Grace Design m501 Mic Preamp 500 Series ModuleThe m501 is Grace Designs 500 series module version of the venerable m101 mic preamplifier. A microphone preamplifier module that brings out the very best in any microphone. Now the signature transparency and detail of our circuit designs is available for your 500 series frame. While the 500 series market has plenty of colored mic preamplifier options, the natural, musical clarity of the m501 makes it a welcome addition to the field. This circuit is