choosing stuff for an audio mixer

[Thunderchild]

I want to make an Audio mixer 2-4 channels I am not sure yet,

if I want volume controls (yes I do) I will need logaritmic potentiometers right ?

whats the best op amp IC to use ?

I intend using something like the attached schematic please give me any comments, the component values are yet to be determined I also want to know if I can eliminate any decoupling capacitors perhaps between the first stages and the last stage ?

 

[Thunderchild]

Should I use a dual power supply ?

 

[Leftyretro]

" if I want volume controls (yes I do) I will need logaritmic potentiometers right ?"

Yes, audio taper log pots, esp if using rotory pots, if linear slide pots then linear pots can work as you will probably be setting levels with a VM meter?

"whats the best op amp IC to use ?"

5532/5534 are time tested in audio applications, cheap and avalible and low noise...

" dual supplies? "

Yes, esp if you have multi stages amps/adders as it can allow you not to have to capacity couple between each stage.

Good luck

 

[Nigel Goodwin]

The diagram above is absolutely horrible! - I suggest you search on the net to find what a mixer looks like. The TL071 or TL081 series opamps are perfectly fine for a mixer, for a very low level mike preamp the NE5532 series will give a slight improvement, but for the mixer stages it's not worth it.

Look here for a nice example **broken link removed**

 

[Thunderchild]

hm I am using matrix board so don't want to be overly complicated and I don't need any equalizer controls really at this time i just want to "join" two or more signals probably coming from a couple of CD players, the mic is an after thought I was thinking a simple capacitor mic like the ones used on computers i might go for a proper mic preamp if it is recomended and will i need a better mic ? it is just a starter attempt / a bit of fun and make a girl happy (thats the best bit)

 

[Nigel Goodwin]

hm I am using matrix board so don't want to be overly complicated and I don't need any equalizer controls really at this time i just want to "join" two or more signals probably coming from a couple of CD players, the mic is an after thought I was thinking a simple capacitor mic like the ones used on computers i might go for a proper mic preamp if it is recomended and will i need a better mic ? it is just a starter attempt / a bit of fun and make a girl happy (thats the best bit)

Check the other circuits on the same site - but the point of a mixer is it's modular, you can add or subtract sections as you wish.

Back in the 70's I found I had a sudden disco to do, I designed and built a two channel mixer (on my bed at my parents) in about half an hour, using bits I had to hand.

 

[Thunderchild]

Well I was thinking on a modular design I could have a connector at the input of the second stage here any number of channels can be added I am considering leaving room for more to come paerhaps I will do more but for Ideas and general design I will consider 2 channels and perhaps add more later,

I don't have much stuff hanging around so Will just order the lot online hoping to find it all on "Rapid electronics"

 

[audioguru]

The horrible design:
1) The mixer has opamps biased for a dual supply at the inputs but an opamp biased for a single supply at the output.
2) It has no gain anywhere. How do you make something louder without any gain?
3) The mic opamp has no gain. If you scream at the mic then the signal might be as loud as a low line level.
4) The mic opamp should have its own input biasing and be capacitor-coupled from the mic.
5) The 1uF coupling capacitors into a 1k resistor cut the bass frequencies. 320Hz is at half power and lower frequencies have less output.

 

[Thunderchild]

Thanks you audio guru I know the component values are scew wiff I haven't thought about values yet I just intended that as a "priciples" diagram, yes I might of forgotten some biasing i intend to use dual power supply I am thinking of a gain of 10-100 what is best ? the main inputs will be cd players or a keyboard or computer output so all of certain strength, Later I'll think of a power amp but that is apart from the mixer.

 

[audioguru]

Use a gain of 11 for the line level inputs and a gain of 101 for the mic input.

 

[Thunderchild]

thank you Audio guru I was thinking a simple capacitor mic like the ones used for computers so will 101 gain be ok for that ?

Anything in my diagram I should alter principle wise ?

 

[Nigel Goodwin]

thank you Audio guru I was thinking a simple capacitor mic like the ones used for computers so will 101 gain be ok for that ?

If it's for disco or any live use, then I suggest NOT using an electret mike, they are FAR, FAR too suscepible to feedback - use a 'real' microphone instead, you can get get very high quality Behringer mikes for very little money, I highly recommend them!.

Anything in my diagram I should alter principle wise ?

As we've both explained, your diagram is completely useless and won't work. The site I posted has proper working mixers, or check this simple one I drew a while back.

https://www.electro-tech-online.com/attachments/mixer-gif.1418/

 

[Thunderchild]

thanks for the diagram nigel I was not too sure if i could have the volume control conected straight to the output stage but if that is what you built it is fine for me as I said I don't want anything sofisticated that other link you gave me was far to complex (and not too wel explained) and I am working on matrix board. however your diagram does not look that complicated to me either the only thing you have that I would not have thought of was the condenser in paralel with one of the biasing resistors, there will obviously be a decoupling condenser between VCC and GND as the circuit will include a power supply anyway

 

[Nigel Goodwin]

however your diagram does not look that complicated to me either the only thing you have that I would not have thought of was the condenser in paralel with one of the biasing resistors, there will obviously be a decoupling condenser between VCC and GND as the circuit will include a power supply anyway

Notice that capacitor was shown in Audioguru's opamp examples as well, it's another PSU decoupling capacitor, as you're generating another supply (a split supply) with the two resistors.

Mixers are extremely simple devices, it's actually an analogue adder - back from the analogue computer days, which is where opamps come from.

 

[Thunderchild]

yes we need to thank computing and analogue computing for op amps they came about as valve bricks at first and then boomed in audio application especially with the advent of the transistor and IC,

yes I see you point about that condenser it is just another decoupeler thanks for the tips