What is stereo?




There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.




H.H. Scott '59





KEF C1 loudspeakers

 C1 Bookshelf Speaker
Compact, versatile and potent. The C1 pairs the superbly accurate 19mm (0.75in.) tweeter and 'tangerine' waveguide from the latest Q Series with a slot-ported 100mm (4in.) midrange/bass driver. Both sit on a dense two-layer front baffle system to deliver a complex, profoundly realistic and spatially accurate soundscape. With excellent power handling and a carefully tuned crossover, the C1 delivers a generously full performance that belies its discreet appearance and modest size. The front firing port makes it easy to position and the integrated wall bracket makes wall mounting a simple operation. 

Aluminium dome tweeter with 'Tangerine' waveguide
The same 19mm (0.75in.) tweeter from the latest Q Series reproduces vocals with spellbinding realism - the unique 'Tangerine' waveguide disperses its sweet natural clarity evenly throughout the room and provides excellent protection from straying fingers. 


Gold-plated terminals
The exceptional acoustic definition you experience depends on the recorded signal being perfectly transmitted, so to eliminate the risk of tarnishing, the binding posts of the C Series are gold-plated. 


Specifications
Type: Two-way bass reflex
Drive Units:
High Frequency: 19 mm (0.75") aluminium
Low Frequency: 100 mm (4")
Frequency Range: 65 Hz - 40 kHz
Crossover Frequencies: 2.5 Hz
Maximum Output: 106 dB
Amplifier Requirements: from 10 - 100 W
Sensitivity: 87 dB (2.83 V/1m)
Magnetic Shielding: Yes
Input Impedance: 8 Ohms
Dimensions (HxWxD): 260 x 150 x 221 mm (10.25 x 5.9 x 8.7 in.)
Weight: 3.2 kg (7lbs)


I like

Onkyo TX-7430 receiver

Quartz Synthesized Tuner Amplifier
Specifications
Amplifier Section
Power Output:  45 watts per channel, min. RMS, at 8 , both channels driven, from 20 Hz to 20 kHz, with no more than 0,08% T.H.D.
Musical Power Output: 
2 x 126 watts at 4  , 1 kHz (DIN)
2 x 78 watts at 8 , 1 kHz (DIN)
Continuous Power Output:
2 x 70 watts at 4 , 1 kHz (DIN)
2 x 55 watts at 8 , 1 kHz (DIN)
Total Harmonic Distortion
0,08% at rated power
0,08% at 1 watt output
Intermodulation Distortion:
0,08% at rated power
0,08% at 1 watt output
Damping Factor:  35 at 8
Frequency Response:  20 - 30,000 Hz ±1 dB
RIAA Deviations:  20 - 20,000 Hz ±0,8 dB
Input Sensitivity / impedance:
Phono :  2,5 mV / 50 k
CD, Tape Play :  150 mV / 50 k
Tape Rec :  150 mV / 3,5 k  (phono)
Phono Overload:  120 mV RMS at 1 kHz, 0,08% T.H.D.
Signal-to-Noise Ratio:
Phono :  85 dB (at 10 mV input, A weighted);  75 dB (IHF A-202)
CD, Tape :  95 dB (A weighted);  80 dB (IHF A-202)
Tone Controls:
Bass : ±10 dB at 100 Hz
Treble :  ±10 dB at 10 kHz
Muting:  -20 dB
Tuner Section
FM
Tuning Range:  87,5 - 108,0 MHz (50 kHz steps)
Usable Sensitivity
Mono :  12,8 dBf, 1,2 µV, 75 ;  1,0 µV (s/n 26 dB, 40 kHz Devi.) 75  DIN
Stereo :  18,0 dBf, 2,2 µV, 75 ; 23 µV (s/n. 46 dB, 40 kHz Devi.) 75  DIN
50 dB Quieting Sensitivity
Mono :  18,0 dBf, 2,2 µV, 75
Stereo :  37,2 dBf, 20 µV, 75
Capture Ratio:  1,5 dB
Image Rejection Ratio:  85 dB
IF Rejection Ratio:  90 dB
Signal-to-Noise Ratio :
Mono :  72 dB
Stereo :  66 dB
Selectivity:  50 dB DIN (±300 kHz, 40 kHz dev.)
AM Suppression Ratio:  50 dB
Harmonic Distortion
Mono :  0,15%
Stereo :  0,30%
Frequency Response:  30 - 15,000 Hz ± 1,5 dB
Stereo Separation:  45 dB at 1 kHz; 30 dB at 100 - 10,000 Hz
AM
Tuning Range:  522 - 1611 kHz (9 kHz steps)
Usable Sensitivity:  30 µV
Image Rejection Ratio:  40 dB
IF Rejection Ratio:  40 dB
Signal-to-Noise Ratio:  40 dB
Harmonic Distortion:  0,7%
General
Power Requirement:  120 V, 220 V, 240 V;  50/60 Hz
Dimension (W x H x D):  435 x 110 x  345mm (17-1/8" x 4-3/8" x 13-1/2")
Weight:  7,5 kg (16,5lbs)

