Studio Projects VTB-1
Microphone Preamp

VTB-1

The new Studio Projects VTB-1 is the ultimate in low cost mic preamplifier technology. Incorporating true class A/B switching, the VTB-1 is a totally discrete circuit. Unique to the VTB-1 is the "Tube Drive". The Tube Drive is a variable drive to a 12AX7, that allows the user to blend as little, or as much of the Tube Drive they want. This VTB-1 allows the user the most flexibility of any mic preamplifier in it's price class.

The VTB-1 allows you to go from a pristine solid state sound, to any combination of Tube Drive you choose...even hard distortion for guitars and bass! The VTB-1 is a must-have device as the perfect mic preamplifier for any microphone.

• 48 Volt Phantom Power
• Phase Reverse
• Variable Input Gain Control On Detented Pot
• 1/4" D.I. Jack On Front Panel
• High Pass Filter
• Descrete Solid State Class A/B Design
• TRS Insert
• Mic/Line Switch
• VariableTube Blend On Detented Pot
• Meter Read Select Between Input and Output level
• Switchable Impedance between 50/200 Ohm
• 5 position LED metering
• XLR mic input
• Balanced outputs on XLR and 1/4"
• External AC Power Supply For extreme Low NoiseOperation
• Output Gain Control On Detented Pot

• Maximum Gain:
  • Mic In to Bal Out: 72dB (60dB preamp gain, 12dB output gain)
  • Line In to Bal Out: 42dB (30dB preamp gain, 12dB output gain)
• Distortion/Noise (THD + Noise):
  • -20dBu input-Mic; 0dBu input-Line
  • Both measured at +15dBu output
  • Mic or Line In to Bal or Line Out: <0.0015% (Blend set full CCW- no tube)
  • Mic EIN: -128dBu (150 ohm source, 60dB gain)
• Frequency response (20-20kHz, ref 1kHz):
  • -20dBu input, +15dBu output
  • Mic In to Bal Out: +0 /-0.25 dB
  • 0dBu input, +15dBu output
  • Line In to Bal Out: +0 /-0.5 dB
• Phase response (20-20kHz, either input):
  • <+/- 15 degrees
• Input impedance:
  • Mic Input (Rear switch in 200 ohm position): 2000 ohms
  • Mic Input (Rear switch in 50 ohm position): 300 ohms
  • Line Input (Front panel TRS jack): 1.5 meg ohms
• Output impedance:
  • Male-XLR Balanced Output: 100 ohms (50 ohms each leg)
  • TRS Line Out: 300 ohms (Impedance Balanced)
• Insert Jack (TRS):
  • Nominal level approx 0dBu
  • Located between SS preamp stage and tube/output stage
  • Tip=Send: 50 ohms output impedance
  • Ring=Return: 7500 ohms input impedance
• Mic Preamp:
  • Discreet, current-source fed, paralleled-transistor balanced input stage feeding a bipolar opamp balanced-unbalanced converter. Dual feedback design for low distortion performance. 2-Stage design for increased performance; transistor stage provides up to 45dB gain, 2nd stage contributes up to 15dB gain.
• Line Input:
  • FET-input opamp buffer with hi input impedance to avoid pickup loading when used as an instrument preamp. 2nd stage provides adjustable gain from 10dB to 30dB, constant hi-impedance is maintained.
• Hi-pass filter:
  • 75Hz hi-pass filter for low-freq wind and rumble elimination (3-pole filter @-18dB/oct).
• Tube Blend:
  • Constant-level blend control allows the user to smoothly change from an all solid-state path to a tube-based preamp. This allows the user to add the desired amount of tube sound to the signal without having to deal with complicated "tube drive" controls and such. Alternately, it allows the user to use only the solid-state portion of the preamp to get a very low distortion, un-colored sound when desired.
• Tube Stage:
  • 12AX7 vacuum tube with DC filament supply for minimum hum and noise. 1st half of tube is operated as a hi-gain amplifier stage, 2nd half operates as a cathode follower to minimize loading of the first stage. A low-voltage plate supply is used to create a "starved-tube" condition for enhanced sound.
• Output Stage:
• Bipolar, lo-noise, hi output-current opamp used for best performance. 1st stage is used to provide additional gain (6dB) and drives the Line out jack and Pin-2 of the balanced out. The 2nd stage provides signal inversion and drive for Pin-3 of the balanced output (effectively an additional 6dB gain).

Our Part #  VTB1-STUDIOPROJECTS