Hi DIYA!
At risk of sounding ignorant, I'm looking for info on building a truly passive mixer with 4 XLR inputs, and one XLR output, to run a battery powered PA for busking.
For those pesky, "No power supply available within 200-feet." situations.
I have the battery powered speakers. (Which have PLENTY of headroom to lift a quiet signal.)
I just need to know how to wire up a simple signal mixer with no frills, and doesn't need to amplify any part of any signal. I understand all adjustments would be cuts, and no boosts. That's 100% cool!
I know it's more than just a set of volume pots and jacks in a box. But I don't quite have the knowledge on what kind of load a mic-level signal places on the output, and how each load affects the next. (From what I've read, that's a real issue I'll need to work around.)
Any info would be a huge help, and greatly appreciated.
At risk of sounding ignorant, I'm looking for info on building a truly passive mixer with 4 XLR inputs, and one XLR output, to run a battery powered PA for busking.
For those pesky, "No power supply available within 200-feet." situations.
I have the battery powered speakers. (Which have PLENTY of headroom to lift a quiet signal.)
I just need to know how to wire up a simple signal mixer with no frills, and doesn't need to amplify any part of any signal. I understand all adjustments would be cuts, and no boosts. That's 100% cool!
I know it's more than just a set of volume pots and jacks in a box. But I don't quite have the knowledge on what kind of load a mic-level signal places on the output, and how each load affects the next. (From what I've read, that's a real issue I'll need to work around.)
Any info would be a huge help, and greatly appreciated.
I'll kick off.
The schematic shows a very crude passive 4 channel mono mixer. If you want (some of) the channels stereo, than ofcourse you need to use stereo pots in (some of) the channels.
The extra 50K resistors at the wipers of the pots are there to prevent shorting out the output when one or more of the pots are turned all the way down. But this comes at a price. The 50K resistor reduces an incoming signal with 50% when the pot is turned all the way up. Turning the pot down ofcourse reduces the signal even more. So this mixer will atleast reduce incoming signals with 50 %.
The output impedance of this mixer will vary with the settings of the pots. And the settings of the different channels will still influence eachother a bit.
Probably others have more elaborate proposals/examples (maybe with dual ganged pots as to minimze output impedance variations? or with signal transformers?).
The schematic shows a very crude passive 4 channel mono mixer. If you want (some of) the channels stereo, than ofcourse you need to use stereo pots in (some of) the channels.
The extra 50K resistors at the wipers of the pots are there to prevent shorting out the output when one or more of the pots are turned all the way down. But this comes at a price. The 50K resistor reduces an incoming signal with 50% when the pot is turned all the way up. Turning the pot down ofcourse reduces the signal even more. So this mixer will atleast reduce incoming signals with 50 %.
The output impedance of this mixer will vary with the settings of the pots. And the settings of the different channels will still influence eachother a bit.
Probably others have more elaborate proposals/examples (maybe with dual ganged pots as to minimze output impedance variations? or with signal transformers?).
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Thanks for taking time to reply to my curiosities!
Do the pots in your example need to be 50k as well?
I'll give it a shot, just to try it out.
I'm thinking of using XLR/TRS combo jacks for added versatility on the little unit.
Do the pots in your example need to be 50k as well?
I'll give it a shot, just to try it out.
I'm thinking of using XLR/TRS combo jacks for added versatility on the little unit.
The pots can be lower than 50K but if you keep the value resistors at the wipers at 50K than with lower valued pots the incoming signals will be reduced with more than 50 %.
Lowering the value of the resistors at the wipers to keep the loss at 50% would lead to lower output impedance. I don't think you can go too far with that but probably others will know this better than me.
Lowering the value of the resistors at the wipers to keep the loss at 50% would lead to lower output impedance. I don't think you can go too far with that but probably others will know this better than me.
Balanced signals or single-ended? What are the sources? Any idea of the source impedance?
If this is microphone signals its a whole different ballgame. Phantom power?
Microphone signals are weak, throwing them 20 dB further down will MURDER your signal to noise ratio.
Even if following stage has gobs of gain, how much do you like hum/hiss?
Typical XLR signals are LOW impedance (think 600 ohm) for very good reason.
Adding 50k resistors to the soup will introduce hum, noise, interference, cellphone buzzing, you-name-it.
You DO have power available: battery power feeding the amp, so build a simple but active mixer.
Worst case, if you don´t want to run an extra 12V power wire from amp to mixer, build a simple 4 XLR to 1 XLR mixer powered by an alkaline 9V battery.
Easy peasy.
Even if following stage has gobs of gain, how much do you like hum/hiss?
Typical XLR signals are LOW impedance (think 600 ohm) for very good reason.
Adding 50k resistors to the soup will introduce hum, noise, interference, cellphone buzzing, you-name-it.
You DO have power available: battery power feeding the amp, so build a simple but active mixer.
Worst case, if you don´t want to run an extra 12V power wire from amp to mixer, build a simple 4 XLR to 1 XLR mixer powered by an alkaline 9V battery.
Easy peasy.
There's no output power supply from the active speaker, but I am open to a 9v battery powered mixer. I didn't realize that was possible. Any chance you might have a diagram of such a thing? I haven't seen anything that I can read on making that possible.
