Eico HF-85 User manual

MODEL HF-85
STEREOPHONIC PREAMPLIFIER
general description
GENERAL
The EICO Model HF-85 is acomplete high fidelity ster-
eophonic control center. It offers proctlcallyevery con-
trol and switching facility anyone could want In aphysi-
cal design adaptable to any type of installation. With it
you can select, preamplify and control accurately, ony
stereophonic source, whether It be from tope, discs or
broadcasts. Every control facility Is both useful and ef-
fective.
Extremely low distortion, bordering on the Immeasurable
(even at high output levels), precludes any degradation
of quollty from the best modern program sources.
The HF-85 Is self-powered, utilizing afull-wove rectifier
tube power supply. It works in conjunction with any two
high quality power amplifiers, such as the EICO HF-I4,
HF-22, HF-30, HF-35, HF-50, and HF-60.
FEATURES
1. Separate low level input in each chonnel for mag.
phono, tope head, and microphone. Circuitry carefully
designed to provide the high gain required by tape heads
and high quality, low output mag. cartridges without hum
and noise problems. Afront panel switch permits choice
of the proper NARTB tape head equalization for either
71/2 &15 or 33/4 ips tape speeds.
2. Separate high level inputs for AM tuner, FM toner,
and FM Multiplex. Also two auxiliary AInputs (one in
each channel) and two auxiliary BInputs (one in eoch
channel). Input selector switch on front panel has posi-
tions forfeedlng FM tuner output to one channel and AM
tuner to the other, or FM tuner to one channel ond FM
Multiplex adapter output to the other.
3. Independent level controls that may be operated sep-
arately or together with abuilt-in clutch.
4. Distortionless, 3-stage, independent bass and treble
tone control circuits In each channel. Each tone control
circuitcortsistsofa feedback amplifier palr(30db of feed-
back) driving true variable crossover, feedback tone
cmtrol stage. Bass and treble controls do not Interact
with each other or affect the level. Bass controls In both
channels and treble controls in both channels are concen-
tric. Controls may be operated indivIduoMy or together
with abuilt-in clutch.
5. Fletcher-Munson loudness compensation for low level
listening which may bedisobled byfront panel slide switch.
6. Extremely versotlle function selector permits listening'
to each channel separatelyfor cheeking purposes; onstereo
listening, to reverse the channel connections; on mono-
phonic record ploying with astereo cartridge, to mix the
,
twochonnelsforconcellotlonof vertical rumble; on mon-"
ophonic tuner, to have the channels unmlxed so as not ta.
Introduce extraneous noise from the unused input,
7. Low impedance output to tape recorder, useful on all
inputs. Output to main amplifier Impedance permits use
of up to 40ft. of 25mmfd/ft. shielded audio coble before
response at 20,000 cis affected.
8. Hum bolance control, pilot lamp, convenience out-
lets.
9. New "low-silhouette" construction matches EICO
tuner. Very attractive when placed on ashelf or out in
the open, yet permits easy console Installation with full
shielding and adaptability to any panel thickness. Em-
ploys one piece horizontol chassis (cadmium plated steel)
attached to the centersof two side pieces (brown enameled
steel). Unit Is self-supporting for easy servicing top or
bottom. Perforated steel cover (metallic-gold painted)
slides In and out on rails in the side pieces. Abottom
plate and front bezel (both brown enameled steel) plus a
solid brushed brass control plate complete the assembly.
Controls may be used as either concentric or ganged with
built-in clutch mechanisms.
1

SPECIFICATIONS
Frequency Response: ±0. 3db 5-2OO/000c at any level
up to 3VRMS out. (Measured from high level In-
puts with level controls set at maximum and tone
controls electrically flat.)
Sensitivity (input for 2V RMS output qt lOOOeps :Mag.
Phono-1 mv; Microphone-l mvj Tc^-Head -0.
5
mv; High Level Inputs -0. 17V.
