Audio Research D-70 power amplifier

If a preamplifier is viewed as the control center of a music system, then an amplifier can be regarded as the "engine" which power the system.. There is a misnomer among the audio community that amplifiers have no distinct "sonic signature" of their own, and that amplifiers varying widely in design and construction exhibit only minimal sound differences. Whit thirty years of design experience Audio Research has discovered this is not the case.

Claims for amplifier similarity have been strictly based on static performance measurements made into purely resistive loads. This is a poor test basis, similar to comparing a racing engine to a road model at identical idling speeds and concluding that they are equal in performance. In fact, amplifiers vary widely in their sonic character and recent advances in amplifier technology make this easily demonstrable .

From a performance standpoint, amplifiers must meet the same criteria for preamplifiers including clarity. High Definition , harmonic accuracy and dynamic range. Perfect linearity under difficult load coditions is impossible to achieve. However, Audio Research has been responsible in extending amplifier performance to new limits for nearly two decades.

 

Design Criteria

When designing a high performance power amplifier, the engineer is faced with four primary considerations:

• Audio quality
• Construction quality
• Power
• Costs.

So successfully blended are these criteria that Audio Research amplifiers now extend state-of-the-art. Performance without sacrifice in power, construction quality or at unreasonable cost.

Because Audio Research has given continuous attention to improving all aspects of amplifier design for many years. Audio Research now manufactures amplifiers which appear modest in price compared to state-of-the-art. Models of just a few years ago. Yet the performance capabilities of these amplifiers are so great that they overwhelm recent state-of-the-art. Amplifieres built without cost constraints.

 

Features

Patented Audio research cross-coupled and fully balanced circuitry

Front panel power switch relay coupled for smooth and reliable turn-on

Front panel LED indicators for line and screen

Front panel fusing for line and screen

Sonically selected components for optimum sound performance

Near military grade construction used hroughout

 

Specifications

Power Output:  65 watts per channel minimum continuous at 16 ohms from 20 Hz - 20 kHz with less than 1% Total Harmonic Distortion

Power Bandwidth:  10 Hz to 60 kHz (-3 dB points)

Input Sensitivity:  95 V RMS for rated output

Input impedance:  75 k Ω nominal

Noise:  greater than 90 dB below rated power, broadband unweighted

Dimensions (W x H x D):  19" x 7" x 16,5"

 

Audio Research SP-12 preamplifier

 

Audio Research Preamplifier

The SP-12 is a musically accurate, High Definition wide bandwidth, vacuum tube preamplifier offering the  serious music enthusiast uncompromised performance. With proper attention to set up the SP-12 can be placed in virtually any quality audio system, from the least costly to the most sophisticated without compromise in system performance. The SP-12 appeals to a variety of music lovers,, from the enthusiast experiencing high quality sound reproduction for the first time to the most seasoned audiophile.

Four Critical performance Areas:

Harmonic Integrity - Audio Research preamplifiers provide the listener with a unique sense of "harmonic rightness". Delicate harmonic structures essential to musical accuracy remain wholly intact, creating a musical performance with a sense of "aliveness".

Clarity - Providing a clarity of sound that immediately  impresses the listener. Audio Research  preamplifier are totally absent of the "heaviness" or "veling" of sound present in other designs. There is also a notable lack of "hardness", "edge" and "grain" that masks fine detail in other preamplifiers.

High Definition - While other preamplifiers obscure important musical information, Audio research preamplifiers reproduce all of the subtle colors, shadings and ambient detail that create the illusion of a "you are there" performance. The Sp-12 efforlessly sort through complex musical material placing every instrument and voice onto the proper acoustic stage. This High Definitionquality is a hallmark of all Audio Research products.

Dynamic Expression - Audio Research preamplifiers excel in reproducing a musically accuarte dynamic range.  Highly stable power supplies and essentially overload-proof output sections result in preamplifiers that reproduce the quietest notes to the loudest and most  complex musical passages. Separation of instruments and voices remains intact at every level without "smearing" or collapse of sound field.

 

Features

Front panel muting for repeat settings, interruptions, etc.