Onkyo TX-7520 receiver

Quartz Synthesized Tuner Low Impedance Drive Discrete Amplifier 

Specifications
Amplifier Section
Power Output:  45 watts per channel, min. RMS, at 8 , both channels driven, from 40 Hz to 20 kHz, with no more than 0,1% T.H.D.
Musical Power Output: 
2 x 130 watts at 4  , 1 kHz (DIN)
2 x 80 watts at 8 , 1 kHz (DIN)
Continuous Power Output:
2 x 70 watts at 4 , 1 kHz (DIN)
2 x 55 watts at 8 , 1 kHz (DIN)
Total Harmonic Distortion
0,1% at 1 watt output
Intermodulation Distortion:
0,1% at 1 watt output
Damping Factor:  35 at 8
Frequency Response:  20 - 30,000 Hz ±1 dB
RIAA Deviations:  20 - 20,000 Hz ±0,8 dB
Input Sensitivity / impedance:
Phono :  2,5 mV / 50 k
CD, Tape Play :  150 mV / 50 k
Tape Rec :  150 mV / 3,5 k  (phono)
Phono Overload:  120 mV RMS at 1 kHz, 0,1% T.H.D.
Signal-to-Noise Ratio:
Phono :  85 dB (at 10 mV input, A weighted);  75 dB (IHF A-202)
CD, Tape :  95 dB (A weighted);  80 dB (IHF A-202)
Tone Controls:
Bass : ±10 dB at 100 Hz
Treble :  ±10 dB at 10 kHz
Muting:  -20 dB
Tuner Section
FM
Tuning Range:  87,5 - 108,0 MHz (50 kHz steps)
Usable Sensitivity
Mono :  12,4 dBf, 2,3 µV, IHF;  1,2 µV,  75  DIN
Stereo :  2,5 µV, 75
50 dB Quieting Sensitivity
Mono :  2,2 µV, 75
Stereo :  22 µV, 75
Capture Ratio:  1,5 dB
Image Rejection Ratio:  85 dB
IF Rejection Ratio:  90 dB
Signal-to-Noise Ratio :
Mono :  70 dB
Stereo :  65 dB
Selectivity:  50 dB DIN (±300 kHz, 40 kHz dev.)
AM Suppression Ratio:  50 dB
Harmonic Distortion
Mono :  0,15%
Stereo :  0,30%
Frequency Response:  30 - 15,000 Hz ± 1,5 dB
Stereo Separation:  40 dB at 1 kHz; 30 dB at 100 - 10,000 Hz
Muting Level:  17,2 dBf, 2 µV, 75
Stereo Threshold:  17,2 dBf, 2 µV, 75  
AM
Tuning Range:  522 - 1611 kHz (9 kHz steps)
Usable Sensitivity:  30 µV
Image Rejection Ratio:  40 dB
IF Rejection Ratio:  40 dB
Signal-to-Noise Ratio:  40 dB
Harmonic Distortion:  0,8%
General
Power Requirement:  120 V, 220 V, 240 V;  50/60 Hz
Dimension (W x H x D):  435 x 110 x  317mm (17-1/8" x 4-3/8" x 12-1/2")
Weight:  7,0 kg (15,4 lbs)

