MC-1 Moving Coil Transformer

Description

The MC-1 transformer takes the low level signal from Moving Coil cartridges and passively increases the level to be compatible with standard phonograph pre-amplifiers.

Both MM and MC cartridges put out a similar amount of electrical energy. Electrical energy is the product of voltage times current. Phonograph pre-amplifiers only amplify voltage making it feasible to directly connect a MM cartridge to their input. The voltage level of a MC cartridge is too low to go directly into a pre-amplifier. Attempts have been made to give them a higher voltage output, but those designs were few and have been abandoned because they could not deliver the performance demanded for critical listening.

The engineering problem is: How can the very low voltage at a very low impedance MC cartridge be made compatible with a pre-amplifier?

The solution is the transformer. This is an electrical device that “transforms” one voltage to another in proportion to the turns ratio of the “primary” input side to the “secondary” output side. Not having active electronics to introduce electrical noise, it brings the signal amplitude up to a useful level without introducing objectionable noise.

The combination of a high quality audio transformer matched to the cartridge – when done properly – makes cable length on the primary side less critical, frequency response can be optimized, and the signal level delivered to the input of the pre-amplifier is optimal for best signal-to-noise ratio.

Just like the MC cartridge, the transformer must be carefully designed and manufactured. If the two do not mate well, the results will be inadequate.

Hum and Noise Rejection

MC cartridges put out very low voltages. The MC-1 step-up transformers are specifically designed to operate optimally in that environment. Stray magnetic fields can cause problems, as most experienced audiophiles working with phono cartridges know. The MC-1 transformers are encased in mu-metal cans which block out a lot of stray magnetic interference (greater than -30dB isolation). Additionally, they are manufactured using a hum-bucking technique which greatly increases the ability of the transformers to reject induced magnetic field pickup typically coming from nearby power transformers and motors.

The MC-1 transformers include internal “floating” (not internally connected to either the primary or secondary) Faraday shielding which ultra-isolates the primary side of the transformer from the secondary. Jumpers are available on the circuit board that allow you to bond the Faraday shields to the system or even float them completely. Detailed instructions are printed on the circuit board. The MC-1 is delivered in the configuration that typically gives best results.