OR-0012
Tekura
Oregon, USA · 1979 – c. 2001
Ser. Type 4400 · Ser. No. 00417-A
1988 · effect
Issued as VST3 · AU
Restored 2024 from 1988 hardware.
Tekura 4400 — Quantization Analyzer
Tekura Type 4400 · Quantization Analyzer · restored from Ser. No. 00417-A · Tekura, Oregon, USA, 1988
The restorer's note
Tekura built this to reveal bit-depth error, not to make it musical — but revealed error, it turns out, is a superb effect. Unit 00417 is the oldest instrument in the archive, hardware revision A, and its scope still draws the quantization staircase in real time. Nothing here is romanticised. That is precisely why it works.
Acquisition
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The plate
The controls
The controls.
- Bits 2–16 bit · 8 bit as issued
- Sets the quantizer's word length, in bits — how many discrete steps remain once the signal is requantized.
- Quantize Truncate as issued
- Chooses how a sample is rounded to its new word length: Truncate, which discards the remainder, or Round, which rounds to the nearest step.
- Dither Off as issued
- Chooses the dither added before quantizing: Off, RPDF, TPDF, or an error-feedback shaped dither, Shaped-Lo or Shaped-Hi, that pushes its noise toward the top of the band.
- Dither Level 0.00–2.00 LSB · 1.00 LSB as issued
- Sets the dither's amplitude, in least-significant bits of the quantizer's step.
- Bias -100–100 % · 0 % as issued
- Sets a DC offset applied before quantizing, in percent of the step size — which becomes even-harmonic asymmetry once the signal is requantized.
- Input -24.00–24.00 dB · 0.00 dB as issued
- Sets the level going in, in decibels, before the signal reaches the restored circuit.
- Output -24.00–24.00 dB · 0.00 dB as issued
- Sets the level coming out, in decibels, after the restored circuit and the Mix blend.
- Mix 0–100 % · 100 % as issued
- Blends the restored circuit against the untouched signal at equal power, from the untouched signal alone at 0 % to the circuit alone at 100 %.
- Bypass Off as issued
- Takes the restored circuit out of the path and passes the untouched signal, delayed to match the circuit so nothing shifts in time.
A stored setting is numbered, never named: the trace's overlay reads SETTING 04/09. The thumbwheel's position is the setting, and it applies as it clicks into place; ▲ ▼ step one at a time and stop at the ends. STORE asks STORE NN?, and a second press keeps the present state as SETTING NN. Holding STORE on a user setting asks CLEAR NN?, and a second press clears it.
Listening
Listening
Demonstration recordings, prepared at the bench.
Eight bits, truncated
The phrase runs dry for five seconds, then the bench default: Bits at 8, Quantize set to Truncate, Dither off. The grain sits in the decays, where the level falls and the staircase shows.
0:00 / 0:30
Sixteen down to two
Bits steps from 16 down to 2 against calibrated tones, Quantize on Truncate, Dither off. The steps are audible by eight; by two the staircase is most of what remains.
0:00 / 0:30
What dither is for
Held at Bits 4 with Quantize set to Round. Dither steps from Off to TPDF, then Shaped-Hi; Dither Level rises to 2 LSB, and Bias tips the staircase off centre at the end. The grain trades for hiss, then the hiss moves up out of the way.
0:00 / 0:30
The exhibit
The exhibit.