Akai X-330 reel-to-reel

Multi-Purpose Program Minder Tape Recorder

The X-330 enables to enjoy different music for 24 hours, in addition to selection and repeating your favorite tune forever.
 Program minder automatic continuous reverse
Sensing tape continuous reverse
Manual reverse
Cross-field head
3-speed capstan drive motor
Magnetic brake
Up to 10-1/2" reel acceptable

Outstandig features:
4-track stereo/monaural recording/playback
Program minder (Automatic continous reverse)
Sensing tape continuous reverse, manual reverse
Cross field head
Magnetic brake with tach generator (stoppage occurs within 3 seconds from F.F. / RWD  condition (10-1/2" reel)
Up to 10-1/2" reel acceptable. Back tension control
3 speeds (7-1/2; 3-3/4 and 1-7/8 ips)
3 motors: A hysteresis synchronous 3-speed motor for capstan drive; Two 6-pole eddy current out rotor motors for supply and take-up reel drive
4 heads: Erase; playback; record and bias heads
40 W all silicon transistorized amplifier
12 hours continuous HiFi stereo recording capacity (total 24 hours) at 1-7/8 ips with 7,200 foot tape
Shield type head for high Signal-to-Noise ratio
Tape lifter in fast forward and rewind operation
Track selector for simple selection between stereo and monaural
Automatic stop/shut off, Automatic pinch wheel release
Sound on sound, Sound with sound, Sound over sound, Echo effect
100 kHz biased for FM multiplex recording
Magnetic cartridge jacks (Direct recording and playback from turntable), Stereo headphones jack, DIN Jack
Remote controllable, AC outlet with automatic shut off switch
Standard/low noise tape selector. Bass and treble controls
Tape cleaner, 4-digit index counter with reset button, VU meters
Fine oil-finished wooden cabinet
Universal voltage selector (from 100 V to 240 V, 50/60 Hz)

Specifications
Tape Speed:  1-7/8, 3-3/4 and 7-1/2 ips
Wow and Flutter:
At 7-1/2 ips :  less than 0,04% RMS
At 3-3/4 ips :  less than 0,07% RMS
At 1-7/8 ips :  less than 0,15% RMS
Frequency Response [Standard Tape / low Noise tape]:
At 7-1/2 ips :  30 to 25,000 Hz / 30 to 26,000 Hz ±3 dB
At 3-3/4 ips :  30 to 18,000 Hz / 30 to 20,000 Hz ±3 dB
At 1-7/8 ips :  30 to 9,000 Hz / 30 to 13,000 Hz  ±3 dB
Distortion:  within 1,5%,  1 kHz,  0 VU at 7-1/2 ips
Signal-to-Noise Ratio:  better than 50 dB
Input Level:
Microphone :  more than 0,5 mV
Line :  more than 50 mV
DIN :  more than 10 mV
Power Output: 
15 W maximum each channel at Undistorted Power, total 30 W.
20 W maximum each channel at Music power, total 40 W
Equalization:  Standard or Low Noise Tape. Correct equalization for playback of tapes recorded to the NABTB curve
Recording Bias Frequency:  100 kHz
Recording Level Indicator:  2 VU meters
Recording System:  4-track stereo/monaural, Cross Field bias system
Fast Forward and Rewind Time:  75 seconds using 1,200 foot tape (7" reel) at 50 Hz , 60 seconds at 60 Hz
Heads:  4 heads - Erase, playback, record and bias heads
Motor:  3 motor - Hysteresis synchronous 3-speed motor for capstan drive. Two 6-pole eddy current outrotor motors for supply and take-up reel drive with tach generator
Reel Size:  10-1/2"; 7' and 5" reels
Speaker:  2 4' x 6" speakers
Power Supply:  AC from 100 to 240 V, 50/60 Hz
Power Consumption:  180 VA
Dimensions (W x H x D):  375 x 436 x 238 mm (14-3/4" x 17-1/8" x 9-3/8")
Weight:  22 kg (48,4 lbs)


