Check the listing for details. Fredenstein F601A 500 Series Microphone Preamp. Condition: New. Listed at 689.00 USD. Pack Your Rack with This Modern Classic Mic Pre Start with a great-sounding 500 Series mic preamp circuit, then give the engineer the option to switch in premium, gain-compensated Lundahl input and output transformers. That's the enticing premise behind the Fredenstein F601A. A fully discrete Class A gain stage with a unique zero-negative-feedback design, the F601A delivers clean, warm low frequencies and superior transient response for silky, detailed highs without a trace of harshness. Facilities include polarity reverse, 48-volt phantom power, a 60Hz highpass filter, and a lo-Z switch that lowers the input impedance to 300 ohms to optimally match up with your ribbon and dynamic mics. And with 78dB of gain on tap, your ribbons will love this pre.