Description
Earthworks Zero Distortion Technology™ (ZDT) precision microphone preamplier 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 com-
pletely differential (the signal is never converted to single-ended). The are no trans-
formers or electrolytic capacitors in the signal path. All connectors and switches are
gold-plated.
The ZDT preampliers have extremely at wideband frequency response from 1Hz
to 200kHz, slew rate of 22V/μs, and the lowest self-noise available from any pre-
amplier on the market. The nonlinear distortion is kept well below one part per
million (.0001%) 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” t-r-s output has additional vernier gain reduction of up to 20dB after
the stepped gain.
The ZDT preampliers are available in single (Model 1021), two-channel (Model
1022), or four-channel (Model 1024) versions. The multi-channel preampliers 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%
Input Noise SD Enoise: 1.6 nV @ 20dB gain; 0.6 nV @ 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” t-r-s 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)
Specications subject to change without notice.
*note: on some units the 1⁄4” t-r-s outputs may be incorrectly labeled as “unbalanced”
Block Diagram of the Signal Path
Front Panel (one channel)
Rear Panel (one channel + power)
48V phantom switch
(yellow LED)
Clip indicator
(red LED)
polarity
reversal
switch
output
standby
stepped gain switch
5 to 60dB to XLR
output
variable gain
0 to -20dB from the
step (1/4” t-r-s output)
Power indicator
(green LED)
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)!
IEC power
connector fuse
compartment
AC voltage and
serial number
variable gain
out (balanced)
stepped gain
out (balanced
symmetrical)
mic input
√ Hz √ Hz