Hum &Noise: Mag. Phono-60db; Microphone-60db;
Tape Head -50db; High level inputs -75db. (For
low level Inputs, values given are equivalent
noise Input in db down from lOmv input level.
For high level inputs, value given is equivalent
noise input in db down from 0. 5V input level.)
ImDistortion (60 and 7000 cps at 4;1);
IM Dl^. VRMS OUT
0.52% 0.5V
0.03% l.OV
0.04% 2.0V
0.07% 3.0V
0.11% 4.0V
0.17% 5.0 V
Harmonic Distortion (2^20, OOOcps) ;0. 1% at 3V RMS
out; 0. 15% at 5V RMS out.
Tone Control Range; At lOkc: 15db boost, 15db cut; ot
”50cps: li^b boost, 15db cut.
Equalization! Phono -RIAA; Tape Head -NARTBfor 15 ips
and 71/2 ips, 33/4ips.
Output to Tape Recorder Impedance; 1,400 ohms.
Output to Main Amplifier Impedance: 8, 000 ohms.
Tubes; 5- 12AX7/ECC83, 1-6X4
Size; 35/8" high, 12" wide, 81/2" deep.
Weight: 91/2 lbs.
2

mechanical installation
GENERAL
a) HEAT DISSIPATION (VENTILATION): Incommonwith
other electronic equipment, the HF-85 produces consid-
erable heat In normal operation. Unless continuous and
adequate air flow is obtained around the heat producing
elements, these elements will over-heat and their useful
life will be reduced.
Adequate ventilation will be provided if the HF-d5 is
installed inan open-back console provided thot the top of
the unit is spaced at least two inches below <xiy shelf
mounted above it. IF the cabinet Is enclosed at the rear,
provide several large holes or slots as low down and as
high up in the cabinet back as possible. As an alternative,
holes may be provided in the sides, bottom, or top of the
cabinet. The important thing to remember is that effective
ventilation requires provision for cool air to enter at the
bottom and hot air to leave ot the top.
If the HF-85 is not installed in a console, it may be sit-
uated on an open surface or on ashelf of abookcose.
Four rubber feet are also provided so that It will not mar
the surface of furniture on which It Is placed.
b) EASY ACCESS TO CONTROLS: Mount the preampli-
fier at aheight which will permit eosy manipulation of
the controls.
e) ACCESSIBILITY TO PARTS: Tubes ore the most fre-
quently reploced items in electronic equipment. If the
preamplifier Is installed in aconsole, sufficient spoce
should be alloted to reach and remove any tube in the
unit. Furthermore, input and output terminals of the pre-
amplifier should be accessible to permit easy Interchang-
ing of system components for comparison. If antennas ore
strung around the back of the console in which the pre-
amplifier is installed, arrange them so they will not in-
terfere with access to fhe unit.
d) ACOUSTICAL ISOLATION: If preamplifier and speaker
are installed inthe same cobinet(not recommended), pro-
vide sufficientseparationtomlnlmize mechanical speaker
vibration reaching the preamplifier which may result in
mtcrophonicsand howling. The minimum separation Is o-
bout one foot. Abaffle, usually the preamplifier mount-
ing shelf, should be present between preamplifier and
speaker. In extreme coses, it may be necessary to mount
the preamp] if ier on sponge rubber pods.
CONSOLE MOUNTING
a) Operations on console front panel preliminory to [ye-
amplifier mounting :(1) Tape the panel template provided
to the face of the console so that the top of the mounting
Mirfoce line on the template is level with the top of the
amplifier mounting shelf. (2) Use an awlornallto pierce
the centers of the four extreme outers holes For mounting
the control plate, to transfer their locations to the con-
sole panel beneath. (3) Trace out the rectangular cut-
out with an awl or nail ond then pierce the centers of the
Four 1/2” holes, one in each corner of the cutout. (4)
Remove the panel template. (5) Drill the four 1/2" holes
in the console panel, one in each corner of the rectan-
gular cutout area. Cut out the rectangular piece with a
keyhole saw, using the four 1/2” holes as starting holes.
b) Preamplifier mounting In console; (1) Pull off the con-
trol knobs. (2) Remove the four screws that fasten the
bezel to the side pieces and remove the bezel. (3) Re-
move the two screws and nuts that Fasten the control plate
to the bezel. The bezel it not used In console mounting.
