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

 

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"

 

Copland CSA-14 amplifier

The Integrated Amplifier CSA 14, combines the benefits of both valve and transitor amplification, in a way unheard of before, usually hybrid Amplifiers dedicate one section of the amplifier to valve in isolation from the rest beacuse, the virtues of solid state and valve design are not the same, a synergy between them can be created, offering an alternative to either.

The Copland CSA 14 uses two valves in the input pre-differential driver stage of the amplifier allowing the notably smooth and transparent properties of the valves to blend with the power and dynamics of transitor electronics.

The synergy achieved surpasses, the found in other Hybrid Amplifier, in its relability while combining only the positive attributes from each element. 

The CSA 14 is build into a slim compact chassis. With the same build and sonic qualities, that have always formed the cornerstone of Copland's philosophy, offering exeptional valvue, whist the design allows the listener to relax and enjoy the astronnishing sound quality.

Due to popular demand, Copland have simplified one of their high-end amplifiers, in this case the CSA 14, to provide a solid state produkt of real quality, at a point within reach of the aspiring audiophile.

Specifications:

Output Power:  2 x 60W

Phono Input Impedance:  47 k Ω

Phono Sensitivity:  3 mV

Line Input Impedance:  33 k Ω

Line Sensitivity:  130 mV

Power Bandwidth:  5 Hz -30 kHz ±3 dB

Frequency Response:  5 Hz - 120 kHz ±3 dB

Total Harmonic Distortion:  better than 0,09%

Hum and Noise

Line :  better than 90 dB

Phono :  better than 76 dB

Phase:  non inverting

Vacuum Tubes:  2 x 6922 All valves are hand selected and identically matched.

Grounding:  Separated grounding on power supply. Signal/chassis connected to signal ground

Power Consumption:  250 watts

Dimensions (W x H x D):  430 x 125 x 375 mm

Weight (shipping):  13 kg

Synthesis Soprano amplifier

Soprano - 12W A-Class Integrated stereo tube amplifier

Following the success of the much-celebrated NIMIS, Synthesis took on the challenge of recreating a 12W A-Class integrated stereo tube amplifier. Using a new technologies a new business development and Luigi Lorenzon’s constant pursuit of perfection, he succeded in creating an entry level amplifier that is able to satisfy even the most dedicated audiophile.

New model of stereo tube amplifiers with DAC's on board, guaranteeing exceptional sonic performance from any digital source.

Made with the finest materials & advanced technology, this series is a sophisticated blend of research & experience.

Designed without compromise far a rich sound & faithful music reproduction.

The SOPRANO provides a minimum of 12 Watts per channel, power output from a pair of EL84's in Ultra-Linear (UL) - push/pull operation.

The SOPRANO features a newly designed custom output transformer resulting in a rich sound stage but with an authority that belies its 12Wpc

FEATURES

- USB -

DAC on board 24bit for a extraordinary listening experience from computer’s file.

- Phono Stage -

Hi quality Phono stage for MM cartridges.

-SPDIF inputs (Coax and Optical) Built around a AKM chip. 24 Bit 192KHz Hi Quality DAC for an extraordinary sound result.

- Output Transformer -

The Output transformer uses a Hi-Grade iron-Silicon for superb frequency reproduction & width. With this newly designed custom output transformer unique to the Soprano we are able to achieving a highly delicate & precise sound reproduction faithful to the original recording.

- Mechanical Chassis Construction -

The power supply & output transformers are held by an extremely rigid structure that keeps the unit free from unwanted vibrations which further helps reduce unwanted noise to the tubes.

- Binding Posts -

Gold plated professional binding posts for a continued oxidization free connection further improve sound refinement.

- Sockets -

Ceramic sockets for a continued oxidization free connection further improve sound refinement.

- Components -

Components for the amplifier have been selected with great care throughout. Only the best available components are considered & all must undergo an exhaustive analysis of their sonic influence prior to final selection.

- Selected Tubes -

All tubes used are selected after 2 stage warm up. A fully computer monitored machine controls the process & at the end of this, selects the perfect tubes which are then matched for a perfect balance.

Technical Specifications:

Power Stage (1 ch.):  Matched pair EL84/6BQ5

Input Stage (1 ch.):  Hi Performance audio OP-AMP JRC4580

Driver (1 ch.):  Matched pair MJD340 (Designed for audio amplifier)

Input Impedance:  100 k Ω  

Input Sensitivity:  100 mV RMS for rated power

Output Tap:  6 Ω  

Power Stage Config.:  Push-Pull Ultra Linear 43% tap

Power Output:  12 W RMS into 6 Ω  A-Class

Power Bandwidth:  15 Hz to 50 kHz  -3,0 dB

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

Distortion:  1% at 1 kHz max power (12W)

Signal-to-Noise ratio:  90 dB A weighted

Analogue Inputs:

