VPD variable inline attenuator configurations:

• XLR-F to XLR-M, 6dB to 30dB balanced microphone level attenuator, in eight 3-4dB steps.
• XLR-F to XLR-M, 6dB to 48dB balanced line-level attenuator, in eight 6dB steps.
• 1/4″ TRS to 1/4″ TRS, 6dB to 48dB balanced mono line-level attenuator, in eight 6dB steps.
• 1/4″ TS to 1/4″ TS, 6dB to 48dB unbalanced mono line-level attenuator, in eight 6dB steps.
• 1/4″ TS to 1/4″ TS, 6dB to 48dB unbalanced mono high-impedance attenuator, in eight 6dB steps.
• 1/4″ TRS to 1/4″ TRS, 12dB to 48dB unbalanced stereo line-level attenuator, in four 12dB steps.

VPD inline filter configurations:

• XLR-F to XLR-M, passive balanced low cut filter for microphones, 50Hz to 200Hz in four 2/3 octave steps.
• XLR-F to XLR-M, passive balanced line-level low cut filter, 50Hz to 200Hz in four 2/3 octave steps.
• 1/4″ TRS to 1/4″ TRS, passive balanced line-level low cut filter, 50Hz to 200Hz in four 2/3 octave steps.
• 1/4″ TRS to 1/4″ TRS, passive unbalanced stereo line-level low cut filter, 50Hz to 200Hz in four 2/3 octave steps.
• 1/4″ TS to 1/4″ TS, passive unbalanced mono line-level low cut filter, 50Hz to 250Hz in eight 1/3 octave steps.
• XLR-F to XLR-M, passive notch filter, -7dB at 250Hz to 6kHz in eight 2/3 octave steps.
• XLR-F to XLR-M, passive three-band equalizer.
  

Custom values for attenuation, input impedance, and frequency corner are available on request.

The VPD is also available as a fixed attenuator or filter; please specify requirements in order comments.  The fixed version may be ordered in any format for input and output connectors as well as attenuation/corner frequency and impedance.  Fixed microphone-level attenuators have a maximum input level of +26dBV; line-level maximum is +36dBV.

Attenuators

Microphone level attenuators are intended for use with condenser microphones on loud sources. Microphone level attenuators have an input impedance of approximately 2kΩ and will thus pass phantom power with minimum voltage drop.  Maximum input level is +20dBV.

Line level attenuators have input impedance of 7kΩ or higher and are thus not intended for use between microphone and amplifiers, but rather between line level outputs and inputs.  Maximum input level is +30dBV.  Also available is a high-impedance version with 100kΩ input impedance, using 1/4″ TS connectors.

All VPD XLR inline attenuators are directional balanced (“U” pads); the TRS attenuators are symmetrical unbalanced or balanced (“T” or “H” pads).  The VPD attenuators use precision 1% tolerance metal film resistors, so matching between units and channels in stereo units will typically be within 0.1dB.

Filters

The passive low-cut filters’ frequency corners will vary slightly with the input impedance of the following device.  The microphone filter is designed for loads between 600Ω and 3kΩ (standard is 1.5kΩ).  For the microphone filter, the stated frequency range will be accurate only for the impedance specified on order.  The microphone filter is a shelving type in order to pass phantom power to connected microphones.  The maximum cut is -12dB at 10Hz (200Hz setting).  Insertion loss is less than -2dB (with source impedance of 150Ω).  Phantom power voltage drop is 2.4V per 1mA draw by the connected microphone (1.5kΩ version).  Maximum input level is +16dBV.

The line-level version is a second-order low-cut filter (-12dB/octave) with insertion loss of less than -0.3dB (with source impedance of 150Ω).  The line-level filter is designed for loads of 10KΩ or higher. Maximum input level is +16dBV.

The passive notch filter is designed for feedback rejection in live sound applications.  The 2/3 octave bands are designed to cover the midrange frequencies where feedback typically occurs.  The notch filter has a cut of -7dB (Q ~ 1.0) with insertion loss of -3dB.  The passive notch filter will pass phantom power with voltage drop of 0.2V per 1mA draw by the connected microphone. Maximum input level is +16dBV.

The passive three-band equalizer contains three filters; a shelving low-cut filter with three settings (200Hz, 100Hz, and either 50Hz or bypass) and maximum cut of -12dB (a line-level version may also be specified with a second-order low-cut filter); a -7dB midrange notch filter with six settings from 350Hz to 4.5kHz, plus bypass; and a high-cut filter with three frequencies (4kHz, 8kHz, 12kHz) and two settings (-6dB shelving and -6dB/octave lowpass), plus bypass. Insertion loss is -4dB.  The passive three-band equalizer’s switches may be set with either a spindle or a screwdriver slot (3mm flathead).  Phantom power voltage drop is 2.4V per 1mA draw by the connected microphone.  Maximum input level is +16dBV.

All filter formats are directional (“U” or “T”).  Due to greater tolerance in reactive components, the frequency corners of the filters may vary up to 5%.