Front panel power switch for activating back-chassis, plug-in power receptacles

High accuracy, close tracking, segmented gain control

Sonically selected components for optimum sound performance

Optional rack mount and automatic mute version available

Near military grade construction used throughout

 

Specifications:

Frequency Response:

High Level :   5 Hz - 30 Hz, +5 dB

Magnetic Phono :  30 Hz to 20 kHz,  +25 dB of RIAA

Total Harmonic Distortion:  less than 0,02% 2V RMS output

Input Impedance: 

Phono :  50 k Ω

High Level :  100 k Ω

Noise:

High Level :  250 µV RMS (max residual unweighed wideband noise)

Magnetic Phono :  5 µV (max equivalent input noise, wideband RMS)

Tube Complement:  5 x ECC88 / 6DJ8

Dimensions (W x H x D):  15,6" x 4,5" x 8,9" (19" W with optional rack mount front panel)

Weight:  4,1 kg (9 lbs)

Audio Research D-110

The D-110 is a linear 2-channel power amplifier of extremely high quality construction designed for the reproduction of speech and music. It represents "second Generation" advancement of Audio Research's analog module technology.

With the D-350 and D-100A technology to draw from, the D-110 was conceived to embody those parts of each design that could be brought together to provide an amplifier having the very highest possible performance level within its power capability.

Assuming a basically linear and stable amplifier design with adequate "slewing rate" to allow possible audio waveforms to be reproduced with low distortion, there are still two most important factors that must be dealt with if it is to be capable of driving loudspeaker loads "fast and clean". One is the "stiffness" or "muscle" of the output-driver stage; the other, a stable high capacity power  supply, capable of providing the instentaneous current demands of the circuit. By utilizing the D-350 power supply, with its 300 joule energy storage, and the D-100A output stage rebiased to a much higher "idle" current (the 3 built-in, superquiet fans keep the ambient temperature to a very reasonable level), an amplifier has been created that provides a new level of music reproduction. To obtain the performance this amplifier is capable of, it is recommended that only commensurate quality preamplifier-control units (such as the SP-3B, SP-5, SP-6) be used with it. Also, only high quality turntables with stable arms and cartridges should be used.

Features:

All solid state featuring Audio Research's analog module technology and unique linear output circuitry.

Power-line monitor meter with operating ranges identified.

Output power monitor meters - peak "averaging" circuitry to monitor safe operating (sine wave power calibration 100 watts/8 ohms top of green arc).

Built-in speaker line fuse holders - user can assure absolute speaker protection.

Front panel power supply fuses for easy acces

Super-quiet built-in fans to assure reliable operation

Front and rear panels are 2-color anodized aluminum for permanent finish and lettering

Industrial grade components and construction for long service life. Rated for continuous commercial service.

Specifications

Power Output:  100 watts per channel minimum RMS (both channels operating) at 8 ohms from 1 Hz to 20 kHz with less than ,25% T.H.D.

Intermodulation Distortion:  less than 0,05% at rated output (80 Vp-p) and load (SMPTE method)

Total Harmonic Distortion and Intermodulation Distortion both decrease with decreasing output (typically less than 0,02% at 1 watt per channel RMS)

Power increases to maximum at 4 ohms

Input Sensitivty:  1,5 volts RMS for rated power and load

Input Impedance:  30 k Ω (nominal)

Damping Factor:  more than 200 at rated power and load (20 Hz to 20 kHz)

Noise:  wide band, unweighted, more than 100 dB below 100 watts at 8 Ω - power line components (hum) 90 dB below 100 watts at 8 Ω

Power Requirements:  105 - 125 / 210 - 240 V AC, 50/60 Hz

Power Consumption:  600 watts maximum

Dimensions (W x H x D):  480 x 265 x 436 mm (19" x 10-1/2' x 17-1/4")

Handles Extend:  41 mm (1-5/8 ") forward of the front panel

Weight:  42 kg (92 lbs) Net 

Audio Research Dual-100

Audio Research Dual-100 Features:

Exclusive New Circuitry (Patented and Patent Pending)

Quality Construction

1/8" anodized aluminum chassis;

Silicon power supply;

Choke filtering;

Heavy duty epoxy-glass circuit board;

Conservative design;

Many precision parts;

Extra quality components;

Thermistor controlled warmup.

Conservative Specifications

Unique Guarantee (Investment protected; 5 years, part and workmanship; 2 years, vacuum tubes/home use; registered warranty transferable)

Ultra Stable Performance: Ideally suited for complex loads such as electrostatic speakers (may be operated into open circuit or any combination of reactive and/or resistive load)

 Unique Circuitry - Delivers superior performance under dynamics of music

 Overload Stability - and lack of crossover distortion provides clean effective loudness of much larger amplifier.

In the evolvement of the Dual 100 design, foremost consideration has been placed on listening quality. Needless to say, there was no place for the "but we've always done it this way" philosophy in its design. Certain well-known principles (but seldom used) are obviously  retained, such as quality of construction, an an adequate power supply. From a circuit standpoint, however, little of it resembles convention.

