Aiwa AS-S30 amplifier

Stereo Integrated Amplifier

Fifteen big Watts per channel of honest-to-goodness high fidelity sound from a 2-stage differential SEEP-OCL integrated amplifier an incredibly compact 7,1 cm high by 21 cm wide. Yet, the A30 has plenty of room to accommodate up to 4 external components including tape, deck, tuner and record turntable.

Power output has been boosted by use of a new extra-stable power transformer with independent coils for power and preamplifier sections, and enlarged heat sinks aid in efficient heat dissipation.

For low noise and dynamic performance from high quality MM phono cartridges, the improved phono equalizer IC has boosted Signal-to-Noise Ratio to an excellent 82 dB, with very low 0,005% distortion at 1 kHz. RIAA equalization is a remarkably precise ±0,2 dB throughout the 20 to 20,000 Hz frequency range. For well-balanced listening at low output volumes a switchable loudness compensation circuit is provided.

 

 

Plus features:

5-LED logarithmic peak output indicator [0,1 - 40 watts]

AUX component terminals

Stereo headphone jack

Power On LED indicator

Bass, treble, balance controls

Quick one-touch speaker connection terminals

Rack handles included

 

Specifications

Type:  Stereo integrated amplifier

Semiconductors:  5 ICs; 5 Transistors; 12 Diodes, 6 LEDs

Power Amp Section

Effective Output Power:  20 W + 20 W (8 Ω ) U model

15 Watts per channel , Min. RMS at 8 Ω , from 20 Hz - 20 kHz, with no more than 1% T.H.D.

Tdh :  0,1% (1 kHz, 5 W + 5 W) U model

Total Harmonic Distortion from 20 to 20 kHz at 250 mW to 15 W power at 8 Ω  , 1 % Max

Output Bandwidth:  10 Hz to 20,000 Hz (less than1%)both channel driven, 8 Ω

Frequency Response:  20 to 20,000 Hz

Pre-Amp Section

Signal-to-Noise Ratio (IHF A curve, short circuit, Weighted):

Phono :  better than 76 dB

Tuner, Aux :  better than 90 dB

Tone Controls

Bass :  ±10 dB at 100 Hz

Treble :  ±8 dB at 10 kHz

Loudness:

6,5 dB at 100 Hz (±1,5 dB)

3,5 dB at 10 kHz (±1,5 dB)

RIAA Deviation: ±0,2 dB (20 Hz - 20,000 Hz)

Channel Separation: better than 40 dB

Phono Overload Level:  better than 100 mV (MM, at 1 kHz)

Channel Balance:  less than 3 dB

Residual Noise:  less than 2 mV

Input Sensitivity/Impedance:

Phono :  2,5 mV/47 k Ω

Tuner :  150 mV/47 k Ω

Aux :  150 mV/47 k Ω

Tape :  150 mV/47 k Ω

Output Level/Impedance:

Tape :  120 mV/47 k Ω

Headphones Load Impedance :  8 to 16 Ω

Speakers Impedance :  8 to 16 Ω

Power Requirements:  AC 110 / 220 / 240 V, 50/60 Hz

Power Consumption:  40 W

Dimensions (W x H x D):  210 x 71 x 200 mm (8-1/4" x 2-3/4" x 7-7/8")

Weight:  3,15 kg (6,9 lbs)

 

Denon PMA-770 amplifier

Zero Dynamic Distortion

A Non-negative feedback amplifier design is ideal for driving speakers properly. Since audio signals are amplified in one direction only, the primary causes of dynamic distortion, such as time delay, are eliminated. Static distortion, which is caused by the non-linear amplification characteristics of amplifying components such as transistors, is reduced to almost theoretical limits by Denon's Distortion Servo Circuit.

Because of Denon's Non-Negative feedback technology and Distortion Servo-Circuit, the dynamic or pulsive music signals (those that change every moment in level and frequency) can be driven at high power through the widest variety of loudspeakers with surprising clarity and resolution.

The circuit is made up of 3 stages of low noise FET differential amplifiers. In the first stage current mirrors operate as the voltage amplification stage. The complementary emitter follower permits low impedance to be obtained; and is separated completely from the current amplification stage. The current amplification stage, a push-pull output configuration uses high quality, high speed power transistors, providing the speed and accuracy required for accurate reproduction of the original signal.