McIntosh MC 250 power amp

Solid State Powerful Amplifier
Speciall Features:
The MC 250 is completely stable when connected to any loudspeaker system or even to reactive loads. The MC 250 has special circuits to prevent damage by short circuit or oen circuit of the output loads, or by any amount of output imedance mismatch. Therminal cutouts are mounted on the output transistor heaat sinks to provide protection against inadequate ventilation.


Specifications
Power Output: 
50 watts RMS continuous power per channel, both channels operating into a 4 Ω, 8 Ω or 16 Ω load
100 watts RMS monophonic
Total Harmonic Distortion:  less than 0,25% at rated power output fromm 20 to 20,000 Hz . Distortion typically measures less than 0,1% and decreases as output power is reduced.
Intermodulation Distortion:  less than 0,25% for any combinations of frequencies between 20 and 20,000 Hz at 100 peak watts output per channel or at any level less than 100 peak watts per channel
Frequency Range:  at rated output, both channels operating +0, -0,25 dB 20 through 20,000 Hz. At reduced output, both channels operating +0, -3 dB 5 through 70,000 Hz
Output Impedance:  output taps are provided for 4 Ω, 8 Ω and 16 Ω loads. Full rated power output is provided at each output tap. The 16 Ω output will provided 25 volts RMS for constant voltage multiple speaker distribution lines. Monophonic Output taps are provided for 2, 4 and 8 Ω. Full rated power output is provided at each output tap. These taps are also available on the octal socket, left center of control panel.
Output Damping Factor:  greater than 15 at 4 Ω ; 38 at 8 Ω, and 16,6 at 16 Ω
Input Sensitivity/Impedance:  0,5 volt will produce rated power output; a gain control for each channel allows independent adjustment of amplification in each channel. Input impedance is 200,000 Ω
Hum and Noise:  greater than 90 dB below rated output
Controls:
Mono - Stereo switch
Left Gain,  and Right Gain
Semiconductors:  24 silicon transistors; 23 silicon rectifiers and diodes
Power Requirements:  117 volts AC 50-60 Hz
Power Consumption:  50 watts at zero signal output; 250 watts at rated output
Dimensions (W x H x D):  10-5/8 x 7-1/16 x 15-5/8 inches
Weight:  35 lbs net; 40 lbs in shipping carton
Chassis:  Chrome and black


McIntosh MTI 100



The MTI100 Integrated Turntable is so much more than just a turntable. A one-of-a-kind product, the MTI100 is designed for those who want maximum flexibility in their home audio system but don’t want – or don’t have the space for – a large audio system in their home.
 Besides playing 33-1/3 and 45 rpm records, it also includes a power amplifier, a vacuum tube preamplifier, a phono preamplifier, analog and digital inputs, a Bluetooth® receiver, a subwoofer output, stereo speaker outputs, and a headphone jack.

 The dedicated phono preamplifier is housed in a custom shielding box that prevents interference or noise from seeping into the vinyl signal.
 Comes with a Sumiko Olympia Moving Magnet cartridge, whose upgraded stylus and cantilever assembly allow for more dynamic punch and improved frequency response.
 Class D amplifier is rated for 80 Watts per channel into 4 Ohms or 50 Watts per channel into 8 Ohms.
 Marries vintage vinyl records with modern music streaming via a High Definition Bluetooth input that ensures you receive the best sound quality possible from your Bluetooth device.