1 Line,

1 Phono MM (47 k Ω) 40 dB gain

Digital Inputs:

1 SPDIF coax, 1 SPDIF optical 1 USB “B” type Windows/Mac/iOs/Android compatible

Max Resolution:  1 SPDIF coax, 1 SPDIF optical 1 USB “B” type Windows/Mac/iOs/Android compatible 24 Bit 192KHz

Remote Control:  Volume and Sources control

Power Requirements:  230 V AC 50 Hz (120 V AC 60 Hz) - 80W maximum

Dimensions (W x H x D) :  310 x 150 x 295 mm (12,2” x 5,9" x 11,6”)

Weight:  10,0 Kg (22.0 lbs)

I like

Audio Innovations - The First Audio Amplifier

The Audio Amplifier Series from Audio Innovations challenges a number of traditionally held beliefs, the most fundamental of which is the insistance that inn order for an amplifier to have a sufficient dynamic range, it must have a very high static power output. The second main misconception is that the amplifier must have low distortion; the third being the bandwidth nevessary to reproduce the audio apectrum.

The First Audio Amplifier is the first amplifier to significantly deviate from these design criteria. It is also first commercially available amplifier using the Direct Heated Triode, this being the most linear and load tolerant amplifying device available.

Special Features and Facilities

7,5 watt Pure Class A

Direct Heated Triodes type 684G or 2A3

No overall or local feedback employed

Fully hardwired circuit. No Printed Circuit Board

Handmade paper in oil capacitors for best possible signal transfer.

Non-magnetic resistors

Signal input wired with Audio Note 99,99% pure silver cable type AN-S

Cathode biased output stage

4 Ω , 8 Ω , 16 Ω output impedances, switchable on the back fascia

I like

McIntosh MC-60

The Mcintosh Model MC-60 is a 60 watt high fidelity power amplifier designed for home entertainment systems and professional applications where high power and distortion free performance is required. The Model MC-60, like all other McIntosh power amplifiers. Uses the exclusive McIntosh high efficiency output circuit and bifilar output transformer to obtain the high standard of performance found in this amplifier.

Some of the more important characteristics of the amplifier are less than 1/3% harmonic distortion at any power output up to 60 watts and at any frequency in the audio spectrum, 20 to 20,000 cps; less than 1/2% intermodulation distortion for all power levels up to 120 instantaneous peak watts; and noise and hum level 90 dB or more below the rated output level.

The MC-60 has two high impedance inputs and many be operated from any signal source deliviring 0,5 volts or more, or directly from a McIntosh Audio Compensator or pre-Amplifier such as the  Models C-4, C-8, C-104 or C-108.

Output impedances of 4, 8 and 16 ohms are provided for direct connection to loudsapeakers. An additional 600 Ω output is present for use with lines.

Specifications

Power Output:  60 watts continuous

Input Level:

Input 1 :  0,5 volts to 30 volts, with gain control

Input 2 :  2,5 volts (for use with McIntosh Audio Compensators and pre-Amp)

Frequency Range: 

20 to 30,000 Hz ±0,1 dB at 60 watts output

16 to 60,000 Hz ±0,5 dB at 60 watts output

10 to 1000,000 Hz ±1,0 dB at 30 watts output

Total Harmonic Distortion:  less than 1/3% at 60 watts output or less, 20 to 20,000 Hz

Intermodulation Distortion:  less than 1.2% if instentaneous peak power is below 120 watts

Impulse Distortion:  Negligible

Noise and Hum level:  90 dB or more below rated output

Damping Factor:  15 or better for 4, 8 and 16 Ω output, 20 for 600 Ω

Input Impedance:

0,5 meg for 0,5 volt input

0,13 meg for 2,5 volt input

20 cycles to 40,000 cycles

Output Impedance:

4, 8, 16 and 600 ohms (600 ohmis balanced to ground)

Phase Shift:  ±8° 20- 20,000 Hz

Tube Complement:

Rectifier :  2-5U4GA

Pre-Amp :  12 AX7

Phase Inverter : 12AU7

Voltage Amp : 12BH7

Driver : 12AX7

Output : 2-6550

Dimensions (W x H x D):  14" x 10" x 8"

Weight:  41 pounds net

Finish :  chrome and black

I like

Quad II Integrated Amplifier

The Quad II-Classic Integrated

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

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

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

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

Design and Engineering

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

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

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

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

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

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

Amplification Process

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

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

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

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

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

Specificastions

Stereo Power Output:  25 W per channel into 8 Ω

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

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

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

Crosstalk: better than 75 dB

Gain :  34 dB

Noise:  -98 dB (275 mV input)

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

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

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

I like

Luxman D-103u CD Player

High-Quality Vacuum Tube Analog Output Stage

The D-103u was designed to make the unique design of the D-105u available to more conservative budgets - without compromising on sound quality. That means using the same basic components in the analog signal path: two triode vacuum tubes in the output stage to recreate the delicate, transparent tones of the original performance.