 

High Efficiency "Direct-A"  Power Amplifier

At the output stage, the Denon developed "Zero-Cross Linear Bias Circuit" eliminates switching distortion caused by the turning On and Off of the power transistors. This circuit enables the PMA-770 to combine both the sound quality of Class A with the high efficiency associated with Class B amplification.

 

Clean Layout and Simple Circuit Construction

The basic construction of the PMA-770 circuit has purposely been kept clean and simple as possible. The entire signal route is totally capacitorless. Even when using MC cartridges, the PMA-770 does not place a single capacitor in the main signal route, all the way from the input to the speaker output. This design speeds up while maintaining the purity of the signal and is what Denon describes as totally "DC construction"

The amplification circuit is of the dual FET differential type, resulting in greatly improved Signal-to-Noise Ratio and reduced distortion. Additionally, the employment of Denon's Direct DC Servo Circuit shut out DC drifts and stabilizes the ultra-low frequencies.

 

Specifications

Power Amplifier Section

Circuit Type:  All stage direct DC servo circuit

Rated Output Power (Both Channel Drive)

100 W + 100 W at 20 Hz to 20 kHz 8 0hm load (DIN, U.K. Europe, USA)

150 W + 150 W at 1 kHz , 4 Ω  load (DIN, U.K. USA)

50 W + 50 W at 1 kHz, 4 Ω  Load (IEC)

Total Harmonic Distortion :

0,008% (20 Hz - 20 kHz at -3 dB rated output 8 Ω  Load)

0,02% (20 Hz - 20 kHz at rated output 8 Ω  Load )

Intermodulation DIstortion :  0,002% below 7 kHz/ 60 Hz : 1/4 (at amplitude output equivalent to rated output)

Output Bandwidth:  5 Hz - 100 kHz (IHF T.H.D. 0,035%)

Transmission Characteristics:  1 Hz - 250 kHz +0 dB -3 dB (at 1 W output)

Input Sensitivity:  150 mV

Input Impedance:  47 k Ω

Output Impedance:  0,08 Ω  (1 kHz)

Output Terminals: 

Speaker A and B Load 4 - 16 Ω or A + B Load 8 - 16 Ω

Headphone/Stereo headphone

Equalizer Amplifier Section

Max. Output:  10 V (at 47 k Ω  load)

Rated Output :  150 mV

Total Harmonic Wave Distortion :  below 0,002% (at 1 kHz, 8 V output)

Input Sensitivity/Impedance

Phono MM :   2,5 mV/47 k Ω

Phono MC :  125 µV/100 Ω

Tuner :  150 mV/47 k Ω

Aux, Tape :  150 mV/47 k Ω

RIAA Deviation:

Phono MM :  within ±0,2 dB (20 Hz - 100 kHz)

Phono MC :  within ±0,2 dB (20 Hz - 100 kHz)

Overall Characteristics

Signal-to-Noise Ratio (IHF A network)

Phono MM 1, 2 :  90 dB (input terminals short-circuited for 2,5 mV input)

Phono MC :  73 dB (input terminals short-circuited for 250 mV input)

Tuner, Tape, Aux :  110 dB (input terminals short-circuited)

Tone Control Adjustable Range

Bass :  ±8 dB at 100 Hz

Treble :  ±8 dB at 10 kHz

Subsonics:  18 Hz at 6 dB/oct

Loudness

Low Frequency :  +7 dB at 100 Hz

High Frequency :  +6 dB at 10 kHz

AC Outlet:  switched x 2 100W Total, unswitched x 1 250 W

Power Requirements:  AC 120 V, 200 V, 220 V, 240 V 50/60 Hz

Power Consumption:270 W (USA); 400 W (IEC); 290 W (Hong Kong); 800 W Maximum Output

Dimensions (W x H x D):  434 x 132 x 407 mm

Weight:  12 kg

 

Denon PMA-750 amplifier

Integrated Amplifier Features:

Non-NFB (Non-Negative Feedback) Amplifier, Zero Dynamic Distortion (Patent Pending)

