Amperite RBHG

In the frequency chart above, the red line is the front or square face of the microphone, and the blue line is the sloping side or rear. The ribbon is closer to the sloping side of the microphone.

Hi-Fi Archive show advertising for the RBHG from 1947 through to 1951. The 1947 document calls it 'the new Amperite Velocity' microphone.

MoMics view:

This RBHG is a unique looking ribbon microphone designed for public address duties. The marketing material of the time claims that it will handle high sound pressures and will even adjust its output level automatically, although there is little inside that really backs up the latter claim - if the ribbon extended out of the magnetic field by a loud sound then the output level would start to fall away, but that could also be said for many other ribbon microphones. Our example had a thick ribbon and a somewhat lumpy frequency response.

Also, it is not obvious which is the front of the microphone. The ribbon is closer to the sloping side with the switch and badge. However, contemporary advertising shows the square face at the front. A studio version, the R80, was also available, which featured vertical rather than horizontal slots in the metalwork.

The RB-G models were also produced and branded for IBM, and were supplied with a special cast desk stand.

From a contemporary advertisement:

Amperite studio microphone at P.A. Prices!

At close talking and distant pick-up you can shout right in to it, or stand away...in either case, Quality will be perfectly natural. Output change reduced to a minimum by the Automatic Volume Control effect achieved by special construction

Leads 7 ways:

1. Blast-proof: No Boom. Shout into it, or stand 12" away, response is always perfect.
2. Lowest Feedback; much less than any diaphragm type mike with equal frequency response.
3. Less distortion; Below 1%.
4. Flat response without peaks over frequency range of 50-11,000 cps.
5. Output (-62 db); automatic volume control effect achieved with special construction.
6. Compact and rugged.
7. Unaffected by changes in climatic conditions, wind, etc.

Models: RBLG-200 ohm; RBHG-Hi-imp. List $42.00

From a contemporary advertisement.

• Frequency range 50-11,000 Hz
• Output -52 dB
• Complete with switch, cable connector and 25 ft cable
• Chrome finish.
• Stand thread, standard N-27
• Model RBHG: High impedance.
• Model RBLG: 200 ohms
• Shipping weight: 10 lbs.

MoMics note: The transformer in our RBHG microphone was suffering from breakdown of the insulation around the wires of both the primary and secondary windings, giving intermittant shorting of signal to ground. The sweep and impulse response shown here were recorded with the original high impedance transformer in place. However the faulty part was later replaced with a suitable low impedance replica.

Vintage Microphone World have an RBLG in their collection, which is the low impedance version of this microphone.

A post about the RBHG and similar models at the Coutant Website