Avalon Design

Avalon VT-747SP Pure Class A Tube Discrete Spectral Opto-Compressor Equalizer

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  • Regular price R 53,967.57

Avalon VT-747SP Pure Class A Tube Discrete Spectral Opto-Compressor Equalizer

The Avalon VT-747SP combines a creative STEREO tube-discrete Class A spectral-opto-compressor with a musical six band program equalizer, L-R output level and gain reduction metering and internal regulated power supplies in a 2U space. Ideal for high performance DAW input signal conditioning, stereo buss compression-EQ, stereo keyboards and analog mastering applications.


The opto-compressor features a minimum signal path design utilizing sealed silver relays for all signal routing and by pass functions. The optical attenuator acts as a passive level controller with a Class A, variable gain make-up amplifier. Full dynamic control from soft compression to hard-knee limiting can be achieved with master threshold, ratio-compression, attack and release controls. Gain reduction indication is a large analog VU meter. Low frequency and high frequency contour parametric spectral controls can be routed into the side-chain path for enhanced frequency dependent compression with variable frequency and threshold levels. SC listen provides side-chain listen mode for monitoring.


The VT-747SP equalizer utilizes 100% discrete, Class A high-voltage transistors for optimum sonic performance. The six band STEREO program EQ incorporates the smooth characteristics of an all passive design. The frequency turnover, Q and amplitude ranges have been carefully chosen for each band to provide the most natural harmonic balance and lowest phase change while offering simple and effective tone control. The EQ can be placed pre or post the opto-compressor for enhanced effects.


The VT-747SP features TSP which gives you the choice of either tube tone or the classic, Class A discrete transistor sound by exchanging, three (3) high-voltage dual triode tubes with discrete amplifiers in the opto-compressor and primary output stages.


Fully balanced DC coupled, Class A discrete amplifiers are utilized for the input and output drive interface with+36dB input headroom. A high quality analog VU meter indicates accurate gain reduction. Twin 60dB range LED meters provide fast L-R output status of all levels.



Circuit topology

Three (3) dual triode vacuum tubes (Sovtek 6922), high-voltage discrete Class A mode.

Input gain range

Balanced, Class A, 20k ohms, -20dB to +16dB with high gain switch

Maximum input level

+36dB balanced XLR pin 2 hot

Maximum output level

+30dB balanced 600 ohms, DC coupled, discrete Class A

Output type

XLR connector, output trim gain -45dB to +6dB

Noise 20kHz unweighted


Distortion THD, IMD


Frequency response -3dB

1Hz to 200kHz

Gain reduction meter

High quality, illuminated gain reduction meter 0dB to -20dB range

Output meter

Twin 20 segment LED VU meters with -27dB to +30dB range

Compressor type

Optical passive attenuator

Make-up gain

Variable 0dB to +10dB stereo tracking

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

Side-chain spectral contour

Variable threshold -15dB to +15dB, frequency 70Hz to 9kHz twin ranges

Equalizer type

Discrete Class A, passive design optimized for full range program material

Frequency bands (6)

Variable amplitude LF +/-24dB 15Hz shelf response
Variable amplitude MF1 +/-8dB 125Hz selected Q response
Variable amplitude MF2 +/-4dB 500Hz selected Q response
Variable amplitude MF3 +/-4dB 2kHz selected Q response
Variable amplitude MF4 +/-10dB 5kHz shelf response
Variable amplitude HF +/-20dB 32kHz shelf response

AC power

Internal toroidal 100v to 240v, 50-60Hz selectable, 70 watts maximum


19 x 12 x 3.5 in (482 x 305 x 89mm)


22lbs (10kg)

Dimensions-shipping carton

21 x 18 x 8 in (533 x 457 x 203mm)


26lbs (11.8kg)