Quad CDP-2 CD player

The Quad 99 CD-P is a versatile CD player with several advanced features. The CD-P will play regular music CDs, music and standard CD-Rs (open or closed) and CD-RWs. Automatic upsampling increases the detail levels in your CD collection, and the ability to add three digital and three optical sources enables you to get the very best from your other digital media. An optical output is provided to connect the CD-P to other digital equipment.

The CD-P accepts three optical and three digital inputs. Minidisc and DAT players, or Digital Audio Broadcast tuners (DAB) will be significantly improved by connecting their digital outputs to the CD-P. The CD-P can accept incoming PCM digital signals to a maximum resolution of 24bit/96kHz.

CD Mechanism

The Quad CDP-2 mechanism was a major engineering project. Whereas most manufacturers use off-the-shelf transports, we wanted a unit which was particularly optimized to static CD players and employed a ‘lazy servo’ mechanism. In all off-the-shelf CD mechanisms – even those used by high-end manufacturers, there are a number of compromises built into the device which mean that they can be used for a number of applications. With a new Quad mechanism, it could be safely assumed that the CD player would be sat on a farily rigid structure and vibration, whilst possible would be limited.

This enabled us to develop a proprietary ‘lazy servo’ mechanism, which involves the way the transport deals with disc data loss. Where most transports, upon loosing a data stream, move the optic (laser) back a forward rapidly to recover the lost data – ours just sits there and waits for the disc to come around. This has a significant benefit in lowering the noise floor of the player. Some innovative timing techniques used, also result in an industry leading jitter measurement of just 8 pS. These technical innovations combined with its versatility of use (particularly the 6 digital inputs and adjustable level output) make the CDP-2 one of the finest CD players on the market today at any price.

Specifications:

Max.  Line Output Level (RCA):  2,4 V RMS

Max. Output Level (Quadlink):  5,3 V RMS (Balanced)

Frequency Response:  20 Hz - 20 kHz (+0 dB -0,5 dB)

Total Harmonic Distortion:  less than 0,002% (at 1 kHz)

Signal-to-Noise Ratio:   better than 110 dB at 24 bit (20 Hz - 20 kHz)

Better than 95 dB at 16 bit (20 Hz - 20 kHz} 

Crosstalk:  less than -100 dB (at 1 kHz)

Gain Error:  less than 0,5 dB (at -90 dB, f=500 Hz)

D/A Converter

Max. Resolution :  24 bit

Max. Samplig Frequency :  192 kHz

Upsampling:  x2

Digital Audio Inputs: 

3 x RCA Coax 75 Ω ,SPDIF

3 x optical Toslink, SPDIF

Digital Audio Output:  Optical Toslink SPDIF

Disc Compatibility:  CD-DA Conventional Audio CD, CD-R Recordable CD

Dimensions (W x H x D):  80 x 321 x 310 mm

Weight:  4,5 kg

Quad II Integrated Amplifier

The Quad II-Classic Integrated

The rekindled interest in 2 channel analogue hi-fi been remarkable to witness. The popularity of vinyl has grown steadily over the last years and now represents a significant proportion amongst real music enthusiasts. Quad has been at the forefront of this trend with its development of some of the world's most stunning amplifiers  loudspeakers and phono stages. Creating a compact audiophile integrated solution for LP and Vintage Hi-End Audio lovers while working in collaboration with one of the industry's edteemed legendry figures, Tim DeParavicini.

Through his contemporary designs based on Qad's novel amplifier technology developed over half a century ago for his invention of the first Quad II Mono Amplifier introduced in 1953, our classic range of amplifier and speaker componenets represent far more than a nostalgic trip down memory lane. Each product represents as significant a design statement as their original counterparts.

The new Quad II Classic Integrated  Amplifier is perfectly balanced and completely integrated amplifier system to resolve system matching and offer exceptional performance nd value within a relatively compact and classically styled chassis.

Performance as you would expect from one of the most famous names in hi-fi, is nothing short of breattaking. The 25 watt per channel specified, belies their power and ability to drive even the most difficult loads. The remarkable output transformer design is characterized through its speed, agility and ability to convey the genuine passion of live performnce.

