Audio Research SP-8 User manual

audio research
H I G H D E F I N I T I O N®
3900 ANNAPOLIS LANE NORTH / PLYMOUTH, MINNESOTA 55447-5447 / PHONE 763 -5 77 - 9700 FAX [phone]
Schematics Included: 7-1-81
7-1-83
4-4-84
SP-8 PREAMPLIFIER
OWNER
1S
MANUAL
(All Versions)

SECTION
INTRODUCTION
PACKAGING
INSTRUCTIONS
SERVICING
MUTING PROVISIONS
SUMMARY OF FEATURES
TABLE OF CONTENTS
WARRANTY TERMS AND CONDITIONS
WARRANTY OUTSIDE THE USA
SPECI FI CATIONS
ADDENDUM: SCHEMATIC & PARTS LIST
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PAGE
1-3
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4
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6-7
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INTRODUCTION
Congratulations on your purchase! Your SP-8 combines the highest possible musical
fidelity with a new level of reliability and serviceability.
With the introduction of power amplifiers such as the D-4O, D-79B, D-9O and D-12O,
and the availability of a number of brands of high performance recordings, pickups
and speaker systems, the need for a new and higher level of preamplifier for the
best systems has occurred.
After a significant amount of research and study we have determined that from a
performance standpoint once again, the vacuum tube must be used.
For best results, only high quality turntables with stable pickup arms and cartridges
should be used with this preamplifier.
We suggest that the SP-8 preamplifier will provide state-of-the-art reference
indefinitely. 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.
For further discussion of performance and system requirements we encourage you to
see your Audio Research dealer.
PACKAGING
Save all packaging. Your Audio Research® preamplifier is a prec1s1on electronic
instrument and should be properly cartoned any time shipment is made. You may never
have occasion to return it to the factory for service, but if that should prove
necessary, or other occasion to ship it occurs, the original packaging may save
your investment from unnecessary damage or delay. ·
SP~8 INSTRUCTIONS
The front panel has a totai of 4 controls and 4 switches:
GAIN: This controls volume or loudness, and is a special metal film segmented
control with approximately 2dB steps and accurate tracking. Although useable results
can be obtained with settings anywhere in the operating range, more convenient control,
best sound quality and signal-to-noise ratio will be obtained if the input signal
levels and amplifier input sensitivity allow normal listening to occur in the
11 01clock to 2 01clock range of the volume control.
In the case of some high efficiency speakers (such as Klipschorn, etc.) and/or high
output cartridges, it may be found with some high gain amplifiers (that d.o not have
an input volume control) that normal listening will occur with the gain control just
barely on, or up to the 9 01clock position. If this proves to be the case, there is
provision internally to reduce the gain by 6dB. Contact your Audio Research dealer
or ARC
1s Customer Service Department
for instruction.
BALANCE: A conventional stereo control. Moves the sound from left to right or
vice versa when rotated. Normally should remain centered.
MODE: Also a conventional stereo control. Allows operation as indicated.
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INPUT SELECTOR: Chooses between various possible source material for
listening c hoi ce .
The "phono" input is an RIAA compensated high gain input for use with most magnetic
cartridges. The input is SOK ohms, with very low (40 pF) input capacitance. If your
cartridge needs more capacitance, there is built-in provision to add whatever is
required. Contact your Audio Research dealer or our Customer Service Department if
you need help with this. ·
PRE-AMP ON SWITCH AND INDICATOR: Turns the unit on in the up position, and the
associated green LED will light up indicating that power is reaching the unit.
During the 2-minute warmup period of automatic mute the green LED will illuminate,
indicating the unit is on; however, the unit will not operate.
OUTLETS ON: Turns the power receptacles on the rear chassis panel on in the up
position, and the associated LED will light up indicating that they are on. This
switch is specifically provided to allow the amplifier to be turned on after the
preamplifier is "warmed up." A vacuum tube device requires up to several minutes to
fully stabilize its operating parameters . Power amplifiers should be turned off with
the outlet switch before the SP-8 is turned off to avoid turn-off thumps. The SP-8
mutes just after turn-off to minimize any excessive output surges.
