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Josephson Engineering C725

Multi-Pattern Tube Condenser Microphone

The C725 from Josephson Engineering is a large-diaphragm, multi-pattern microphone with a unique FET/Tube circuit design. Its “cascode” front end combines a JFET for low noise with a pentode tube for character. A switch on the power supply can be set to reveal more or less of the character associated with tubes, allowing for enhanced versatility.

The C725 offers five polar patterns, switchable on the body of the power supply. Options include: omnidirectional, sub-cardioid, cardioid, hypercardioid and birectional (figure-8). There are no pads or filters on the mic body or power supply, but when in the “moon” mode, greater headroom and more linear response can be achieved.

This microphone employs the same dual-diaphragm capsule as on the C700 and C716 models, and provides a frequency range of 20-20,000 Hz. The capsule is internally shockmounted via urethane vibration isolators, making an external shockmount unnecessary and allowing the user to attach the microphone directly to a stand using the integral yoke.

The mic’s housing is made of durable aluminum alloy in a satin nickel finish. The head grille features Josephson’s patented aluminum foam. The head grille is rigid and therefore needs no bracket for support and is molded directly to the body of the mic. The foam is intended to minimize and randomize internal reflections. It includes an ultrafine mesh to prevent contamination of the capsule assembly.

As with other Josephson offerings, the C725 features cascode circuitry. Rather than using two FET stages, however, this mic uses a custom low-noise FET in the voltage-gain section and a pentode EF806 tube in the current gain stage. The intent here is to combine the clean and quiet characteristics of the FET with the more colorful tube characteristics. This circuit feeds a custom nickel-core transformer with independent windings for output and gain control.

As mentioned, the power supply contains a switch providing five polar patterns. It also features a switch with the astrological graphics for “sun” and “moon”. The Josephson literature describes this feature thusly:

Josephson Engineering

The “sun” setting operates at full gain, with a high sensitivity of 40 mV/Pa, and the warmth characteristic of many vacuum tube mics. In the “moon” setting, a small amount of negative feedback is provided from a dedicated winding of the output transformer back to the front end of the amplifier. This reduces the sensitivity by 12 dB, to 10 mV/Pa, and linearizes the circuit to provide a more neutral sound at high levels. Switching between the two modes is accomplished with a precision reed relay inside the microphone. Five separate power supply sections are used: a preregulator for the vacuum tube filament along with a final regulator inside the microphone so that filament voltage is not changed by cable length, two low noise supplies for the high voltage regulator, and a precision shunt regulator for the vacuum tube plate and polarization voltages.

The power supply features a 12-pin “large Tuchel” connector (which is captive at the microphone end) and a standard 3-pin XLR output.

The C725 ships with the power supply, captive cable, user’s guide and mic sock in a Pelican molded travel case.

The Josephson Engineering C725 is also known as: C-725.

The mic was released in 2018.

Specifications

Pickup Patterns	Pads & Filters
Omnidirectional (20-20,000 Hz) Cardioid (20-20,000 Hz) Hypercardioid (20-20,000 Hz) Bidirectional (20-20,000 Hz) Wide Cardioid (20-20,000 Hz)

Capsule Dimensions	Impedance	SPL/Noise
Diameter n/a	n/a	Max SPL: 142 dB

Weight	Length	Max Diameter	Interface(s)
1200g (42.33oz)	261mm (10.28'')	63mm (2.48'')	3-pin XLR male (1)

Power Specifications
Includes tube power supply

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