Grace Design m501: 500-Series Microphone Preamplifier

The Grace Design m501 brings the signature transparency, detail, and musicality of Grace Design preamps to the 500-series format. As the module version of the highly respected m101 mic preamplifier, the m501 is designed for audiophile recording where the goal is the ultra-accurate capture of the sound source with minimal coloration or distortion.

Transformerless, Trans-Impedance Design

The m501 achieves its exceptional performance through a technologically superior architecture, delivering improved dynamic performance compared to typical voltage feedback designs.

• Topology: Fully balanced, transformerless design featuring a trans-impedance (current feedback) gain core.
• Dynamic Performance: Trans-impedance amplifiers maintain a nearly constant bandwidth over the wide gain range, resulting in improved dynamic performance without adding any metallic or "solid-state" character.
• Precision Components: Uses 0.5% precision metal film resistors and a precision switch for the 12-position, gold-plated rotary gain control to prevent unwanted dynamic distortion.
• Outputs: The balanced output stage is capable of driving extremely long cable runs and load impedances down to 50 ohms.

Key Features

The m501 is built to get the best performance out of any microphone, while ensuring safety for delicate ribbon elements.

• Gain Range: Wide 10 dB to 75 dB gain range (10 dB to 65 dB via rotary switch in 5 dB steps, plus 0 dB to 10 dB trim).
• Ribbon Mic Mode (Unique Feature): Activates ribbon mic mode with a single push, which performs 3 critical functions:
  • +48 V phantom power is locked out.
  • Input impedance is raised from 8.1k ohm to 20k ohm.
  • 48 V DC blocking input capacitors are bypassed with sealed gold contact relays.
  • Note: This mode is also ideal for many dynamic mics.
• HI-Z Instrument Input: Front-panel 1/4" TRS Hi-Z instrument input switches the input source using a sealed gold contact relay. The input impedance is 2.5 M ohm unbalanced and 5 M ohm balanced. The gain range is -10 dB to +55 dB (using the trim control).
• Filters: Includes a 75 Hz, 12 dB/Octave High-Pass Filter (HPF).
• Indicators: LED indicators for +48 V, Ribbon mode, and HPF, plus a Peak Indicator that illuminates green at -14 dBu and red at +16 dB (10 dB before clipping).
• Made in the USA and backed by a Five-year warranty.