Super Equalizer; Super Wide RIAA Deviation 20 Hz - 100 kHz ±0,2 dB (Patent Pending)

High Power Direct-A Amplifier 80 W + 80 W

Real Drive Circuit: Significantly Reduces Distortion Under Real Operating Conditions - When Driving Speakers

Clean Simple Circuit Design Combined wirh High Quality Construction

Real-Time Tone Control

Dual Speakers Output Terminals (A or B, A+B)

Dual Input/Output Terminals for Interconnection with Two Tape Decks

A Defeatable Subsonic Filter (18 Hz, 6 dB/oct) Eliminates Unneeded Ultra Low Frequency Noise

Direct Coupling Switch Removes Tone Controls from The main Circuit

Mode Switch with Facilities for Stereo Reverse and Monaural Reproduction

Loudness Control Switch

High Speed Protection Circuity

 

Principle of the Non-Negative Feedback Amplifier

The fundamental block diagram is shown as under. At first, input signal e, and inversed output signal e, are mixed at the input of the direct DS. amplifier. Then, the distortion component d is extracted. This d is amplified by the direct DS. amplifier and is inversed and fed into the main amplifier A, with the original signal e, Thus distortion is finally reduced dramatically and static distortion is brought to zero.

 

Specifications

Power Amplifier Section

Circuit Type:  All stage direct DC servo circuit

Rated Output Power (Both Channel Drive)

80 W + 80 W at 20 Hz to 20 kHz 8 0hm load (DIN, U.K. Europe, USA)

100 W + 100 W at 1 kHz , 4 Ω  load (DIN, U.K. USA)

50 W + 50 W at 1 kHz, 4 Ω  Load (IEC)

Total Harmonic Distortion :

0,008% (20 Hz - 20 kHz at -3 dB rated output 8 Ω  Load)

0,02% (20 Hz - 20 kHz at rated output 8 Ω  Load )

Intermodulation DIstortion :  0,002% below 7 kHz/ 60 Hz : 1/4 (at amplitude output equivalent to rated output)

Output Bandwidth:  5 Hz - 100 kHz (IHF T.H.D. 0,035%)

Transmission Characteristics:  1 Hz - 250 kHz =0 dB -3 dB (at 1 W output)

Input Sensitivity:  150 mV

Input Impedance:  47 k Ω

Output Impedance:  0,08 Ω  (1 kHz)

Output Terminals: 

Speaker A and B Load 4 - 16 Ω or A + B Load 8 - 16 Ω

Headphone/Stereo headphone

Equalizer Amplifier Section

Max. Output:  10 V (at 47 k Ω  load)

Rated Output :  150 mV

Total Harmonic Wave Distortion :  below 0,002% (at 1 kHz, 8 V output)

Input Sensitivity/Impedance

Phono MM :   2,5 mV/47 k Ω

Phono MC :  125 µV/100 Ω

Tuner :  150 mV/47 k Ω

Aux, Tape :  150 mV/47 k Ω

RIAA Deviation:

Phono MM :  within ±0,2 dB (20 Hz - 100 kHz)

Phono MC :  within ±0,2 dB (20 Hz - 100 kHz)

Overall Characteristics

Signal-to-Noise Ratio (IHF A network)

Phono MM :  88 dB (input terminals short-circuited for 2,5 mV input)

Phono MC :  72 dB (input terminals short-circuited for 250 mV input)

Tuner, Tape, Aux :  110 dB (input terminals short-circuited)

Tone Control Adjustable Range

Bass :  ±8 dB at 100 Hz

Treble :  ±8 dB at 10 kHz

Subsonics:  18 Hz at 6 dB/oct

Loudness

Low Frequency :  +7 dB at 100 Hz

High Frequency :  +6 dB at 10 kHz

AC Outlet:  switched x 2 100W Total, unswitched x 1 250 W

Power Requirements:  AC 120 V, 200 V, 220 V, 240 V 50/60 Hz

Power Consumption:230 W (USA); 400 W (IEC); 200 W (Hong Kong); 680 W Maximum Output

Dimensions (W x H x D):  434 x 132 x 407 mm

Weight:  12 kg

 

Unison Research P70 amplifier

Fully balanced dual mono valves amplifier in Push-Pull

Designing the P70 has required about one year of work. The very first prototype has been developed in 2006, and it immediately showed all the critical elements related with this kind of design. It took time to find all the electronic solutions that have lead to the current circuitry.