(4) Fasten the control plate to the console panel with the
two ^4 X3/6 wood screws supplied. (5) If the rubber feet
hove been inserted in the bottom plote, remove them.
(They moy be pried out with athin screwdriver.) (6)
Place the unit on the mounting shelf and slide It forward
until the slideswitch support l^oekets are up against the
panel and both slide switches oceeuible from the front;
the control shafts should be approximately centered In
the corresponding holes in the control plate. (7) With a
sharp pencil, draw the outline of the side and rear bottom
edges on the chassis shelf. As the bottom plote falls short
of the full width by 3/16” on each side, draw new side
edge lines 3/16^ Iruide the original side edge lines. (8)
Now remove the knobs and take the chassis off the shelf.
{9) Remove the 6screws which fasten the bottom plate to
the chassis. (10) Place the bottom plate exactly in the
outline drown on the shelf and mark the position of the
center hole on the left side and the center hole on the
right side. (11) Remove the bottom plate and drill each
of the marked holes on the shelf to adiameter of 1/4".
(12) Refesten the bottom plate to the chassis, with the
four of the six screws previously removed, using
the two holes at the rear and the two holes at the front
of the chassis. (13) Replace the chassis on the shelf,
positioning it exactly in the outline previously drawn,
and restore the knobs. This time make sure that the In-
dicator dot on each knob agrees with the control position.
(14) From the bottom side of the shelf, insert a^Sx!"
screw, with a1/2" flat washer against the head, through
both the left and right side center holes. These screws
engage the stamped nut over each hole on the chassis
flange ondwhen tightened secure the chosslsto theshelf.
3

relectrical installation
GENERAL
a) INPUTS: There are identical pairs of MAG. PHONO,
TAPE HEAD, MICROPHONE, AUXILIARY A, and AUX-
ILIARY Binputs— oneof each pair in channel land chan-
nel 2—and each Is identified accordingly by the suffix
1or 2. The MAG. PHONO, TAPE HEAD, and MICRO-
PHONE pairs of inputs are all "low level" Inputs, mew-
ing that they all feed through apreamplifier/equalizer
stage In either channel 1or 2. The AUXILIARY A«id
AUXILIARYB pairs of inputs are "high level" inputs, mean-
ing that they enter either channel 1or 2at apoint after
the preamplifier/equalizer stages. The AM, PM and FM-
FM Multiplex inputs are also "high level inputs", which
are internally selected in pain— one for each channel
-by the SELECTOR switch. At the TUNER, AUX, posi-
tion of theMODEswitch,AMonly is selected at the AM-
FM position of the SELECTOR switch, and FM only Is
selected at the FM-FM MULTI, position of the SELECTOR
switch.
1)
MAG. PHONO 1, MAG. PHONO 2: These inputs
are intended for the two outputs ofa stereo magnetic cart-
ridge, or for astereo ceramic cortridge with ode^tors.
Four-terminal cartridges (each sensing element brought out
to aseparate pairof terminals)are generally advantageous
as compared to three-terminal cartridges (one terminal of
each sensing element brought out to acommon terminal)
because the possibility of Increased hum due to aground
loop can be avoided. The correct method for wiring o
four-terminal cartridge it shown In Fig. I. (If the cart-
ridge is athree-terminal type, the two Inside contacts
of the cartridge shown in Fig. 1ore effectively replaced
by 0common terminal.) The loodlng presented to each
output of the cartridge by each MAG. PHONO Input Is
100, 000 ohms. If alower loading resistance is required
by the particular cartridge used, connect oshunt resistor
ofopproprlote voluefromeochoutside terminal of the car-
tridge to the center (common) terminal. This can be done
actually bymounting a3-post terminal strip on the under-
side of the phonograph mounting boord ot apoint neor the
lead break-out fromthepickup arm. These shunt resistors
ore then wired to this terminal strip os shown in Fig. 1.