Specifications:
Power Output:
50 Watts per channel into 8 Ω
80 Watts per channel into 4 Ω
Total Harmonic Distortion:
Amplifier :  0.5% maximum (from 20 Hz to 20 kHz)
Preamplifier :  0.2% maximum (from 20 Hz to 20 kHz)
Signal to Noise Ratio:
Amplifier :  93 dB
High Level :  90 dB
Phono :  75 dB
Dynamic Headroom:
1,0 dB at 8 Ω
1,3 dB at 4 Ω
Damping Factor:
Greater than 200 at 8 Ω
Greater than 100 at 4 Ω
Frequency Response:  from 20 Hz to 20 kHz (+0, -0.7dB)
Inputs : 1 Unbalanced input; 1 Coax input; 1 Optical input
Outputs: 1 Unbalanced output (bridged to AMP IN); 1 Sub output
Tonearm:  Damped machined aluminum tube arm with lateral type bearing
Overall Dimensions (W x H x D):489 x 171,5 x 356 mm (19-1/4” x 6-3/4” x 14”)
Weight: 15,2 kg (33.5 lbs) net;  18,4 kg (40.5 lbs) in shipping carton


Fostex A-4 tape recorder


Introducing the A-4.
Four tracks on quarter-inch tape (a format our engineers pioneered) at a price that's as irresistible as we could make it. The A-4 drives 7" reels at either 7½ ips or 15 ips. So you can decide between the ultimate in multitrack economy or push for those extra dB's of sound quality.
Like its 8-track big brother, the A-4 has a transport system built from the ground up specifically for multitrack recording. Three low power consumption D.C. motors are used to eliminate the heat problems typical of A.C. motors. And an FG servo controls the capstan motor to prevent line voltage fluctuations from playing havoc with your sound.
The A-4 is a classic three-head design. Separate heads are used for recording, playback and erasing. We;ve even designed a new specially contoured head that gives you extended frequency response and fewer low frequency head bumps.
Operation is fast and easy, too. Select the tracks you want to record on. Then enter the record mode . The A-4 is set up to record where you want to record and automatically play back the other tracks. It also lets you punch in or out at the touch of a botton with no cliks or pops.
You can buy an optional remote foot-switch that gives you a third hand for punching in and out. Just play along with your song, then tap the footswitch to start recording. You'll be able to concentrate onn your music instead of your machine.
The A-4 brings you the kind of convenience we introduced on the A-8. easy to use digital tape counter with bright LED readout. And the Return To Zero memory function for fast tape checks. There's a ±10% pitch control for special effects, optional Dolby C noise reduction system, easy to use. Edit mode with tape dump capabilities and modular electronics for fast economical servicing.
It all adds up to an easy to use, easy to afford multitrack recorder. That's the A-4.

Specifications
Tape:  1/4 inch tape width, 1 mil base
Format :  4 track, 4 channel
Heads:  4 track record; 4 track reproduce, 4 track erase
Reel Size:  7 inch
Tape Speed:  15 and 7½ ips (38 and 19 cm/s) ±0,5%
Pitch Control:  ±10%
Line Input:  -10 dBV (0,3 V) / impedance 30 k Ω unbalanced
Line Output:  -10 dBV (0,3 V) load impedance 10 k Ω or higher unbalanced
Record Level Calibration Equalization:  0 VU referenced to 250 nWb/m of tape flux NAB
Wow and Flutter: 
±0,06% peak (IEC/ANSI) wtd., at 15 ips
±0,10% peak (IEC/ANSI) wtd., at 7½ ips
Fast Wind Time:  130 seconds typ typ. for 1800 ft of tape
Overall Frequency Response: 
At 15 ips :  40 Hz - 20 kHz ±3 dB
At 7½ ips ;  40 Hz - 18 kHz ±3 dB
Signal-to-Noise Ratio (Sync/Reproduce)
At 15 ips ;  65 dB wtd.
At 7½ ips :  referenced to 1 kHz , 3% T.H.D. level
Total Harmonic Distortion:  less than 1% at 1 kHz 0 VU
Crosstalk (Reproduce):  50 dB (at 1 kHz)
Erasure:  better than 70 dB at 1 kHz
Power Requirements:  120 V AC 60 Hz , 35 W
Dimensions (W x H x D):  360 x 340 x 170 mm (14" x 13-1/2" x 6-3/4")
Weight:  13 kg (29 lbs)