The P70 is now an amplifier capable of delivering more than 70 W per channel into a 6 Ω  load, with Total Harmonic Distortion lower than 0,2% over the whole audio band. Its performances are comparable to those of a good single ended amplifier.

 

Structure of P70

The amplifier is laid out in dual mono configuration. Both the amplifier stages and the power supply circuits are completely independent. The signal path in the amplifier is fully balanced from the input through the output. This means that the signal at the output terminals is balanced with respect to the amplifier ground.

The P70 has four line inputs. All of them can be balanced or unbalanced, an external switch allows the selection. The volume potentiometer is a four sections motorised Alps blue series potentiometer. The selection of the channel is performed by four high quality relè.

All the operations of the amplifier, included the safety functions, are controlled by a microprocessor to ensure maximum reliability and intuitive user interface.

The amplifier itself is constituted by an input stage featuring two double triodes ECC83 and one double triode ECC82, and a power stage with two KT88 per channel.

The output transformer has been custom designed by Unison Research and ensure a bandwidth of more than 30 kHz at full power.

 

The preamplifier is constituted by a double differential pair in an original configuration. The two differential stages are DC coupled and allow to reach the needed gain. They are followed by a couple of cathode followers, again DC coupled, which guarantee the low output impedance required. The power supply for the whole preamplifier stage has a very high voltage, around 600 V.

The input stage has a local feedback, characterised by different feedback factors for the bias component and the signal. The two different values are set keeping into account the different need for precision on the value of the bias and of the signal.

The importance of a stable controlled bias in the amplifier is due first of all to the choice of the DC coupling between the stages and also to the need to allow the same signal excursion along the paths of the balanced signal.

The circuit we have designed amplifiers signals up to 200 V p-p. conversely, the feedback factor affecting the signal has been kept to the lowest possible value.

 

Specifications

Power Output:  70 W +70 W RMS

Output Impedance:  6 Ω  (4 - 8 ohms)

Input Sensitivity:  500 mV

Input Impedance:  47 k Ω

Frequency Response:  10 Hz to 40,000 Hz (0,5 dB, 1 W)

Signal-to-Noise Ratio:  83 dB A

Total Harmonic Distortion :  0,3% (10 W)

Negative Feedback:  12 dB

Damping Factor:  8

CMRR:  59 dB

Power Requirements:  105 - 120 / 210 - 240 V , 50/60 Hz at rest 360 W

Dimensions (W x H x D):  460 x 450 x 200 mm

Weight:  35 kg

 

Toshiba SC-410 4-channel

4-channel QM Decoder/Amplifier S.C.-410

Decodes almost any type of encoded matrix 4-channel discs at four modes of 4-channel effect.

Decodes 4-channel programs from ordinary non-encoded discs into quasi-quadraphonic stereo sound

Built-in IC power amplifier for two sets of rear channel speaker systems

Connectable to any type of stereo amplifier furnishing DIN socket and PIN "pre out/in" jack

 

Specifications

Power Output:  30 W rms, 8 Ω , T.H.D. 0,8% (total)

Frequency Response:  20 - 40,000 Hz (exlude QM section)

Power Bandwidth:  20 - 40,000 Hz (exclude QM section)

Semiconductors: 

2 Transistors for AF amplifier

1 Diode for power Supply

2 ICs (TH-9015P's) for power output section

4 FET's and 4 Transistors for QM decoder

Controls:  Main volume, Sub volume, Selector (2-ch/4-ch/tape/aux), Power Off, Speaker A & B, QM effect (concert hall/studio/surround/stage), Hi-cut

Jack and Terminal:  DIN socket, Input/output jack, AC unswitched outlet, speaker terminal

Power Source:  AC 100/120/220/240 V 50/60 Hz

Dimensions (W x H x D):  300 x 115 x 385 mm (11-3/4" x 4-1/2" x 15")

Weight:  6 kg (13-1/4 lbs)

 

JVC AX-Z1010TN amplifier

Digital Pure-A. New possibilities for class-A

There's no doubt an amplifier operating in class-A mode provides lower distortion and cleaner sound than those in popular class-B or class-AB. Their inefficiency, however, makes class-A amplifiers require elaborate heat sinking, and still the amps waste much of their power in the form of heat. This results in inflated cost and relatively low power output. But to enjoy the dynamic sound of digital programs, you need a lot of power.

