Red-Eye Twin Instrument Preamplifier™

The Red-Eye Twin Instrument Preamp offers a simple, one-box, direct-connect solution for musicians that play two instruments at the same gig.  It is designed for use with instruments having high-impedance piezoelectric pickups or magnetic pickups.   Performers that would find the Red-Eye Twin useful are, for example, those playing fiddle and mandolin, guitar and mandolin, or string bass and electric bass.

The Red-Eye Twin Preamp’s high input-impedance allows piezoelectric pickups to operate essentially unloaded, which results in a smooth, natural, acoustic instrument tone.  Low distortion, low noise, and generous headroom mean clear tone comes through even when an instrument is played percussively and loudly.

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•    Input: high-impedance, 1 million ohms, maximum 1 volt peak-to-peak level.

•    Low-impedance, balanced, XLR output, 600 ohms, will drive long cables to mix-board.

•    A / B Stomp Button selects alternate instrument. 

•    Mode Switch allows playing alternate instruments or both instruments 

•    Separate Treble controls and Gain controls for each instrument.

•    Boost Stomp Button with Boost Gain control for amplifying solos.

•    Long 9-volt battery life (~100 hours).  

•    Automatically uses XLR Phantom Power, when available, instead of the battery.

•    Plugging an instrument in or connecting XLR phantom power turns the Red-Eye on.

•    Automatic power check: Pwr Chk Light flashes for 1 second if power is good when preamp is powered up.  When powered up on the battery (without XLR Phantom Power) the battery gets tested and the flash happens if the battery is in the first ¾ of its life.

•    ¼ inch output and input for accessory loop, suitable for stomp-tuners or effects boxes or for output to on-stage guitar amps or PAs.

•    Internal filtering to reject radio-frequency interference from neon lights and cell phones.

•    Small Size: 1.25 x 3.5 x 4.5 inches.  Weight: 18 ounces.


Balancing Instrument Levels with the Red-Eye Twin Preamp:

It is important to set the sound level the same for both instruments so that, when you switch instruments on stage, the apparent loudness will stay consistent.

•    First, turn both A and B Gain controls straight up (centered).  (When Gain is centered, the Red-Eye Twin has the same gain profile as the single-channel Red-Eye Preamp.)

•    Second, compare the sound level each instrument makes.  Use the A/B Stomp Button to swap instruments and play them as you would during a gig.

•    Third, turn the Gain control for the loudest instrument down or turn the Gain control for the softer instrument up to balance both instruments.  

•    Fourth, adjust the Treble control for each instrument to suit your taste.  Likely, the Treble settings will be different for each instrument because of differences in the pickups and differences in the instrument’s character.

•    Take note of the positions of the Gain and Treble controls so you can use the same settings at your next gig without having to compare instruments again.

Overall gain level:

The gain controls for both Red-Eye Twin channels provide a lot of range, allowing very different instruments to be balanced well.  If the rare case arises that instruments are being used that have exceptionally low or high signal levels, there is an internal, overall, gain control on the circuit board inside the Red-Eye Twin that can be adjusted with a small screwdriver or guitar pick.  For normal ranges of gain the overall gain control should be centered.  Turning the overall gain control clockwise will increase the Red-Eye Twin gain, and turning it counter-clockwise will reduce the gain. 


Red-Eye Twin Preamp Signal Path:

•    The Instrument Input impedance is 1,000,000 Ohms.

•    The Effects Loop Output impedance is less than 4,000 Ohms.

•    The Effects Loop Input impedance is 4,000 Ohms.

•    The XLR Output impedance is 600 Ohms.

•    Frequency response is flat from 10 Hz to 20 KHz (+/- 1 dB) when Treble Control is centered.

•    Boost level above no Boost:  Minimum Boost = +3 db, Maximum Boost = + 7 db


Using the Red-Eye Twin Preamp to simply connect your instruments to a club’s sound system:

•    You have control over each instrument’s treble and gain.

•    You have control over solo boost if you need it.

•    Stomp Tuner is optional.

•    When you turn on the Stomp-Tuner, the XLR output to the Mix Board will be muted.


Using several effects boxes or a pedal board with the Red-Eye Twin Preamp:

•    Connect Effects Boxes and/or a Stomp-Tuner in series to the Red-Eye Preamp Effects Loop.

•    Effect Boxes and/or Stomp-Tuner will affect the XLR output to the Mix Board.


Using the Red-Eye Twin Preamp with an on-stage Guitar Amp or Instrument PA:

•    Red-Eye Preamp works to control the instrument’s treble and gives you a solo boost button.

•    Add any effects boxes you want in series between the Red-Eye Preamp and the PA.

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Using the Red-Eye Twin Preamp to convert a Single-Ended signal to XLR Balanced Output:

•    The Red-Eye Twin can also be used as a high-quality passive direct box.  The isolation transformer used in the Red-Eye Twin Preamp has a nearly linear response from 18 Hz to over 30 KHz.

•    Power is not required.

•    4,000 ohm input-impedance, single-ended input

•    600 ohm output-impedance, balanced output


For additional information, contact:


Fire-Eye Development:

Fire-Eye Development:  512-346-6944 

Daren Appelt:

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