 One patent has been issued, another is pending, and even beyond thgis, the circuitry is unique. Interestingly enough, it is also very straight-forward and remarkably long-term stable.

 The output stage is one of these unique circuits, and needless to say, it does main fixed regardless of amplitude or complexity of signal.

Specifications:

Frequency Response:

30 Hz to 15 kHz at 1 watt ±1 dB

30 Hz to 15 kHz at 75 watts ±1 dB

Sine Wave Power:  at least 75 watts RMS 30 Hz to 15 kHz

Harmonic Distortion:  less than 0,15% at 1 kHz at 75 watts

Hum and Noise:  at least 80 dB below rated output

Input Sensitivity:  1,0 V RMS for rated output

Impulse Distortion:  essentially none 30 Hz to 15 kHz

Permissible Loads:  Open circuit, resistive, capactive, inductive, or any combination, series or parallel

Output Impedance:  4, 8, 16 ohms

Load Regulation:  from 16 Ω resistive load to open circuit less than 1 dB change 1 kHz

Dimensions  (whd):

Power Supply :  17" x 13" x 10-1/2"

Amplifier :  17" x 13" x 8"

Weight

Power Supply :  88 lbs

Amplifier :  45 lbs

Audio Research SP11

 The SP11 is a hybrid unit, utilizing both vacuum tubes and FETs (Fiel Effect Transistors). It is not intended that this product should somehow continue the controversy of "vacuum tubes" vs. "solid-state". Rather, in keeping wit Audio Research's design philosophy of advancing the state-of-the-art., each type of device is used where it performs best.

One important result, aside from the dramatically improved quality of sound reproduction, is the use of only six vacuum tubes - tubes which need not be selected low-noise types. A significantly longer time between tube replacement is also expected.

As a last word, this preamplifier may well change your thinking about music reproduction. Because it is so incredibly "open" sounding, much information not previously sudible is available, providing new insight and enjoyment from many sound sources. To be appreciated, the SP11 preamplifier must be personally experienced; it cannot otherwise be adequately related.

 Operational Features:

Automatic warmup, brown-out power-line interruption muting and manual muting at all preamplifier outputs, with new shunt circuitry.

Subsonic phono filter with 6 dB /oct rolloff (to eliminate ringing) with transition to 12 dB/octave.

Bypass switch for use with "audiophile quality" program material.

Absolute phase switch for main outputs, plus unswitched inverting and non-inverting outputs.

Full tape functions; two inputs, two recording outputs, plus tape copy and tape monitor functions.

Input/output connectors have heavy gold plating and connect "ground" before "hot".

Level set control in addition to normal gain control. Allows essentially unlimited input signal range while preserving optimum gain control usage.

Toroid power transformer for low mechanical noise and low external magnetic field.

 In Octobr of 1985, Audio Research Corporation introduced the SP11 preamplifier. During the first year, our introductory claim of "a new reference standard" has been confirmed by reviewer after reviewer throughout the Free World.. It is improbable that any audio product, including previous Audio research products, has ever received such unanimous acclaim. We believe that once you hear the SP11 reproduce music, you will find that acclaim justified.

Specifications

Frequency Response:

High Level Input :  0,2 Hz to 100 kHz ±1 dB (-3 dB below 0,1 Hz and above 200 kHz)

Phono Input:  20 Hz to 40 kHz ±2 dB of RIAA (±1 dB of RIAA, 1,0 Hz to 100 kHz)

Harmonic Distortion:  less than 0,005% at 2 V RMS output, 5 Hz to 20 kHz (Typically less than 0,001% at midband, phono or line input)

Intermodulation Distortion:  less than 0,003% at 2 V RMS output

Gain (aat 1 kHz , bypass mode):

Phono Input to Tape Output :  46 dB (0,2V output from 1mV input)

Phono Input to Main Output :  75 dB (0,175 mV input for 1 V output)

High Level Input to Main Output :  29 dB (36 mV input for 1 V output)

Inputs:  Phono, Tuner, CD, Video, Spare, Tape 1, Tape 2,

Outputs:  Tape 1, Tape 2, Main 1, Main 2, Direct, Invert

Filter:  25 Hz Hi-pass phono subsonic 6 dB/octave rolloff (to eliminate ringing) with transition to 12 dB/octave at 10 Hz. Front panel switchable, phono only

