|Rogers Cadet III stereo integrated amplifier|
I wonder if Mr. Rogers and his team felt any nostalgia as the first of these new Mark III Cadets came off the production line; for the familiar deep maroon paintwork, which had become almost a trade mark, is replaced now by two sharply contrasting shades of grey. More important perhaps, the heavily framed brushed brass panel, the outward sign of Rogers units for some years, has gone too and a simple and possibly rather delicate aluminium pressing finished in black and silver has taken over.
Looking at this model, one must agree that the new cosmetic has produced a visual improvement, but at the same time one might hesitate to approve the plastic surgery which has removed one of the few designs to resist the present fashion of a long low line. Indeed the control unit is deliberately longer than need be, for there is a substantial overlap at each end to accommodate the pickup adaptor and lead out wires. This is a practical disadvantage, which might prevent the inclusion of a radio tuner in some cabinets. The integrated version is housed in an extremely plain walnut Formica case with a brown ventilation grille in the top surface. Extension leads take the input connections from the control unit to an accessible position at the rear.
Setting appearance aside, what other changes distinguish the Mark III ? Well, in the power amplifier section the answer is very little; and this is not due to any lack of enterprise on the designer's part, but merely because the Mark II was itself a peak of ingenuity in extracting the last ounce of performance for a given expenditure (see August 1962, page 125). Substitution of silicon rectifiers in a voltage doubling circuit in the power supply, together with the incorporation of somewhat improved output transformers, has raised the available power; but otherwise the circuit remains identical.
It is in the control unit one finds the improvements, one of them of major importance. So many people thought the performance of the older Cadet was worthy of the superior Magnetic pickup cartridges that an equalised preamplifier was put on the market as an accessory. Now this facility has been built in by adding a further double triode to the two already in the preamplifier circuit. This is incidentally the first time we have come across the new ECC 807 low noise, double triode valves in a manufacturer's circuit.
Versatility in the connection of various pickup cartridges has been preserved by adopting the Quad technique of putting some of the pickup matching components into a plug-in adaptor. Two of these adaptors are provided, and four others are available. Other new features are the two slide switches to bring in fixed rumble and low pass filters, and the provision of a tape monitoring facility. This is achieved by the clever but simple ruse of divorcing the tape button from the latching mechanism so that it may be depressed in- dependently of the other input selector buttons. As there are now many more recorders on the market which offer monitoring or low-level replay outlets, it is nice to see it provided in this unobtrusive way. A 5-way DIN socket on the front panel gives record and replay stereo connections for operation with a tape recorder. Another possible new trend has not been catered for, and that is provision for stereo headphones; but one can easily add this.
Listening tests from various pickups and other sources produced the usual very musical sounds which enable the Rogers ensemble to present their annual high spot at the Audio Fair. If ever proof was needed that it is quite unnecessary to spend vast sums eliminating the last .000 . . .1% of distortion, extending frequency response from one to a million c/s and incorporating negative feedback running into three figures, this is it, or rather another example of it. A selective ear which takes account of those things which actively degrade the music, which provides controls designed to assist its reproduction and ignores the expensive fads of fashion, this is the secret of Mr. Rogers' progress: and I am inclined to think it is worth more than all the instruments in the N.P.L.
This amplifier cannot fail to be a success, for it offers exceptional value for money and there is not the slightest sign of skimping anywhere; including the printed instruction booklet.
Test measurements and notes
Frequency response, controls at level, radio input, ±0.5dB between 100 and 10,000 c/s, ± 1dB between 30 and 20,000 c/s.
RIAA response, disc input (gold adaptor), within 1dB above 80 c/s falling 2dB at 50 c/s and 4dB at 30 c/s.
Input sensitivities for maximum output. Disc (gold magnetic adaptor) 4.2mV, Disc (silver ceramic adaptor) 78mV, Radio 110mV, Tape 620mV (N.B. some tape recorders have less output).
Power output at onset of clipping, 10 Watts at 1 Kc/s when supply mains at maximum e.g., 250 volts applied to 240 volt tap; 8.5 Watts at nominal supply volts between 80 and 16,000 c/s, falling to 6 Watts at 50 and 20,000 c/s/
Distortion at 1 Kc/s at 6 Watts output 0.3%.
Negative feedback 14dB; stability was very good as was the square wave pattern.
Range of tone controls. Bass at 50 c/s 4- 12 to -15dB, Treble at 10 Kc/s +12 to -17dB.
Low pass filter characteristic, —3dBat 6.5 Kc/s, -6dB at 9 Kc/s, -9dB at 12 Kc/s.
Rumble filter characteristic, —3dB at 70 c/s, -6 db at 50 c/s, -9dB at 45 c/s.
Range of balance control, 12dB.
Signal to noise ratio, radio input 65dB, disc input (magnetic) 44dB.
Crosstalk: -44dB at 1 Kc/s, -27dB at 10 Kc/s.