How to combine the low-distortion sound of class-A with efficiency and power demended by digital audio?

Enter the Digital Pure-A Type II

JVC has the solution - the Digital Pure-A Type II circuit featured in the Ax-Z1010TN "Digital" Integrated Amplifier. This ingenious design takes the advantage of the fact that digital signals can be stored in memory temporarily without changing their frequency response or phase response.

In the Digital Pure-A Type II, digital signals fed directly from digital equipment are split into two: the main signal and the "prediction" signal.

The main signal is sent to a time base processor where it's stored in memory for a fraction of a second before it goes to the D/A converter. The prediction signal is sent to the bias circuit to optimize bias applied to the power transistors depending on dynamics of the upcoming signal. What you get out of this is low-distortion class-A sound with high efficiency and high power.

The AX-Z1010TN is a "Digital" integrated amplifier incorporating a D/A converter system complete with the K2 interface, 8-times oversampling and quadruple D/A converters.

And the amp features a special design for analog programs too - Opt Super-A, another JVC exclusive combining low distortion and high efficiency.

 

Specifications

Circuitry

Preamplifier:  ICL, MC/MM equalizer with EL-FETs in its initial stage

Power Amplifier: "Digital Pure A Type II", "Dynamic Super-A" with Gm circuit

Output Power

105 watts per channel, min. RMS, both channels driven into 8 Ω  from 20 Hz to 20 kHz, with no more than 0,004% Total Harmonic Distortion (USA, Canada)

100 watts per channel, min. RMS, both channels driven into 8 Ω  at 1 kHz, with no more than 0,002% Total Harmonic Distortion (Europe, UK, Australia)

100 watts per channel, min. RMS, both channels driven into 8 Ω  at 1 kHz, with no more than 0,7% Total Harmonic Distortion DIN  (Europe, UK, Australia)

160 watts 1 kHz, 4 Ω , T.H.D. 0,7% DIN

Total Harmonic Distortion (USA, Canada)

CD IN to SP. OUT :  0,004% (20 Hz - 20 kHz, 8 Ω ) at 100 watts

Phono IN to SP. OUT (Volume -20 dB) :  0,009% (20 Hz - 20 kHz, 8 Ω ) at 100 watts

Total Harmonic Distortion (Europe, UK, Australia)

CD IN to SP. OUT :  0,004% (20 Hz - 20 kHz, 8 Ω ) at 90 watts

Phono IN to SP. OUT (Volume -20 dB) :  0,009% (20 Hz - 20 kHz, 8 Ω ) at 90 watts

Intermodulation DIstortion (USA, Canada)

CD IN to SP. OUT :  0,004% (60 Hz : 7 kHz = 4:1, 8 Ω ) at 100 watts

Intermodulation DIstortion (Europe, UK, Australia)

CD IN to SP. OUT :  0,004% (60 Hz : 7 kHz = 4:1, 8 Ω ) at 90 watts

Power Bandwidth

CD IN to SP OUT :  5 Hz - 60 kHz (IHF, 0,03%, 8 Ω  both channels driven)

Frequency Response:  5 Hz - 100 kHz +0 dB -3 dB (8 Ω )

Damping Factor:  200 (1 kHz, 8 Ω )

Input Sensitivity/Impedance

Phono MM :  4 mV/47 k Ω

Phono MC :  300 µV/470 Ω

CD, Line1, 2, 3, DAT 1, 2, Tape 1, 2 :  300 mV/30 k Ω

Signal-to-Noise Ratio )'66 IHF/DIN)