The value of each of the two shunt resistors (Rj) ccm be
determined from the desired loading resistance (R|)bythls
formula _100, 000 xR|
*100, 000 -R|
orthi5table;forR| =50K£5,u$eRs =lOOKfi; for R] =33KQ,
use Rj =50KG; for R| =25Ka use R* =33Kfl.
*NOTE: All ceromic cartridge manufacturers hove de-
veloped simple networks which when connected to the out-
puts of their cartridges result in acharacteristic identical
to that of magnetic cartridges. By interposing the re-
commended adaptor for the porticulor ceramic cartridge
between the cartridge outputs and the MAG. PHONO
inputs of the amplifier. It Is possible to use the MAG.
PHONO Inputs for the ceramic cartridge with excellent
results. Adaptor networks ore given in the literature for
the particular ceramic cartridge and can be built on a
terminal strip mounted on the underside of the phonograph
base, or maybe available in convenient component form
from the cartridge manufacturer. Stereophonic crystal
cartridges (Ronette "binofluid" OVand BF40) can be con-
nected directly to auxiliary high level Inputs.
2) TAPE HEAD ],TAPE HEAD 2: These inputs are intend-
ed for direct connection to stackedstereoploybockheods.
The tape heads can be either two-track or the new four-
track type. Afront panel slide switch permits choice of
NARTB tope head equalization eitherfor? l/2ipsor3 3/4
tope speeds. Note that the equalization required for the
new four-trock type at the stondard 33/4 ips tope speed
for four-trock 1$ the same as for the older two-track at
7l/2ips. The TAPE speed switch Is therefore set ot 71/2
for both two-trock at7 1/2 Ips ond four-trock at3 3/4lps.
The 33/4 position of the TAPE speed selector is set at
33/4 for ployback of 33/4ips two-track tq}es on two-
trock machines. The loading resistance presented by each
tope heod input is 1megohm. Appropriate shunting resis-
tors can be Installed In the tape deck if the loading re-
sistance specified for the particular heads is substantially
lower.
3) MICROPHONE 1, MICROPHONE 2: These inputs ore
Intended for receiving the output signals directly from
two separate microphones. It ispreferably that themicro-
phones used be of the high impedonce type.
4) AUXILIARY Al, AUXILIARY A2: These inputs are
Intended for either astereophonic or monophonic high
level source. Astereophonic high level source might be
astereo tape deck with built-in playback equalization
for both tracks. Amonophonic high level source might
4

be a monophonic crystal cartridge or tv sound. Plug a
monophonicsource IntoAUXlLlARYAI, leaving the AUX-
ILIARYA2 input unused. Note that the input impedance
at all these high level inputs is 0. 5megohm, w4iich is
too low for ceramic cartridges requiring 2to 3megohms
input impedance. For ceramic cartridges, use the MAG.
PHONO inputswith the simpleodoptor networks recom-
mended by the manufacturers. For stereophonic crystol
cartridges (Ronette "Binofluid" OVturnover and BF40sin-
gle needle), the 0.
5
megohm load provided at the high
level inputs is exactly the loading impedance required.
5) AUXILIARY Bl, AUXILIARY B2: Same os for AUX-
ILIARY Al, AUXILIARY A2 obove.
6) AM: This input is intended for AM tuner or the AM
output of an FM-AM tuner where the FM and AM sections
are independent.
7} FM; This Input is Intended for an FM or FM-AMtuner
where the FMond AMsections are not independent. Also
the main carrier or equivalent output from an FM Multi-
plex odaptor.
