Op amp newb question

[thereelman77]

I have somewhat of a simple question. When following a basic schematic when it shows an op amp, must that component be powered? Or can you use the signal from a preamp going into it as the power?



I'm trying to build a simple mixer (above) with stereo outs. (2 mono ins with pan-pots) I'm wondering if in the op amp section, if each op amp needs individual powering, or if a boost from a preamp (if I added one into the input chain) will work, and I can just solder an op amp in that part of the component.

I'm guessing, but would putting a preamp where the op amp is, essentially make a powered op amp?

To avoid confusion, my main question is: Do op amps need to be powered or can they just be soldered together, much like a passive mixer would be?

I'm obviously new to electronics and want to learn what I can. I don't really have electricians I can call up and talk to, so if another forum or site would be more useful, any help will be greatly appreciated.

Thanks.

 

[kip4]

Op amps definitely need a power supply. And are usually biased. And also grounded
You note the power supply for the schematic is not listed in your posted picture.
Putting a preamp on the input will not power the op amp.
There's not enough info in your picture to say which op amp is being used.
Single, dual or quad op amps.
If you want to start building op amp mixers I suggest you head over to run off groove or check some of jack Ormans designs.
Diystompboxes might be a good place for you to learn about op amps.
Can I suggest also that you start with a smaller project and work your way up, so that you understand what the componants in the schematic do and how the affect the whole.
I'm no electrical engineer. I'm more of a hack but I've learnt a lot in the last year building stomp boxs.
Google is your friend for op amp tutorials buddy.
Nice to see a fellow R2R man in search of a bit further knowledge too.

 

[kip4]

I found it here
Simple Mixer Schematics


Take a look at this it may help
In this example lm741 op amps are used
You will note that pin 7 is the +voltage and pin 4 goes to ground
I recommend reading pages 1 and 2 also
The OP-AMP

 

[ecc83]

I agree with all said so far.

Best way to power that circuit to start with is 2 PP3 batteries in series. The junction of the two becomes the ground terminal shown as the + or "non-inverting" input on the op amps.

+ and -9volts is plenty for a knock about projjy circuit. Max out would be about 6V rms about +15dBV or +18dBu. A "proper" supply would be +&-15V and that is as high as you need to go.

Types to use? TL072 is, err, ok! But far better and really little dearer is the NE5532. Note this a dual op amp. The single version which has slightly better noise performance (but wasted in THIS circuit|!) is the NE5534.

I have taken some noob electronics enthusiasts under my wing from time to time but am helping no one at the moment. If you want a bit of 1 on 1, PM me.

Dave.

 

[thereelman77]

Good information! Thanks for the responses. I forgot to check the posting over the past few days. I'll be looking into the links posted> I know for sure I'll have some more questions I'll need answering.

 

[kip4]

Your welcome.
Ask away if I can help I will

 

[ecc83]

I have somewhat of a simple question. When following a basic schematic when it shows an op amp, must that component be powered? Or can you use the signal from a preamp going into it as the power?

View attachment 84260

I'm trying to build a simple mixer (above) with stereo outs. (2 mono ins with pan-pots) I'm wondering if in the op amp section, if each op amp needs individual powering, or if a boost from a preamp (if I added one into the input chain) will work, and I can just solder an op amp in that part of the component.

I'm guessing, but would putting a preamp where the op amp is, essentially make a powered op amp?

To avoid confusion, my main question is: Do op amps need to be powered or can they just be soldered together, much like a passive mixer would be?

I'm obviously new to electronics and want to learn what I can. I don't really have electricians I can call up and talk to, so if another forum or site would be more useful, any help will be greatly appreciated.

Thanks.

Further thoughts on that circuit. The input caps are a little low if you want a 20Hz low end. Go for 10mfd and non-polarized, you never know what the world will throw at you.

If using bipolar opamps, NEs say, there will be a bit of an offset voltage at the output and this will make the pot noisy, daft place to put a 10k pot anyway! Also if using NEs the caps are the wrong way around but always check offset polarity anyway.

Dave.