AN-106: Replacement Transformers for the Ampex 351 Amplifier

The Ampex 351 Amplifier Stage and Its Enduring Appeal

The Ampex 351 tape recorder and 351 mixer featured a vacuum tube amplifier stage that has remained popular for decades due to their outstanding sound quality.  CineMag has created updated transformers specifically for this circuit that maintain the sonic signature of the originals while meeting contemporary performance expectations.

This amplifier stage is used even today in a number of very successful audio mixers and preamplifiers.  It does not require an interstage transformer to give the push-pull output tube grids the correct signal phases, with one 180 degrees out of phase with the other.  It is simple and very effective.  

CineMag’s Modern Replacements: CM-351 and CM-9600T

CineMag analyzed a number of the original Ampex output transformers to develop the CM-351.  It is a replacement with enhanced performance to meet modern standards without compromising the sound characteristics of the best of the original exemplars that were analyzed while developing it.  Another CineMag transformer, the CM-9600T, also works in this circuit providing even higher performance than the original.