Sennheiser 421-U
Documentation on the Sennheiser 421-U is thin. What survives is essentially a single 1972 equipment listing, but it pins down the basics. The 421-U (written MD421U in that listing) was a dynamic microphone with a cardioid pickup pattern and 200-ohm impedance. Its frequency response was rated at 30-17,000 Hz ±5 dB, with sensitivity of 0.2 mV. HiFI-Stereo (1972, p.113) listed it at $129.00.
The same listing also shows a variant, the MD421-U2. It is the same microphone fitted with a large Tuchel connector, priced at $125.00.
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