NOTE: Ashielded coble with ashielded "phono-type"
plug should be used to connect from eoch of the otove
mentioned sources to the corresponding amplifier input
jack. Unless the source hos alow-impedance output such
as acathode follower (with which up to 50ft. of coble
can be used), use the shortest possible connection and
low-capacity shielded coble (cable having os low os 25
mmfd capacitance per foot is available).
b) OUTPUTS TO TAPE RECORDER: The TAPE OUT CH. 1
and CH. 2faeks permit feeding the channel 1and chan-
nel 2ilgnals to astereo tape recorder. With ameitophonic
source connected to achannel 1Input, the TAPE OUT
CH. 1jack is used for feeding out to a monaural tape re-
corder. Lew-capacity shield audio cobles wIthRCA-type
phono connectors at the end may be used in lengths up to
50ft. to connect each jack to the tape recorder ir^juts.
Note that any inputs chosen by the SELECTORswitchfeed
out through these jocks. All inputs ore affected by the
LEVEL control and the LOUDNESS compensation switch,
but not the tone controls.
c) SIGNAL CONNECTIONS TO MAIN POWER AMPLI-
FIERS: The PREAMP OUT CH.1 and CH.2|acks are eoch
connected to the input of abasic power amplifier*. The
two basic power ampllfien may be separate or combined
on one chassis. Low capacity shielded audio cables with
RCA-type phono connectors at the ends should be used in
lengthsupto 10 feet normally. If the cable cc^ocity is os
low os 25 mmfd per foot, lengths up to 40 feet may be used
if necessary. However, the shortest possible cable length
should always be used.
*NOTE: If the user already has an integrated amplifier
from his original monophonic system, it may be used os a
basic power amplifier by connecting to one of its high
level inputs (tuner, radio, auxiliary), setting its tone con-
trols to the "flat" positions, its loudness compensotlon
control or switch (if ony) to where it has no affect, ar>d
its level control to maximum. In the case of the EICO
HF12, HF20,or HF32 integrated ampl1fiers,a more direct
connection to the power amplifier sections may be made
by connecting to the TAPE OUT jacksof these units, set-
ting the LEVEL control and LOUDNESS control (if any)
to maximum. In the case of the EICO HF52 integrated
amplifier, connect to the ELECTRONIC CROSS-OVER
OUTPUT jack and snip the connection between the ELEC-
TRONIC CROSSOVER INPUT &OUTPUT jocks inside the
chassis; the control settings on the HF52 ore then im-
material. ElCOnowoffers a complete lineof basic power
ompi if iers which maybe used in pairs for stereo. Included
ore the HF60 (60watts roted) HF50 (SOwatts rated), HF35
(35 watts rated), HF22 (22 watts rated), and the HF14
(14 watts rated).
d) POWER CONNECTIONS: The power cords of the
basic power amplifiers, the tumtoble, and the tuner may
be inserted in the convenience outlets provided on the
rear chassis apron. The receptacle marked 117VAC is
intended for use primarily witha phonograph and provides
117VAC regardless of whether the power switch of the
amplifier Is turned on or off In order to protect the phono-
graph mechanism. The receptacle marked 117VAC
SWITCHED is "llve"or''dead"depending on whether the
preamplifier power switch it turned on or off and is in-
tended prlmarilyfor use with the basic power amplifiers.
The recommended method Is to plug the line cord of one
basic power amplifier into the 117VAC SWITCHED re-
ceptacle of the HF85ond the line cord of the other basic
power ompllfler into either convenience receptacle on
the first power ompllfier. Tunersond otherdevleei which,
may be turned on and off with the preamplifier power
switch should be plugged Into the remaining receptoeles
on the basic power amplifiers.
