Electrodyne 501 Preamp

Electrodyne 501 discrete two stage studio preamp:

The Electrodyne 501 is a two stage discrete transistor, transformer coupled preamp with active DI, using classic (1969? / 1970?) design technology. Each amp stage is individually optimized for peak performance using Electrodyne factory engineering notes and selected high performance components identical to the originals. The transformers are made by Electrodyne’s original manufacturer to exacting factory specifications. The active DI circuit presents an almost immeasurable load to sensitive musical instrument outputs allowing incredibly accurate capture of the instruments true tone. The output of the DI circuit is designed to directly connect and interact with the mic input transformer to allow maximum tone options.

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.