EApreq500
The EApreq500 is the 500-series version of our EAPreQ, the 2-channel rackmount preamp and EQ that we've been building since 2011. Born out of a desire to add an original, versatile, transformer-based preamp to our arsenal, it has been in constant use here at Electrical Audio and many other studios worldwide. It is a microphone preamp with two-band equalizer that is dead-simple to use. Sonically, it features the subtle character of its input transformer with very little amplifier noise or distortion. The equalizer section offers separate high- and low-shelf boosts to broadly and quickly supplement bass and/or treble as needed.
Lundahl’s best microphone input transformer
-20dB input pad switch - sealed gold contact relay
Polarity reverse switch - sealed gold contact relay across the output for quietest operation
48v phantom power switch - standard application
16-position, gold contact rotary gain switch, ranging from 20 to 65 dB of gain, with 3 dB per step
Low and high-frequency shelf boost EQ - Controlled with a solid multi-section gold contact switch, with 5 gain positions. A sealed relay bypasses the EQ circuit when not in use.
DC servo for both preamp gain and shelf EQ make-up gain amplifiers. This ensures long-term predictable operation and sound quality, avoiding the gradual decline associated with electrolytic capacitor-coupled circuitry
Ground-sensing solid-state balanced output amplifier, capable of driving 600Ω loads with ease, balanced or unbalanced
Clear green LEDs indicating which shelf band is engaged.
Bright, amber coloured "peak" LED signal just before clipping.
TECHNICAL SPECIFICATIONS
FREQUENCY RESPONSE
± .5dB from 7 Hz to 102 kHz (3dB down @120kHz)
MAXIMUM OUTPUT LEVEL=
+27dBu Balanced 10kΩ Termination (typical modern equipment inputs)
+26.5dBu Balanced 600Ω Termination (“vintage” input impedance standard)
+21dBu Unbalanced 10kΩ Termination
NOISE AND DISTORTION
THD+N (1kHz, 35dB gain) ≤ .003%
THD+N (30Hz, 35dB gain) ≤ .012%
IMD (50Hz/7KHz) ≤ .0015%
Noise floor (22- 22kHz unweighted, lowest gain setting) ≤ -99dBu
Noise floor (22- 22kHz unweighted, EQ engaged) ≤ -86dBu
Equivalent Input Noise = (44dB gain, 150Ω input source, no EQ) ≤ -128dB
Power Consumption is typically < 50mA per 16 volt rail, and < 100mA per rail in the extreme (1kHz sine wave @26dBu into a 600Ω load, all relays on).
