Прочие устройства — Line Magnetic PR-5

The PR-5 is a valve-rectified excitation power supply made by Line Magnetic Audio, a Zhuhai firm founded in 2005 by Zheng Cai and his brother Zheng Xi, whose catalogue grew out of repairing and copying Western Electric equipment. A field-coil driver has no permanent magnet - its magnetic gap is created by an electromagnet, and that coil must be fed with direct current from a separate unit such as this one. Line Magnetic states that the PR-5 was designed specifically for low-voltage field coil speakers. The PR family around it also contains the PR-3 for high-voltage coils and the PR-22, a three-output unit built around a WE 4144 circuit with four rectifier valves and a weight of 39 kg.

Key specs that matter

Two mains settings are provided, 220 to 240 V AC or 100 to 120 V AC, both at 50 to 60 Hz. The DC side is split into two terminals. The high terminal is adjustable from 6 to 23 V at 0.5 to 2 A, and the low terminal from 2.6 to 8 V at 0.25 to 2.5 A. The rectifier valve is an EL-6C, and Line Magnetic lists the EQ1-6/0.325 as the alternative type. The case measures 290 x 210 x 316 mm and weighs 10 kg per unit. A needle meter on the front shows the current flowing into the coil.

Engineering and use context

A field coil works as intended only when it receives the current its maker specifies, since the flux in the gap follows that current. The adjustable output and the analogue current meter let the owner set the value for each driver instead of relying on a fixed rail. Rectifying with a valve rather than with silicon diodes is the approach Line Magnetic chose for this model, while its PR-12 uses transistors. The maker publishes a matching list for each terminal. For the low terminal it covers two 597 tweeters, one 597, one 555 compression driver, one LM-755ex, one 594 or one RCA-1428. For the high terminal the list gives two 555, two 594, two LM-755ex or one TA-4181 18 inch woofer. So the low terminal handles a single coil or a pair of 597 tweeters, while the high terminal can feed two 555, 594 or LM-755ex coils together or the single large bass coil.

Pairing

The natural partners are Line Magnetic's own field-coil drivers of the Western Electric type, the 555 and 594 compression drivers and the LM-755ex full-range unit, in horn systems where every driver needs its own excitation.

Alternatives

The Line Magnetic PR-12 is a transistor excitation supply for low-voltage units that draw a large current.