Mic preamp I'm working on

Here's the e ruff draft pcb design I've come up with.

Resistors are 1k, 2.2k, 100k, 100 ohm and 1m. All are metal film and of 1%.

Caps are all 1% polystyrene except for the 47uf which is an aluminum electrolytic. Caps are 1nf, 0.1uf, and 47uf.

Any tips before pcb order? Using a 1512 preamp stage and a OPA137 output. Still configuring Triad TY-250P output. Tips with wiring the two output wires to transformer?

Btw the input +\- is for voltage. The Xlr connects to the circuit itself.

Leek said:

Any tips before pcb order?

Click to expand...

Slow down!

What are you trying to archive with this design? Isn't there any other design that meet your specs? maybe buy a kit or a PCB?

JS

It's just a basic mic preamp? It's literally a componentless version of the following


What's the problem?

I'm new to diyt but eager to learn. I need 4 more Preamps or line amps to mix 16 channels. O don't have the money for high dollar never API or ask build either. Only bout 150$ for 4 channels

  That's not a good layout either, I wouldn't trust it. There are better preamp designs around here, even ready to etch files.

  I encourage you to learn more, but you shouldn't expect a top performance preamp as your first project and add over that time and money restrictions. You can build a decent mic preamp but you need more research to do so, and it's quite a tricky project to start with.

  If you only need them for a make up for a mixer I'd said don't go there, build a summing amp, you said you have a few 5532 which would do for this. You could probably get away with a prototyping PCB for this, the opamp, a bunch of 10k resistors going to the inverting input, one as feedback with a 22pF in parallel for stability, 1k resistor from ground to the non inverting input, decoupling caps and you are good to go. Be tidy with the grounds, use one going straight to the 1k resistor from all the inputs, from there to the output and from there to the bypass caps. Take the PS gnd from the same place as the output. Use 100µF36V caps for decoupling.

2x5532, 40 resistors, 4x47µ caps and 4x22pF caps. Maybe add a few screw terminals to it so it's easier to connect everything. You still need a PS, if you don't have one a 15+15V 500mA transformer, a fuse , two diode bridges, 2x2200µF 50V, one 7815 and one 7915 is all you'll need. If you don't feel confortable dealing with mains ask for help, it can get dangerous pretty quickly... You need to add all the wiring and connectors for this and a case, that's probably more expensive than the unit it self.

  Please, don't take it wrong, but don't flush the forum with topics asking people to do your job, one topic explaining what you want to do and what are your resources would get help, 3 topics asking people do your job for a hand full of OA won't.

JS

In essence I only need to add a few line amps to get 16 or more channels from the mixer for mixdown. I have a schematic for a baxandall 3 band style EQ as well to add afterthe output of the line amp. I have a PS as I have 15v +/- from the mixer where I removed 4 graphic EQ's. But, I don't know where to start. Could
D you recommend a good sounding line amp to perhaps build?

  I think you are failing to communicate what your needs are, both here and in PM where there's no need to, since the idea of a forum is to solve issues publicly so the next guy doesn't have to ask (if he did the homework).

  First you asked for mic preamps, you should build a mic preamp if you have a mic and a line input and nothing to put in the middle. It solves that problem. Then you said you needed to connect 16 inputs with 4 amps, so that's a summing amp, you have 16 line level inputs and you send that to a single output. Then you bring a SSL4k line amp, which there is no real need other than conditional a signal if you don't know where it's coming from but you do know it's line level and you want to go from there to a summing card, and  you want to add an eq after that. Or after the line amp but before the summing?

  What equipment do you have? What do you need to interconnect? What do you want to do?

  Take your time and answer those questions to you, then sit in the computer and write a post explaining all that with detail, examples of what you'd like to do, then read it 3 times and think if someone who is not you and is not sitting right next to you will be able to understand it. I do take some of my time to answer and as you see not many people is doing so, we do want to help but you are making it quite hard.

JS

Good post Joaquin.

It would also be a good idea to draw a block diagram of your final outcome with pencil and paper, and mull over it for a couple of days.

It will put everything in perspective and allow final changes.

Peter