MUTE OPERATE SWITCH: Shorts the output of the preamplifier for the warmup (and
cooldown) period. Also, to allow changing records (and maintaining a previous gain
setting), answering the telephone and the like.
INPUT MONITOR: Primarily aimed for use with tape recorders, but may be used with
any line level signal source where bypassing the input selector is desirable.
The rear panel has 4 power receptacles, a fuse holder, a ground terminal, 4 output
jacks, 12 input jacks and a pair of banana jacks:
RECEPTACLES: There are two unswitched outlets which may be used for turntables and
the like, where switching is not needed or wanted. There are also two outlets, relay
controlled, capable of providing power to large amplifiers and the like. Incidentally,
the "click" you hear internally when activating the receptacle switch is the relay
operating. · (The line cord is a 3 conductor, #14 guage, providing ample safe
grounded pwoer to these 3 outlets.)
It should be noted that the SP-8 line cord grounds the convenience outlet grounds
only. The preamplifier chassis is not connected to the line cord ground in order
to minimize system ground loops.
FUSE: Always use the same size and type as indicated on the rear of the chassis
for safety. For best results use Buss MDL or MDX fuses.
OUTPUT CONNECTORS: Main outputs should be connected to your power amplifier inputs.
Tape outputs should be connected to your tape recorder AUX inputs.
INPUT CONNECTORS: These are all clearly marked and are all SOK ohms.
GROUND TERMINAL: To be used for "grounding" associated input equipment, s uch as
tonearms, turntables and the like. Should not be connected to tape recorders and/or
amplifiers.
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"CH ASSIS
11
AND "B -1' BANANA JACKS: Special emphasis has been placed in the design
of this product to redu ce and/or eliminate
11
hu m,'
1
11
TVI,
11
1
'RFI
11
and
11
CB
11
type
interferences.
For normal use a jumper MUST be placed b~tween these connectors. Otherwise,
severe hum and/or oscillation will occur.
Special of f-chassis construction is employed to accomplish these interference
reduction methods , and this connection is the Q!8_y one from the
11
common
11
or
11
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11
circuit to the chassis so that it can act as a shield to outside interferences.
For rack cabinet mounting, when ground connections are used (via inputs/output s ),
this jumper may be removed to allow only one s hield ground path, thereby eliminating
what is known as
11
ground-loop
11
induced hum. Note that thi s may or may not necessarily
be helpful in a given sys tem.
If your SP-8 is ever removed from the rack, be sure to remember that a jumper MUST
be rein stall ed .
Discussion, feature and specification sheets are also included herewith to provide
you with additional information you may want or need.
A schematic diagram, complete with voltages, references, values, etc., is also
included. These three items should provide all the basic information you will need.
SERVICING
First of all, a very serious caution: This unit contains over 500 volts of DC, with
suf ficient voltage and current available to be lethal. So, lease, do not poke around
inside the unit. Refer any needed service to a qualified technician. Even with the
unit turned off, a charge remains in the energy storage capacitors for some time.)
Bas ically, this unit is constructed to the highest commercial sta ndards and should
require a very minimum amount of service over the years.
The vacuum tubes furnished with your SP-8 are quality tubes, and should not have to be
changed for approximately two thousand hours of use. Tubes can fail, however , and the
following service hints are offered:
If excessi ve noise should develop in the phono section only, it is most likely Vl.
If degraded sound should occur in the phono section only, it is most likely V 2.
V3 is not normally critical, although occasionally excessive hum can be caused by
failure of this tube.
If excessive noi se developes in the hi gh l evel s ection (ie: inputs other than phono),
it is mo st likely V4.
If degraded so und developes in the hi gh level sect ion, it is most likely V S.