Phono MM :  89 dB / 73 dB

Phono MC :  71 dB

CD, Line1, 2, 3, DAT 1, 2, Tape 1, 2 :  112 dB / 73 dB

Signal-to-Noise Ratio )'78 IHF)

Phono MM :  82 dB (Rec Out)

Phono MC :  73 dB (Rec Out)

CD, Line1, 2, 3, DAT 1, 2, Tape 1, 2 :  86 dB / (Speaker Out)

Bass Control:  0 - +5 dB (50 Hz, Master Level -30 dB)

Recording Output

Output Level/Impedance : 

Analog :  300 mV/ 1 k Ω

Digital :  2,0 V/ 1 k Ω

Digital Input/Output

Digital 1 :  -23 - -14 dBm

Digital 2 :  0,5 Vp=p/75 Ω

DAT Rec :  0,5 Vp-p/75 Ω

DAT Play :  0,5 Vp-p/75 Ω

D/A Converter Section

Sampling Frequencies :  32 kHz; 44,1 kHz; 48 kHz (Auto Selection)

Total Harmonic Distortion (1 kHz):  98 dB

Signal-to-Noise Ratio :  107 dB

Equalizer

Phono Overload Capacity

Phono MM :  100 mV (1 kHz, 0,02% T.H.D.)

Phono MC :  7 mV (1 kHz, 0,03%, T.H.D.)

Phono RIAA deviation:  ±0,2 dB (20 Hz - 20 kHz)

Power Requirements:  AC 120 V , 60 Hz (USA) AC 110, 127, 220, 240 V , 50/60 Hz  (Other areas)

Power Consumption:  550 watts/ 720 VA (USA); 400 watts (other areas)

Dimwnsions (W x H x D):  435 x 173 x 459 mm (17-3/16" x 6-13/16" x 18-1/8")

Weight:  16,8 kg (38 lbs)

 

Sugden A28 amplifier

The Sugden A28 once again gives you the unsurpassed quality of pure Class "A"

This is how we regard the Sugden A28 amplifier. Based upon well proven Sugden output circuitry, we now bring you an Amplifier which is second to none in its sound reproducing quality.

Let's start with the input circuitry, accessed via easy to use phono plugs and sockets and selected by four simple push-on, push-off switches. On the disc input not only do we have the facility for an internal plug in Moving Coil Module (the A 28 CTHA) deriving its power from within the Amplifier, but also a brand new "series-shunt" disc Amplifier with precision RIAA equalization and two level gain adjustment. In fac, everything to suit the cartridge of your choice.

Next the Tuner, Auxiliary and Tape inputs. All these three have identical input impedances, allowing a wide range of ancillary equipment to be used without interface problems.

The Tape output signal can, of course be fed from any of the input signals. For those people with 3 head Tape Machines, the Tape button will allow immediate post tape recording/replay through the Amplifier, i.e. Tape Monitor.

 

No tone controls here to marr distortion figures, just volume and balance controls with simple but effective filter circuits for hiss and rumble attenuation. Don't forget the Mono Button. Still essential for much recorded material.

Observe the neat, unfussy and easy to clean case style. Front and rear sections are matt black extrusions, whilst the side and top plates are covered in grey textured "Nextel" paint, giving a very attractive two tone finish.

As to how it sounds, well the specification, amy give you some clue, but we believe you will be delighted at the clear transparent sound.

The very low harmonic distortion of a class "A" Amplifier gives fatigue free listening to please even the most discerning ear. All this and more. Sugden expertise brings you the "S.Q.C" circuitry to give an amazingly compact pure class "A" output stage with up to 35 watts in class "B" allowing all but the most inefficient loudspeakers to be driven. Backed by the Sugden workmanship for life guarantees, we are justifiably proud to present this high quality British product.