I'm still learning how to translate schematics into physical renditions, but any source material is better than nothing to go from. 😉
That all said, my signals would be a guitar through a preamp/cab sim pedal, a vocal mic running from a lithium battery powered wireless receiver (no controls, just straight signal), a kick mic, and an iPod(1/8"-XLR)
I'm still learning how to translate schematics into physical renditions, but any source material is better than nothing to go from. 😉
That all said, my signals would be a guitar through a preamp/cab sim pedal, a vocal mic running from a lithium battery powered wireless receiver (no controls, just straight signal), a kick mic, and an iPod(1/8"-XLR)
I don't know about single ended vs balanced.
The sources are:
AKG D112 @ 210 Ohms
SM58 @ 150 Ohms
I don't know about the guitar signal.
No phantom power needed.
The goal is to be as bare-bones as possible, but not crappy.
Less than ideal is acceptable if it functions. I can always hit something with a boost pedal if need be. I'll just build a board for it all to keep load-time short and simple.
Less than ideal is acceptable if it functions. I can always hit something with a boost pedal if need be. I'll just build a board for it all to keep load-time short and simple.
This is a DIY site, but...
Given your lack of experience, and the fact that building a decent mic pre-amp is difficult to get right for a beginner, I recommend you just get something like this: Galaxy Audio JIB/MM Four Channel AC/DC Mini Mixer
Mike
Given your lack of experience, and the fact that building a decent mic pre-amp is difficult to get right for a beginner, I recommend you just get something like this: Galaxy Audio JIB/MM Four Channel AC/DC Mini Mixer
Mike
I had found this one, as the simplest cheapish "real" submixer but it has only 3 XLR and nothing else:
ART PROMIX 3-Channel XLR Microphone Mono Mixer - Sound Productions
Michael found another, only 2 XLR but apparently that´s all you really need since you have only 2 mics, plus electric Guitar (1/4" plug) and phone backing track (1/8" plug) so give his a good hard look.
If you want/dare to DIY, I can draw a dedicated circuit for you, which you can build on Vero/strip board to avoid burning/etching/drilling a PCB , fed from 1 or 2 9V batteries (which will last at least 70 hours if using TL072 and 5 X more if TL062) .
But you "should" have some basic build experience under your belt, such as successfully building a Guitar Pedal or equivalent; if not "buy ready made".
IF you have pending shows, by all means "buy"; if no hurry and you want to learn/practice, welcome to DIY 🙂
ART PROMIX 3-Channel XLR Microphone Mono Mixer - Sound Productions
Michael found another, only 2 XLR but apparently that´s all you really need since you have only 2 mics, plus electric Guitar (1/4" plug) and phone backing track (1/8" plug) so give his a good hard look.
If you want/dare to DIY, I can draw a dedicated circuit for you, which you can build on Vero/strip board to avoid burning/etching/drilling a PCB , fed from 1 or 2 9V batteries (which will last at least 70 hours if using TL072 and 5 X more if TL062) .
But you "should" have some basic build experience under your belt, such as successfully building a Guitar Pedal or equivalent; if not "buy ready made".
IF you have pending shows, by all means "buy"; if no hurry and you want to learn/practice, welcome to DIY 🙂
That is a cool piece of gear.
The goal is for me to learn, and get to where I won't need to buy something like that.
I could spend the same money building exactly what I want instead of something I'll have to modify anyway.
I can screw up a few times and accept it.
I'm not a total n00b. lol
I've managed to avoid tube amp repair places for years with research and the right people guiding me toward the right things TO research. (Woohoo lethal voltages!)
I'm here to learn from your experience.
I'm no engineer, by any stretch. But that's what I'm here to learn.
I would absolutely love that!!
I'm here to learn and grow! Thank you!!!
I do have pedal building experience, actually. 🙂
Even built a 12AT7 based light-overdrive pedal.
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An observation: if there is no AC power around, you *may* not need to be balanced at all. I've run long recording microphones unbalanced in an old church "wired for candles" and had no hum. (Did need clean plugs or I got the local radio station.)
Are your mikes "Phantom powered"? SM-57 is your friend here.
🙂
In my old days I used to go on Tour with Rock Bands and many bought my 9V battery powered Guitar amps, a "Pignose killer", for fun/practice on the Bus or Hotel rooms.
Many were used in Studio recordings, go figure.
Typical test to check a Guitar preamp input is to briefly touch Plug tip and hear STRONG Hum/buzz.
It was eerie touching plugs in the middle of nowhere, surrounded by cows and wheat, and only hearing a faint click! click! which I guess was from body capacitance static.
Or discharging input capacitor through body resistance, but NO HUM.
Today impossible because cellphones are little pits of Electromagnetic filth.
I´m drawing a little 9V battery powered submixer for Mr Toast and making everything UN-balanced, not needed at all within the short distances and low impedances involved.
Mis-edit:
me> ...long recording microphones unbalanced...
S/B "...long recording microphone lines unbalanced..."
me> ...long recording microphones unbalanced...
S/B "...long recording microphone lines unbalanced..."
I can't express my appreciation enough!
I'll make sure to take pictures of the progress and final product along the way! I just got my hands on a couple of Micro USB-A rechargeable lithium 9v batteries. So hopefully I can make it a rechargeable unit with it's own power port for convenience. 😀
Microphones are low impedance and balanced, and very low level - not really suited to passive mixing.
Guitar pickups are high impedance and need to be very lightly loaded. But they are usually 1/4 inch jacks, not XLR, so not really sure from this description.
Passive is not workable for a mix of microphone level and instrument level, you definitely need mic preamps for the mic channels.