HUM ADJUSTMENT
Aftercheckingthe preamplifier for proper operation, re-
move all input cables to the preamplifier and make the
following control settings which hold throughout the proc-
ess of hum adjustment: SELECTOR switch at PHONO,
MODE switch at STEREO NORM., both LEVEL controls
ot 10, LOUDNESS compensation switch at OFF, both
BASS controls at 0, both TREBLE controls at -5. The pre-
amplifier should be connected to the two basic power
amplifiers which must in turn be connected to the two
speaker systems. The two speokersystem must be in phase
and placed near one another for this adjustment. Connect
theline cordsof the two basic power amplifiers as recom-
mended in POWER CONNECTIONS above. Plug the
preamplifier line cord Into a117VAC wall outlet. Touch
one end of alength of hook-up wire to the preamp chassis
and check for aspark when the other end Is touched to
an unpointed chassis point on both power amplifiers. If
aspark occurs in either ctse, reverse the prong position
of the line cord plug for that power amplifier. Now place
your ear close to both loudspeokers and listen to the hum
level. Reverse the prong posltionof the preamplifier line
cord plug in the wall outlet and listen again. Choose
the prong position glvlngthe least hum. Now connect the
5

funer input connector to the appropriate input jack on
the preamplifier andwith the tunerset inbetween stotions
and the tuner volume control set at minimum, find the
prong position of the tuner line cord in one of the con-
venience receptacles on the basic power amplifiers that
gives the least hum. Finally, connect the phono Input
connectors to the PHONO CH. 1and CH. 2Inputs (stereo
mag. cartridge), or through the recommended odaptors to
these inputs (stereo ceramic cortridge), or to one set of
auxiliary Aor Binputs (stereo crystal cartridge) and do
the some with the power plug of the turntable (turntable
off and pickup arm at rest position) using the 117VAC
convenience receptacle on the preamplifier. When all
of this Is completed, adjust the hum balance control on
top of the preamplifier chassis for least hum.
operation
PRELIMINARY: Be sure all tubes arefirmlyseotedin their
sockets and that the tubeshlelds are making good contact
with their bases. As initial adjustments, set these controls
as follows: LEVEL controls 1&2at 0, BASS controls 1&
2at 0, TREBLE controls 1&2at 0, LOUDNESS compen-
sation switch at OFF. Turn the system on by setting the
POWERswitchatON. Please note that in the irutnjctions
that follow, it is assumed that ostereo pickup and/or a
stereo tape head is being employed in the system.
LEVEL, BASS, &TREBLE controls: The LEVEL, BASS, ond
TREBLE controls each consist of two concentrically mount-
ed controls, one In each channel. Abuilt-in clutching
device is effective when the smaller diameter inner knob
(Amplifier 2control) Is pressed in against the larger di-
ometerouterknob (Amplifier 1control). At the in(clutched)
position, turning either knobwill cause both knobs to turn
together, to moke the some odjustments in both chonnels
simultaneously. The clutching device is disengoged when
the smaller Inner knob Is pulled out, making it possible to
turn and adjust eachof the controls Independently. Pleose
note that the clutching mechanism Is designed to permit
slipping, so thot either the Inner or outer control con al-
ways be turned to either minimum or maximum even If the
other control is engoged to It In amore odvanced position
In the desired direction of turning. The optional clutching
arrangement just described In intended to be used in the
following manner: to adjust level balance, bass balance,
and treble balance between the two chonnels(to accomo-
date the Inevitable gain differences between channels due
to tolerances and aging of components, loudspeaker re-
sponse differences, room acoustics), the controls ore dis-
engaged for independent adjustment; once bolonce has
been achieved, the controls are engaged to permit sim-
ultaneous adjustments of level, bass and treble in both
channels for different records, program material, cmd de-
sires os to listening level.
