Recording Instruments

Guitar Amps

Single Mic

The SM57 on a guitar cab is probably the most documented microphone placement in recording history. Fifty years of records. Three variables:

Distance from the speaker: Close (1-2 inches from the grille cloth) gives you a focused, present sound with more low-mid weight. Farther back (6-12 inches) lets the room into the picture — more natural, more open, less intense.

Position on the cone: Aimed at the center of the dust cap (the small circle in the middle of the speaker) = brightest and most aggressive. Aimed at the edge of the cone = darker, warmer, rounder. Start at the edge of the dust cap and move outward until you like what you hear. One inch of movement makes a real difference.

Angle: Straight-on captures the full blast. Angling the mic off-axis softens the high end and reduces harshness. Useful on amps that are already bright.

Multiple Mics

Adding a second mic gives you a second perspective — and introduces phase concerns. Any time two mics pick up the same source at different distances, the time difference creates cancellation and reinforcement at different frequencies. The result can be fuller or thinner than either mic alone, depending on the alignment.

Close mic + room mic: The close mic captures the direct tone; the room mic, placed several feet back, captures ambience and space. Blend to taste. Always check mono compatibility — sum both tracks to mono and listen for thinning. If the combined signal sounds worse than either mic alone, you have a phase problem.

Close dynamic + ribbon: A classic combination. SM57 up close for attack and edge, a ribbon a few feet back for warmth and air. The two characters blend well because they’re spectrally different.

The polarity check: When combining mics on the same source, flip the polarity of one channel (the phase button in your DAW). If the sound gets fuller, the mics were partially out of phase — leave the polarity flipped. If it gets thinner, flip it back. This takes three seconds and can save a recording.

The Direct Out

Many amps have a direct output that taps the signal after the preamp stage but before the power amp and speaker. This gives you a clean capture of the amp’s preamp tone — no speaker coloration, no room, no bleed. Often recorded alongside the mic’d signal as a safety track. If the mic recording doesn’t work out, you still have the DI to re-amp later.

DI Recording

A DI signal is the raw electrical output of the instrument, captured directly — no amp, no speaker, no room. Clean, dry, and infinitely flexible. Process it with amp simulation plugins, blend it with a mic’d signal, or re-amp it through a real amplifier after the fact.

When to go DI:

• Bass guitar: DI bass is standard practice. The clean, punchy low end sits in a mix without fighting the kick drum the way a mic’d bass cab can. Many final bass tracks are DI only.
• Acoustic guitar with a pickup: The pickup signal goes straight to the interface. Useful when you want the direct sound without room ambience, or when the room sounds bad.
• Keyboards and synths: Already line-level electrical signals. Plug them in. No transduction required.

This is where the signal level types from Chapters 3 and 4 become practically important. A guitar plugged into a Hi-Z input is at instrument level. Run it through a DI box first and you’re converting to mic level. Plug a synth’s line output into a mic preamp and you’ll clip the input. Know what level your source is putting out and match it to the right input on your interface.

Re-Amping

Record the DI. Then send it back out of your interface, through an amplifier, mic the amp, and capture the result. That’s re-amping. The performance is locked — the guitarist doesn’t need to play again. You can experiment with different amps, different settings, different mic positions, different rooms. All after the fact.

You need a re-amp box to convert the interface’s balanced line-level output back to the unbalanced instrument-level signal an amp expects. Without it, the impedance mismatch makes the amp sound thin and wrong. Re-amp boxes are small and inexpensive — worth owning if you record guitars regularly.

Pickups

Understanding what generates the signal helps you record it better.

Single-coil pickups: A single coil of wire around a magnet. Clear, bright, articulate, with a characteristic snap. Prone to picking up 60-cycle hum from electromagnetic interference — lights, power supplies, monitors. That hum is part of the deal with single coils. You can minimize it by facing away from interference sources, but you can’t eliminate it entirely.

Humbuckers: Two coils wired in opposite polarity. The hum appears equally in both coils and cancels out — hence “hum-bucker.” Warmer, fatter, and quieter than single coils. Less high-end articulation, more mid-range power.

Piezo pickups: Sense physical vibration rather than magnetic field. Found in acoustic guitar bridge saddles, some electric guitars, and upright basses. Piezo signals can sound thin or quacky on their own and often benefit from an active preamp or a DI with proper impedance matching.

Capture Samples Before You Tear Down

Before you break down the microphones, capture isolated hits of every drum — kick, snare, each tom, cymbals ringing out, maybe a kick and crash together. Not to build a sample pack, but because you’re likely to need them for edits later, and this is your only chance to get those drums in isolation with the same mics, same room, same tuning. This applies to any instrument where the mic setup took time. Once those mics come down, the moment is gone.

What to Practice

1. Move the mic on the cone. Set up an SM57 (or any dynamic) on a guitar amp. Record four clips: dead center of the dust cap, edge of the dust cap, halfway to the cone edge, and at the cone edge. Don’t change anything else. Listen back — the tonal range from a few inches of movement is dramatic.
2. Record DI and mic’d simultaneously. Split the guitar signal with a DI box — DI into one input, mic’d amp into another. Record both. In the mix, try blending them at different ratios. Notice how the DI adds clarity and the mic adds character.
3. Do the polarity check. With two mics on the same source, flip the polarity on one track. Listen in mono. Pick whichever sounds fuller. Make this a habit with every multi-mic setup.
4. Record a DI for safety. Even if you’re happy with the mic’d tone, print a DI track alongside it. If you decide you want a different amp sound later, you can re-amp without needing the guitarist back in the room.