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| | == Bilder == | | == Bilder == |
| − | * Bild: Fisher 504 | + | * Bild: Fisher 404 |
| − | [[Datei:Fisher Model-504-1.jpg]] | + | [[Datei:Fisher Model-404-1.jpg]] |
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| | == Testberichte == | | == Testberichte == |
| − | * Fisher 514 stereo-quadraphonic Tuner-Amplifier (entspricht 504x nur zusätzlich mit CD-4 Modul)
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| − | * Price: 450' 00 (plus VAT). Manufacturer: Fisher Radio, 11-40 45th Road, Long Island City, New York, USA. Distributor: Hayden Laboratories Ltd., 17 Chesham Road, Amersham, Bucks.
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| − | * ALTHOUGH some people might not agree with the Fisher Radio slogan "We in vented high fidelity", very few would deny that Fisher Radio produce some of the finest domestic equipment in the USA. For many years their tuners in particular have had a standard of performance seldom approached by other manufacturers, and more recently they have extended their interests to high power amplifiers, tuner amplifiers, quadraphonic systems and loudspeakers.
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| − | * In the current range there are three AM/FM tuner-amplifier models 304X, 404X and 504X which include an SQquadraphonic decoder, and three other models 314, 414 and 514 which also incorporate a CD-4 demodulator. In all the six models the AM/FM tuner section is approximately the same, the main differences being in the audio power output and the control facilities. The model under review is the most expensive of the range, and represents the peak of Fisher designs. It is one of the largest tuneramplifiers on the market and weighs some 20kg (441b).
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| − | * As will be seen from the photograph, the upper half of the front panel carries the tuning scales, which are illuminated in blue with two meters on the left. The first is a tuning indicator which also includes a red lamp to show when a stereo signal is being received. The second meter is an arbitrarily calibrated signal strength meter, and operates on both AM and FM. On the extreme left are figures which illuminate to show whether one is using 2 or 4 channels, and whether the SQ circuits are in operation. To the right of the tuning scales are four legends that are illuminated by the input selector switch showing phono, FM, AM or auxiliary. The tuning scale on FM gives the whole number of MHz: it is not sub-divided, but there is an ancillary logging scale. Similarly the AM scale is calibrated in rather large steps in kHz, though again the logging scale can be used.
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| − | * To the right of the tuning control is a small panel with four red coloured dots representing the layout of the loudspeakers in a quadraphonic format. Dependent on whether one is listening to stereo or quad, two or four of the dots are rear illuminated, the intensity being a function of the audio power. Finally, there is another legend which is illuminated "CD-4" when the appropriate position is chosen on the selector switch.
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| − | * On the lower half of the front panel one finds what at first sight might appear to be a complex range of controls; but on further inspection the layout is most logical. On the extreme left is the mains power switch and sockets for stereo or quadraphonic headphones. Next are five slider tone controls for front bass, front treble, midrange, rear bass and rear treble. Next is a vertical row of four press-buttons. The top button reduces the output volume by some 20dB and is useful when answering a telephone call, for example, without touching the master volume control. Next is the FM muting switch which eliminates noise whilst changing from one FM station to another. Below this is the SQ decoder button for SQ four-channel reproduction: when this button is pressed, the tone controls affect the front and rear channels simultaneously. The fourth button is the FM noise filter, which reduces the high frequency response under noisy conditions. The lever marked "Master Balance" is a j oystick control for the adjustment of volume from front to rear and also from side to side. Where four loudspeakers are used, one can control the balance of signal level between the front and rear pairs, and also between the left or right pairs.
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| − | * To the right of the Master Balance control are four further press-buttons. The top one is labelled "AM DNL" and brings into operation
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| − | * The Fisher 514 tuner-amplifier is ready for CD-4 and SQ records a 'dynamic noise limiter' which, on weak AM signals, reduces inter-station noise and limits high frequency response. Then follow the treble and bass filters and the loudness control, the effect of which is shown in the graphs. On the right of the press-buttons is the speaker control switch and lamps labelled "2" and "4". This is a seven-position switch having positions for main, remote and main-plus-remote speakers, for either two or four channel operation, plus a headphones position. Whilst the Fisher 514 is basically for four-channel operation, the twochannel positions put the front and rear channel amplifiers in parallel thus giving greater output power to the front speakers.