SELECTOR Switch: The SELECTOR switch selects corre-
sponding pairs of Inputs to both channels. The progron
source being fed to any of these poirs of inputs may be
either stereophonic or monophonic. The M^OE switch
takes care of setting up the preamplifier according to the
type of the program source (stereophonic or monophonic^
tuner or phono, etc.) and also' performs other functims
detailed In the description of the MODE switch. The
AUX A, AUX B, AM-FM and FM-MULTI ore all high
level pairs of Inputs suitable for stereophonic or mono-
phonic crystal cartridges, AMor FM toners, AM-FMstereo,
FM-FM Multiplex stereo, pre-omplified equalized tope
ployback, tv sound, etc. As to monophonic tuner, use
the AM-FM position for AM tuner selection, and FM-
MULT! for FM tuner selection. When Independent AM
and FM tuners are used, and/or an FM Multiplex adaptor
is used in conjunction with or is incorporated in the FM
tuner, the some two positions can be used for AM-FM or
FM-FM Multiplex stereo broadcast selection. The MIC,
PHONO, and TAPE positions of the SELECTOR switch an
all low level pairs of Inputs; the MIC pair provide straight
amplification for microphones, the PHONO pair RiAA
standard equalization and ompllfleatlensuitable for mag-
netic cortridges or ceramic cartridges with appropriate
adaptors, the TAPE pair NARTB tope equalization and
ampllficotion for tope heads.
TAPE Switch: Adjusts the equalization ot theTAPE (head)
position of the SELECTORswlteh according to the NARTB
stondord for the 71/2 (& )5) ips tope speeds and the 33/4
ips tape speed.
MODE Switch: The STEREO NORMAL and STEREO RE-
VERSE positions ore both used for stereophonic reproduc-
tion. At the STEREO REVERSE position, the channel 1
and channel 2amplifien from the tone controls to the
amplifier connections are Interchanged. These two posi
tions permit Interchanging thesignaisfed to the twospeakei
so that the correct left to right display of the orchestra
can be achieved on all recordings or broadcasts. The
CHECK AMPL. Iand CHECK AMPL. 2positions permit
hearing either channel 1alone or channel 2alone for
comparison or balancing purposes during stereophonic use.
The MONOPHONIC TUNER, AUX position is used for
monophonic FM, AM, tv sound, monophonic phono cort-
ridg^rrtonophonicpre-amplifiedtape etc., fed Into chan-
nel 1inputs. At this position, the channel 2Inputs which
are unused In this type of operation, ore disconnected
from the active channel so that they cannot contribute
Interference. At the MONOPHONIC PHONO position,
the channel 1and 2corresponding inputs are mixed, which
is useful when playing rmnophonic records with ostereo-
phonic cartridge to cancel vertical rumble components.
The Internal arrangements of the HF-85 at each of the
positions of the MODE switch are shown in Fig. 2.
6

_PREAMP OUT
FIG. 2A. CHECK AMPLIFIER 1
LEVEL INPUTS
FIG. 2B. CHECK. AMPLIFIER 2
CH. tHIGH CH. 1
LEVEL INPUTS TAPE OUT
CH.2 LOW
LEVEL INPUTS
LEVEL/
LONSS
CH.2 HIGH
LEVEL INPUTS
FEEDBACK
PAIR AMPL.
CH-2
BAKENDALL
TONE CONTROLS
CH.2
CH. 2
TAPE OUT
PREAMP OUT
CH.2
FIG. 2C. STEREO NORMAL
CH, lHIGH CH. 1
LEVEL INPUTS TAPE OUT
CH. ILOW
LEVEL INPUTS
CH.2 LOW
LEVEL INPUTS
CH.2 HIGH CH.2
LEVEL INPUTS TAPE OUT
PREAMP OUT
CH. 1
PREAMP OUT
CH.2
FIG. 2D. STEREO AVERSE
CH. 1HIGH CH. 1
LEVEL INPUTS TAPE OUT
PREAMP OUT
CH. 1
CH.2
TAPE OUT
FIG. 2E. MONOPHONIC TUNER, AUX.