Design and Engineering

The KT-66 output valves, in push-pull configuration are visually stunning, even when safely secured within the cage tht protects them. Each valve produces around 25 watts per channel output in "Pure ClassA" which allows a suebrbly refined sound that appropriately matches modern as well as contemporary loudspeakers.

The package had to retainn the retro look of it famous preamplifier predecessor with th epower amplifier and transformers blended into a modern compact look. It has an understated elegance which lies beneath its smooth curves and lustrous finish because it uses a circuit dating back over fifty years to the time when vacumm tubes ruled the electronics industry and peter Walker was considered by many to be the master of audiophile design.

All Quad products are expected to last a lifetime - even longer. Many Quad customers still derive immense pleasure listening to products built over fifty years ago. The new Quad II Classic Integrated Amplifier is no exception, and with periodic servicing and a caring hand, you can expect its performance to continue for decades to come.

The Quad II Classic Integrated Amplifier operates in Pure Pentode (Beam Tetrode) output with partial cathode loading, this being more linear than so called ultralinear. It is a pure Class A operation, whereas its push pull operation's efficiency can only rach 50% max and its power supply is the usual capacitor filter with diode bridge rectifier, AC 6,3 volts heaters to the valves that is shared between both channels.

Equipped with a bi polar transistor phono amplifier that uses 4 transistors per channel with low feedback to provide correct RIAA equalisation. Also has a gain switch for moving coil caartridges, 0,25 mV at 1 kHz , a circuit which operates from a regulated 36 V derived directly from th emain HT valve. It ensures a very high overload performance from rcords.

The phono circuit is housed in a shielded compartment providing low noise RF proofing within th emain package.

Amplification Process

The Quad II Classic Integrated Amplifier output is 25 watt per channel  Integrated Amplifier had to obey Peter Walker's Philosophy  of cathode loading of the output stage and simplicity of design.

Upon Input, a selector switch routes the required signal to the volume control then on the first of 3 small driver valves. This first valve is an ECC83 acting as a differential balance circuit that is a phase slitter.

The output going into a pair of ECC88 valves that both operate as a cascode circuit for high gain and wide bandwidth directly drives the output valves (KT 66) via capacitors.

The circuit had to have high gain than a normal power amplifier to offer a nominal 250 mV input sensitivity on the various inputs.

Push pull feedback is arranged from the cathodes of the output back to the ECC88 valves to provide low distortion and noise with consistent performance.

Specificastions

Stereo Power Output:  25 W per channel into 8 Ω

Total Harmonic Distortion:  0,06% (at 15W &700 kHz )

Signal-to-Noise ratio:  better than -95 dB (ref 25 W into 8 Ω)

Frequency Response:  20 Hz - 20 kHz +0 dB -0,5 dB

Crosstalk: better than 75 dB

Gain :  34 dB

Noise:  -98 dB (275 mV input)

Valve Type:  4 x KT66; 4 x ECC88; 2 x ECC83

Input Channel:  3 x Line Level; 1 x MM/MC Phono and Tape monitor

Dimensions (W x H x D):  200 x 310 x 380 mm

I like

Quad FM4

 At the touch of button the Quad FM4 gives access to a variety, breadth and quality of programme material that the most dedicated gramophile would find difficult to equal. Indeed the emotional satisfaction which can be gained froma well engineered live broadcast is second only to being at the concert itself. A FM tuner is thus an essential piece of equipment for any serious listener to music. The FM4, as one might expect from Quad is deceptively simple and original. Good ergonomics and advanced electronics are combined to procedure a tuner with exceptional audio performance and ease of handling.

The Quad FM4 is designed as an adjunct to a high quality music system.  As such emphasis in design is placed upon obtaining audio performance from a reasonable input signal rather than the ultimate in selectivity.  Performance of the Fm4 is such that given adequate signal strength,  it makes no audible contribution to the incoming programme, and provides absolutely faithful reproduction of the original transmission.

