Electrodyne 501 500 Series Preamp

The Electrodyne 501 is a two-stage, discrete transistor, transformer-coupled preamp with active DI based primarily on the modules found in the classic 1608 console.  Each amp stage is individually optimized for peak performance using detailed Electrodyne factory engineering notes and select high performance components identical to the originals. In fact, the 501’s transformers are made by Electrodyne’s original supplier to exacting factory specifications.

The new preamp’s active DI circuit presents an almost immeasurable load (over six megohms) to sensitive musical instrument outputs allowing incredibly accurate capture of the instrument’s true tone.  Furthermore, the output of the DI circuit is designed to directly connect and interact with the mic input transformer to permit an extremely broad spectrum of tonal options.

The faceplate of the Electrodyne 501 features a large rotary gain control offering up to 68dB of gain – adjustable over 50dB in 2dB steps with two ranges via a 20dB pad switch – and a smaller output level pot infinitely adjustable from 0 (off) to +6dB over unity.  Additional switches for impedance selection (50 or 200 ohms), phase reverse, +48V phantom power and DI (with 1/4" input jack) are also present, as well as a clip LED that monitors all three amp stages and illuminates when any stage is 3dB from clipping.

Specifications:

• Maximum Gain: 68db – adjustable over 50db in 2db steps with two ranges using 20db pad
• Output level control: Infinitely adjustable from 0 (off) to +6db over unity
• Input impedance: Microphone, 50 / 200 ohms selectable. DI, over 7 megohms
• Output impedance: 150 ohms
• Distortion: 0.02% typical over entire gain range
• Maximum output: +30db at less than 0.8%thd. (+29.5db at 0.06%thd)
• Frequency response: +/- 0.25db, 10hz to 60khz
• Signal to noise: -80db typ, -60db at absolute maximum gain
• Clip indicator: Monitors all three amp stages and illuminates when any stage is 3db from clip