V6 is also not norm a lly cr itical, although it al so ca n introduce hum.
If tube c han ging is to be done, t he uni t should be disconnected from the amplifier
a nd turned off whil e the ch ange is made.
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DISCUSSION OF THE SP-8 MUTING PROVISIONS
The SP-8 has 4 provisions to guard against possible misuse of the exceptional dynamic
range and wide bandwidth that it offers. The SP-8 is not subject to damage itself,
but some power amplifiers and speakers are more limited in their ability to withstand
signal extremes. These provisions, both manual and automatic, are designed to give a
flawless listening experience with unprecedented realism, while giving protection
against operator error or other improper conditions beyond the operator's control.
1. OUTLET SWITCH to allow the power amplifier to be off during warmup or shutdown
of the SP-8. A minimum of 5 minutes warmup time is recommended to insure optimum
performance.
2. MUTE/OPERATE SWITCH to manually disable the SP-8 outputs during any moving
of the tone arm or switching of equipment. This will minimize stress on your power
amplifier even when it is off.
3. WARMUP TIMER that mutes the SP-8 outputs for approximately 2 minutes after the
power switch is turned "ON," to ensure circuit stabilization before the outputs
come "ON."
4. IMPROVED POWER SUPPLY to tolerate power line disturbances or "brown-outs" down
to lOOVAC or less, without degredation of circuit performance.
The automatic muting operates as follows:
1. The manual mute switch always disables both outputs and overrides any automatic
provisions, even when the SP-8 is turned off. (The "Operate" position of the manual
mute switch is functional only after the unit is no longer in automatic mute mode.)
2. The 2-minute warmup timer will restart automatically if the power is temporarily
interrupted for 0.2 seconds or more, which is sufficient time to disturb the heater
temperature in the tubes.
3. The automatic muting of the SP-8 is designed to be effective only against all
kinds of power line interruptions and power supply failures. It will not mute against
subsonic signal transmissions from your turntable, etc. Proper fusing of speakers is
essential to protect against excessive audio level or power amplifier faults.
4. The muting is accomplished without clicks by "soft-switching" photocouplers, with
pure resistive photoconductive elements. No electrical contacts or moving parts are
used in the audio path to insure no degredation of sonic performance. All photocoupler
lamps are light-emitting diodes to provide essentially infinite service life.
5. Qualified service personnel may wish to disable the warmup muting and output
sensor muting for testing purposes. This may be done by reconnecting the output
leads to the other side of the photocouplers.
SUMMARY OF SP-8 FEATURES
As expected with a product of this caliber, the SP-8 offers many outstanding features
to the audiophile perfectionist .
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AUTOMATIC MUT ING: A two -m inute warmup timer insures muting of u nd esirab le s ub so nic
output during c ircuit stabi li zat ion . No trouble s ome relays or electrical conta cts
are use d. (Not e that there is no vi sual indi ca tion of automatic muting as, fo r
example, in the S P- 6C. )
MANUAL MUTING: A front panel mute switch is included for repeat set ting s,
int e rruptions, etc.
HIGH ACCURACY, CLOSE TRACKING, SEGMENTED GAIN CONTROL: Ametal -f ilm stereo volume
control assures trouble fre e, close tracking volume se lection in 2 dB steps
(guaranteed l .5dB tracking, .5dB typical).
GAIN ''RANGE'': An internal wiring change allows for better gain m atc hing or high
efficiency loudspeakers , hi gh output cartridges, transformers, etc.
SEPARATE FRONT PANEL POWER RECEPTACLE SWITCH: A front panel switch operates two
relay-controlled outlets with a 1600 watt capacity for power amplifiers and other
outboard devices.
SPECIAL OFF-CHASSIS CONSTRUCTION: The special isolated ground construction floats
all inputs and outputs from the chassis. Special rejection filters are also included
to minimize or eliminate RFl, TVI and CB interference.