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| − | * The next rotary switch is marked "model monitor" and has positions for mono, stereo, 4-channel, tape monitor and accessory. The 'accessory' position can be used to insert a multi-frequency graphic equaliser, Dolby noise reduction unit or a reverberation unit etc. The final rotary control selects the signal source from phono, FM, AM, Aux I or Aux 2-CD-4 and illuminates the appropriate lamp.
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| − | * The master volume control, which controls all four channels simultaneously, is a horizontally mounted slider situated below the tuning control. Adjacent to it is the audio display on-off switch which, when used in conjunction with the balance joystick, shows the electrical balance between the four speakers. It should be noted that the four lamps indicate only the electrical balance between the channels, and the joystick might require adjustment for acoustic balance, particularly where different types of speaker are used for front and rear channels. As some might find the sound modulated lamps somewhat annoying in a darkened room, the press-button turns them off. Below this switch are two sockets to connect the front and rear channels to a two or four channel tape recorder.
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| − | * The Fisher 514 tuner-amplifier has a built-in CD-4 demodulator, which accounts for a difference of about C65 in the retail price compared with the model 504. The CD-4 demodulator is placed to the extreme right of the front panel and has two press-buttons, one marked "CD-4" and the other "2-channel phono". With the main selector switch in the Aux-2-CD-4 position and the CD-4 press-button in, the legend "CD-4" is illuminated. The demodulator automatically recognises a CD-4 record by means of the pilot-tone. At the bottom right corner are two screwdriver adjustments for controlling the left and right CD-4 separation.
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| − | * At the rear are massive matt-black heat sinks for the four pairs of output transistors, each of which is protected by a perforated metal screen. On the extreme left is the add-on CD-4 demodulator, carrying two input phono sockets for the signal from a suitable CD-4 cartridge and lowcapacity screened leads. Four leads from the demodulator feed to the Aux 2-CD-4 input sockets. Screw terminals are provided for external AM and FM antennas but, for local Station conditions, there is a built-in but not rotatable ferrite AM rod antenna, and one can use the mains coed for FM stations. For less favourable conditions, and where one wishes to have the least possible background noise, one must use an outside FM antenna. The tuner is designed for use with a 300-ohms antenna which uses a balanced feeder. The British 75-ohms coaxial cable can be used either by connecting the centre conductor to one of the FM screw terminals and the screen to the ground (earth) terminal, or with a 300-75 ohm matching transformer, known as a balun. All the phono sockets are in groups of four with the exception of the stereo phono input. Thus there are groups labelled Aux 1, Aux 2, which is normally connected to the CD-4 demodulator, Tape Monitor in, Tape Recorder Out and Accessory in. Connections to the four loudspeaker channels are made by means of
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| − | * July 1975 small spring-loaded toothed clips. The spacing between clip centres is small and, as there is a total of 16 clips, one has to take great care to avoid short circuits between clips due to an odd wire whisker. The upper row of 8 clips is for the main loudspeakers, whilst the lower row is for the remote speakers. As the upper row is near the heat sinks, it would be desirable if the upper and lower rows were reversed in function, and it would simplify connections. The 2-metre heavy duty mains lead is permanently connected to the chassis and, if one wishes to earth the the system, there is a separate earth terminal. There is only one mains output socket, which is switched, though it is rated at 200 watts and so could run more than one unit.
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| − | * The massive chassis is housed in a strong walnut-finish wooden cabinet. The base is slotted and electrically screened with a perforated metal grille, whilst the top surface carries four neat black moulded plastic grilles for heat dissipation. To describe the circuit arrangement in detail would require many pages: there are ten sheets in the Service Manual covering the circuit only, and some of the sheets have two folds. There are ten printed circuit boards mounted on a heavy pre-fabricated plated chassis. As the total power demand at full volume can reach 530 watts (though the average power is only around 280 watts) the mains transformer is quite massive. It is fully screened, with the primary winding tapped at 120, 220 and 240 volts, and protected by a 3-15A slowblow fuse in the mains lead; this fuse does not protect the switched outlet socket.
