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Product :	Beomaster 4400
Produced from :	1977 - Oct 1980
Designed by :	Jacob Jensen
Finish :	Rosewood, Teak, Oak
Desirability :	4

Delivering a massive 75 watts of pure, undistorted sound from its stereo/ambiophonic amplifier, Beomaster 4400 stood at the top of the range of desirability in the late 1970s. Technology was changing, and when compared to the Beomaster 1900, which was a runaway success, this receiver represented the old, sedate school with its more up-to-date cousin representing modernity and the way to the future.

Beomaster4400 replaced Beomaster 4000, with both models representing the style that Jacob Jensen did best. Perhaps that was the problem… expense apart, the whole of the B&O product range was beginning to look rather tired by this stage of its history and something new, more exciting, was needed.

However, the remit of the company was to deliver something top-of-the-range and all-powerful, and Beomaster 4400 fitted the bill very well. However, because so much power could be created by the amplifier, special overload circuitry was built in, with a button displaying just when distortion of sound was beginning to take place. The ambiophonic circuitry remained in the machine - a hangover from Beomaster 4000 - although the receiver could be used as a normal stereo machine, offering sound to another room through its second set of loudspeakers connection. The range of facilities continued with connections for two tape recorders or cassette units, and a ‘linear’  button made ‘flat’ the sound (cutting out the loudness control) to give the user complete control of the receiver’s tonal qualities.

Bang & Olufsen tuners have always been very accurate, being able to pull in exceptionally weak signals from far-off transmitters and Beomaster 4400 went just a step further. Five pre-set FM radio buttons remained and the tuning meter and balance display were continued from the style of its predecessor, with the tuning range increased right up to the 108MHz frequencies.

A record deck could also be connected, of course, as well as two tape/cassette recorders, a pair of headphones, and as mentioned, two sets of loudspeakers.

It is interesting to note that Beomaster 4401 (type 2416) possessed the same technical specifications Beomaster 4400 but was finished in black, to differentiate between the two models.

When connected to other similar products in the Bang & Olufsen range, Beomaster 4400 became a part of Beosystem 4400.

LET me say at the beginning of this review that I think the Beomaster 4400 is the finest tuner-amplifier that the engineering staff in Denmark have produced to date. Its external design follows the pattern of the Beomaster 4000 with a shallow flat cabinet, a sloping panel carrying left-right slider controls, below which is a vertical panel carrying a number of operational tab switches, meter and pre-tuned FM controls.

The five slide-rule type controls on the sloping panel are volume, bass, treble, balance and FM tuning, covering 87,5 to 108MHz, the volume and tuning controls having two finger wheels for fine adjustment. The vertical panel carries the following: stereo headphones jack, tab switches for loudspeakers A and/or B, mono, linear (for flat response) and loudness. Then comes a lamp which is illuminated if either channel is overloaded, low and high filter, and Tape 1. This group is followed by an indicator lamp to show the tuner-amplifier is switched on, and is activated by pressing any of the programme switches. Next is the mains off switch, phono, Tape 2, FM, six switches for pre-tuned FM stations, and finally the AFC switch which also introduces muting between stations. To aid correct tuning, there are two lamps which are adjusted for equal brightness and used in conjunction with a signal level meter above which is a mono-stereo lamp indicator. Behind a removable transparent panel are six calibrated thumb-operated controls for the six pre-tuned FM stations.

Recessed on the rear panel is the aerial input for either 75-ohm coaxial cable or 240-300-ohm parellel wire feeder, and DIN sockets for phono, Tape 2, Tape 1 and two pairs of loudspeakers. Also there is a switch which introduces a Hafier-type Circuit, using the second pair of loudspeakers as an ambiophonic rear channel. The mains lead is captive, measures 170cm and is terminated in a continental two-pin plug. There is also a mains voltage adjuster and twin 25A protective mains fuses.

The underside of the chassis is protected by a tapered metal base through which one can adjust the volume levels of phono, Tape 1 and Tape 2 to match the signal level from the FM tuner section. There is a further control which sets the muting level, giving silent tuning between stations. For high field strength areas, B&O can supply a table-top FM aerial which plugs into a moulded socket at the rear of the cabinet. The top and end cheeks are made from teak or rosewood, and above the output transistors’ heat-sinks is a black moulded fluted grille. Heavy satin finished aluminium extrusions carry the horizontal controls and the row of tab switches.

A massive fully-screened mains transformer with three separate secondary windings gives unstabilised and stabilisedpower lines to various parts of the complex circuitry. In the case of gross overloading of the output transistors, such as by accidentally short-circuiting the loudspeaker leads, a high-speed relay comes into operation. If this occurs, it is then necessary to switch off the amplifier and switch on again. To cover the European and American market, alternative aerial connections are used, the British 75-ohm coaxial type and the continental 300-ohm parallel feeder with DIN socket. To obtain correct matching, a balun transformer is used between the aerial and the tuning head. Variable capacity diodes are used to cover the FM band with integrated circuits used for the IF amplifier and stereo decoder. All the components are mounted on printed circuit boards which carry the individual component circuit reference numbers, and the main board also has a grid reference system so that one can easily find a particular section or component - a valuable feature for the service engineer.

Inter-PCB wiring is carried out in most cases with miniature plugs and sockets, though in some cases the wiring harness is terminated by soldering to the board. Although it should never be necessary to remove a board to change a component, the permanent wiring will slow down the change. It was noted that two fuses are mounted on the underside of the main chassis but no reference is made to them in the operating instructions. The base cover does state that any fault should be dealt with by qualified service personnel.