Fostex A-2 reel-to-reel


The A-2 is two track on quarter-inch tape, mastering machine. The standard of the industry. But with one added attraction. The A-2 has sync. Which means you can extend its usefulness. When you need to cut a high quality, low noise, low distortion master, ecord on the A-2 in its normal mode. But when you need to perform a little fixing up, or you want to do some added production (like adding a few ideas at the last minute), use the A-2's Sync mode. It's built-in to give you added performance flexibility for your dollar. Another way personal Multitrack fits the equipment to your needs. And your wallet.
The A-2 packs all the features and functions of our multitrack recorders into a rugged, relatively lightweight mastering machine. It includes LED indicators of peak transient overload in record or playback modes. The A-2 gives you the kind of quality needed to help you produce stereo masters that truly showcase your talent.

Specifications
Tape:  1/4 inch tape width, 1 mil base
Format :  2 track, 2 channel
Heads:  2 track record; 2 track reproduce, 2 track erase
Reel Size:  7 inch
Tape Speed:  15 and 7½ ips (38 and 19 cm/s) ±0,5%
Pitch Control:  ±10%
Line Input:  -10 dBV (0,3 V) / impedance 30 k Ω unbalanced
Line Output:  -10 dBV (0,3 V) load impedance 10 k Ω or higher unbalanced
Record Level Calibration Equalization:  0 VU referenced to 250 nWb/m of tape flux NAB
Wow and Flutter: 
±0,06% peak (IEC/ANSI) wtd., at 15 ips
±0,19% peak (IEC/ANSI) wtd., at 7½ ips
Fast Wind Time:  130 seconds typ typ. for 1800 ft of tape
Overall Frequency Response: 
At 15 ips :  40 Hz - 20 kHz ±3 dB
At 7½ ips ;  40 Hz - 18 kHz ±3 dB
Signal-to-Noise Ratio (Sync/Reproduce)
At 15 ips ;  65 dB wtd.
At 7½ ips :  referenced to 1 kHz , 3% T.H.D. level
Total Harmonic Distortion:  less than 1% at 1 kHz 0 VU
Crosstalk (Reproduce):  50 dB (at 1 kHz)
Erasure:  better than 70 dB at 1 kHz
Power Requirements:  120 V AC 60 Hz , 35 W
Dimensions (W x H x D):  360 x 340 x 170 mm (14" x 13-1/2" x 6-3/4")
Weight:  13 kg (29 lbs)


Aiwa SA-C30 mini pre-amp

Stereo Pre-amplifier - Control Unit

Features:
RIAA deviation of ±0,2 dB (20 Hz - 20 kHz) and phono Signal-to-Noise of 87 dB
Low-noise transistors, used in the first stage, are combined with high gain ICs to reduce noise and improve stability. Carefully selected polypropylene capacitors and high-precision metal-film resistors are used as the RIAA elements for an RIAA deviation of less than ±0,2 dB over a frequency range of 20 Hz to 20 kHz, thereby yielding an extremely accurate frequency response. The maximum rated input of 200 mV (at 1 kHz) assures an ample margin for the input signals.

Two power supplied (plus and minus) with high-performance differential amplifier ICs.
A plus-minus dual power supply design is used for the high-performance differential amplifier ICs in the amplifier circuit. This allows a faithful amplification of the signals with a minimum of distortion.

A high-performance tone control circuit that is bypassed when the knobs are set at the center "0" position.
A low-cut filter suppresses noise components in the ultra-low-frequency range such as those generaated by a warped record.
With just a flick of the muting switch, the power output can be reduced to one-tenth of the set level.
The loudness switch enhances the low-frequencies when listening at low volumes.