Controls:  Gain, level (to set gain Range), balance, Mode, Input, Impedance

Switches: Tape Monitor, Copy, Tape 1/2, Tape 1 to 2/2 to 1, Mute, Invert Phase,Bypass, Filter

Input Impedance:

Phono :  47 k Ω, 100, 30, 10, 3 Ω (front panel selectable)

Phono Input Capacitance:  150 pF at 10 kHz

High Level:  20 k Ω or higher, depending on switch functions

Maximum Inputs Level Undistorted:

Phono :  350 mV RMS at 1 kHz, 1200 mV RMS at 10 kHz (0,1 second maximum duration, 6 dB less if continuous)

High Level :  25 Volts RMS

Output Impedance:  250 Ω main, direct, invert outputs, 500 Ω tape output. Recommended load 60 k Ω and 100 pF (25 k Ω minimum, 1000 pF maximum)

Rated Output:  2V RMS 1 Hz to 100 kHz main, direct, invert outputs (Maximum 80 V RMS output at 0,2% T.H.D. at 1 kHz into 60 k Ω load with 2,85 V RMS high level input)

Phase:

Tape Outputs, Direct Output;  Non-inverting

Invert Output :  Inverting

Main Outputs :  selectable non-inverting or inverting. All outputs may be used simultaneously.

Noise (IHF Weighted, shorted input):

Output (Gain down) :  6 µV (110 dB below rated output)

Input High Level) :  3 µV equivalent input (110 dB below 1 V input)

Phono :  0,15 µV equivalent input (76 dB below 1 mV input)

Tube Complement (Hybrid FET/Tube Audio Circuit, Solid-State Power Supply):  6 - 6DJ8/ECC88

Power Requirements:  95 - 135 V AC 60 Hz (Export 190 - 270 v AC 50/60 Hz)

Power Consumption:  130 watts maximum

Dimensions (W x H x D) Each Chassis, EIA Rack panel Mounting:

480 x 134 x 260 mm (19" x 5,25" x 10,25")

Weight Net:

SP11 :  6,4 kg (14 lbs)

SP11PS :  6,8 kg (15 lbs)  

Audio Research M300

M300 Hybrid Monaural Power Amplifier - Audio Research Corporation developed and patented new circuitry allowing hybrid utilization of Fets with vacuum tubes in ways which can bring out the best in both devices. This circuitry is used in the relatively new, but already widely-acclaimed SP-11 preamplifier. Drawing from this technology, Audio Research has designed a new hybrid power amplifier, designated the M300 - a monaural unit rated at 300 watts.

Hybrid Monaural Power Amplifier

Most hybrid power amplifier designs use small signal-input vacuum tubes, then rely on FETs for the output stage. Audio Research has chosen instead to eliminate these low-level input tubes - tubes which can be prone to problems with hum, noise, microphonic, drift and, of course, require periodic replacement. The new FET "front end" is combined with Audio Research's long-famous, patented cross-coupled circuit to provide a design offering exemplary stability, reliability (low maintenance), and superior performance.

These design advances have been coupled with yet another Audio Research patent; an output stage utilizing vacuum tubes, and partially cathode-coupled (as all previous Audio Research vacuum tube amplifiers have ben), but with the screen (or accelerating) grids operating with a signal voltage precisely in phase with the cathode voltage. True "pentode" operation and efficiency is thereby achieved; however, all thr advantages of partial cathode coupling are maintained .

Advantages include:

Efficiency up to 60% above. (Class "A" designs achieve 25% to 50% typically 30% to 35%)

Inherently better cross-coupling

Output transformer with lower "turns" and "impedance" ratios, resulting in greater bandwidth.

Partial cancellation of saturation effects of the "DC" inn the output transformer's core

Switching transients essentially eliminated, rendering the question of class of operation ("A", "AB", etc.) irrelevant. The virtues of Class "A" operation without the usual drawbacks

Bias adjustment is essentially non-critical.

Output tubes need not be matched, although slighty better performance will result if they are.

Lower internal impedance improves handling of complex speaker loads.

Operationsl Features:

Front-panel replaceable line and screen voltage fuses, with LED indicators.

Two integral, low-noise fans for cooler operation, longer tube life. Front-panel switch allows "Hi" and "Lo" speeds.

"Standby" switch for lower power consumption and less heat during warm-up periods or telephone interruptions.

Automatic muting circuit provides silent shutdown upon power shut-off or interruption. No "thump" from speakers.

Gold-plated input connectors connect "ground" before "hot".

1, 2, 4 and 8 ohms output taps.

