FEA Labs 2 Channel Mixer

Various

FEA Labs

The FEA 2 Channel Mixer is the ideal solution for mixing two independent audio sources before sending the signal to your amplifier or DI (Direct Input) box.  So, why use a 2 channel mixer pedal?  Well, if you've ever attempted to blend two audio paths into a single output for a live performance, then you've probably run into some of the issues that this pedal was designed to overcome.  Let's take a look at some of these issues and how the 2 Channel Mixer helps you resolve them.

Probably the most basic function of any mixer is independent channel gain adjustment.  The 2 Channel Mixer by FEA Labs provides adjustable gain controls for each input channel ranging from -5dB to +12dB so you can achieve that perfect blend between the two audio sources.   Like many mixing consoles, clipping indicators have been added for each channel and the output to assist with taming very hot signals.  This is, after all, what a mixer is designed to do at its most basic function. However, there is still more to consider...

One of the other notable problems that the 2 Channel Mixer corrects is phase inversion.  Phase inversion occurs when the two signals being mixed are out of phase with one another and the most common result is the loss of combined signal amplitude.  While many of the mixer products on the market today offer a phase inversion switch which rotates one of the signals by 180 degrees, that solution doesn't completely solve the problem when the phase is off by 90 degrees (or some other amount).  The 2 Channel Mixer by FEA Labs is equipped with a variable phase adjustment allowing you to adjust between 0 and 180 degrees so you can find that "sweet spot" where the phase issues can be minimized between both input sources.

Another very useful feature is the adjustable boost option which gives you that additional "POW" when it's needed.  While some might argue that a boost option isn't necessarily a part of a standard mixing solution, to them we say think outside the box!  The boost option included in the 2 Channel Mixer by FEA Labs provides you with the ability to control the boost level (from +3dB to +10dB) and to which channel(s) it is applied when activated.

Want the option to switch the output between class AB op-amp and class A FET (field effect transistor) type amplification?  Well, we've added that ability as well to satisfy the audiophiles out there (like us)!  The 2 Channel Mixer by FEA Labs provides both of these types of output amplification options and the ability to switch between them depending on your tonal preference.

Finally, the 2 Channel Mixer by FEA Labs is designed to handle all frequencies from 5Hz (extremely low bass) to 20KHz (above the cymbal range) and everything in-between.

Recommended uses:  Mixing any two audio signals into a single amplifier such as an acoustic and electric guitar; two keyboards; recombining the split signal from an FEA Dual Band compressor (of course); or any other 2 channel mixing application you might need.

Features:

  • Small footprint - 4 1/2 inches by 3 1/2 inches
  • Input GAIN control on both mixer channels can be adjusted from -5dB to +12dB.
  • Channel 2 has an adjustable PHASE control to correct for signal inversion from some FX pedals.  This is to help minimize frequency peaks and notches when mixed with channel 1 having a similar harmonic structure.
  • Channel 2 has a footswitch to enable or disable the channel.  Channel 1 cannot be disabled and is always active.
  • The BOOST amplifier is activated by the BOOST footswitch.  The BOOST amplifier can be set to either channel or both via the rotary selection switch.
  • The jumper on the back of the circuit board enables a low pass filter in the BOOST circuit at 15KHz to help minimize white noise (hiss) while BOOST is activated.
  • Output amplifier type is selected via a rotary selection switch.  There are two output amplifier topologies available in the 2 Channel Mixer.  The first type is the BJT, “class AB” output of the op-amp.  This amplifier is usually considered the most accurate and has a clean and sterile sound.  The second type is a discrete JFET “class A” amplifier.  Some prefer this type of amplifier for its sonic character resembling tube amplification.
  • There are three clipping monitoring circuits for detecting excessive signal levels.  The clipping monitors will light before the signal actually clips and the monitor for channel 2 is always active, even if the channel is disabled by the footswitch.
  • NOTE: If a clipping LED illuminates then the gain should be reduced for the affected channel or output.
  • The 2 Channel Mixer has minimal components in the signal paths to maintain the utmost signal quality.   All resistors in the circuit are low noise 1% metal film type. The signal coupling capacitors are tight tolerance, quiet, multi-layer and metallized polyester film type. The operational amplifiers used in the signal path are JFET input, low-noise, low-distortion “hi-fi quality” devices.
  • The power supplies onboard voltage charge pump allows the circuitry to operate at 18volts (+9 and –9 volt rails) from a single 9-volt battery or DC power adapter of 9 volts. This allows the signal plenty of headroom from active electronic guitars and aggressive playing techniques (i.e. pop and slap).
  • This pedal is unique in which the OUTPUT jack is used for turning the power ON when a plug is inserted in lieu of the more common INPUT jack switch.
  • The “switch on” power supply current is less than 1µA (micro amp) on the signal ground at the OUTPUT jack. This is approximately 45,000 times (-93dB) less than the commonly used method of connecting the battery’s negative terminal to ground via the sleeve of the plug inserted into the INPUT jack. The “switch on” sensing method used in the FEA 2 Channel Mixer keeps nearly all of the circuit’s generated white noise and transient currents out of the OUTPUT stage signal ground.  Extreme measures have been taken to keep the power and signal paths as clean as possible.
  • The power and grounds for the signal path circuitry are separated from the clipping monitors circuit power and grounds to protect the audio signal from spurious noise. The power for the signal amplifiers is exceptionally clean, filtered twice for each rail and all filter stages are oversized.

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