How it performed

This is one of the quietest amplifiers I have tested: with the volume control at maximum, there is no suspicion of mains hum but only a gentle breathing sound. The accompanying graphs show the effect of the tone controls and filters (Fig. 1), and the loudness switch (Fig. 2), the latter having no effect above ‘4′ on the volume control. Compensation for the RIAA recording curve shows a gentle droop below 100Hz (Fig. 3), possibly designed for use with B&O record players. In any case, a slight increase of the bass control will compensate for the loss. In the past, some B&O phono input circuits could run into overload with high-output cartridges, but with the Beomaster 4400 there is an adequate safety margin.

It will be noted that DIN sockets are provided for two tape recorders, and these should be of a type designed for DIN connections, for the output at the DIN socket is only about 12mV from both the tuner section and phono. A rather annoying thump comes from the loudspeakers when the unit is switched on and, although it is unlikely to damage a loudspeaker, one feels that in an expensive system it should not occur.

Square-wave response was checked by applying the signal to the tape input and connecting the oscilloscope across a non-inductive 8-ohm load with all controls set to flat. The rise time on the 1kHz square wave (Fig. 4a) is nearly as rapid as the input signal, and even with a 5kHz square wave it shows little degradation (Fig. 4b). Toneburst tests were made with the 8-ohm load and also with the 8 ohms in parallel with a 2 microfarad capacitor (lower trace). The resultant oscillograms are virtually identical, showing the high stability of the amplifier (Fig. 5). With gross overloading, when the overload indicator lamp illuminates, the oscillogram taken at a power output of 66 watts shows symmetrical clipping, identical on left and right channels (Fig. 6). The RF signal-to-noise ratio for mono and stereo is plotted in Fig. 7.

The tuner is unusually sensitive, which enabled me to receive a number of foreign mono and stereo transmissions, provided that my aerial was rotated toward the continent. Dutch and French transmissions predominated, and German stations were heard on rare occasions. The only difficulty lies with the rather fast action of the tuning control. Although it is operated by two finger wheels which give smooth movement, the reduction is small and requires delicate operation to tune correctly to a weak signal. The tuning indicator lamps are more useful than the signal strength meter for, as one approaches a station, one lamp will light then, as one continues through the station, the other lamp lights and the correct tuning point is where both lamps are equally illuminated. Setting the controls for the six pre-set switch tabs is also difficult for, although the dials are calibrated on edge, there is no reduction gearing. However, once they are tuned accurately with the aid of the two lamps and the automatic frequency control is depressed, the selected stations are rock steady and any drift is well within the AFC operation.

The tuning scale calibration is reasonably accurate, the worst error being 0.2MHz, but generally within 0.1MHz. The signal strength meter is calibrated in five arbitrary units, and a signal showing under two on the scale will not cause the tuning lamps to operate. The audio response from the tuner decoder section is as wide as that of the transmission being received, extending flat to 15kHz and falling to —3dB at 16kHz. Rejection of the pilot signal at 19kHz measured 68dB, whilst the 38kHz multiplex tone was greater than 88dB, and did not cause any audible whistles whilst making tape recordings.

The tuner-amplifier was used with a pair of B&W DM7 loudspeakers for the front channel and a pair of Rogers Compact loudspeakers for ambiophonic reproduction. For tape recording I used a Sony TCI77SD three-head cassette recorder and, for disc playing, a Garrard GT25P fitted with a Shure M24H cartridge (as both the tape and disc machines have DIN output sockets which match the B&O 4400).

As I stated at the commencement of this review, the Bang & Olufsen Beomaster 4400 is the finest tuner-amplifier that the company has produced. Reproduction from all signal sources was almost completely neutral. On disc, however, with all the controls set to flat or with the linear tab switch in operation, the extreme bass is thin. Though one can improve it by a slight increase on the bass tone control, this also tends to accentuate the lower-middle frequency response.

Tape recordings from FM radio or disc were completely free from interference and, provided one makes use of DIN-to-DIN connectors, the matching between units is accurate.

However the output signal at the 4400 DIN socket will be too low to modulate some tape recorders fully. Similarly it may be necessary to attenuate the signal from some tape recorders for playback through the 4400.

Radio reproduction, particularly of direct transmissions, was of a very high order. Although I am not a supporter of artificial rearchannel sound, the Hafler system used in this tuner-amplifier added a degree of realism particularly to pop music. The output from the headphone socket is more than adequate for conventional headphones, and even with less sensitive types such as the Wharfedale Isodynamic headphones I found the signal level sufficient.

Bang & Olufsen distribute through selected dealers who have trained personnel to advise on correct installation and, if ever necessary, complete servicing facilities. In many ways Bang & Olufsen are leaders, particularly in aesthetic design, and in the 4400 they have combined appearance with outstanding performance. It can be strongly recommended.

Taken from ‘Gramophone’ April 1978 (page 142)

Beomaster 4400 types:

2417 (1977 - Oct 1980)

US 2419 (1977 - Aug 1980)

Details:

Power output: 2 x 75 W / 4 ohms

2 x 50 W / 8 ohms

Speaker impedance: min. 4 ohms

Harmonic distortion: < 0.05 %

Intermodulation: < 0.1 %

Frequency range: 20 - 35000 Hz

Bass control at 40 Hz::+/- 10 dB

Treble control at 12,500 Hz: +/- 10 dB

FM tuner range: 87.5 - 108 MHz

Power supply: 110 - 130 - 220 - 240 V

Power consumption: 30 - 310 W

Weight: 10 kg

RIAA amplifier: built-in

Connections: Speakers, Phono, Tape 1, Tape 2

Dimensions W x H x D: 57.5 x 9.5 x 28cm