX mixer. I'll list all the things I'd like the mixer to have and then I'd really appreciate if you guys told me your honest opinion if my dream is completely unrealistic or if is workable.

The mixer needs these things:

1. MIC INPUT with 48v phantom power
2. A good clean preamp with about 50-60(?) dB of gain
3. The dream would be a three band EQ with the mid band to be variable.
4. After the EQ, I need it to have two mono sends with pots
5. I need two foot-switch inputs to be able to bypass the sends with a foot.
6. Both of the sends needs stereo recieve inputs.
7. A mix knob for dry wet
8. One left and one right pan pot (like in pro tools)
9. Stereo TRS outputs


Okey. I can see that this is ambitious. And I know about the Radial Voco Loco, but it doesn't have foot switches, which is the unique thing about this (yet to be build) box.

thanks for your time
Reknes
 
1,2,3,4 all readily available in commercial mixer products. We refer to your mono sends as post EQ Aux sends.

6, 7. stereo returns are also commonly available. And they can be blended in simply.

8,9 again are common

5. No one makes a mixer with such foot switch as far as I know, but really, where are those sends going? If they go to a delay unit or other processor, that unit ought to have a bypass switch, and THAT can be made remote easy enough.

If nothing else, a simple kill switch in a box can connect to the AUX sends as desired.
 

Reknes

Member
2020-03-01 10:09 pm
Thanks for the replies guys.

A kill switch might not be a bad idea actually. The idea for the foot switches comes from this Yamaha mixer.
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The smartest might be to customize an already existing mixer, but I really doen’t need faders and many channels. One channel mixers either suck or doesn’t have two sends.

And one more thing. The pan would be an output pan, I guess that’s not common?
 

turk 182

Member
2012-10-26 3:03 pm
i'd look for an old Soundcraft 200b mixer, if you look hard enough you might find someone selling individual channel strips and go from there. it's got a four band eq with two mid sweeps & 4 aux's.
modding the aux's to be remote switched would be easy.
or perhaps look at updating the mixer that's currently being used to mix the whole band.


the Radial Voco Loco does supply effects switching but effects returns are not stereo, is that really important?
 
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turk 182

Member
2012-10-26 3:03 pm
not completely familiar with the Kaos Pad but if a stereo return is important then the 200b idea might be moot.(other than returning the aux across two standard channels and panning them appropriately)
what is currently being used as a mixer for the band? perhaps that could be modded to get what you need!?
 
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Reknes

Member
2020-03-01 10:09 pm
Since mixers are generally stereo, the idea of an output pan is confusing. That is why each input channel has a pan control.

Yes, I get that. I also want a mix knob for dry/wet (to get completely wet signals when improvising). A solution to the output pan would be to make a section on the mixer that sums the dry signal and the two stereo returns together and that I can make a mix knob at this stage, followed by a pan. After the pan it goes straight to an output (fader or pot for output volume, preferably a pot) and then to the physical outputs.
 
Look at your AUX sends on the input channels. Some are "pre-fader" and some "post-fader". Some mixers have this switchable, some have jumpers inside you can change. Lesser mixers are set one way or the other, check the spec sheet.

Anyway, if you want effect only, and no dry, use a pre-fader aux send. That way you can send the audio to your effect, then simply drop that channel fader to zero. That way the effect will be coming in the return and the dry will be killed by the fader.

So for example I set up one channel to send pre-fade signal to an outboard FX unit. I can either turn the aux send to zero or the return to zero leaving only dry controlled by the channel. fader. I can then bring up the FX along with the dry, so IO have both. Then I can bring down the channel fader leaving ONLY the FX for some echo fade out thing. No need for a bunch of external controls.

By the way, some mixers have AUX sends that are pre-EQ or post-EQ. Depends on whether you want the channel tone controls to affect what you send out the AUX. This is a separate thing from pre and post fader.
 
I think I could do most of what you want with my Peavey PV8 and some cables and effects.
4 channels have an insert jack after the input gain. These are the channels that also have 48 v phantom power on the microphone jack. Inserts go out to an external effect on tip and back on ring. If your external effect is a footswitch with an analog switch that switches to silence, you've got item 5. My digitech quad 4 might be programmable to to silent, it has a footswitch. I think graphic equalizer effect with master slider to minimum would do the job. If you use a graphic equalizer as the effect, many have a bypass controlled by footpedal.
If you have both a vocal mike and an instruments mike, put vocal on channel 1 and instrument mike on channel 2. They can have different external effects.
You can bring in stereo line level inputs on channel 5&6 or 7&8, then there is a pan pot at the bottom for each.
Each channel 1-4 or pairs 5-8 have 3 band equalizers after the inert and before channel gain.
If I use the reverb in the digitech, I return it to 5 or 6, and turn the amount of reverb in the master mix up & down with the channel out pot or the 5&6 balance pot. Haven't needed to hook the digitech to the efx input (stereo) jacks yet. The efx return has its own in & out pots.
There are tape sends, monitor sends, stereo effects sends, control room sends (parallel headphone output) main sends. Monitor send and effect send mix can be different than main+controlroom+tape send mix.
If you absolutely have to send with a stereo plug, you can use the headphone output. But you'll get better hum rejection over long distances to the PA mixer using the TRS main mono sends, with a twisted pair cable for each.
I bought my first PV8 for $48 with freight from ebay, then replaced the master volume pot and fixed a broken PCB via that was killing all the left outputs. Very instructive exercise. I donated that PV8 to a church and bought a new one for $149 off ebay. the one at the church sits at the edge of the stage where it mixes the 2 wired vocal mikes into the organ amp+speakers. It sits on a Peavey 15 band stereo graphic equalizer. Each equalizer channel has a different slider turned down to kill the howl that comes from that mike. If only 1 of 15 sliders is down, a voice sounds more like itself than if the howl is killed with a 1 of 3 midrange pot on the stage mixer. The graphic equalizer was about $60, had one bad solder joint killing 1 channel. Trace it reheat it, just like new. Pots are fine on the graphic equalizer.
Beware, replacement PV10 has autotune for vocalists that never learned how to sing.
Happy shopping, and learning the ins & outs of performance PA gear.
 
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Seems to me adding a foot switch controlled mute to a send is just adding a small relay to an existing board at the right point on the circuitry. However as this will void the warranty, I would start with a used mixing board.

As you will already be playing with the insides you can even go for one with some bad inputs.

For your first try I would suggest you buy the cheapest one you can find. Playing with it will allow you do do a much better version 2!