 

Features:

20 watts pure Class "A" per channel

Continuous reserve capability of 35 watts per channel

Budget price (top quality sound at a price you can afford)

With additional module, can be used with Moving Coil cartridge

Variable gain disc input

Very low distortion

New precision RIAA equalisation network

Built to Sugdens uncompromising standards

Carries Sugden workmanship "for life" guarantee

 

S.Q.C. is short for Switched quiescent Current

And its development gives new potential to the cless "A" amplifier. We at Sugden have always believed in the class "A" amplifier and , in fact, were the first company in the world to produce the all transistor class "A" amplifier in 1968. it was only the demand for more output power which forced us away from the 12 watt A21 pure class "A" amplifier into the higher power "AB" amplifiers, such as the A48 and the P51 in the majority of casses were music is played through reasonably efficient 8 Ω  loudspeakers, the average power used is probably not more that 3 to 4 watts with excursions to higher levels depending upon the dynamic rrange of the recorded material.

Also what is the point of burning off power when it is not required. This then is the philosophy around which the S.Q.C. circuit has evolved. The availability of high speed, low level, switching components enables us to control the "AB" circuit to its very best advantage.

The A28 operates continuously at a quiescent level of 10 watts in Class A, i.e. with a current in the output transistors of about 800 mA. By looking at the incoming signal level, after the potentiometer, we can determine whether the 10 watt output level will be exceeded and should this be the case increase the quiescent current level up to 1,2A or 20 watts. The current will stay at this level for as long as the heavy signal exists and also for a short time afterwards, before reverting back to the lower quiescent level. There is, however, a finite switching time of the S.Q.C. circuit, admittedly it is only about one millionth of a second, but under some very fast transient signal conditions there is just a possibility that if the switch sensing point is set at the same level as the quiescent current level, the Amplifier may slip momentarily into class "B" before reverting back to class "A". This is obviously unacceptable and in order to prevent it, we set the sensing a elactronics to switch at a level of 7 watts allowing a 3 watts reserve, giving time for the output stages to react to the increased demand.

Using this technique we can absolutely guarantee a full 20 watts in class "A" at all times.

The additional overhead level between 20 and 35 watts in class "B" allows for the wide dynamic range of some recorded material and since it is far into the linear range of the devices, there is little increase in distortion right up to 35 watts.

 

Specifications

Disc Input Magnetic

Sensitivity :  Internally Selectable to 1,7 mV or 3,5 mV for 35 watts into 8 Ω

Signal-to-Noise Ratio :  better than 65 dB unweighted

Frequency Response:  Equalised to within ±0,5 dB of RIAA characteristics 20 Hz to 20 kHz

Input Impedance:  47 k Ω  in parallel with approx. 50 pF

Overload :  margin better than 35 dB at all frequencies

Moving Coil Amplifier

Provision is made with the A28 to lift the A28-CTHA Moving Coil Amplifier Module.

Inputs sensitivities for this unit are 40 µV, 90 µV, 180 µV depending upon the internal sensitivity switch position in the Module and also in the main Amplifier.

This head amp. Uses a novel input circuitry which obviates the need for impedance matching.

Tuner, Aux, Tape Inputs:

Sensitivity :  100 mV into 180 k Ω  for 35 watts into 8 Ω

Tape output

Dependent upon input selected Typically 100 mV from disc Amplifier

Tape Monitor

Allows direct "AB" comparison from Tape Recorder on 3 head Machines

Filters

Low Filter:  is a rumble filter with attenuation of 18 dB /octave below 30 Hz

High Filter :  is a hiss filter with an attenuation of 18 dB/octave above 10 kHz

Mono Button:

Allows the incoming signal to be mixed and applied equally to both channels

Loudspeakers:

The Amplifier is suitable for any 8 to 16 Ω  loudspeaker - 4 Ω  speakers can be driven with reduced power output.

Connection is via 4 mm "banana" plugs

Headphones

Any headphones of 8 Ω  to 2 k Ω  impedance may be operated. Connection is by standard 1/4" stereo jack socket on the front panel. The loudspeakers are automatically muted when headphones are used.

Frequency Response:  20 Hz to 20 kHz ±1 dB referred to 1 kHz

Cross Talk (stereo):  better than -35 dB at all levels

Load Stability:  Unconditional

Damping Factor: better than 35 into 8 Ω

Power Output (Both Channel):

20 watts in Class "A" into 8 Ω

35 watts in Class "B" into 8 Ω

Distortion

Class "A" :  0,04 at 1 kHz (20 watts)

Class "B" :  0,06% at 1 kHz (35 watts)

Power Supplies:  Internally adjustable to 110, 120, 220, 230, and 240 V AC

Mains Supply Frequency:  48 / 60 Hz

Total Power Consumption:  220 watts

Auxiliary Power Output:  a 3 pin IEC socket with mating plug is provided. The output is switched live via the Amplifier power on switch. Max. Load from socket is 250 watts

Power ON Lamp:  indication that the Amplifier is operating is given by a light emitting diode on the front panel adjacent to the power on switch.

