Avalon design VT-737SP DATASHEET

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

The Avalon VT-737 SP features a combination
of TUBE preamplifiers, opto-compressor,
sweep equalizer, output level and VU
metering in a 2U space. The VT-737 SP
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 high­level 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 SP’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 SP 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, high­current, balanced and DC coupled low noise
output amplifier.

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

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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

•

EQ to sidechain for de-ess

•

High-voltage circuits + 200v

•

Headroom to +30dB

•

Low noise -92dB

•

Internal discrete power supply

•

Soft-start tube life extender

•

Stereo link

•

All discrete Class A equalizer

•

Sealed silver relays

•

Professional VU meter

VT-737SP

MONO CLASS A, VACUUM TUBE-DISCRETE
PREAMP-OPTO-COMPRESSOR-EQUALIZER

AVALON DESIGN

VT-737SP FEATURES

AVALON DESIGN

P

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© 1999 AVALON INDUSTRIES, INC. PO Box 5976, San Clemente, California, U.S.A.

Tel: [phone] Fax: [phone] www.avalondesign.com e-mail: avalon@avalondesign

Avalon reserves the right to incorporate changes in design and in the specifications of this product without prior notice.

VT-737SP SPECIFICATIONS

Circuit topology
Gain range

Maximum input level
and connector types

Maximum output level
Output type and gain
Noise 20kHz unweighted
Noise microphone EIN
Distortion THD, IMD
Frequency response -/+0.5dB
Frequency response -3dB

VU meter and gain reduction
High cut filter

Compressor type
Threshold - Ratio
Attack - Release
Equalizer type
Frequency bands (4)

AC po wer
Dimensions
Weight
Dimensions-shipping carton
Weight-packed

Four dual triode vacuum tubes, high-voltage discrete Class A
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

Microphone +16dB @ 25Hz, +30dB @ 1kHz balanced XLR, pin2 hot
Instrument +30dB unbalanced front panel jack socket
Line +36dB balanced XLR, Pin 2 hot

+30dB balanced 600 ohms, DC coupled, pure Class A
XLR connector, output trim gain -45dB to +10dB

-92dB

-116dB, 22Hz to 22kHz unweighted

0.5%
10Hz to 120kHz input filter included
1 Hz to 200kHz line in-out

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

Optical passive attenuator incorporating twin vacuum tubes and stereo link
Threshold variable -30dB to +20dB, ratio-compression variable 1:1 to 20:1
Attack variable 2mS to 200mS, release variable 100mS to 5 seconds
Discrete Class A, variable active and switched passive design
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
Internal toroidal 100v to 240v, 50-60Hz selectable, 75 watts maximum
19 x 12 x 3.5 in (482 x 305 x 89mm)
22 1bs (10kg)
21 x 18 x 8 in (533 x 457 x 203mm)
261bs (11.8kg)

AVALON DESIGN