The loaded gain, measured from the grid of the first triode to the top of the volume control, The output impedance and 1MΩ volume control form a voltage divider with a voltage "gain" of The Preamp Gain and Output Impedance calculator shows that the unloaded gain and output impedance are 35.8dB and 38kΩ, respectively. Gain at 82Hz, low E on a guitar with standard tuning, is attenuated by less than a tenth of a dB compared to midrange. The Cathode Bypass Capacitor calculator shows that the 25μF capacitor fully bypasses the cathode resistor. Well beyond the output of a typical pickup. It indicates that the grid voltage can swing from 0V to -3V, so the bias is relatively neutral and input headroom is 1.4V peak ( -0.1dBV), The green AC load line is based on the 1MΩ AC load established by the volume control. The purpose of the grid stopper is to attenuate only radio frequencies.Īccording to the 12AX7 calculator, for a plate supply voltage of 260V, a 100kΩ plate load resistor, and a 1.5kΩ cathode resistor, the DC grid bias is -1.4V. The #1 input jack connects to a classic gamma network comprised ofĪ 1MΩ grid-leak resistor and an effective 34kΩ grid-stopper resistance comprised of two 68kΩ resistors in parallel.Īcross the network there is very little treble attenuation due to Miller capacitance. The simplicity of this design and part and parcel to that, the purity of its tone make it a universal starting point for the virtues of tube amps et al for many players.Īs such it's a vintage amp that every guitarist should experience at least once." -Dave Hunter 1 The First Stage Preampįrom a technical perspective, the tweed Champ is an elegantly simple design. The isolation transformer used in the Red-Eye Preamp has a nearly linear response from 18 Hz to over 30 KHz."For many players and amp-o-philes alike, the tweed Fender Champ is ground zero for vintage tube amps. ? The Red-Eye can also be used as a high-quality passive direct box. Using the Red-Eye Preamp to convert a Single-Ended signal to XLR Balanced Output: ? Effect Boxes and/or Stomp-Tuner will affect the XLR output to the Mix Board.
#High headroom high impedance preamp series#
? Connect Effects and/or a Stomp-Tuner in series to the Red-Eye Preamp Effects Loop. Using several effects boxes or a pedal board with the Red-Eye Preamp: ? If you turn on a Stomp-Tuner, the XLR output to the Mix Board will be muted. ? You have control over solo boost if you need it. ? You have control over your instrument's treble. Using the Red-Eye Preamp to simply connect your instrument to a club's sound system: ? Boost level above no Boost: Minimum Boost = +3 db, Maximum Boost = +7 db ? Frequency response is flat from 25 Hz to 18 KHz when Treble Control is centered. ? The Effects Loop Input impedance is 4,000 ohms. ? The Effects Loop Output impedance is less than 4,000 ohms. ? The Instrument Input impedance is 1,000,000 ohms. SAVE when you add a battery or cable now! Boost level above no Boost: Minimum Boost = +4db, Maximum Boost = +9 db.Frequency response is flat from 25 Hz to 18 KHz when Treble Control is centered.The Effects Loop Output impedance is less than 4,000 ohms.The Instrument Input impedance is over 1,000,000 ohms.Internal filtering to reject radio-frequency interference from neon lights and cell phones.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.Automatically uses XLR Phantom Power, when available, instead of the battery.Automatic battery check: OK Light flashes for 1 second when preamp is powered up.Treble control to boost or reduce treble.Boost button with volume control for amplifying solos.Low-impedance, balanced, XLR output, 600 ohms, will drive long cables to mix-board.Input: high-impedance, 1 million ohms, maximum 1 volt peak-to-peak level.The Red-Eye Preamp also works well with instruments that have magnetic pickups, such as electric guitars and electric basses. Low distortion, low noise, and generous headroom mean clear tone comes through even when an instrument is played percussively and loudly. The Red-Eye Preamp’s high input-impedance allows piezoelectric pickups to operate essentially unloaded, which results in a smooth, natural, acoustic instrument tone. Any passive instrument pickup is supported. The Red-Eye Instrument Preamp offers a simple, one-box, direct-connect solution to musicians playing instruments with high-impedance piezoelectric pickups…for example, the L.R. Red-Eye Musical Instrument PreamplifierTM