DIY Hi-Fidelity Recording for the Cheapass Geek

I think my Facebook update a few days ago was something along the lines of, "is doing some recording with an SM-57, a home brew mic preamp, and Audacity. I'm an amateur music tech and I'm a PC."

The Sure SM-57 is the mic that people think of when they think instrument recording. It's an omnidirectional mic, which means it doesn't just pick up the sound in front of it, it picks up the sound all around it. But the thing is, it has a fairly focused range.

What this means is that I suspended a single SM-57 from the ceiling above my drums and recorded using a home brew mic preamp. And the playback sounded like someone was sitting there playing the drums. That is, by definition, Hi-Fi.

And I did it on the cheap.

The key was to make a high-quality +-15V power supply. You'll recall this from an earlier post to which I won't link because I'm lazy (use the search function darn you!).

So anyway I had some fun last night recording drums, cranking up my amplifier, and playing my guitar along with myself on the drums in Hi-Fi. It roxed.

Mic Preamp Specs

I think there's an audiophile or 2 listening. So now its time to brag.

I've finished designing my mic preamp on paper. Gonna order some parts and build a prototype.

So basically here's all of the specs on it:

Power Supply: 15VAC, low ripple, low noise. It will feed 48 for phantom power as well as, obviously, powering the preamp circuits. It will have a seperate auxiliary power for "noisy" things like LEDs and such.

Backplane: I'm making a modular preamp. Essentially the chassis will consist of the power supply and that's about it. Each module will plug into the backplane with a 15-pin connector.

Back panel: Each module will have an XLR in and 1/4" phone out. The in is "mic level" (see below) and the out is line-level.

Front panel: Each module will have:
- Level: The final level out
- Gain: The mic gain. The sound will be a function of gain and level of course.
- Input Impedence: 500-ohm or 2K-ohm.
- +48V Phantom Power
- High pass (select to cut at 160Hz or 1KHz)
- Low pass (select to cut at 160Hz or 1KHz)
- LED VU bar
- Clip LED

I'm going to put it all in a 2U rackmount enclosure with enough spots for up to 16 mics. I expect each module to cost me about $10 - $20 in parts, so no need to go straight to the 16.

I'm really excited to put the thing together. I look forward to doing the build. I'm coming in with a 15VAC AC/AC adapter because, well frankly I'm not comfortable doing the transformer / mains thing. Scares the hell outta me to be honest.

When all is said and done, I'll have a studio-quality preamp that would probably cost a good $10,000 if I were to buy retail. No exaggeration.

Next will be my mixer. I'm looking forward to that too. :)

I'm Such a Nerd

When I was a kid I was a nerd. Everyone knows that. I was picked on in elementary school. No biggie.

In my 20s I was a geek. And I was damn proud. Dot-coms were all the rage and suddenly it became cool to be a geek. Everyone was a geek.

In my 30s I'm back to being a nerd.

(Google your way around if you don't know the difference between a geek and a nerd.)

So in all my nerdy glory... well, let me back up a bit.

I like music. I like recording music and playing with that kinda stuff. However, the necessary equipment is expensive. Very expensive.

So what's a nerd to do? Build your own!

So last night I put the finishing touches on my headphone amplifier. Cost me all of $8 or so to build.

Tonight I'm going to work on my microphone preamp. That is, an amp that brings the mic to line level so it can go into a mixer. I've played with a couple of mic preamp circuits that I didn't like so I'm going ultra-nerd, grabbing my calcuator, and throwing down some mad algebra to design my own mic preamp circuit.

I'm such a nerd. But that's why you love me.

Hey SMGSI Dave, everything ok? Earthquake, that is....