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| − | * The tuner board carries a three-gang FM variable capacitor plus two sections for AM. The input stage uses a dual-gate field effect transistor followed by a mixer FET stage. The local oscillator uses a silicon NPN transistor and Fig. I. Fisher 514 radio frequency performance Fig. 2. Frequency response and range of tone controls Fig. 3. Loudness contour and filters Fig. 4. Equalised pickup response is tuned by one section of the capacitor. The resultant IF signal operates at 107MHz using a highly selective ceramic filter, followed by a high-gain integrated circuit which also acts as a quadrature type demodulator and amplifier for the FM centre-of-channel tuning meter. A second IC acts as a phase locked loop Stereo multiplex decoder which also operates the beacon lamp built into the tuning meter and the AM-DNL dynamic noise limiter.
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| − | * The power amplifier boards use a differential amplifier and a pair of Darlington driver-power amplifier output stages to drive the loudspeakers. A minor point of criticism on the construction of the board is concerned with a ferrite core filter inductor. The winding on the core is about 18swg copper wire which terminates in the PCB. As the mass is unsupported, it is possible that the leads would be strained and possibly shear under severe transit conditions, as might occur on board ship. The ten boards are inter-connected by means of tough tags and push-on sockets. Though one does not anticipate the removal of the boards for service reasons, they are reasonably accessible and the leads are colour-coded.
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| − | * The four-channel Master Balance control consists of four special potentiometers, each mounted on one side of a fabricated square. Opposite potentiometers have their spindles connected by means of a slotted semi-circular strip. The control shaft is mounted on a spherical universal ball joint and the internal extension engages in the slots of the two semi-circular strips. The specially designed potentiometers have only a 900 track, compared with the more conventional 2700 type, and hence the possible 900 movement in any direction of the control shaft enables one to control the volume level of any channel from zero to maximum.
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| − | * How it performed
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| − | * As will be seen from the Table, the Fisher 514 meets the designer's figures in all respects, and often improves on them. The performance of the FM tuner (Fig. 1) shows that, even with a signal as small as 16 microvolts, there is 30dB separation between signal and combined hum and noise under mono conditions, and 50dB separation at 3 microvolts. Due to the very high selectivity and steep sides of the ceramic filter, the capture ratio is extremely good, and in fact difficult to measure. I would rate it at approximately 13 to 14dB. On the AM side, selectivity cannot be so good but it was adequate to receive a large number of European stations with reasonable frequency response. There is precious little audio output above 5kHz but that is about the highest frequency radiated. The DNL noise control system is designed to operate as an interstation quieting device and, provided the signal is above a certain level, noise is eliminated. But there was some audible distortion on local AM stations and, for such situations, the DNL button should not be used.
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| − | * On the audio side, the curves indicating the range of the bass, middle and treble controls fig. 2) are in agreement with the manufacturer's specification. The introduction of a mid-range control gives greater flexibility of control compared with the normal bass and treble arrangement. The bass and treble filters (Fig. 3) also meet the specification but possibly it would be better if the treble filter started higher in the spectrum. The loudness control operates only at low volume control settings: it mainly boosts the bass response, but there is a small lift above 5 kHz. The RIAA correction curve (Fig. 4) is considerably better than the maker's claim, being - 15dB at 30Hz and 0dB at 15,000Hz. Input overload on the pickup is at G5mV.
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| − | * Measurement of total harmonic distortion gave the following results:
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| − | * Distortion (%)
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| − | * Power into 8 ohms 20Hz 1kHz 20kHz (watts) 50 024 047 037 20 024 007 016 10 028 007 018 1 08 021 043 01 26 07 12
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| − | * Fisher do not quote the frequency at which their distortion figures were taken but, assuming this is to be 1,000Hz, the measured results are better than the maker's figures. As is often found, harmonic distortion increases at very low volume levels and also at extreme frequencies. However, none of these figures would cause any audible distortion. Square wave response at 1,000Hz (Fig. 5a) shows only a slight rounding of the leading edge. Care was taken in adjusting the bass, middle and treble tone controls to give the best waveform and this confirmed that, for the best response, all three controls were set at zero on their respective scales. To simulate the use of an electrostatic loudspeaker, the usual noninductive 8-ohm resistors were loaded with parallel-connected 2 tkF capacitors. Slight ringing will be seen in the oscillogram (Fig. 5b). Using a 10kHz square wave, one must expect some distortion of the output waveform (Figs. 5c and 5d) unless the amplifier is flat to at least ten times the input frequency, and also free from phase distortion. As will be seen from the frequency response curve in Fig. 2, the curve starts falling after 20kHz and is - 6dB at 50kHz. But again the distortion would be inaudible, being far above the limits of human hearing.