Front and rear handles for easier handling

Tube Saver protection Circuit

The M300 Power amplifier contains a remarkable new circuit called the :Tube Saver" it's a small secondary circuit board located on the back side of the main board in the amplifier. Primarily, the "Tube Saver" reduces stress to tubes and associated driving Fets. As an overload protection circuit, it is triggered only when abnormal current is sensed from a cause like those listed  below. Under even extreme conditions of normal use (i.e. extremely high playback levels), the circuit is designed to remain inactive. When triggered, the circuit immediately shuts down th eoutput stage and indicates protection mode by dimming the "Screen" LED. At this point, the amp should be manually switched off, then restarted after a period of 30 seconds.

Specifications

Power Output:  300 watts minimum continous at 8 Ω, from 16 Hz to 25 kHz with less than 0.5% T.H.D. (typically below .005% at 1 watt).

Approximate Actual Power Available at Clipping:  330W at 1 kHz, nominal.

Power Bandwidth:  10 Hz - 60 kHz (-3 dB Points)

Input Sensitivity:  1,5 V RMS for rated output

Input impedance:  60 k Ω, nominal

Output Regulation:  Approx. 0,3 dB, 8 Ω load to open circuit (Dampping factor approx. 30)

Negative Feedback:  20 dB

Slew Rate: 25 volts/microsecond

Rise Time: 3 microseconds

Hum and Noise: less then 2 mV RMS 90 dB below rated output (broad-bandwidth unweighted, inputs shorted)

Power Supply Energy

Storage:  approx. 350 joules

Power Requirements:  105 - 125 V AC 60 Hz (210 - 250 V  AC 50 Hz); 900 watts at rated output, 450 watts at "idle" - 130 watts at "standby"

Dimensions (W x H x D):  480 x 270 x 410 mm (19" x 10,5" x 16")

Weight:  50 kg (110 lbs) net

Tubes required:  8 - 6550 Power Output (matched pairs will yield marginally better performance)

Audio Research Classic 60

 Audio Research now proudly introduces the Classic,  new , moderately priced stereo hybrid amplifiers that come surprisingly close to the benchmark set by the acclaimed Classic 150 hybrid monaural amplifier.

It doesen't take a "golden ear" to immediately perceive the emotinal power and sonic authority the Classic 60 bring to any good musical program. Silences are more silent by an order of magnitude; the soundstage is broad, deep tall; instrumental timbres have an uncommon truth to them; dynamics soft and loud are unbelievably convincing.

 And the Classic 60 are designed to provide years of trouble-free service. You don't need to be a technican to use and enjoy them. Quite simply, the Classic 60 bring world-class audio performance within reach of most music lovers. Audition one today at your nearest Audio Research dealer.

For effortless musicality and value second to none,  it has to be the Classis 60.

The Classic 60 Hybrid Stereo Power Amplifier resembles the long-popular D115 in Audio Research's family of High Definition power amplifiers. But its lineage is strictly Classic 150. which means nothing less than state-of-the-art. In design, construction, musicality and operational convenience, at an affordable price.

Like the Classic 150, the Classic 60 proceeds from the notion that power ratings don't always describe a power amplifier's real capabilities. Far more important are such qualities as dynamic stability, lucidity, subtlety. And to achieve those, audio Research has used its traditional partial cathode coupling along with triode operation of the Classic 60's eight 6550 power output tubes. Additional circuit improvements as well as the usual rigorous parts selection and manufacturing Audio Research is noted for also contribute sonically.

 Translated into the language of listening, this signifies stunning bandwidth, a noise floor virtually beneath audibility and musically fulfilling SPLs at dramatically lower gain settings. Dynamics, timbers of individual instruments, soundstage and musical emotion all surge out rom a black velvet of silence.

Simply put, the Classic60 resolves far more of a musical program than amplifiers rated at two, three or four times its seemingly modest 60 WPC.

But the Classic 60 is easily up to the task of driving all but the most demanding loudspeakers, even in spacious listening rooms. And while it shows modest preamplifiers in their best light,it also shines when coupled with premiere designs, such as Audio Research's Sp14 or Sp15.

 Convenience figures high on the Classic 60's list of attributes, as well. For example, DC balance of the output tubes is maintained automatically, while tube biasing continuously adjust to changes in incoming line voltage. Performance stays razor-sharp without bother some tweaking or adjustments. And quiet fan cooling, along with triode operation, means significantly longer tube life. A Classic 60 owner can look forward to years of low-maintenance performance.

