H.H. Scott 208 Service manual
H.H.SCOTT
III Powdermill Road, Maynard, Mass.
INSTRUCTIONS FOR THE MODEL 20s SO-watt
STEREOPHONIC LABORATORY POWER AMPLIFIER
The 208 is a precision, dual power amplifier designed for high quality audio appli-
cations. It is ideally suited for use with the 355 AM-FM multiplex stereo control center
or a good quality preamplifier. The 208 is completely stable under all conditions and may
be used with any electrostatic loudspeakers. . .
INSTALLATION
The 208 can be placed on a shelf. in a cabinet, or in a bookcase. When used with
the 355 it may be as close or as far as desired. If you wish, the 208 may actually be
clamped to the 355 to make an integrated unit. The two clamps for this purpose are avail-
able at no charge by writing to the Parts Dept., H. H. Scott, III Powdermill Rd., Maynard,
Mass.
Wherever the 208 is placed, adequate provision for ventilation should be made •. Never
enclose the amplifier completely. If it is placed inside a cabinet, either the back or the
front should have openings to allow dissipation of the warm air.
-
CONNECTIONS
To the Model 355 -- If you plan to use the 208 bolted to the 355, or next to it, the
short leads supplied with the 208 are ideal. Connect one cable from the 355 left output to
the left 1.5v input on the 208. Connect the other cable from the 355 right Output to the
ri~ht channel l.5v input on the 208. If you intend to separate the 208 fram the 355, use
lon~er audio cables but follow the same connection instructions.
To a Preamplifier -- Shielded audio cables are provided with most preamplifiers. If
you are using preamplifiers with over 2.0 volts output connect ~ shielded cable from the
preamplifier's Left or Channel A output to the Left 2.5 volt input.on the 208. Connect
another cable from the Right or Channel B output of the preamplifier to the right 2.5 volt
input on the 208. If you use a preamplifier with 1.0 to 2.0 volt output, follow the same
directions except use the 1.5 volt inputs on the 208.
Power Connections -- The power cord
60 cycle, AC source. Do not use with DC.
liary AC outlets on the back of the 355 or
ner, leave the on-off switch of the 208 in
preamplifier) is turned on or off, it will
Auxiliary AC outlets -- The 208 has an auxiliary AC outlet. You may connect any units
like a turntable or tape recorder to this outlet. When the 208 is turned off, these units
will go off as well.
shoul~ be plugged into any 105 to 125 volt, 50 to
The amplifier can be connected to any of the auxi-
of your preamplifier. When connected in this man-
the "on" position at all times. When the 355 (or
turn the 208 on or off at the same time.
Speakers -- Terminal strips for making speaker connections are located on the back •••
The one marked Channel A Speaker is for connecting the left speaker (as you face them). The
one marked Channel B Speaker is for the ri~ht. Below each strip are the numbers 4, 8, 16 and
O. This permits you to match the amplifier output to the impedance of the speaker. Each
speaker is rated by its manufacturer at a certain impedance. This information is either
marked on the speaker or can be supplied by the dealer.
D-208-1
(Continued Inside)
To make the connections use standard twin lead lamp wire. Simply connect one end Jf
the twin lead wire to the two terminals on the speaker or speaker enclosure, as the case may
be. At the other end connect one lead to the
"0"
terminal and the other lead to the terminal
whose number is closest to the value of the loudspeaker impedance. When making the conne~-
tions, be extrenely careful to prevent any strands of wire fran one screw accidentallytoucn-
ing a strand on the other screw, as the speaker will not perform properly.
After the speakers are connected, they should be properly phased to ~ive a full stere~
effect with good bass. The simplest way to accanplish this is to feed the same monophonic
pr-ogram mater ial simultaneously into both channels. "Amale speaking voice is ideal for this
purpose. Turn the volume to full roan level. Stand in front of the two speaker systems and
midway between them. Have saneone reverse the leads of one speaker. In one position, the
voice will sound full and appear to be caning fran directly between the two speakers. In
the other position, the voice will lose some of its bass, and will appear to be coming from
both speakers. The first is the correct position.
SPECIFICATIONS
Maximum power output each channel at-IOoo cycles:- Mus1c wave orms •••••;:•••~•••• 40 watts
Steady state •••••••••••••••••• 35 wat~s
Maximum total harmonic distortion at rated output ••••••••••••••••••••••• "••••••••
0.5%
Frequency response for 35 watts steady state at less than 2.0%
total distortion ••••••••••••••••••••••••••••••••••••••••••••••••••••••
Maximum usable power output at 20 cycles: Music waveforms ••••••••••••
~.20
to
to 20,000 cycles
db.
!••
42 watts
Steady state •••••••••••••••••• 36 watts
Power bandwidth at rated distortion (IHFM method) ••••••••••.•••••••••••. below 19 cycles to
above 25,000 cycles
(limits of test equip)
Intermodulation distortion ......•...••.•..•••.•••.....•....•....•......•...•.... below 0.5%
HlDTl
and noise.. . ................•..•.••.•..•••...•.•.•....••.••••.•• ~,80 db. below rated
power
(These characteristics are measured at a line voltage of
60 cycles per second. No significant changes of characteristics should be experienced
normal variations of line voltages or a line frequency of
Range of line voltage and frequency •••••••••••••••••••••••••••••••••••••••••••
117
volts rms and line frequency o~
50
cycles per second).
105-125
:or
volts,
50-60 cycles
t?ower con·stL'il-ptic""'
*
All H. H. Scott amplifiers and preamplifiers incorporate a low frequency rolloff which be-
·--~l-1:1..v-o.l+C!
.::1+
~0 cp~·A-..L.
---on.1Y)~9." •.
e-• .--.~.~·.~'O-C-;,~T~~-c.--.:'"
2QO...-Wa.:t..t.s
comes full operative below 20 cycles. This is designed to prevent overload of the output
sta~e and the loudspeaker due to subsonic rumble frequencies and "record eccentricity. This
means that the full power of the amplifier can be concentrated into the audible range.
*
Loading...