Dimensions (W x H x D):  400 x 88 x 267 mm

Weight:  6,5 kg

 

Harman/Kardon hk750 amplifier

The new hk750 is the logical extension of our widely acclaimed 700 Series High Technology Separates - a sophisticated integrated amplifier that produces 45 watts per channel into 8 Ω

As with the rest of the 700 Series, the 750 has been designed with low negative feedback to keep TIM and Total Harmonic Distortion well below audible levels.

The 750 also has features you might not expect on other comparable integrated amps. Like a 5 stage, fully discrete phono pre-amp section that's extremely fast and quiet. Plus a toroidal power supply that can easily handle two pairs of speakers while substantially reducing both hum and stray noise. Two tape copy/monitor positions are provided for dubbing and monitoring. And the 750 also features loudness control, subsonic and hi cut filters, as well as tone defeat.

The hk750 integrated amplifier is the pefect solution for the audiophile who wants the sophistication of our High Technology Separates with the simplicity and economy of an integrated amplifier.

 

Specifications:

RMS Power (20 - 20,000 Hz into 8 Ω , less than 0,03% T.H.D.) :  45 watts

Frequency Response (at rated output):  below 1 Hz - 150 kHz (-3 dB)

Intermodulation DIstortion :  0,05%

TIM Distortion (at rated output):  0,01%

Slew Rate/Power Amplifier:  60 Volts/µsec

Overall Negative Feedback:  25 dB

Hum and Noise (A Weighted):

Phono :  -88 dB

Aux :  -100 dB

Residual :  -100 dB

Phono Overload:  better than 150 mV

 

Kenwood KA-660D amplifier

Stereo Integrated Amplifier

Features:

Digital-ready power amplifier with excellent low-impedance drive capability

Dynamic Power Output (EIA) 2 x 165 W into 2 ohms

Ultra-short signal paths and circularised linear circuit layout to produce high-quality, high-definition sound especially for the UK market

Type monitor Source Direct position

Super Bass switch

Independent L/R channel volume control

MM/MC phono cartridge selector

Relay operated A/B speaker selectors with protection

Headphone Jack

 

 

Specifications

Power Output:  60 watts per channel minimum RMS, both channel driven at 8 Ω  from 20 - 20,000 Hz with no more than 0,08% Total Harmonic Distortion.

Maximum Continuous Power Output

DIN,  at 4 Ω  :  100 W + 100 W

IEC, at 8 Ω  :  70 W + 70 W

Total Harmonic Distortion : 

20 Hz - 20,000 Hz, 8 Ω  :  0,08%

1 kHz, 8 Ω  :  0,009%

Intermodulation Distortion:  0,03% at rated power (60 Hz : 7 kHz= 4 : 1)

Frequency Response:  10 Hz to 90 kHz +0 dB -3 dB (IHF)

Damping Factor:  250 (50 Hz input 8 Ω )

Signal-to-Noise Ratio (IHF-A)

Phono (MM) :  78 dB

Phono (MC) :  74 dB

Tape, Tuner, Aux, CD :  106 dB

Input Sensitivity/Impedance:

CD, Aux, Tuner, Tape :  150 mV / 47 k Ω

Phono (MM) :  2,5 mV/47 k Ω 

Phono (MC) :  0,2 mV/47 k Ω 

Tone Controls

Treble :  ±10 dB at 10 kHz

Bass :  ±10 dB at 100 Hz

General

Power Requirements:  110, 120, 220 - 240 V 50/60 Hz

Power Consumption:  250 W

Dimensions (W x H x D):  440 x 102 x 345 mm (17-5/16" x 4-1/16" x 13-9/16")

Weight:  8,8 kg (19,0 lbs)