A clipping problem arose one day while recording a really loud vocalist singing through a U47 microphone. The problem was assumed to be the clipping of the microphone since every mic preamp in the studio also was clipping in this signal chain.

Upon further measurement it was determined that the U47 output was not clipping, it was outputing a signal of -15 dBm. Too much output for most mic preamps.

The solution was the A9033. This microphone preamp was designed for this situation. However, the added benefit of passive voltage gain possibly makes this the most transparent and open sounding microphone preamp ever.

Passive transformer gain

Switch for phantom power

Phase reverse switch

20 dB mic preamp

All voltage gain from transformers

All discrete / class A

Input and output transformers

No negative feedback

Extremely open and uncolored

Single-space 500 series rack format

Microphone Input Impedance: 1.2K, balanced

Output Impedance: less than 50

Max. Output Level: +32dBu, transformer balanced

Gain: 5 to 20 dB in 3 dB steps

Frequency Response: +/- 1 dB from 7Hz to 85kHz

Noise Level: better than 86dB below +4dBu, 0-30kHz