Before I put it away I measured the inductance and resistance and low and behold the VM95E's measured inductance, at 534 mH, was close enough to the "standard" value of 500 mH I decided to put it into service as a dummy cart for noise tests. Most of my previous noise comparisons were made with a Stanton 681 mounted on an arm.

The DC resistance of the VM95E was nowhere near the required 1350Ω, at 517Ω, so I added two 412Ω resistors in series with each terminal. The cart resides temporarily in a ginger tin to provide electrostatic shielding.

To make a long story short one of my experiments was to measure the Flat Moving Magnet Preamp with the test cart and compare it to a shorted input, 2K resistive source, cart with 47KΩ/294pF termination and whatever equivalent resistive source it took to equal the same noise level as the cart.

The gain of the flat preamp is 28X or 28.9 dB. The reason for this particular gain is to produce -23 dBFS (relative to a 2V RMS 0 dBFS) with a 5 mV output cart at a 1 kHz 5 cm/s (lateral) reference. -23 dBFS relative to 2V RMS is about 140 mV RMS. 140 mV/5mV is 28.

A shorted input measurement is a relatively worthless MM phono preamp spec except that it provides a meaningful measurement of input voltage noise.

A 2K termination was chosen since it's used by JRC to characterize the "DD" rank of NJM2068 in an RIAA-equalized preamp. 2K is close to the reference cart's DCR and can be used to estimate current noise but not as well as the dummy cart which, as we shall soon see, presents a much higher source impedance.

Here are the measurements. They are unweighted, flat and can't be directly compared to an RIAA de-emphasized measurement.

**Shorted input: Ein -119.8 dBu, 1.02 µV (20 Hz - 20 kHz BW)**

2KΩ||47KΩ||200pF: Ein -117.5 dBu

Dummy Cart||47K||294pF: Ein -110.7 dBu (5Hz - 20 kHz BW)(94 pF of cable C)

2KΩ||47KΩ||200pF: Ein -117.5 dBu

Dummy Cart||47K||294pF: Ein -110.7 dBu (5Hz - 20 kHz BW)(94 pF of cable C)

**The resistive input termination that produces -110.7 dBu is 30K||47K|200 pF.**

Thus the test cart in parallel with the termination has an Rnv equivalent to an 18.34K resistor (measured) or 16K5 (theoretical.)

**Using 16K5 and subtracting the termination in parallel shows the cart to have a source impedance, over a 20 kHZ BW, that can be approximated by a 25KΩ resistor. 18K34 works out to be around 30KΩ.**

FFT of the spectrum.