Technical Specifications & Dimensions

Microphone preamplifier

Measured to the balanced DB25 analogue outputs.

Specification	Value
Microphone gain	0–70 dB
Switchable pad	−15 dB, all channels
Line gain	−10 to 60 dB; −25 to 45 dB with pad
Phantom power	48 V ±4 V at 10 mA per channel
Microphone EIN	<−127.0 dBu
CMRR	>80 dB from 100 Hz to 2 kHz
Maximum input level	+20 dBu; +35 dBu with pad
Microphone input impedance	>2 kΩ balanced; approximately 2.2 kΩ
Line input impedance	>8 kΩ balanced; approximately 8.6 kΩ
Frequency response	±0.5 dB, 10 Hz–100 kHz at minimum gain
Crosstalk	<−90 dBu, 10 Hz–10 kHz
THD+N at 0 dBu, 1 kHz	<0.003% (−90.5 dBu), mostly third harmonic
SNR	>90 dB at minimum gain
XLR wiring	Pin 2 hot, pin 3 cold, pin 1 shield
1/4-inch TRS wiring	Tip hot, ring cold, sleeve shield

Discrete JFET D.I.

Measured through the microphone-preamplifier circuitry.

Specification	Value
D.I. gain	0 dB unity gain into the 0–70 dB preamp range
Maximum input level	+17 dBu
Input impedance	1 MΩ unbalanced
Frequency response	±0.5 dB, 10 Hz–50 kHz
THD+N at 0 dBu, 1 kHz	<0.01% (−80 dBu), mostly second and third harmonic
SNR	>85 dB at minimum gain
1/4-inch TS wiring	Tip hot, sleeve shield

Balanced analogue line outputs

Specification	Value
Output circuit	Ground-sensing compensation
Maximum output level	+22 dBu
Output impedance	<200 Ω ground-sensing; <100 Ω unbalanced
Connector	8-channel, 25-pin Tascam-format DB25

A-D converter

Measured to AES-17 without the microphone preamplifiers.

Specification	Value
Chipset	Burr-Brown PCM4204, 24-bit PCM
Digital reference	Selectable: 0 dBFS = +18 dBu or +12 dBu
Frequency response	±0.1 dB, 20 Hz to Fs/2 (Nyquist)
Crosstalk	<−110 dBFS at 1 kHz; <−90 dBFS at 10 kHz
THD+N at −1 dBFS, 1 kHz	0.0015% (−96.5 dB)
THD+N at −6 dBFS, 1 kHz	0.0009% (−101 dB)
Dynamic range	113.5 dB unweighted; 116.0 dB A-weighted
Peak LED line-up	−2 dBFS, moves with reference level
Signal LED line-up	−38 dBFS, moves with reference level

Digital output and clock

Specification	Value
ADAT SMUX	8 channels, 44.1–96 kHz
Clock	Internal crystal or external source
Word-clock input	75 Ω BNC with switchable 75 Ω termination

HMX MOSFET saturator

Specification	Value
THD+N at 0 dBu, minimum drive, 1 kHz	0.35%, second and third harmonic only
THD+N at 0 dBu, maximum drive, 1 kHz	2.73%, dominated by second to fourth harmonics
Noise at minimum drive	−73 dBu, described in the source as “like an old tube amp”
Frequency response effect	Low-frequency emphasis from 30–150 Hz
Waveshaping	Asymmetrical, tube-like soft clipping

HMX uses pre-emphasis and de-emphasis filtering and three cascaded Class-A MOSFET amplifiers. Its output level is held constant as drive changes. The source manual notes that the added noise can act as analogue dither inside a DAW.

IRON transformer saturator

Specification	Value
THD+N at 0 dBu, minimum drive, 1 kHz	0.11%, mostly second and third harmonic
THD+N at 0 dBu, maximum drive, 1 kHz	0.006%; the source notes that it cleans up as the driver load changes
Low-frequency THD+N below 300 Hz	Complex variation with level and frequency; distorts bass content
Noise at minimum drive	−84 dBu, described in the source as “like a 2-inch tape machine”
Frequency response effect	Rising air boost/resonance from 4–15 kHz
Waveshaping	Symmetrical magnetic-loop saturation, transient shaping and phase shift

IRON combines magnetic-core saturation with a small amount of asymmetrical saturation in its drive and recovery amplifiers. Secondary loading of the 1:1 transformer shapes the high-frequency response.

Power supply

Specification	Value
Design	Low-noise, shielded linear PSU with custom transformers; fanless operation
Maximum consumption	35 W
Internal DC rails	±15 V, +48 V, +32 V and +9 V
Selectable mains voltage	100, 120, 220 or 230 V AC
Fuse	T200mA for 220–250 V or T315mA for 90–120 V; time-delay slow-blow type

Physical specifications

Specification	Value
Rack size	1RU
Width	482 mm
Maximum depth	286.5 mm
Chassis depth shown in drawing	250.4 mm
Height	44 mm; drawing also marks 44.04 mm
Weight	4.5 kg