7

PREAMP OUT
FIG. 2F MONOPHONIC PHONO
LEVEL BAUNCE BETWEEN CHANNELS; The use of in-
divlduol level conTroU in each channel, concentrically
mounted and with an optional clutching arrangement, elim-
inates the need for aseparate "balance" control and is
indeed preferrable os to electrical performemce. During
the balancing procedure, alwoys set the MODE switch to
one of the MONOPHONIC positions (appropriate to the
program source) in order to ensure that the some signal
level appears at the Inputs to both LEVEL controls. Start
with both LEVEL controls turned down to 0and disengaged
(smaller inner knob pulled out). Next, turnup one LEVEL
control until you have obtained normal room volume from
the corresponding speaker. Then turn up the other LEVEL
control until the sound source is apparently mid>way be-
tween the two speakers, indicating proper balance. (It is
ossumed that the two speaker systems are connected in
phase os they olwoyt should be. See note on "Speoker
Phasing" for clarification.) When this has been achieved,
push the smaller inner knob inward to engage the two
controls, which will then move together, should either be
turned, to maintain the balance over normal level adjust-
ments. (Please note the "slipping" feature described in
an earlier paragraph.) After balancing, theMODEswitch
can be set to one of the STEREOPHONIC positions for
stereo listening.
AMPLIFIER 1BASSCONTROL,AMPLiFIER2BASSCON-
TROL (CONCENTRIC WITH CLUTCH): The plus sign on
therightsideofthe dial indicates that cloctcwise rotation
from the mid-point (0) of either control increases Qroosis)
boss response in that chonnel; the minus sign on the left
side indicates that counter-clockwise rotation from the
mid-point decreoses (cuts) bass response in that channel.
These controls hove no effect on the trebleor the volume.
Start by pulling the smaller inner knob out to disengage
the two controls, and then set both at the mid-point (0),
which is called the “flat" position since bass response is
neither cut nor boosted at thlsposltion. If dissimilar loud-
speakers are used undone provides somewhat thinner bass,
or if location In the rooms seems to Favor alittle the bass
response of one speaker over the other, turn up the boss
in the less favored channel (within reason) until amore
satisfactory balance is achieved, leaving the bass control
for the more favored channel at the Oor "flat" position.
If the discrepancy is great, turn down the bass in the more
favored channel as well os turning up the bass In the less
favored channel In order not to use excessive bass boost
in the less fovored channel. (Note that excessive boost
in the less favored channel will usually increase distortion
considerably In that channel because the speaker is being
forced beyond its natural capabilities. )When satisfactory
balance is achieved, press in the smoller Inner bass knob
to engage the two boss controls. They maybe then turned
In tandem to provide the varying degree of boss boost or
cut thot seems to be required by different program material
(Please note the "slIpping"feoture described in on earlier
paragraph.
)
AMPLIFIER 1TREBLE CONTROL, AMPLIFIER 2TREBLE
CONTROL (CONCENTRIC WITH CLUTCH): The plus
sign on the right side of the dial indicates clockwise ro-
tation from the mid-point (0) of either control increases
(boosts) treble response In that channel; the minus sign
indicates that counter-clockwise rotation from the mid-
point decreases (cuts) treble response in that channel.
These controls have no effect on the bass or the volume.
Start by pulling the smaller inner knob out to disengage
the two controls and then set both at the mid-point (0),
which is called the "flat" position since treble Is neither
cut nor boostedat this position. Ifdissimilar loudspeakers
ore used, or position in the room favors the treble response
of one loudspeaker over the other, turn up the control for
the less favored speaker and turn down the control for ths
more favored speaker (or both) until amore satisfactory
balance is achieved. When this Is done, press in the
smaller Inner treble knob to engage the two treble controls.
They may be then turned in tandem to odjust the treblefor
room acoustics as awhole and to provide the varying de-
gree of treble boost or cut that seems to be required by
different program material.
LOUDNESS Switch: The LOUDNESS switch is used to
insert, when desired, compensation for the inefficiency
of the human ear In hearing bass and treble at alow volume
level. Compensation is inserted at the IN position and Is
effective over the range below Son the LEVELcontrol dial;
compensation Is removed at the OUT position. We recom-
mend no compensation (OUT position) for any situation

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