SONICALLY SELECTED COMPONENTS: E xc lusive use of quality tubes, special met al film
resistors and multiple shunt capacitors provide optimum sonic accuracy.
OTHER FEATURES INCLUDE: A rear panel provision for disconnecting the common ground
from the chassis so that rack mount installations may be accomplished without ground
loop induced hum. Front and rear panels are of two -color anodized aluminum construction
for permanent fini sh and lettering. Industrial grade components and con s truction are
used fo~ long service life.
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3-YEAR LIMITED WARRANTY TERMS AND CONDITIONS
1. LIMITED WARRANTY. Audio Research warrants the product designated herein to be
free of manufacturing defects in material and workmanship, subject to the conditions
hereinafter set forth, for a period of three (3) years from the date of purchase by
the original purchaser or no later than five (5) years from the date of shipment to
the authorized Audio Research dealer, whichever comes first, excepting vacuum tubes
which are warranted for 90 days only (See 6).
2. CONDITIONS. This Warranty is subject to the following conditions and limitations.
The Warranty is void and inapplicable if the product has been used or handled other
than in accordance with the instructions in the owner's manual, abused or misused,
damaged by accident or neglect or in being transported, or the defect is due to the
product being repaired or tampered with by anyone other than Audio Research or an
authorized Audio Research repair center. The product must be packed and returned to
Audio Research or an authorized Audio Research repair center by the customer at his
or her sole expense. Audio Research will pay return freight of its choice. A RETURNED
PRODUCT MUST BE ACCOMPANIED BY A WRITTEN DESCRIPTION OF THE DEFECT AND A PHOTOCOPY OF
THE ORIGINAL PURCHASE RECEIPT. This receipt must clearly list model and serial number,
the date of purchase, the name and address of the purchaser and authorized dealer and
the price paid by the purchaser. Audio Research reserves the right to modify the design
of any product without obligation to purchasers of previously manufactured products and
to change the prices or specifications of any product without notice or obligation to
any person.
3. REMEDY. In the event the above product failj to meet the above Warranty and the
above conditions have been met, the purchaser's sole remedy under this Limited Warranty
shall be to return the product to Audio Research or an authorized Audio Research repair
center where the defect will be rectified without charge for parts or labor, except
vacuum tubes (See 6).
4. LIMITED TO ORIGINAL PURCHASER. This Warranty is for the sole benefit of the
original purchaser of the covered product and shall not be transferred to a subsequent
purchaser of the product.
5. DURATION OF WARRANTY. This Warranty expires on the third anniversary of the date
of purchase or no l ater than the fifth anniversary of the date of shipment to the
authorized Audio Research dealer, whichever comes first.
6. VACUUM TUBES. Vacuum tubes are warranted for the original 90-day period only.
7. DEMONSTRATION EQUIPMENT. Equipment used by an authorized dealer for demonstration
purposes is warranted to be free of manufacturing defects in materials and workmanship
for a period of three (3) years from the date of shipment to the dealer. Vacuum tubes
are warranted for 90 days. Demo equipment needing warranty service must be packed and
returned to Audio Research by the dealer at his sole expense. Audio Research will pay
return freight of its choice. A returned product must be accompanied by a written
description of the defect on an AUDIO RESEARCH RETURNED GOODS AUTHORIZATION form.
Dealer-owned demonstration equipment sold at retail within three (3) years of date of
shipment to the dealer is warranted to the first retail customer to be free of
manufacturing defects in materials and workmanship for the duration of the 3-Year
Limited Warranty remaining (as measured from the date of shipment of the equipment
to the dealer). Vacuum tubes are not warranted for any period under these conditions
of sale. In the event warranty service is needed under these conditions, the owner of
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the equipment must provide a copy of his purchase receipt, fulfilling the requirements
described under
11
2. Conditions
11
above. The product must be packed and returned to
Audio Research or an authorized Audio Research repair center by the customer at his or
her sole expense. Audio Research will pay return freight of its choite.