Specifications

Power Output:  60 watts (minimum continuous at 16 Ω from 15 Hz - 20 kHz with less than 1,0% T.H.D.)Power  Bandwidth:  12 Hz to 40 kHz (-3 dB Points)

Input Sensitivity:  0,55 V RMS for rated output

Input Impedance:  100 k Ω nominal

Output Regulation:  approx.0,3 dB (16 Ω load to open circuit , damping factor approx. 30)

Negative Feedback:  20 dB

Slew Rate:  20 volts/microsecond

Rise Time:  2,0 microsecond

Hum and Noise:  less than 2,0 mV RMS, 84 dB below rated output (20 kHz bandwidth unweighted, inputs shorted)

Power Supply Energy Storage:  approx. 280 joules

Power Requirements:  105 -125 V AC 60 Hz (210-250 V AC 50 Hz)

Power Consumption:  500 watts at rated output; 700 watts maximum, 370 watts at "idle"

Tubes Required: 

for Power Output :  4 x matched pair 6550 (low gas);

for Drivers :  4 x 6FQ7/6CG7

Dimensions (W x H x D):  approx. 480 x 180 x 400 mm (19" x 7" x 15,75")

Handles extend :  41 mm (1-5/8") forward of the front panel

Weight:

Net :  28,6 kg (63 lbs)

Shipping :  34,5 kg (76 lbs)

Audio Research Classic 30

Audio Research now proudly introduces the Classic 30; new , moderately priced stereo hybrid amplifiers that come surprisingly close to the benchmark set by the acclaimed Classic 150 hybrid monaural amplifier.

It doesen't take a "golden ear" to immediately perceive the emotinal power and sonic authority the Classic 30 bring to any good musical program. Silences are more silent by an order of magnitude; the soundstage is broad, deep tall; instrumental timbres have an uncommon truth to them; dynamics soft and loud are unbelievably convincing.

And the Classic 60-30 are designed to provide years of trouble-free service. You don't need to be a technican to use and enjoy them.

Quite simply, the Classic 30 bring world-class audio performance within reach of most music lovers. Audition one today at your nearest Audio Research dealer.

Putting the state-of-the art. Within everyone's reach… the Classic 30

It's tempting to regard the Classic 30 as merely the smaller sibling of the Classic 60 and Classic 150.

But the skeptical music lover or audiophile who auditions the Classic 30 is in for quite a shock. Because this "little" hybrid stereo amplifier - rated at 30 WPC - packs a sonic authority and eloquent musical veracity that larger, more conventional power amplifiers might envy. Our engineer have discovered that sometimes less is very definitely more.

Of course, the Classic  30 features almost all the same technology as its bigger brothers, scaled down for more modest applications. It has four 6550s instead of eight, two 6FQ7 driver tubes instead of four; no fans, because it runs remarkably cool without any help whatever.

But this smaller design still retains a similar degree of exceptional musical resolution. Even at low gain settings, the Classic 30 is far more musically lucid than amplifiers objectively far more powerful.

The Classic 30 is at its pristine best with moderately efficient loudspeakers in smallto medium sized listening rooms; with program materials that demand high resolution and subtlety rather than pure muscle. In that context, it reveals the same sonic mastery as its more powerful siblings.

But don't take our word for it. Audition a Classic 30 today and discover just how much more music can come alieve , with" less"

Specifications

Power Output:  30 watts (minimum continuous at 16 Ω from 17 Hz - 20 kHz with less than 1,0% T.H.D.)Power  Bandwidth:  15 Hz to 50 kHz (-3 dB Points)

Input Sensitivity:  ,4 V RMS for rated output

Input Impedance:  100 k Ω nominal

Output Regulation:  approx.0,4 dB (16 Ω load to open circuit , damping factor approx. 23)

Negative Feedback:  19 dB

Slew Rate:  15 volts/microsecond

Rise Time:  3,5 microsecond

Hum and Noise:  less than 0,5 mV RMS, 93 dB below rated output (20 kHz bandwidth unweighted, inputs shorted)

Power Supply Energy Storage:  approx. 150 joules

Power Requirements:  105 -125 V AC 60 Hz (210-250 V AC 50 Hz)

Power Consumption:  300 watts at rated output; 400 watts maximum, 200 watts at "idle"

Tubes Required: 

for Power Output :  2 x matched pair 6550 (low gas);

for Drivers :  2 x 6FQ7/6CG7

Dimensions (W x H x D):  approx. 480 x 180 x 370 mm (19" x 7" x 14,5")

Handles extend :  41 mm (1-5/8") forward of the front panel

Weight:

Net :  20,9 kg (46 lbs)

Shipping :  28,2 kg (62 lbs)

Audio Research SP-10

 Four Critical Performance Areas

The SP-10 have been widely acclaimed as representing the state-of-the-art. In music reproduction and each of these preamplifiers can provide the critical listener with true reference sound quality in the four critical areas of performance.