The only controls on the FM4 are an on/off switch, tuning knob and eight pushbuttons which are used to store and recall stations in the tuner's memory. The tuned frequency is shown in figures and an ingenious bar graph display provides simultaneous information of signal strength and centre tuning. A specially developed dedicated imcroprocessor makes all decisions about muting and AFC and also controls the tuner's memory in which are stored the  preset stations.

 Operating the Quad FM4 issimplicity itself. Once programmed it is only necessary to press one of the seven preset buttons for the wanted station to be tuned in perfectly.

Programming stations into the tuner's memory is very straightforward. The desired frequency is located by rotating the tuning knob, which will have conspicuous advantages for anybody who has tried to find a station using pushbuttons to track up and down. The bar graph confirms that the station is correctly tuned and being received with sufficient signal strength to give acceptable signal to noise.

AFC and muting is taken care of automatically. Stereo over-ride, required if the signal is very weak, is achieved by switching the Quad 44 to MON and adjusting the balance control for minimum noise.

Programmes will remain stored in the tuner 's memory almost indefinitely provided that the tuner is used once in a awhile, and for up to five years even if it is disconnected from the mains.

When switched on the tuner remembers the station last used and automatically reverts to it.

Specifications

Frequency Range:  88 - 108 MHz

Sensitivity

-30  dB Quieting  [mono] :  1 µV 

50 dB Quieting [mono/stereo] :  2,7 µV / 25 µV

Full Limiting:  less than 1 µV

Signal-to-Noise Ratio (Input signal 1 kHz at 1 mV, A weighted):

Mono :  76 dB

Stereo :  70 dB

Distortion Input Signal (1 kHz):

±75 kHz [mono/stsreo] :  0-15%/0-15%

±25 kHz [mono/stsreo] :  0-05%/0-10%

Selectivity:  53 dB

Capture Ratio: 2-5 dB

IF Rejection:  100 dB

AM Suppression:  60 dB

Image Rejection:  80 dB

Pilot Tone Suppression:  60 dB

Crosstalk at 1 kHz:  40 dB

Frequency Response:  20 - 15 kHz :  +0 -1 dB

Output Level 30 % Modulation:  100 mV recommended load Impedance

Source Indepedance:  100 Ω

Recommended Load Impedance:  more than 20 k Ω

Aerial Input:  75 Ω unbalanced

De-emphasis:  50 µSec or 75 µsec)

Power Input:  100-125 or 200-250 50/60 Hz  6VA

Dimensions:  (W x H x D):  321 x 64 x 207 mm

Weight:  3 kg

Quad 34

 The Quad 34 provides the serious music listener with ererything necessary for thr full enjoyment of music from radio, disc, tape and compact disc and continues a process of evolution which began more than thirty years ago with the original Quad control unit.

Inputs are selected by bushbutton controlled solid state switches and all inputs are fully isolated so that one can switch from one to the other without turning down the volume control or switching off unwanted sources.

 Filters, selected by pushbutton, provide optimum characteristics to remove distortions inherent in the record playing system and leave more of the music.

The Tilt control changes the programme balance to compensate for the difference between the reverbration of the actual listening room and the recording engineer's concepts. The tilt control is a highly sophisticated eight pole filter that is smooth in operation with no abrupt changes of response and no unwanted colouration.

The Bass control fulfils one of two functions: as an equaliser for use with small loudspeakers in the lift mode when it provides smooth progressive bass boost to compensate for the low frequency roll-off of small enclosures, and as correction for low frequency exaggeration due to floor or corner placement, in the step mode.

 In short, the Quad 34 provides correct input matching and compensation for programme  and room effects with excellent ergonomics, everything necessary to obtain enjoyment from the widest possible variety of programme. The Quad 34 also incorporates those intangibles which existing Quad owners take for granted but can come as something of a pleasant surprise to those who have not dealt with a serious but friendly and helpful manufacturer before, intangibles which make ownership of Quad a pleasure which improves with time.