Advanced Digital Output Stage

The D-103u also offers 18-bit , 8-times oversampling digital filters, and independent dual D/A converters. The STAR Circuit helps preserve signal purity at all stages.

"Mid-Ship" Mechanism

The ideally balanced, central position of the disc tray combines with Luxman's High-Rigid Lock mechanism to enhance the anti-resonance of the D-103u

Features Emphasize Ease of Use

Convenient D-103u features include: remote volume control, switchable front panel display dimmer, vacuum-tube warm-up switch, and 32-track random access and track programming.  In sum, the D-103u offers everything that a music lover could ask for  - and more.

Direct link to the LV-103u

The D-103u is the mainn playback source in serial remote control with the Luxman LV-103u Ultimate Fidelity integrated amplifier.other D-103u features include:

Memory Auto Check;  Automatic Scan/Pause; Fade-In/Out; Emphasis Display; CD Single Compatibility

Specifications:

Frequency Response:  5 Hz - 20 kHz (±1,0 dB)

Total Harmonic Distortion:  0,05% (at 1 kHz)

Signal-to-Noise Ratio:  105 dB

Dynamic Range:  89 dB

Channel Separation:  89 dB

Analog Output

Fixed :  2,0 V/ 47 k Ω

Variable :  0 -  2,0 V / 47 k Ω

Digital Outputs:

Coaxial :  0,5Vp-p / 75 Ω

Optical :  -21 to -15 dBm / 660 nm Wavelength

Dimensions (W x H x D):  438 x 145 x 320 mm

Weight:  6,5 kg

I like

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

Lafayette LA-226C

Features:

Dual 20 watt Stereo Amplifier

FM/AM Tuner with built-in FM Multiplex

Duplex 3-gang tuning condenser provides tuned RF stages for greater sensitivity and selectivity on FM and Am

Automatic Stereo monitor

17 front panel controls

20 tubes plus 8 diodes

Just add a turntable and speakers for a complete stereo system

The  Lafayette LA-226C is a self-contained instrument designed for the control and reproduction of all stereophonic and monophonic sources. Features a "pilot monitor"  stereo indicator which tells you instantly whether or not an FM station is broadcasting in stereo multiplex. The receiver section consists of an AM/FM tuner with built-in multiplex which provides more than 30 dB separation at 400 cycles. A sensitivity of 2 µV for 20 dB of quieting is achieved by the FM circuit with AFC defeat assuring reception of even the weakest signals. FM noise and filter slide switch cuts out unwanted station noise. The AM section features a superheterodyne circuit with AVC, and built-in ferrite loop antenna. The 40 watt amplifier section features large power fransformers and a frequency response of 20 - 20,000 cps ±2 dB. Less than 1,5% harmonic distortion on all modes.complete stereo preamp facilities provide dual concentric front panel controls for bass and treble, volume control balance, blend for variable channel separation from 5-position selection switch stereo to mono, (AM, FM, Stereo, Phono, Aux), 4-position amplifier mode switch (A, B, AB, REV), rumble filter slide switch, loudness slide switch, jack for stereo headphones, and On-Off power switch. Read controls include: Speaker phase switch, 8-16 Ω impedance selector switch , dimension control adjustment, speaker on/off switch, AC outlet, fuse and stereo tape outputs

" for the finest in electronic equipment  . . .  choose Lafayette"

Conceived and developed by Lafayette Radio, these products offer every desirable feature that 43 years of experience can provide. Precise engineering and the use of quality components assure you of the best  possible performance and the utmost reliability from the finished product. Whatever your need and budgetary level, there is a wide range of fine quality electronic equipment from which to choose. Each embodies the same fine engineering and handsome styling

Specifications

Frequency Response: 

FM :  20 - 20,000 cps ±0,5 dB

AM :  20 - 5,000  cps ±3 dB

FM Sensitivity:  2 µV for 20 dB of quieting

Harmonic Distortion:  0,7% on FM for 100% modulation

Hum level:  60 dB below 100% modulation

MPX Separation:  30 dB at 400 cps

Image Rejection FM :  -50 dB

Amplifer Section

Power Output: 20 watts per channel

Sensitivity:

2 mV at full output (mag. Phono)

30 mV at full output (crystal input)

Hum And Noisse:

65 dB below full outputfor low level

75 dB for high level

Tone Control Range:

Bass Control :  ±12 dB at 50 cps

Treble Control :  ±9 dB at 10 kc

Output Impedance:  8 and 16 Ω, switch selected

Input impedance: 

Phono :  47 k

High level :  22meg

Rumble Filter:  -8 dB  at 50 cps

Phono Equalization:  Riaa Standard

Finish:  handsome enclosure in contrasting brown and brass

Dimensions (W x H x D):  17-1/2" x 5-1/4" x 15"

Weight:  45 lbs (shipping)

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)