Groove Tubes Professional Condenser Microphones
LINE INFORMATION & MIC PERIPHERAL PRODUCTS
SPECIFICATION
Preamp Topology
Polar Patterns

75Hz High Pass Filter

GT33
Class A FETInterchangeable

GT44
Class A Tube
Interchangeable

GT Convertible
Low-Noise FET
Fixed

GT55
Class A FET
Fixed

GT66
Class A Tube
Fixed

• Cardioid (standard)• Hyper-Cardioid (opt.)• Omni (opt.)• Cardioid (standard)• Hyper-Cardioid (opt.)• Omni (opt.)• Hyper-Cardioid• Cardioid• Cardioid

Switchable

Switchable

n/a

Switchable

Switchable@ 12dB per octave

Attenuation Pad
Frequency Response
Equivalent NoiseSensitivity
Maximum SPL
Maximum Output
Typical Load Impedance
Output Source ImpedanceDimensions

Switchable -15dB
Switchable -15dB
n/a
Switchable -10dB
Switchable -10dB
20Hz - 18kHz
20Hz - 20kHz
20Hz - 18kHz
20Hz - 18kHz
20Hz - 20kHz
20dB SPL - A weighted 20dB SPL - A weighted 28dB SPL - A weighted 22dB SPL - A weighted 23dB SPL - A weighted
26mV/Pa
28mV/Pa
5mV/Pa32mV/Pa
35mV/Pa
140dB-155dB (pad adj.) 130dB-145dB (pad adj.) 146dB
134dB-148dB (pad adj.) 130dB-147dB (pad adj.)
3.2V RMS for 1% THD 2.8V RMS for 1% THD 3.2V RMS for 1% THD 3.2V RMS for 1% THD 2.8V RMS for 1% THD>500 Ω>500 Ω>500 Ω>500 Ω>500 Ω
200 Ω transformer iso.
200 Ω transformer iso.
200 Ω transformerless
200 Ω transformer iso.
200 Ω transformer iso.
7.5” x 0.85” max.dia. 7.5” x 0.85” max.dia. 7.5” x 0.85” max.dia. 7.5” x 2.5” max.dia. 7.5” x 2.5” max.dia.
(19cm x 2.1cm max.dia.)(19cm x 2.1cm max.dia.)(19cm x 2.1cm max.dia.)(19cm x 6.4cm max.dia.)(19cm x 6.4cm max.dia.)

Weight12 oz. (0.4kg)

12 oz. (0.4kg)

12 oz. (0.4kg)

1.5 lbs. (0.68kg)

1.5lbs. (0.68kg)

SPECIFICATION
Preamp Topology
Polar Patterns

GT57
Class A FET
Switchable

GT67
Class A Tube
Switchable

MD1b-FETClass A FET
Fixed

MD1b
Class A Tube
Fixed

• Cardioid• Omni• Fig-8• Cardioid• Hyper-Cardioid• Omni• Fig-8• Cardioid• Cardioid

Switchable

Switchablen/an/a75Hz High Pass Filter@ 12dB per octave

Attenuation Pad
Frequency Response
Equivalent Noise
Sensitivity
Maximum SPL
Maximum Output
Typical Load Impedance
Output Source ImpedanceDimensions

Switchable -10db
Switchable -10dB
n/an/a20Hz - 18kHz
20Hz - 20kHz
20Hz - 18kHz
20Hz - 20kHz
22dB SPL - A weighted 23dB SPL - A weighted 22dB SPL - A weighted 23dB SPL - A weighted
32mV/Pa
35mV/Pa
32mV/Pa
35mV/Pa
134dB-144dB (pad adj.) 130dB-140dB (pad adj.) 134dB
130dB
3.2V RMS for 1% THD 2.8V RMS for 1% THD 3.2V RMS for 1% THD 2.8V RMS for 1% THD>500 Ω>500 Ω>500 Ω>500 Ω200 Ω transformer iso.
200 Ω transformer iso.
200 Ω transformer iso.
200 Ω transformer iso.
7.5” x 2.5” max.dia. 7.5” x 2.5” max.dia. 7.5” x 2.5” max.dia. 7.5” x 2.5” max.dia.
(19cm x 6.4cm max.dia.)(19cm x 6.4cm max.dia.)(19cm x 6.4cm max.dia.)(19cm x 6.4cm max.dia.)

Weight12 oz. (0.68kg)

12 oz. (0.68kg)

1.5 lbs. (0.68kg)

1.5 lbs. (0.68kg)

ViPRE™

Glory Comp™

The Brick™

PF-1™ & PF-2™

Variable Impedance
Mic PREamplifier

All Tube Variable
Transconductance CompressorTube Preamplifierfor Mics and Instruments

Professional
Pop Filters• Variable Impedance Input• True All Tube,• Tube mic preamp for the studio• Custom All-Steel Mesh Design

5 options:Balanced bridge,Transformer input options(300Ω/600Ω/1200Ω/2400Ω)• Variable Rise Times
5 options:Slow, Med-Slow, Medium,
Med-Fast, Fast

• Pure 8 Tube Signal Path
• Balanced Class A,
fully differential floating signal path

• Precision gain control
75dB total gain in 5db and 1db steps• Authentic VU meteringwith 5 viewing modes

variable transconductance design(no FET, no OpAmp, no Opto controllers)• Balanced Class A,
fully differential floating signal path

• Built-in Sidechain EQ
with Boost and Cut LF and HF controls• Glory Effectenhances low-order harmonics.
Produces chimier guitars, fuller bass
guitar, and distinctive vocals• Authentic VU meteringwith 9 viewing modes• Wide Ranging & Repeatable
dynamics processing controls

with +55dB of gain

• Built-in +48V phantom power
for condenser mics

• Tube Hi-Z instrument preamp
with +30dB of gain

• Custom-wound output transformer
can drive over 1000 feet of cable withno signal loss

• All Tube Line Driveror unity gain DI• Rugged Portable Designfor use in studio or on stage

Groove Tubes’
exclusive
Disk Resonator™
allows large
diaphragms toremain sensitive tohigh frequencies
and preserve linearity

is both indestructable and washable!

• Redirects Airflow
to reduce pop problems• Will not dull high frequencies
like cheaper fabric pop filters• PF-1:Large Oval Design
for side address microphones• PF-2: Medium Size Round Design
can be mounted vertically or horizontallyfor use on side or top address
microphones, in studio or stageapplications• Includes gooseneck
and mounting bracket

www.groovetubes.com
All specifications subject to change without notice