Specifications

Distortion:    Worst case, any inputs .05%

Residual Noise:  "A" weighting (Volume control at minimum -105 dB)

Frequency Response:  Any input except Disc, any output ±0,3 dB. Disc RIAA ±0,5 dB

Outputs [level / Impedance]:

Power Amplifier :  0,5V / 830 Ω

Tape Recorder :  100 mV / 2,2 k Ω

Inputs [Sensitivity / Impedance]

Disc 1 :  3 mV / 47 k Ω (220 pF)

Disc 2 :  100 µV /100 Ω (22 pF)

Radio, Aux ;  100 mV / 100 k Ω

Tape Replay :  300 mV / 120 k Ω

Maximum Input at 1 kHz:

Disc 1 :  150 mV

Disc 2 :  5 mV

Radio & Aux :  5 V

Tape replay :  15 V

Signal-to-Noise Ratio:

Disc 1 :  -75 dB

Disc 2 :  -68 dB

Radio,Aux :  -88 dB

Tape Recorder : _87 db

Interchannel Balance:  ±0,5 dB with Volume control varied from max. to -60 dB

AC Input:  100 - 130 V or 200 - 250 V 50/60 Hz

Power Consumption:  4,5 VA

Dimensions (W x H x D):  321 x 64 x 207 mm

Weight:  3,2 kg

Quad 306

 The Quad 306 is a two channel power amplifier primarily intended for use in high quality sound reproducing systems. The amplifier is usually used wit a Quad control unit though other signal sources can readily be accommodated.

The amplifier uses a current dumping output circuit  a Quad invention which eliminates many of the problems associated with transistor amplifiers, and covered by patents in several countries. In a current dumping amplifier there is in effect both a low powered very high quality amplifier and a high powered heavy duty amplifier. The low power amplifier controls the the loudspeakers at all times, calling upon the high power section to provide most of the muscle. The small amplifier is so arranged - it carries an error signal - that provided the larger power transistors (the dumpers) get within the trget area of the required output current it will fill in the remainder accurately and completely. The reproduced quality is solely dependent on the small amplifier which because of its low power can be made very good indeed.

Problems of crossover, crossover distortion, quiescent current adjustment, thermal tracking, transistor matching, all disappear. There are no internal adjustments or alignments and the choice of power transistor types is less restrictive.

 Amplifier protection

The amplifier is protected by a resettable trip which interrupts the incoming AC supply if the amplifier is grossly overdriven for a period of time. To restore operation simply press the red reset button on the back panel. The amplifier is thus fully protected against gross overload, short-circuited output etc. But not necessarily against seriously inadequate ventilation.

Input Connections

Signal input is via phono sockets, clearly marked L and R. if the amplifier is used with a Quad 33/34/44 control unit with a DIN output socket, you wiull need a 4-pin-DIN-to-2-phono-plugs load.

Loudspeakers Connections

The Quad 306 is fitted with standard 4 mm sockets and two red and black plugs are packed with the unit. The amplifier is unconditionally stable and may be used with any type of speaker cable.

The Quad 306 is entirely compatible with the ESL-63 loudspeaker but should not be used with the earlier model which could easily be damaged.

Specifications

Power Output:  50 watts per channel at 8 ohms

Distortion (continuous sine wave  into 8 Ω resistive load):

20 Hz (any level up to 50 watts) :  less than 0,01%

1 kHz (any level up to 50 watts) :  less than 0,01%

20 kHz (any level up to 50 watts) :  less than 0,03%

Output Internal

Inpedance and offset:  1,5 µH in series with 0,05 Ω . Offset tipically 7 mV

Frequency Response: 

-0,25 dB at 20 Hz to 20 kHz

-1,0 dB at 13 Hz to 40 kHz

Power Response:  -0,25 dB at 20 Hz to 20 kHz

Signal Input Level:  0,375 volts for 50 watts into 8 Ω

Signal Input Overload:  Instantaneous recovery  up to 15 dB overload

Crosstalk (input loaded by 1 k Ω):

100 dB at 100 Hz

85 dB at 1 kHz

65 dB at 10 kHz

Hum and Noise:  -105 dB (unweighted)

Stereo Separation:  85 dB at 1 kHz

AC Input:  110 - 120 V;  220 - 240 V,

Power Consumption:  30  - 250 watts, depending on signal level

Dimensions (W x H x D):  321 x 64 x 207 mm

Quad ESL-63

 "The Quad ESL-63 sets new standards in three important areas of loudspeaker technology, low distortion, low colouration and controlled directivity, resulting in a a level of performance limited solely by the quality of programme source.

