Avalon VT-737SP Tube Microphone Preamp


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Product Code: 9999-00201
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The Avalon VT-737SP Tube Microphone Preamp is a mono mic preamp designed to deliver optimum performance. Combining tube preamps, opto-compressor, sweep equalizer, output level and VU metering,the Avalon VT-737SP makes your sound a quality production.

The Avalon VT-737SP features a combination of TUBE preamplifiers, opto-compressor, sweep equalizer, output level and VU metering in a 2U space.

The Avalon VT-737SP has three input selections: 1. The Avalon VT-737SP features a higher-performance microphone input transformer with +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 Class A 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.

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 side-chain 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 Avalon VT-737SPs 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.

The Avalon VT-737SP 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.

Avalon VT-737SP Tube Microphone Preamp Features

  • Vacuum tube triode signal path
  • Transformer balanced microphone input
  • High-voltage circuits for maximum headroom to +30dB
  • Low noise (-92dB)
  • Internal discrete power supply with toroidal transformer
  • Soft-start tube life extender
  • Stereo link for compressors
  • All discrete Class A equalizer with musical passive filter design
  • Sealed silver relays for signal routing
  • Large control knobs with professional conductive plastic potentiometers
  • VU meter for output level monitoring and compressor gain reduction

Avalon VT-737SP Tube Microphone Preamp Specifications

  • Circuit topology: Four dual triode vacuum tubes (Sovtek 6922), high-voltage discrete Class A
  • Gain Range
    • Microphone: Transformer balanced 850/2500 ohm, 0dB to +58dB
    • Instrument: Unbalanced 1 meg ohm, 0dB to+30dB
    • Line: Balanced Class A 20k ohms, -27dB to 28dB
  • Maximum input level and connector types:
    • Microphone: 26dB@25Hz, +30dB@1kHz balanced XLR
    • Instrument: +30dB unbalanced front panel jack socket
    • Line: +36dB balanced XLR
  • Maximum output level: +30dB balanced 600 ohms, DC coupled, discrete Class A
  • Output type and gain: TRS connector, output trim gain -45dB to 20dB (XLR connector by special request)
  • Noise 20kHz unweighted: -92dB
  • Noise microphone EIN: -116dB, 22Hz to 22kHz unweighted
  • Distortion THD, IMD: 0.5%
  • Frequency response -/2.5dB: 10Hz to 120kHz input filter included
  • Frequency response -3dB: 1Hz to 200kHz line in-out
  • VU meter and gain reduction: High quality illuminated OVU =+4dB and gain reduction to -20dB
  • High cut filter: Variable 6dB per octave 30Hz to 140Hz
  • 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: 22lbs (10kg)
  • Dimensions-shipping carton: 21 x 18 x 8 in (533 x 457 x 203mm)
  • Weight-packed: 26lbs (11.8kg)

4 Reviews Hide Reviews Show Reviews

  • 4
    Everything great but......
    Ashur Esho

    Change the tubes. Spend yourself a good extra 200 and find some great tubes and this thing will keep you in awe. It sounds great stock, but nothing like when you tune it up/

  • 5
    The Swiss army knife of preamps
    peter Simeon jr

    This is no plug n play unit ,you need to spend time with it,create your dream vocal sound works with most microphones very well ,the Eq is fantastic ,great flexibility placing compressor or Eq before or after in chain the hi input gain very useful when tracking using ribbon microphones.....give your studio the edge get it use it, make your clients happy

  • 5
    Love or Hate
    christopher smith

    I realize people either love or hate this channel strip, haven't seen any in between. Well I'm on the side that loves it! Classic pre for hip-hop vocals. Before using my empirical labs mike-e this was hands down my favorite mic pre. Paired with a U87 and you have magic. I've used it for a bass DI and once again it blew me away. The EQ goes way up there above 20k, and the compressor has been fine to me tracking vocals. I haven't used the baby face modded version (which is now standard if you buy a new 737) but the old stock unit was fine for me. The baby face mod was requested by babyface and it speeds up the attack of the compressor. If I had to knock the 737 I do have 2 complaints, but certainly not deal breakers. 1, its heavy, lugging this from the car to the studio will give you a workout. 2, it needs 30 mins to warm up, so you can't get to the studio plug it up and go.

  • 4
    Interesting channel strip
    Jordan Ross

    The sound of the 737 is a bit different than I was used to. Everything seems a bit farther back, vs. very forward sounding like a lot of preamps. Sometimes this works, sometimes it doesn't. Best bass DI I have ever heard, period with some eq and compression. EQ sounds really nice, compressor ok. Good on some vocals, but don't love on some instrument sources. Things seem either hit or miss with this depending on the source, but when it works, it really works.