Audio

Digital Audio

Free VSTs: https://forums.cockos.com/showthread.php?t=249859

Spitfire audio: trying drums

C2 - Bass D2 - Snare F#2 - Closed Hi G#2 - Half-Open Hi A#2 - Open Hi

Midi map at https://spitfireaudio.zendesk.com/hc/en-us/articles/360010575337-LABS-Drums-MIDI-Map

• C1 - Bass Drum
• C#1 - Bass Drum Alternative
• D1 - Snare
• D#1 - Snare (Rim Hit)
• E1 - Rim Click
• F1 - Rim Click Alternative
• F#1 - Closed Hi-Hat
• G1 - Floor Tom
• G#1 - Half-Open Hi-Hat
• A1- Mid-Tom
• A#1 - Open Hi-Hat
• B1 - Ride Cymbal
• C2 - Ride Cymbal Bell
• C#2 - Small Crash Cymbal
• D2 - Stopped Small Crash Cymbal
• D#2 - Medium Crash Cymbal
• E2 - Stopped Medium Crash Cymbal
• F2 - Slow Snare Flam
• F#2 - Slow Snare Flam Alternative
• G2 - Quick Snare Flam
• G#2 - Quick Snare Flam Alternative
• A2 - Floor Tom Flam
• A#2 - Medium Tom Flam
• B2 - Hi-Hat Close (Foot Pedal)
• C3 - Hi-Hat Open (Foot Pedal Close)
• C#3 - Hi-Hat Closed

iPhone / iPod

Voltage amplitude appears to be around 1.5v, fitting nicely into a 3.3v range for ADC.

Power around 30mW per channel

Will need to apply a voltage divider style bias circuit

File:Audio bias.GIF

0.1uF capacitor should be OK
Resistors as closely matches as possible to divide Vref voltage

                Vref
                 |
                 R
                 |
  vIn ----| |----*------ vOut
                 |
                 R
                 |
                Gnd

Wave RMS

Square root of time-average square of signal. Assume zero bias.

RMS = sqrt[ Int(t1, t2, [f(t)] ^ 2) / (t2 - t1) ]

Shape	RMS
Square	1.0
Semi-Square / Sine	1/sqrt(2) ~ 0.707
Triangle / Saw	1/sqrt(3) ~ 0.577

Power, Voltage, Current

• V = I * R (Ohm)
• W = V * I
• W = (V ^ 2) / R
• W = (I ^ 2) * R

dB

Zero-dB in audo: 0dB = 1mW in 600 Ohm resistance

(Unit is dBm)

From voltage ratio:

• A = 20 * log10( V2 / V1 )
• V2 / V1 = 10 ^ (A / 20)

From power ratio:

• A = 10 * log10( P2 / P1 )
• P2 / P1 = 10 ^ (A / 10)