808 Cymbal & Hi-Hat Synthesis

808808 Synthesis
Written By Peter Barata
A block diagram for a simplified 808 cymbal.

The following is an outline for creating a simplified 808 / 606 cymbal.

Cymbal & HiHat Oscillator Frequencies:

Cymbals and HiHats all share the same bank of 6 oscillators. In the article, “The TR-808 Cymbal: a Physically-Informed, Circuit-Bendable, Digital Model” (linked below), the authors use a spice simulator to replicate the 808 oscillators’ ideal frequencies. These come out as follows:

1: 800 Hz = G5 +35¢, Range = 359.4 to 1149.9 Hz = F4 +50¢ to D6 -37¢

2: 540 Hz = C#5 -45¢, Range = 254.3 to 627.2 Hz = C4 -49¢ to D#5 +14¢

3: 522.7 Hz = C5 -2¢

4: 369.6 Hz = F#4 -2¢

5: 304.4 Hz = D#4 -38¢

6: 205.3 Hz = G#3 -20¢

Oscillators 1, and 2 are tuneable via internal trimpots. They are factory tuned to 800 and 540 Hz. Oscillators 1 & 2 are also used for the cowbell.

Oscillators 3 to 6 are not tuneable, and resistor variance could cause the measured frequencies of any particular real 808/606 to be out by 20%. If you’re trying to get the 808 cymbal/hihat sound, don’t worry about nailing the exact frequencies. What’s important is that the summed frequencies add up to an inharmonic hum. Avoid even multiples.

All oscillators are square waves.

Patching up 6 oscillators would be an expensive mess. Fortunately, the Deeper A-117 has two 808 sound sources specifically for recreating 808/606 cymbal and cowbell sounds. The A-117 6 oscillator output is for cymbals and hi-hats. The 2 oscillator output is for cowbells.

On the other end of the price spectrum, Intellijel Cascadia has 3 flavours of cymbal noise that are great for these patches.

The oscillators are mixed together, then passed along to two band pass filters.

Cymbal Band Pass Filters:

The cymbals have 2 band pass filters.

Band pass filter 1 has a centre frequency at 7100 Hz = A8 +15¢.

Band pass filter 2 has a centre frequency at 3440 Hz = A7 -40¢.

Each band pass filter then feeds separate VCAs and high pass filters.

Cymbal & HiHat Decay Times:

The cymbal and open hat have decay time potentiometers. The closed hat has a fixed decay time. Decay times listed in the 808 service manual are:

Cymbal = 350 to 1200 ms.

Open Hat = 90 to 600 ms

Closed Hat = 50 ms.

The cymbal’s decay potentiometer only controls the time of the envelope modulating the VCA for the lower 3440 Hz band pass filter.

Envelope Smoother:

The cymbals have an envelope smoother applied to create a short attack.

Tone Control:

Tone control adjusts the mix of the two parallel signal paths.

A block diagram for a more simplified 808 cymbal.

This reduces the parallel paths to individual high pass and band pass filters, mixes them, then sends the sum to a single VCA and envelope.

A block diagram for an even more simplified 808 cymbal.

This removes the parallel paths and replaces them with a single multi mode filter, VCA and envelope.

A block diagram of the 808 hihat.

Open & Closed Hats:

The 808 and 606’s open and closed hats use the same bank of oscillators from the cymbal.

The signal breaks out after one of the band pass filters, then runs through an envelope controlled VCA, and into a high-pass filter.

HiHat Decay Times:

The open hat has a decay time potentiometer. The closed hat has a fixed decay time. Decay times listed in the 808 service manual are:

Open Hat = 90 to 600 ms

Closed Hat = 50 ms.

Further Reading

Peter Barata
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