| Compact and modular by design. Each circuit board [measuring just 1.75" (44mm) x
4.00"(101mm)] supports a separate function, i.e. there is an infrared circuit board, numeric display board, stepped attenuator board and source
selection board. This modularity allows you to pick and choose only the functions you want. The boards can be stacked, as shown in the photo above
or laid out end-to-end. One very nice feature of this modularity is that the stepped attenuator and source selection circuit boards can be
positioned at the rear of your chassis (very close to the rca jacks for minimal wiring) while keeping the infrared board and LED display board at the
front of the chassis. 
Source Selection is accomplished via the use of very high grade, sealed reed
relay switches. Provisions are included for LED illumination for each source selected (LEDs not included). Only the signals are switched
(not the grounds). If you wish to also switch the ground associated with each input, you can purchase an additional Source Selection circuit board
(RCASEL) and connect the two selector boards in parallel. This add-on board is sold separately below. Note: most preamps connect the input grounds
to a star-ground layout.
Pushing the source selection button, on the remote control, sequences through the
inputs 1 through 5 and then returns to source 1 again. The Source Selector board can be set for 2, 3, 4 or 5 inputs. If you need fewer than
5 inputs, the number required can be chosen during assembly.
Manual Gain Adjust is a feature that allows you to increase the attenuation
level should you encounter a source with too high of an output signal or an amplifier or preamp with too much gain. A resistor network and dip
switch provide the ability to select an additional 6dB, 10dB or 15dB of attenuation. Alternatively, this feature can be bypassed with the dip switch or
not installed during assembly.
Stepped Attenuation is achieved through our proprietary control circuitry.
60 steps of attenuation are provided. Each step is approximately 0.6dB providing a total attenuation of 35dB. If more attenuation is
required, the Manual Gain Adjust feature can be used adding up to an additional 15dB of attenuation. A single push of the remote control volume
button results in a single step (up or down). If the volume button is pushed and held, the attenuator will automatically step (up or down) through
all of the steps until the end of the range is reached (0 or 60). The operation of the stepped attenuator is noiseless so no clicks are heard between
steps. The 'series' resistor of each attenuator is mounted right at the edge of the circuit board minimizing onboard signal path length to less
than 1/4" and also allowing for easy access should you want to roll different brands of resistors in and out of the circuit.
Balance Control is provided for balancing the left and right channels. The
balance steps are also 0.6dB.
Mute Function temporarily mutes the sound. Pushing the mute button again
returns the volume level to its previous setting. If you have the LED display option, when the sound is muted, the display will flash repeatedly
providing an indication that the unit is in the mute mode.
 Power
On/Power Off provides the capability to turn on or off the LED display and attenuator control circuitry using the remote control. This is a
nice feature when using the stepped attenuator in a passive linestage. If the stepped attenuator is used in an active linestage, this feature can
be disabled, or you can use the stepped attenuator's 5 volt supply to switch a relay that powers on and off your active linestage circuitry thereby
using the remote control to activate your linestage's power.
Remote Control Unit - The Welborne Labs remote controlled stepped attenuator
kits include a compact and light-weight InfraRed Remote Control unit shown to the right. Line of sight works best but with a fresh set of
batteries this remote can bounce the signal off of walls, ceilings, floors, etc. The component leads of the IR sensor are long enough to permit
bending at various angles or it can be mounted off of the IR circuit board via an umbilical cable (not included).
Balanced Operation - Balanced operation can be accomplished by adding a second
attenuator board (RCATTN) and a second Source Selector board (RCASEL) to the package. These add-on boards are sold separately below.
Manual Control - The Welborne Labs remote controlled stepped attenuator also
includes provisions for manual control, via external pushbutton switches (switches not included). This feature allows you to install manual
pushbuttons on the chassis of your preamp, linestage, etc. to control the Power, Volume and Source Selection functions. Momentary SPST pushbutton
or toggle switches should be used for these functions.
Specifications:
|