With Quad Esl-63's and  a CD player less than 0,1% THD intrudes between the listener and the studio master tape, reproducing exactly what was recorded, nothing added, nothing taken away and bringing the listener that much closer to the original sound."

From Quad Advert

 An electrostatic loudspeaker consists of light thin membrane on which is placed a charge, suspended between two acoustically transparent, (i.e. with holes), electrodes. When asignal is fed to the electrodes a field is generated between them and the charged diaphragm complled to move by an electrostatic force. Reversing the polarity of the signal on the electrodes causes the diaphragm to move in the opposite direction and thus sound pressure is generated.

The electrostatic loudspeaker has several inherent advantages. Since the diaphragm is driven over its whole surface it does not ned to be stiff and can be made extremely light and thus have negligible stored energy. Because of the good impedance match with the air it is not necessary to load the loudspeaker into a box and the problems associated with cabinet resonance disappear. Designing and manufacturing electrostatic loudspeakers is by no means easy but the potential is there for a higher degree of performance than with conventional loudspeakers.

An ideal loudspeaker would consist of a single point source reproducing all frequencies. The Quad ESL-63 uses the electrostatic principle to achieve just this. 

 Imagine a theoretically ideal point source loudspeaker radiating sound pressure waves and a plane in the air a short distance from the source at right angles to the direction of propagation. Were we able to make the air at the plane visible we should see concentric waves radiating out from the centre, as if we had just thrown a stone into a still pool.

If we replace the plane with a very light membrane, induce it to reproduce the air particle motion already observed and suppress the original source, the results to a listener on the far side are absolutely indistinguishable from those of the ideal source.

The Quad ESL-63 does exactly this.

It consist of a diaphragm suspended between two sets of concentric annular electrodes. Signal is fed to the electrodes via sequential delay lines and the diaphragm motion produces a sound pressure pattern which is an exact replica of that from an ideal source placed some 30 cms behind the plane of the diaphragm. The ESL-63 is a totally homogeneous sound source, phase true and very aperiodic with a frequency response both on and off axis quiete free from the irregularities which are inevitable with any multiway loudspeaker system.

The designer has complete control over the directivity of the loudspeaker and by increasing the directivity index smoothly with increasing frequency, optimum stereo performance is achieved.

The Quad ESL-63 is a dipole which has significant benefits in terms of room placement and stereo perception. With a sound dispersion pattern which resembles a figure of eight, a dipole radiates no energy in the plane of its diaphragm and does not excite room modes whose axes lie in this plane.

The nett result is a loudspeaker of unsurpassed accuracy which given the right programme material will produce a more realistic and satisfactory illusion of a live musical performance than has previously been possible.

Development of the Quad ESL-63 has taken many years. Much of the time has been spent in investgating and experimenting with new materials and production techniques, the result of which has been that variations due to manufacturing tolerances have been virtually eliminated, sample variation being to within less than ±½ dB and stability of the materials used is such that the performance will be maintained for the loudspeaker's useful life without the need for regular maintenance.

The impedance characteristic of the lodspeaker is nominally 8Ω and largely resistive, presenting no problems at all to the amplifier, but amplifiers which are not short circuit protrcted must not be used with this loudspeaker.  The amplifier should have an output capabilty of 40 V peak (100 watts into 8Ω). Amplifiers with output capability of up to 55V peak (190 watts into 8Ω) can be used, but to no advantage.

The loudspeaker is fitted with two protection circuits, one which limits the maximum input voltage fed to the loudspeaker and the other which detects fault conditions and instantaneously shorts the signal being fed to the loudspeaker. It is impossible to damage the loudspeaker elements, but the input voltage limiter has limited thermal capacity and persistent overdrive will overhear it.

