KOA Acoustic Guitar Preamp
Carvin
Introduction
The Carvin KOA Acoustic Preamp offers classic, natural acoustic tone with unprecedented tonal control and extended headroom. It begins with a boutique flat response, enhanced by extensive tone control allowing users to carve out their signature sound. Harmonic content increases as the INPUT GAIN control is turned up, producing rich harmonics. Its lightweight, compact design and bullet-proof construction ensure the KOA will be a central part of your tone for years to come.
Key Features
- Preamp GAIN and master VOLUME controls
- BLEND control adjusts the EQ/dry mix
- Mid sweep semi-parametric EQ
- COMPRESSOR: Threshold and Strength controls
- Effects Loop
- True Bypass
- Switchable MUTE
- DIRECT OUT balanced XLR and 1/4-inch
- Switchable Ground Lift for AC ground isolation
- THRU/TUNER output jack independent of MUTE switch
- -10dB attenuation switch
- Solid metal shaft controls with threaded metal bushings mounted to top panel
- 9V Power supply included (90-230VAC, 50-60Hz)
- Battery compartment for 9V battery operation
Specifications
| Parameter | Value |
|---|---|
| Frequency Response | 25Hz-18kHz |
| Input Gain | 13dB |
| Input Impedance | 2.2MΩ |
| Maximum Input | -6dB |
| Maximum Output | MAIN +6dB, EFF SND/RTN +4dB, THRU/TUNER -6dB |
| Tone Controls | +/-10dB BASS (25Hz-100Hz), MID (semi-parametric sweep 100Hz-2.5kHz), TREBLE (3kHz-18kHz) |
| Power Requirement | 9VDC / 50mA (Center Negative Plug) |
| Power Supply | 90-230VAC, 50-60Hz (included) |
| Dimensions | 6"W x 5.5"D x 2.5"H |
| Weight | 2 lbs. |
Control Descriptions
The front panel features a comprehensive array of controls and connections for shaping acoustic guitar tone. The pedal includes three footswitches: COMPRESSOR, MUTE, and BYPASS. Rotary controls manage GAIN, VOLUME, BLEND, BASS, MID, FREQ, TREBLE, COMPRESSOR THRESHOLD, and COMPRESSOR STRENGTH. Additional switches include PWR/CLIP and a -10dB ATTENUATION switch. The rear panel provides input and output jacks, including 1/4-inch INPUT, THRU/TUNER, EFF SEND/RETURN, OUTPUT, and a balanced XLR OUTPUT with a ground lift switch.
1. THRU/TUNER JACK (UNMUTED)
A mono 1/4-inch jack for connecting a tuner or sending the acoustic signal to another device. This output is unaffected by the MUTE switch and other functions, allowing for silent tuning.
2. INPUT JACK
The 1/4-inch input jack is voiced for guitar and compatible with active or passive instruments using piezo or magnetic pickups.
3. PWR/CLIP LED
Indicates unit status: Green for powered on. Flashing Red indicates signal nearing clipping. Solid Red indicates clipping and distortion.
4. -10dB ATTENUATION SWITCH
Attenuates the input signal by 10dB when in the up position. Useful for strong incoming signals that cause distortion even at low gain settings.
5. LED INDICATORS
Provide status for features: COMPRESSOR (Green: ON, Red: OFF), MUTE (Red: ON), BYPASS (Red: Pedal bypassed, Green: Signal flows through preamp).
6. BYPASS
Bypasses the EQ and preamp section. The LED indicates status: Green (ON), Red (OFF). Input Gain, -10dB attenuation, Compressor, Volume, and Ground Lift still affect the signal.
7 & 8. EFFECTS LOOP (SEND/RETURN)
SEND jack outputs the preamp signal after TONE CONTROLS and BLEND, before BYPASS/MUTE. RETURN jack receives signals from external effects processors. Plugging into RETURN breaks the connection to the internal power amp. The RETURN signal passes through COMPRESSOR and VOLUME. RETURN signal is before BYPASS.
9. MUTE
Turns off the pedal's output. A red LED indicates the MUTE switch is ON. Ideal for changing guitars or silent tuning. THRU/TUNER and EFF SEND outputs are not muted.
10. DC IN / Battery Operation
Uses the included 9V power supply. Can operate on a 9V battery, but the unit will only turn on when a 1/4-inch plug is inserted into the input. Leaving the unit plugged in without use drains the battery.
11. COMPRESSOR
Engages or disengages the compressor effect.
12. 1/4-INCH Output
Connect this output to your amplifier.
13 & 14. XLR OUTPUT JACK and GROUND LIFT
DIRECT OUT XLR jack provides a balanced output for direct connection to a main PA or recording input. Output level is controlled by the VOLUME knob. The GND/LFT switch helps eliminate hum when connecting the XLR to a mixer by lifting pin 1 of the XLR connector.
15. BLEND
Controls the amount of signal sent to the EQ tone section. When set to FLAT, no signal enters the EQ.
16. VOLUME
Master volume control for the overall output level.
17 & 23. BASS and TREBLE TONE CONTROLS
Custom-shaped tone controls for full lows and sparkling highs. Turning clockwise boosts, counter-clockwise cuts. Bass frequencies affected are from 40Hz to 140Hz. Treble frequencies affected start at 4kHz.
18 & 20. COMPRESSOR (THRESHOLD/STRENGTH)
THRESHOLD: Sets the point at which the compressor activates. Clockwise rotation lowers the activation level. STRENGTH: Sets the amount of compression. Counter-clockwise (left) provides mild compression; clockwise increases compression.
19 & 21. SEMI-PARAMETRIC MID SWEEP (200-2kHz)
The FREQ control adjusts the mid-frequency sweep (200Hz-2kHz) when the MID control is not at the center "0" position. This allows for powerful tone shaping and feedback control. To control feedback, turn the MID control to the left, then sweep FREQ until feedback stops, then adjust MID level.
22. INPUT GAIN
Increases the sensitivity of the 1/4-inch inputs. Use to compensate for low-output instruments or to achieve desired dynamics with high-output instruments.
Warranty
This Carvin product is guaranteed against electrical and mechanical defects for one year from the date of purchase under normal use. Proof of purchase is required. This warranty replaces all other express or implied guarantees and excludes recovery for consequential or incidental damages.
Carvin Audio, carvinaudio.com