Clarity - Providing a clarity of sound that immediately impresses the listener. Audio Research preamplifiers are totally absent of the "heaviness" or "veiling" of sound present in other designs. There is also a notable lack of "hardness", "edge" and "grain" that masks fine detail in other preamplifiers.

High Definition _ While other preamplifiers obscure important musical information, Audio research preamplifiers reproduce all of the subtle colors, shadings and ambient detail that create the illusion of a "you are There" performance. The SP-10 effortlessly sort through complex musical material placing every instrument and voice onto the proper acoustic stage. This High Definition quality is a hallmark of all Audio Research products.

Harmonic Integrity - Audio Research preamplifiers provide the listener with a unique sense of "harmonic rightness". Delicate harmonic structures essential to musical accuracy remain wholly intact, creating a musical performance with a sense of "aliveness".

Dynamic Expression - Audio Research preamplifiers ecel in reproducing a musically accurate dynamic range. Highly stable power supplies and essentially overload-proof output sections result in preamplifiers that reproduce the guietest notes to the loudest and most complex musical passages. Separation of instruments and voices remains intact at every level without "smearing" or collapse of sound field.

Features

Automatic muting for continuous protection

Front panel muting for repeat settings, interruptions, etc.

Front panel power switch for activating 1600 watt capacity back-chassis, plug-in power receptacles.

Selectable front panel impedance matching for optimizing moving coil and moving magnet cartridge performance

Front panel gain selection for matching low output or high output cartridges

Front panel "bypass" switch for optimizing performance

Sonically selected components and near military grade construction

Specifications

Frequency Response:

High Level :  + .25 dB; 5 Hz - 30 kHz

Magnetic Phono :  + ,25 dB of RIAA, 30 Hz - 40 kHz

Harmonic Distortion:  less than ,01% at 2V RMS output, 20 Hz -20 kHz

Input Impedance: 

High Level :  50 k Ω, all inputs

Magnetic Phono :  10,30, 100, 10 k, 47 k Ω (selectable)

Noise:

High Level :  250 µV RMS maximum residual unweighted wideband noise

Magnetic Phono :  2 µV  RMS above 1 kHz

Dimensions (W x Hx D):  19" x 5,25" x 10,25"

Audio Research SP-8

 The single greatest requirement of a preamplifier is to amplify the given signal input without adding or subtracting musical information. This extremely complex, intricately defined, highly dynamic signal creates heavy demands on a preamplifier. Only Audio Research preamplifiers so accurately meet these demands that they transmit the listener beyond the reproduction chain to experience the "live event".

For optimum signal amplification the SP-8 utilize vacuum tube audio circuitry. While the transistor has replaced the vacuum tube in most popular consumer electronics, the vacuum tube still offers a number of design adventages over solid-state devices.  The vacuum tube has ceratin unique electrical properties that make it highly attractive for use in quality audio electronics.

Audio Research continues to incorporate the vacuum tube in its designs many years after tube technology was considered impractical. However, experience dictates that for state-of-the-art. Music reproduction the vacuum tube is difficult to surpass. Because of its long-term involvement in vacuum tube design Audio Research  is regarded as the leader in vacuum tube technology.

Features

Automatic muting for continuous protection

Manual muting for repeat settings,interruptions, etc.

Front panel power switch for activating 1600 watt capacity back-chassis, plug-in power receptacles.

High accuracy, close tracking segmented gain control

Sonically selected components for optimum sound performance

Near military grade construction used throughout.

Specifications

Frequency Response:

High Level :  + .25 dB; 5 Hz - 30 kHz

Magnetic Phono :  + ,25 dB of RIAA, 30 Hz - 40 kHz

Harmonic Distortion:  less than ,01% at 2V RMS output, 20 Hz -20 kHz

Input Impedance:  50 k Ω, all inputs

Noise:

High Level :  250 µV RMS maximum residual unweighted wideband noise

Magnetic Phono :  5 µV maximum equivalent input noise, wideband RMS

Dimensions (W x Hx D):  19" x 5,25" x 10,25"

Audio Research SP-6 (1978)

 Audio Research SP-6 High Definition music  stereo preamplifier features:

Close tolerance segmented gain control; 2 dB steps (guaranteed, 1½ dB tracking, ½ dB typical)

Front panel "mute" switch for repeat settings, interruptions, etc.

