links to differential op amp mic preamps (single or dual opamps)

[TimWaldvogel]

looking for mic preamps that use a very commonly used opamp dual or single. one that is balanced using a differential op amp design preferably. i keep looking but i only find ones that seem to be specifically designed for electret mics. i want this for studio use

[Enzo]

Specifically desogned for electrets? Or do you mean they include phantom power?

You can always omit the phantom power.

Your description sounds overly specific. You want a generic low-impedance balanced mic input?

Every mixer in the world has a circuit for you in its mic inputs. Look over some Peavey, Mackie, yamaha, you name it, mixer schematics. You will find them all pretty similar.

Are you looking for some circuit to build?

[TimWaldvogel]

exactly i want a studio grade op amp based mic preamp that preferably uses no transistors. my plan was to base it off a differential op amp circuit as the balanced input. and to modify the gain by changing the pot size or resistance for gain. my hope was to modify an existing circuit.

you guys wanna help me design it? lol

balanced op amp in... probably a dual op amp, use one half for pre gain, a bypassable baxandall tone control possibly, maybe another modified tonecontrol. and another gain stage i may attempt to wire in a pot\rotary switch for the center being unity gain and anything below 12 o clock would attenuate and anything above it would add gain. IDK just an idea.

i am using a 18v power supply from a guitar pedal that will have a +18v and be biased to +-9v. i should have some decent headroom. right?

any ideas? i suck at transistor circuits, they are not interchangeable enough for more and require too much thinking :-p

[Enzo]

Some thoughts.

When you talk "studio grade" systems, then you really ought not be also talking about a single ended 18v system for power. Make a real split supply, it is not difficult.

Why "no transistors?" You do realize, I hope, that op amps are made of mostly nothing but transistors inside.

If you are not comfortable designing with them, then learn about them. You won;t learn anything by not challenging yourself.

And on top of that, if you just lift the circuit from a schematic, you don;t have to design anything or understand it, you just duplicate what you see.

If you plan a little project powered by guitar pedal stuff, really, unless the main point is to have a fun project, then just get a commercial mixer or mic preamp. All the issues with layout and design are taken care of, you won;t find any hard luch hum issues or layout issues like you would in a home brew.

A quick look through Musicians Friend, and I find numerous small mixers for under $100 in various brands. They have nice enough mic preamps in them. Will they sound like $1100 tube mic pres? No, but neither will something you build. I also found there a wide variety of mic preamps that stand alone, rather than as part of a small mixer. There are some nice enough mic pres under even $50. ART has one there based on tubes even for $30.

I don;t know what your application is, but if you are recording into your computer, many of these small mixers also come in models that include a USB interface.

[Enzo]

Here is a basic mixer with nice mic pres and some features. Look up the Peavey PV6 mixer at Musicians Friend if you want to see the product itself.

[Steve Conner]

According to my mom (a science teacher) and my dad (a molecular biologist) there was no such thing as "too much thinking".

When I got older, I discovered "paralysis by analysis", but this mic pre thing seems more like paralysis by complete apathy.

The simplest way to make a mic pre is the chip I mentioned in that last thread: the INA217 or whatever it was. You can literally connect it to some 9V batteries, a gain pot, and a mic, and off it'll go. It actually won a round of blind tests against some $2000 preamps, but then a Behringer came second.

There's also this one: Low Noise Balanced Microphone Preamp

Regular op-amps like the TL07x are not low-noise enough to amplify a dynamic mic by themselves. The above project shows the extra circuitry needed, but the INA217 has it built in.

All of this is going to involve the dreaded "T" word to some extent, so there's never been a better time to blow the cobwebs off that gray matter.

[TimWaldvogel]

I don't have any nice transistors on hand and I DO have nice op amps on hand. I dont have a mic input transformer but I have one that will work as an output
Transformer, I do not wish to design power supplies. I would much rather buy one or use one I have on hand. And the 18v supply I have just need to be biased differently than a bipolar supply. I have no problem using what have on hand. I do not wanna have to make another order.

The ne5532/5534 I have is low noise as is my lm833. And you can socket op amps and play around with them to have low noise.
I am aware transistors are in op amps but biasing an op amp is much simpler than a transistor and op amps are more consisant from part to part.

I want a fun project where I can get something useful for my studio with what I have on hand.
Other people have done it, I should be able to modify it and do it too.

I just would prefer a simple balanced differential op amp input

[imaradiostar]

Have opamps? Then build a really nice tubescreamer or distortion +.

If you want interesting coloration and are unwilling to try to build the Hamptone jfet preamp then I say you're being lazy. Biasing a jfet is pretty darn simple and it uses less parts than a properly configured op-amp.

You are going to have to work to build any decent mic preamp, even a kit with a pre-made board.

If you're willing to work, here are many excellent designs.

jamie