EApreq500

EApreq500 – 500-Series Microphone Preamplifier & EQ

The EApreq500 is the 500-series version of the EAPreQ, the two-channel rackmount preamp and EQ that Electrical Audio has been building since 2011. Developed to provide a versatile, transformer-based microphone preamp with simple, musical equalization, the design has remained in constant use at Electrical Audio and in studios worldwide.

The EApreq500 combines a microphone preamp with a two-band equalizer that is intentionally straightforward to use. Sonically, it delivers the subtle character of its input transformer with very low amplifier noise and distortion. The equalizer provides broad, musical high- and low-shelf boosts to quickly supplement bass and/or treble as needed.

Product Details

• Lundahl microphone input transformer
• –20 dB input pad switch (sealed gold-contact relay)
• Polarity reverse switch using sealed gold-contact relay across the output
• 48 V phantom power switch (standard application)
• 16-position gold-contact rotary gain switch, 20–65 dB in 3 dB steps
• High- and low-frequency shelf boost EQ with 5 gain positions
• Sealed relay EQ bypass when EQ is disengaged
• DC servo-controlled preamp and EQ make-up gain amplifiers
• Ground-sensing solid-state balanced output amplifier
• Capable of driving 600 Ω loads, balanced or unbalanced
• Green LEDs indicate active EQ shelf bands
• Amber peak LED indicates signal just before clipping

Technical Specifications

Frequency Response

• ±0.5 dB from 7 Hz to 102 kHz
• –3 dB @ 120 kHz

Maximum Output Level

• +27 dBu balanced, 10 kΩ termination
• +26.5 dBu balanced, 600 Ω termination
• +21 dBu unbalanced, 10 kΩ termination

Noise & Distortion

• THD+N (1 kHz, 35 dB gain): ≤ 0.003%
• THD+N (30 Hz, 35 dB gain): ≤ 0.012%
• IMD (50 Hz / 7 kHz): ≤ 0.0015%
• Noise floor (22 Hz–22 kHz, unweighted, lowest gain): ≤ –99 dBu
• Noise floor (22 Hz–22 kHz, unweighted, EQ engaged): ≤ –86 dBu
• Equivalent Input Noise (44 dB gain, 150 Ω source, no EQ): ≤ –128 dB

Power Consumption

• Typically < 50 mA per ±16 V rail
• < 100 mA per rail under maximum load conditions