Rear panel gain "range" switch (+10 dB) for high efficiency speakers, high output cartridges, etc.

Special "off-chassis" construction, with all inputs/outputs isolated form chassis, plus circuit filters to eliminate or minimize "RFI", "TVI", and "CB" interference.

Rear panel provision to disconnect "common" from chassis so that rack mount installations with power amplifiers, etc., may be accomplished without ground-loop induced hum

Separate on-off switch and indicator for amplifier (etc.) power receptacles (3), relay controlled, 1600 watt capacity.

Front and rear panels are of two-color anodized aluminum construction for permanent finish

Industrial grade components and construction for long service life. Rated for continuous commercial service.

 With the introduction of power amplifiers such as the D-52, D-110 and D-350, and the availability of a number of brands of high performance speaker systems, the need for a new and higher level of preamplifier performance for the best systems has occurred.

After a significant amount of research and study , we have determined that from a cost-effectiveness standpoint, once again, the vacuum tube must be used.

We then felt that if such a project were to be undertaken, it would be desirable to execute it to the highest standards reasonable, recognizing that in all probability it would be the last significant vacuum tube product offered to the music world.

One of the expensive (and little recognized) requirements for such a concept would be a power supply capable of providing isolated and regulated voltages to each circuit section. This has been accomplished in the SP-6 by utilizing an all solid state triple section regulator with massive "filtering" at the output of each section.

With such a power supply available, it now becomes possible to increase the bandwidth of an AC coupled vacuum tube design without compromising the all important circuit stability. We have done this, drawing upon the Sp-3 basic circuit design. Increased interstage time constans, larger output coupling capacitors, and "DC concept" feedback circuit innovations, all combine with the new power supply to provide a new standard of sound reproduction.

Only high quality turntables with stable pickup arms and cartridges should be used with this preamplifier.

We suggest that this preamplifier will provide the state-of-the-art. Reference well into the '80s. We further suggest that inclusion of this unit in any otherwise good music reproducing system will effect more improvement than any other single component change.

Specifications

Frequency Response: 

High level Section : ± .25 dB, 10 Hz to 30 kHz, -3 dB points approx. 1hz and 250 kHz into hi-Z load. (-3 dB point approx. 1 Hz into 100 k Ω load)

Magnetic Phono : ±1 dB of RIAA from 30 Hz to 15 kHz

Harmonic Distortion:  less than .03% at 5 volts RMS output, IHF load, 20 Hz to 20 kHz (typically about .003% in midband)

Intermodulation Distortion:  less than .008% at 5 volts RMS output, IHF load, SMPTE method

Gain:

Magnetic Phono Input to Tape Output : 34 dB

Magnetic Phono Input to Main Output : 60 dB

High Level Input to Tape Output : 0 dB

High Level Inputs to Main Output : 26 dB

Input Impedance:  50 k Ω , all inputs (Magnetic phono may have any value from 10 Ω to 100k Ω subsituted. Also has provision to add input capacitance for matching certain magnetic cartridges)

Output Impedance:  500 Ω at 1 kHz, rising to 2,1k Ω at 20 Hz , all outputs (recommended minimum load for maximum audio quality, 20 k Ω)

Maximum Inputs:

Magnetic Phono : 700 mV at 1 kHz (.2 volts RMS, 100 kHz)

High Level Inputs : esentially overload proof.

Rated Outputs:  5 volts RMS 20 Hz to 30 kHz, all outputs, IHF load.  (Main output capability is 60 volts RMS output at < 1% THD at 1 kHz into 100 k Ω load with 3 volts RMS high level input)

High Level Noise:

250 uV RMS max. Residual unweighted wide-band noise at main output with gain control minimum (86 dB below 5 volts RMS output)

More than 90 dB below 1 volt RMS input (less than 20 uV equivalent input noise)

Magnetic Phono Noise:  5 uV equivalent input noise, wide-band RMS (-66 dB reference 10 mV input)

Tube Complement:  6 premium grade ECC 83/12AX7

Power Requirements:  105 -120 / 210 - 240 V AC, 50/60 Hz,

Power Consumption:  35 watts

Dimensions (W x H x D):  480 x 134 x 260 mm (19" x 5¼" x 10¼")

Handles extend : 41 mm (1-5/8") forward of front panel

Rear Chassis fittings extend : 23 mm (7/8")

Weight:  10 kg (22 lbs) net