Avalon design VT-737 DATASHEET

The Avalon VT-737 features a combination of
TUBE preamplifiers, optocompressor, sweep
equalizer, output level and VU metering in a 2U
space. The VT-737 preamplifier has three input
selections: 1. Transformer balanced microphone
input, +48v phantom selection. 2. Instrument DI
high source input with jack located on front
panel. 3. Balanced line input, discrete high-level
Class A. The high-performance preamplifier
utilizes two cascaded, dual vacuum tube triodes
configured with minimum negative feedback. A
high gain switch boosts the overall gain of the
preamplifier. The four high quality tubes are
configured as singled ended anode coupled
followers. A passive-variable high pass filter and
hard-wire relay bypass completes the input signal
conditioning. The phase reverse relay is available
on all three inputs.

Opto-Compressor

The opto-compressor features a minimum signal
path design with twin class A vacuum tube
triodes for gain matching. The optical
attenuator acts as a simple passive level
controller. Full dynamic control from soft
compression to hard-knee limiting can be
achieved with threshold, ratio-compression,
attack and release controls plus gain reduction
selection on the large VU meter.

Special spectral control including de-ess is
available with the dual sweep mid EQ to
sidechain switch. The EQ section can be flipped
pre or post the opto-compressor via a front
panel switch for alternate effects and tone
shaping. Two VT-737’s can be linked via a rear
panel link cable for stereo tracking. The
compressor bypass is a sealed silver relay for
the most direct signal path.

Equalizer

The VT-737 equalizer utilizes 100% discrete,
Class A-high-voltage transistors for optimum
sonic performance. The high and low frequency
bands provide the smooth characteristics of an
all passive design, while the dual mid bands
include variable frequency and switched Q-width
selection. The enhanced range of the mid bands
is extended into the high and low bands by the
use of X10 frequency multipliers. The bypass
switch incorporates a sealed silver relay for the
most direct signal path. When the EQ to
sidechain is engaged, the high-low EQ remains in
the audio path for tone enhancement. The output
level control provides a variable control of the
overall signal path. The output amplifier utilizes
another dual triode vacuum tube driving a 100%
discrete, Class A, high-current, balanced and DC
coupled low noise output amplifier.

D I R E C T S I G N A L P A T H

AVALON DESIGN VT-737 VACUUM TUBE DIRECT SIGNAL PATH

D I R E C T S I G N A L P A T H

AVALON VT-737 FEATURES

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Minimal signal path design

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Four Class A vacuum tube triodes

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Transformer balanced microphone input

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EQ to sidechain for de-ess

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High-voltage circuits + 200v

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Headroom to +30dB

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Low noise -92dB

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Internal discrete power supply

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Soft-start tube life extender

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Stereo link

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All discrete Class A equalizer

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Sealed silver relays

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Professional VU meter

AVALON DESIGN PO Box 5976, San Clemente, CA 92673 U.S.A. Tel: [phone] Fax: [phone] www.avalondesign.com

Circuit topology Four dual triode vacuum tubes, high-voltage discrete Class A
Gain range Microphone: Transformer balanced 850 ohm, 0dB to +58dB

Instrument: Unbalanced 1 meg ohm, 0dB to +30dB
Line: Balanced Class A 20k ohms, -27dB to +18dB

Maximum Input level Microphone +10dB @ 25Hz, +20dB @ 1kHz balanced XLR
and connector types Instrument +30dB unbalanced front panel jack socket

Line +36dB balanced XLR

Maximum output level +30dB balanced 600 ohms, DC coupled, pure Class A
Output type and gain XLR connector, output trim gain -45dB to +10dB
Noise 20kHz unweighted -92dB
Noise microphone EIN -116dB, 22Hz to 22kHz unweighted
Distortion THD, IMD 0.5%
Frequency response -/+0.5dB 10Hz to 120kHz input filter included
Frequency response -3dB 1 Hz to 200kHz line in-out

VU meter and gain reduction 0VU = +4dB and gain reduction to -20dB
High cut filter Variable 6dB per octave 40Hz to 200Hz

Compressor type Optical passive attenuator incorporating twin vacuum tubes and stereo link
Threshold - Ratio Threshold variable -30dB to +20dB, ratio-compression variable 1:1 to 20:1
Attack - Release Attack variable 2mS to 200mS, release variable 100mS to 5 seconds

Equalizer type Discrete Class A, variable active and switched passive design
Frequency bands (4) Treble - switched 10kHz,15kHz, 20kHz, 32kHz, +/- 20dB range, shelf

High mid - variable 200Hz to 2k8Hz and 2kHz to 28kHz, +/- 16dB range, hi-lo Q
Low mid - variable 30Hz to 450Hz and 300Hz to 4k5Hz, +/- 16dB range, hi-lo Q
Bass - switched 15Hz, 30Hz, 60Hz, 150Hz, +/- 24dB range, shelf

AC power Internal toroidal 100v to 240v, 50-60Hz selectable, 75 watts maximum
Dimensions 19 x 12 x 3.5 in (482 x 305 x 89mm)
Weight 221bs (10kg)
Dimensions-shipping carton 21 x 18 x 8 in (533 x 457 x 203mm)
Weight-packed 261bs (11.8kg)

VT-737 SPECIFICATIONS

AVALON DESIGN VT-737 VACUUM TUBE DIRECT SIGNAL PATH

AVALON DESIGN PO Box 5976, San Clemente, CA 92673 U.S.A. Tel: [phone] Fax: [phone] www.avalondesign.com

Avalon Design is a division of Avalon Industries, Inc. ©1997