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| − | * The Fisher 514 decoder for reproducing SQ quadraphonic discs would appear to be of the simple type, without the more sophisticated logic circuits. However, although the separation between the individual loudspeakers is not so great with the simple arrangement, it gave (a) 1kHz into 8 ohms (c) 10kHz into 8 ohms (b) 1kHz into 8 ohms + 21LF (d) 10kHz into 8 ohms + 2sF
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| − | * Fig. S. Square wove oscillograms (input is lower trace) SPECIFICATION AND TEST RESULTS FISHER 514
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| − | * Amplifier section
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| − | * Total continuous power (all channels driven, 840,000Hz)
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| − | * Harmonic distortion Damping factor
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| − | * Input sensitivity (my) Phono
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| − | * Auxiliary 1 & 2 Tape monitor Recorder output (mV) Hum & noise (dB) Phono
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| − | * Aux. 1 & 2 Frequency response Phono
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| − | * Auxiliary 1 & 2 Bass control
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| − | * Mid-range control Treble control
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| − | * High frequency filter Low frequency filter
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| − | * FM Tuner Section Tuning range
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| − | * Usable sensitivity
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| − | * Harmonic distortion
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| − | * Signal/noise ratio (dB) FM stereo separation (dB) AM Tuner section Tuning range
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| − | * Usable sensitivity
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| − | * Maker's Specification 4 ohms: 2 x SOW or 4x40W 8 ohms: 2 x 90W or 4x32w Full power 05% into ohms 80 (4 channels at 8 ohms) 27 200 300 850 —56 —65 30-15,000Hz ±2dB of
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| − | * RIAA 20-20.000Hz ±2dB at 50Hz ±15dB at 1,500Hz ± 8dB at 10,000Hz ±12dB at 10,000Hz —10dB at 20Hz = —10dB 88-108 MHz 18 microvolts 400Hz, 100% modulation Mono 02%, stereo 03% 70 38 510-1620kHz 200eV/metre
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| − | * Test Results 2x64Wor 4x48w 2XlO3Wor 4x45w
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| − | * See table 35 28 245 310 345 —57 —64 see agreed 1-6 microvolts
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| − | * Mono 03%, stereo 0-45% 72 36 agreed see text excellent audible results from a wide range of SQ records.
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| − | * To use the CD-4 demodulator for CD-4 records demands a special CD-4 cartridge, whereas the SQ quadraphonic system requires only a first-grade stereo cartridge. Several different CD-4 cartridges were used, such as the Bang & Olufsen MMC6000, the .JVC 4MD20X and two others still on the secret list. With the aid of a CD-4 test record, I was able to adjust the left and right channel separation within a few minutes, no instruments being required. Changing from one cartridge to another requires re-setting of the screwdriver controls, but once set there was no suggestion of drifting. When playing CD-4 'discrete' records, the pilot tone caused the CD-Matic legend to be steadily illuminated. This is not the occasion to discuss the relative merits of the various quadraphonic disc systems, but the improved separation between the loudspeakers using CD-4 discs with a suitable cartridge, and the demodulator carefully adjusted, produced outstanding quadraphonic performance. The Master Balance control is a joy to use. for one can 'place' each loudspeaker in the required position, and adjust the relative volume to meet one's personal requirements. Assuming that equal level signals are available at each loudspeaker, and the loudspeakers are identical, then one would have surround sound with the control knob placed centrally. By moving the knob upwards towards the front speakers position, the sound from the rear speakers is reduced giving overall sound nearer to that heard in a concert hall.
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| − | * The cost of C450 (plus VAT now at a rate of 25%) might raise the question—is the Fisher 514 worth the investment? Considering that it possesses facilities to play stereo and quadraphonic records, has a greater power output than normally required for even large domestic listening rooms, superb FM tuner performance, and means of introducing any foreseeable device such as Dolby noise reduction for FM radio, I would consider the Fisher 514 to be good value and well up to the most modern requirements.
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| − | * JOHN GILBERT.
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| − | * The grammophone magazine 1974
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