Block Diagram of the Signal Path
Important: the XLR stepped output is fully differential, that is, it has equal and opposite
signal present on pins 2 and 3. NO extra gain stage is used, and the preamp relies upon
the signals on pins 2 and 3 to be equal and opposite for distortion correction. Never
short pin 2 or pin 3 of the male XLR output connector to ground (pin 1)!
Front Panel (one channel)
48V phantom switch Clip indicator
(yellow LED) (red LED)
stepped gain switch
5 to 60dB to XLR
output
variable gain
0 to -20dB from the
step (1/4” output)
output
standby
polarity
reversal
switch
power indicator
(green LED)
variable gain
out (balanced)
stepped gain
out (balanced
symmetrical)
AC voltage and
serial number
IEC power
connector fuse
compartment
mic input
Rear Panel (one channel + power)
Description
Earthworks Zero Distortion TechnologyTM (ZDT) precision microphone preamplifier is a discrete-component Class A bipolar input circuitry device. The primary signal path from the balanced XLR input to a balanced and
symmetrical XLR output is completely differential (the signal is never converted
to single-ended). The are no transformers or electrolytic capacitors in the signal
path. All connectors and switches are gold-plated.
The ZDT preamplifiers have extremely flat wideband frequency response from 1Hz to 200kHz, slew rate of 22V/μs, and the lowest self-noise
available from any preamplifier on the market. The nonlinear distortion is kept
well below one part per million even at the highest signal levels (below clipping).
Each channel has separate phantom power switch, polarity reversal, and mute
switch that turns off the output while keeping the microphone powered and the
gain unchanged. A separate 1⁄4” output has additional vernier gain reduction of
up to 20dB after the stepped gain.
The ZDT preamplifiers are available in single (Model 1021), two(Model 1022), or four-channel (Model 1024) versions. The multi-channel preamplifiers have separate signal boards divided by electromagnetic shields to minimize crosstalk.
Specications
Frequency Response: 2Hz to 100kHz ±0.1dB, 1Hz to 200kHz ±0.5dB
Settling Time: 1.4μs
Distortion: XLR out: less then 1ppm (0.0001%); 1⁄4” out: 0.001%
Inp ut Noise SD Enoise : 1.6nV/Hz1⁄2 @ 20dB gain; 0.6nV/Hz1⁄2 @ 60dB gain
EIN: -132dBV @ 20dB gain; -143dBV @ 60dB gain
Slew Rate: 22V/μs
Output DC Offset: ±1mV typical, servo balanced
Power Requirements: 120V AC (100V and 220-240V versions available)
Inputs: XLR3-F balanced transformerless
Input Impedance: 10kohm phantom ON, 100kohm phantom OFF
Outputs: XLR3-M balanced transformerless (stepped)
1⁄4” TRS Jack balanced transformerless (variable)*
Output Impedance: 5 ohm nominal
Max. Output Level: +33dBu (37V peak-to-peak)
Dimensions H x W x D: 1 rack space 1.75” x 19” x 10.375” (1021 is 1⁄2 rack)
Weight: 1024, 1022: 6lb (ship.: 10lb); 2.7kg (ship.: 4.5kg);
1021: 4lb (ship.: 7lb); 1.8kg (ship.: 3kg)
*note: on some units the 1⁄4” TRS outputs may be incorrectly labeled as “unbalanced”
Specications subject to change without notice.
Version 4, June 7, 2011