Home Forums Ask Ted JM preamp only differences/similiarities. Reply To: JM preamp only differences/similiarities.

#15499
Ted FletcherTed Fletcher
Keymaster

    This is a brief history of the mic amps in JM equipment…
    The first mic amp was the VC1 ‘Brick’. This circuit was a conventional transformer into a multi-stage integrated circuit amplifier. This gave a very low noise and low distortion amp, very suitable for recording and broadcasting.
    The same amplifier was used in the early VC1 2U rack units.
    In 1999 I introduced a new transformerless amplifier in the VC1 (called the VC1QCS) this was actually very slightly more noisy than the earlier type, but had a couple of huge advantages…. it was almost impossible to overload, and it works very well with very long mic cables. In addition, the distortion is very low and does not increase at low frequencies like the transformer.
    The VC2 was a special low-gain mic amp using a transformer, but the main gain section was a valve (vacuum tube).
    The circuit of the VC1QCS was taken over to the ‘VC Twin’, and became the standard mic-amp circuit; it proved to be extremely rugged and versatile.
    I designed a new version of it for the VC3, with a better ‘feel’ to the mic gain control and this same circuit was used in the VC6.
    The mic transformers used were all made by ‘OEP’ in the UK and were of a type normally used for line level circuits… I configured the circuitry so that the noise, distortion and overload margins were all optimised.

    To complete the picture, I need to mention the present generation of mic amps used in TFPRO gear….. These are all transformer based, but with circuitry that eliminates overload…. present mic amps will easily take +26dB at all frequencies!
    In terms of quality and ‘sound’, there is no doubt that the early ‘Brick’ was very good, but I think it is equalled by the P110. :)

    Menu