Specifications
Signal-to-Noise Ratio (IHF A curve short circuited):
Phono :  87 dB
Tuner :  98 dB
Aux :  98 dB
Tape :  98 dB
RIAA Deviation :  ±0,2 dB )20 Hz to 20 kHz)
Inputs Sensitivity/Impedance
Phono :  2,5 mV (200 mV max. input)
Tuner, Aux 1, Aux 2 :  150 mV/47 k Ω
Tape Monitor: 
Play :  150 mV/47 k Ω
Rec :  150 mV/47 k Ω
Output Level/Impedance:  0,8V/47 k Ω
Tone Controls
Bass  :  ±8 dB at 100 Hz (600 Hz)
Treble  :  ±8 dB at 10 kHz (3,5 kHz) 
Low Filter:  30 Hz/6 dB/octave
Muting:  -20 dB
Loudness :  +7 dB at 100 Hz ; +3,5 dB at 10 kHz (with -40 dB)
Semiconductors:  2 ICs; 10 Transistors; 10 Diodes; 5 LEDs
Power Requirements:  220 V, 50/60 Hz
Power Consumption:  5 W
Dimensiond (W x H x D):  250 x 71 x 229,5 mm
Weight:  1,85 kg


Aiwa SA-P30 mini power amp


DC Stereo Power Amplifier SA-P30

Features:
Toroidal power transformer for compact size and high output power
The large capicty power supply is composed of a toroidal transformer with particularly high efficiency and two 10,000 µF large-sized design capacitors. This exhibits ample margin, and more than enough power is supplied for an effective output of 35 W + 35 W. this enables dynamic, high quality sound reproduction.

A wide-range DC Amplifier that reproduces the original sound with faithfully
With this DC Amplifier, no condensers are used within the load return loop since condensers can cause a phase distortion

The system can be upgraded to a 70 W monaural amplifier with just a flick of a switch.
A switch makes a BTL connection turning this 35 W + 35 W stereo amplifier into a 70 W monaural amplifier. If one more of this unit is added on in the future, the system can be upgraded into a 70 W + 70 W power amplifier

Protection Circuits
The protection circuit employs a newly developed IC and a relay eliminates "pop" noise produced when the power is switched on and off. Other features protect the transistors from short-circcuits in the output and also the speakers which are isolated when leakage of DC is detected in the output.

LED bar graph display to indicate the output level.

Specifications
Power Output:  35 W + 35 W with 4 Ω impedance (0,5% distortion, 20 Hz to 20 kHz)
Distortion:  0,02% (1 kHz)
Input Sensitivity/Impedance:  560 mV/47 k Ω
Signal-to-Noise Ratio:  112 dB
Damping Factor:  more than 30 (8 Ω, 1 kHz)
Circuit System:  DC amp
Semiconductors:  4 ICs; 10 Taransitors; 2 FETs; 25 Diodes; 6 LEDs
Power Requirements:  220 V, 50/60 Hz
Power Consumption:  240 W
Dimensions (W x H x D):  250 x 71 x 218 mm
Weight:  4,1 kg


Sugden A 48 mkII (1976) amplifier


Circuit Configuration
The amplifier is electrically and physically in two sections, the pre-amplifier or control unit and the power amplifier. The pre-amplifier is again in two electrical sections. The first section is a feedback triple of high gain transistors forming the disc amplifier. The output of the disc amplifier or one of the high level inputs is selected and fed to an emitter follower circuit which in turn feeds the tone control, filter snd output stages. Each power amplifier has a low noise input transistor coupled to a high voltage bootstrapped stage to convert the input EMF to a high amplitude EMF approx equivalent too the required output voltage. The voltage amplifier is followed by a bootstrapped medium power emitter follower stage working into a resistive load. This circuit is followed by twin complementary pairs of output emitter followers with emitter coupled drivers. The quiescent current is fairly high at 100 mA. This method has been found to produce a linear output even without feedback thus only 30 dB or so of negative is used with  a much greater attendant stability into complex loudspeaker loads. The output stage is protected by reverse  fast diodes across the output devices and  curent limiting cicuiry. Cartridge fuses protect against over  dissipstion from a sustained short circuit.