Specification

Impedance:  8 ohms nominal

Sensitivity:  1.5 µbars per volt referred to 1m. (i.e. 86dB/2.83V rms) 

Maximum Input: 

Continuous input voltage : 10 V rms;

Programme peak for undistorted output : 40 V;

Permitted peak input : 55 V

Maximum Output:  2 N/m² at 2m on Axis

Directivity Index:

125 Hz : 5.0 dB

500 Hz : 6.4 dB

2 kHz : 7.2 dB

8 kHz : 10.6 dB

Axis Band limits:  -6 dB at 3 Hz 3rd order

(Low Level) :  -6dB > 20kHz

Power Supply:  AC 240/200V 120/100V, 50/60Hz, 5 VA

Dimensions:

Height : 925 mm

Width : 660 mm

Depth : 270 mm including 150 mm base

Weight Net:  18.7 kgs

Gross:  23 kgs

QUAD 33 (1969)

The external design continues the Quad tradition of practical simplicity, which has won prizes and worldwide acclaim. The internal appearance is unmistakably Quad and reflects cocnern with quality of manufacture and ease of service.

The Quad 33 select and controls the radio tuners, gramophone pickup and tape recorder connected to it and feeds the loudspeakers via the power amplifier, providing for stereo or mono on either or both channels, from all inputs, plus monitoring and track selection facilites for tape.

Quad units may be used either free-standing or mounted in a cabinet, with plenty of scope for individual preference in layout design.

The standard Quad system of mounting is used, requiring only a rectangular cut-out for whiche a template is provided.

Controls

The controls are comprehensive but simple and are logically grouped to facilitate selection and control of the programme.

Filters

The filter is essential with modern good quality speakers and helpful at any time. It removes surface noise, tracing distortion and similar shortcomings in the upper frequency range of the recording or broadcast, and the two control filter system achieves this to a very fine degree without intruding unnecessarily into the harmonic range so essential for realistic reproduction.

Another fixed, built-in filter cuts out (without affecting the normal low frequency response of the equipment) unwanted signals at frequencies below 20 Hz, due to mechanical causes in motors and turntable mechanisms.

Bass and treble

Entirely separate from the filters are the bass and treble controls which provide independent adjustment of tonal balance when required. This operations is symmetrical and smooth without any unpleasant 'steps' in the response.

Every pickup correctly matched

To change the pickup matching merely remove the Disc Adaptor and plug it in again with another edge leading; four matching circuits on one board with provision to accomodate any future development in pickup design simply by changing the board. The input load is purely resistive over the entire audio bandwidth.

Tape

Any signal passing through the Quad 33 may be recorded without affecting normal reproduction on monitored off the tape (AB monitoring) as desired. The plug-in tape adaptor carries independent pre-set adjustments of signal level for both recording and replay on each channel, to suit the tape recorder in use. Again since this is a plug-in board, any future or special requirements can be met merely by replacing the board, thus adding further to the versatility of the Quad 33.

The Quad 33 control unit is designed to give maximum flexibility to the whole audio system combined with ease of operation. The unit features a simple and novel method of matching pick-up inputs, using a square printed circuit adapter board: each side of the board carries one circuit which can be plugged into the rear of the unit, so that the four sides offer four alternative circuits; tape recorder inputs are matched with a similar plug-in board. The controls are arranged in logical sequence suiting the importance of their function. While it is possible to adjust and correct for every eventuality required by the avid enthusiast, the design is such that once the minor controls are correctly set,

day by day operation becomes extremely simple. Two switched mains outlets at the rear of the unit supply the amplifier and radio tuner.

