Parmeko

The device mentioned in May 1934:

 

There folllowed a complete suite of equipment, reviewed in the Wireless World, 3rd April 1936.

It is by no means an easy matter to give a precise definition of a home recorder, as a large percentage of the apparatus evolved for recording sound could be so described, for it can acquired by anyoneto whom the initial cost is of consequence. A price limitation seems hardly practicable at this Stage of development, so in an arbitrary classification we might be justified in including apparatus that will operate from wireless receivers and amplifiers of the type designed for ordinary broadcast reception.

Within this category, which is admittedly a wide one, since price does not enter into the question, can be included the recording apparatus made by Parmeko, Ltd., of Leicester, for with an amplifier giving an undistorted output of about four watts perfectly satisfactory records can be made.

Thus, the Wireless World Quality Amplifier is quite capable of operating the recorder. though for best results its frequency characteristic, which is practically uniform throughout the audible scale, will require slight modification to match the characteristics of the cutting head. We understand that the makers of the machine will be able to advise interested exerimenters as to the degree of tone correction necessary to achieve this end.

The recording machine and its motor are embodied in two separate units joined together by a driving shaft with flexible couplings.

Solid teak cabinets are used for both units. The former comprises a gear box, turntable, cutting head, and traversing mechanism, while the latter houses a heavy-duty synchronous electric motor. An endless rubber belt drives the traversing mechanism from a three speed pulley on the turntable spindle, the three ratios available giving respectively 85, 95 and 120 grooves to the inch on the recording disc. A steel worm driven from the belt pulley by a two-to-one reduction gear propels a cast gunmetal carriage, to which the cutting head is attached, the carriage being engaged with the lead screw by a split nut, and  released or engaged by a quick-acting pawl.

The cutting head can raised or lowered by a lever, while the depth of cut is controlled by an adjustable counter-weight.

The cutter has an impedance of 600 Ohms, and is designed for on cellulose acetate discs only. It requires approximately six watts for full modulations, though adequate amplitude is obtainable with four watts, as we have found by test.

The amplifier supplied with this apparatus is a four-stage model terminating in two PX25 valves in push-pull, and gives between 10 and 12 watts output when fully loaded. Frequency correction circuits to suit the cutter are embodied, and, as full correction is not required for reproduction, for which three amplifying stages only are usually sufficient, the change-over switch from recording to play-back automatically adjusts the frequency response. Separate volume controls are fitted for all input points.

Recordings of broadcast as well as of speech were made, and for the latter we used the Parmeko Junior microphone, a good-quality carbon model at a reasonable price.

Excellent results were obtained, though the radio version was somewhat superior to the the microphone recording, which is perhaps quite natural, for to achieve comparable quality a really high-grade microphone would be necessary. However, Parmeko include a Piezoelectric microphone among their various recording accessories.

The impression gained from our tests was that a little too much high-note lift remained on the reproduction side of the amplifier, for when the records were played with The Wireless World Quality Amplifier there was a noticeable improvement in general balance. On the other hand, the correction is necessary for recording as records made with the Q.A. receiver and amplifier, uncorrected, but for fitting a suitable ratio output transformer, were less brilliant than with the Parmeko model. A corrected Q. A. would undoubtedly produce a first-class record.

Most noticeable of all was the almost entire absence of surface noise, or needle scratch. Steel trailing needles were used for the reproduction.

The whole equipment is a fine engineering job, soundly made, and capable of hard wear. It is AC operated, and comparatively simple to handle. The one criticism we venture to make regarding the play-back side of the amplifier is of small consequence, as it could be corrected with very little trouble.

Prices are as follows: Recording machine and motor unit, £70; recording amplifier, £68. Junior Microphone and battery box with table stand, £5 10s.; and crystal microphone with pre-amplifier, £35.

Recording blanks cost 2s. 6d. each for double-sided 10 in. and 3s. for 12 in. Single-sided blanks cost 1s. 9d and 2s each in 10in. and 12 in sizes respectively.

H.B.D.

 

British disc records of the 'Acoustic' Era.