8. MISCELLANEOUS. ANY IMPLIED WARRANTIES RELATING TO THE ABOVE PRODUCT SHALL BE
LIMITED TO THE DURATION OF THIS WARRANTY. THE WARRANTY DOES NOT EXTEND TO ANY
INCIDENTAL OR CONSEQUENTIAL COSTS OR DAMAGES TO THE PURCHASER. Some states do
not allow limitations on how long an implied warranty lasts or an exclusion or
limitation of incidental or consequential damages, so the above limitations or
exclusions may not apply to you. This Warranty gives you specific legal rights,
and you may also have other rights which vary from state to state.
9. WARRANTOR. Inquiries regarding the above Limited Warranty may be sent to the
following address:
WARRANTY OUTSIDE THE USA
Audio Research Corporation
6801 Shingle Creek Parkway
Minneapolis, MN 55430
Audio Research has formal distribution in many of the countries of the free world.
In each country the Audio Research Importer has contractually accepted the
responsibility for product warranty. Warranty should normally be obtained from
the importing dealer or distributor from whom you obtain your product.
In the unlikely event of service need beyond the capability of the Importer,
Audio Research does, of course, back up the warranty. Such product would need
to be returned to Audio Research, together with a photostatic copy of the bill
of sale.
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SP-8 SPECIFICATIONS (AC line set @120V 60Hz for these specifications)
Frequency Response:
High level section:
~.25dB, 5Hz to 30Hz
Magnetic phono:
-3dB points below lHz and above lOOkHz
~.25dB of RIAA, 30Hz to 40kHz
Harmonic Distortion:
Less than .01 % at 2V RMS output, 20Hz to 20kHz (Typically less than . 0005 %in midband)
Intermodulation Distortion:
Less than .002% at 2V RMS output
Gain:
Magnetic phono input to tape output: 34dB
Magnetic phono input to main output: 60dB
Input Impedance:
High level inputs to tape output: OdB
High level inputs to main output: 26dB
SOK ohms, all inputs (Magnetic phono may have any value from 10 ohms to lOOK ohms
substituted. Also has provision to add to the 40pF input capacitance for matching
certain magnetic cartridges.)
Output Impedance:
1000 ohms main output and tape outout. Recommended m1n1mum ln~8
for maximum audio quality 20K ohms and .OOluF maximum capacitance.
Maximum Inputs:
Magnetic phono, 900mV at lkHz. (3.5V RMS, lOkHz) High level inputs essentially
overload-proof.
Rated Outputs:
2V RMS 5Hz to 30kHz, all outputs; 60K ohm load (main output capability is 60V RMS
output at 1/2% THO at lkHz into a lOOK ohm load with 3V RMS high level input)
Power Supplies:
Electronically-regulated supplies utilizing both vacuum tube and solid state
elements. Line regulation better than .01%
Noise:
High Level
(1) 250uV RMS maximum residual unweighted wideband noise at main output
with gain control minimum (86dB below 5V RMS output)
(2) Mote than 90dB below lV RMS input (less than 20uV equivalent input noise)
Magnetic Phono
SuV equivalent input noise, wideband RMS (-66dB reference lOmV input)
(Approximately luV · above 200Hz or -80dB reference lOmV input)
Tube Complement:
2 - 6DJ8 or equivalent dual triodes
1 - 12BH7A
4 - teference grade E83CC or equivalent triodes
1 - l 2AX7 /ECC83
Power Requirements:
100-125VAC 60Hz (190- 240 VAC 50Hz) 60 Watts
Dimension s:
19
11
(48 cm) Wx 5 1/4
11
(13.4 cm) H (standard rack panel) x 10 1/4
11
( 26 cm) D.
Handles extend 1 5/8
11
(4.1 cm) forward of front panel. Rear chassis fittings
extend 7/8
11
(2.3 cm).
Weight:
22 lbs. (10 kg)Net, 30 lbs. (13.75 kg) Shipping
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