Construction and finish
The basic chassis is a U section front panel joined to a U section rear panel with two tray section side members and a lateral U section member also joining the two side members. One side member caries the large main transformer, the lateral member the power smoothing and loudspeaker coupling capacitors together with the two bridge rectifiers, the front panel carries the pre-amplifier and the rear panel the power amplifier. The pre-amplifier components except for the controls which are mounted on the front panel are carried on a printed circuit board supported on special nylon stand off pillars. The entire pre-amplifier is screened in a two part cover formed from 22 gaue steel. All other steel parts are formed from 18 or 16 gauge mild steel. The power amplifier circuits are mounted on nylon stand off pillars carried by the rear panel and the power transistors are mounted on four massive heatsinks carried outside the rear panel and machined from from a special aluminium extrusion produced for JE Sugden by Alcan Booth Aluminium. The heatsinks are anodized matt black and all the ferrous metalwork is zinc plated and chromate passivated for maximum corrosion resistance. The chassis is clad in the "trim" consisting of a nextel finished strip behind the knobs and two aluminium trims which carry the front lettering. These trims are acid etched and anodized and printed with an epoxy ink. The top and sides trims are made from aluminium and finished in Nextel - a very durable paint with a suede effect feel to it. The push button knobs are of hard moulded black plastic and the rotary knobs are centre collet fixing (for perfect positioning and for not coming loose) in a rather pleasing matt black finish. The rear trims are aluminium faced with matt white PVC upon which the connector details are printed using a scratch resistant vinyl solvent ink. Non-staining soft plastic feet are fitted to the bottom.

Specification
Power Output (from Loudspeaker Sockets): 
8 Ω Loads :  45 W RMS per channel (90 W from both channels simultaneous operation)
16 Ω Loads :  35 W RMS per channel
4 Ω Loads :  50 W RMS per channel
Headphone Output:  600, 300 and 8 Ω (from TRS jackk socket on front panel, fed via an attenuator network from the loudspeaker circuits)
Tape Recorder Outputs:  '
DIN 5 Pin : 200 mV / 100 k Ω
Harmonic Distortion:  less than 0,1% into 8 Ω at 1 kHz (just prior to clipping)
Output Impedance:  0,2 Ω (in series with 10,000 µF)
Frequency Response:  30 Hz - 20 kHz ±1 dB
Power Response:  15 Hz - 35 kHz (at constant input level the output is -3 dB relative to 45 W at 1 kHz)
Load Stability:  Unconditional (reactive loads such as electrostatic loudspeakers will not cause malfunctioning of the power amplifier section)
Input Selection:  Disc 2; Dosc 1; Radio; Tape 1; Tape 2
Input Connections:  by 5 pin DIN sockets on the rear panel
Input Sensitivity (ref. To 25 Watt output level, 8 Ω loads):
Disc :  2,5 mV/47 k Ω
Radio :  100 mV/180 k Ω
Tapes :  100mV/200 k Ω
Signal-to-Noise Ratio: 
Disc Input :  75 dB
Aux, Radio, Tape :  85 dB
Disc Equalization: to BS1928 i.e. RIAA
Filter Controls
Low :  70 Hz / 12 dB per octave
High :  choice of 4, 7, 10 kHz / 18 dB or 6 dB per octave
General function
Mains Supply Required:  110  - 120 - 220 - 230 - 240 V AC 50/60 Hz (set by adjustment on transformer)
Dimensions (W x H x D):  400 x 130 x 290 mm (15,8" x 4,9" x 11,4")
Weight:  10,7 kg 23,5 lbs