Specifications

Distortion: All controls level, 0.5V rms output, with any input 0.2%; any control settings and any level within overload ratings <0.1%; both at 30 - 10 kHz

Residual Noise: 0 - 30 phon weighting 15.7 kHz bandwidth: <-90 dB controls level or cancel

Frequency Response: Any input, any output, RIAA or flat as appropriate: ±0.5 dB, 30 Hz - 20 kHz

Tone Controls: ±1 dB of curves shown opposite

Filters: To curves shown opposite at 5 kHz, 7 kHz and 10 kHz ±5%

Interchannel Balance: Within 1 dB with volume control varied from maximum to -45 dB

Balance Control Range: 9 dB either way

Crosstalk: Dependent on input sourec impedences. Replay/record typically better than 70 dB; interchannel typically better than 40 dB: both at 30 Hz - 10 kHz

Power input: 100 - 130 or 200 - 260 V, 50/60 Hz, 1.5 watts

Dimensions: Width 260 mm, Height 92 mmfree-standing, 83 mm panel only. Depth 165 mm free-standing, 140 mm behind cabinet panel when mounted.

Weight: 3 kg

QUAD 303 (1969)

The Quad 303 power amplifier is intended for normal domestic use with loudspeakers of moderate efficiency, but is also used by broadcasting and recording studios, groups and discotheques world wide, who appreciate its excellent performance and dependability.

The outstanding performance of the Quad 303 is largely due to the unique output circuit developed by Quad.

The Quad 303 is normally used with the Quad control unit, but can readily accommodate other signal sources. Since it has no controls it can be mounted out of sight in a well ventilated cabinet.

The amplifier won a Council of Industrial Design Award in 1969

The circuit employs symmetrical triples, greatly reducing distortion and rendering the quiescent current independent of output transistor temperature.

This development enables the designers to reduce distortion to any desired degree without sacrificing stability, and to maintain this excellence under all dynamic conditions.

To put this in perspective, the lowest theoretical distortion present on the very best tape and disc will still be some hundred times greater than that of the Quad 303.

Such a level is, of course, completaly inaudible no matter how refined the test.

The use of triples, permits simple and effective control of the output current and since the voltage is also controlled, the output transistors are completely protected and must always operate within their ratings with the obvious advantages of greatly improved reliability under all conditions, without the use of elaborate and expensive circuitry.

The amplifier cannot be upset even when overdriven by an asymmetrical signal or by shorting or disconnecting the loudspeakers.

The chassis and covers of the Quad equipment are in die cast aluminium and sheet steel finished in stove-enamelled

metallic beige and brown with off-white and marigold push buttons and control panels. The control unit, top left, and

the tuner, lower left, can be positioned together or separately. The amplifier, above, has no controls, and can

therefore be housed out of sight in a cabinet or cupboard, heat dissipation being greatly assisted by the aluminium

fins at the rear.

Specifications

Power Output:

The amplifier is intended for use with loudspeakers of 4 - 16 Ω nominal impedance.

Poweroutput and distortion for various frequencies.

Continuos sine wave into 8Ω resistive load.

100 Hz any level up to 45 watts<0.03% Dtot

1 kHz any level up to 45 watts <0.03% Dtot

10 kHz any level up to 45 watts <0.1% Dtot

Output Internal Impedance: 0.3Ω in series with 2000μF and 6μF

Frequency Response: Ref. 1 kHz -1dB at 30 Hz and 35 kHz into 8Ω

Signal Input Level: 0.5V rms ±0.5 dB for 45 watts into 8Ω.

Amplifier loads the input by 22kΩ in parallel with 60 pF

Signal Input Overload: Instantaneous recovery up to +20 dB overload.

Crosstalk (input loaded by 1 kΩ): 30 Hz - 10 kHz > 60 dB

Hum and Noise (input loaded by 1 kΩ): "A" weighted -100 dB ref full power. Unweighted (15.7 kHz measurement bandwidth) -95 dB ref full power

Protection: This amplifier is suitable for use under the most arduous music conditions with speakers of impedances between 4 and 25Ω and for high level sine wave duty with loads of 8Ω or greater.

Stability: Unconditionally stable with any load

Power Input: 100-125 or 200-250 V, 50/60 Hz, 40-200 watts depending on signal level.

Dimensions: 120 x 159 x 324 mm (W x H x D)

Weight: 8,2 kg