Dynaco 120 Stereo Amplifier, PAS 3X, PAS 2X, PAS 2, PAS 3, PAT 4, PAM 1 Preamplifier, FM 5 Tuner, TC 3X Tone Control Operating Instructions

 cc = | о 3
Ds E) a
== © %
wu) — N
az < Е =
LI e De à ;
> e ES = =
>= E 5.2 о =
A © ==
ow ORL on u
ml 1 © == ED
< e. | =
> =
Li EDO a
N „Фе a
eE q
==.
= 5 © ===
к.
o
"=
A
r=
а.
5
Nn
=
o
7)
: 8
©
Le
сх:
En
т
9
de)
©
cn
== a =
|
1 S
>
=) = = ен)
‚= |
| 5
=
я я U
3 : =
= 1) В
; =
Lv
=
o
CONTENTS
Opératingnstruetions 2 3 Assembly Instructions << 7
Tecnica Information = as 0 5 i 5 Schematic Diagram. vad so 10
СТС Description aia 0 8 5 In Casetof Difficulty. nn 17
Performance Тесно = 5 Service Information for the Technician ........ 18
Dynaco Preampmlifies. 6 Fictonal Diagram 0 0 Back Cover Foldout
4-Dimensional Sound System ............ 6 Factory Service and Warranty ........ Back Cover
240:V0lE Confniectións 2. nL 7 Paris lis о Back Cover
SPFCIFICATIONS
FREQUENCY RESPONSE: 5 Hz to 100 kHz +0.5 db.
POWER BANDWIDTH (IHF): 5 Hz to 50 kHz half
power output at less than 0.5% total harmonic
distortion into an 8 ohm load.
HARMONIC DISTORTION: Less than 0.5% at any
power level up to 60 watts per channel into 8
ohms at any frequency between 20 Hz and 20
kHz. Distortion reduces at lower power levels.
INTERMODULATION DISTORTION: Less than 0.5%
at any power level up to 60 watts per channel
into 8 ohms with any combination of test frequen-
cies. Distortion reduces at lower power levels.
100 Hz
1 kHz
NCISE: 25 db below rated output unweighted with
shorted input; 100 db down by IHF standards.
DAMPING FACTOR: Greater than 40 from 20 Hz to
20 kHz.
SEPARATION: More than 70 db from 20 Hz tc 20
kHz.
INPUT: 100,000 ohms; 1.5 volts for 60 watts output.
SEMICONDUCTOR COMPLEMENT: 15 transistors;
15 diodes.
SIZE: 137 x 10/2” х 4”. WEIGHT: 20 lbs.
MAXIMUM POWER CONSUMPTION: 400 watts.
10 kHz
SQUARE WAVE PERFORMANCE: This is a good indication of linearity from
10 Hz to 100 kHz, since good square wave reproduction requires bandwidth
in excess of 1/10th to 10 times displayed frequency.
2 kHz 20 kHz
INPUT-OUTPUT LINEARITY AT 60 WATTS
TONE BURST:
4 cycle 20 kHz through amplifier at 60
watts is indistinguishable from gener-
ator (below).
a
aaa НЫ,
то ый A ru
a ee
THE DYNACO STEREO 120
Do not attempt to install or use this amplifier until the section “Operating Instructions” has been carefully read.
INTRODUCTION
The Dynaco Stereo 120 is an all silicon transistor basic
power amplifier for use with separate preamplifiers such as
the Dynaco PAS-3X or PAT-4, or for use with tape record-
ers or tuners such as the Dynaco FM-5 which have their
own volume controls. The Stereo 120 contains two 60 watt
amplifiers on one chassis with a common power supply.
Although the Stereo 120 is a solid state device, contain-
ing transistors and similar semi-conductors, it has been
designed to be used under normal conditions without
special safety precautions, just as if it were a high grade
tube amplifier. Thus it can be connected to source and
speaker components and used with confidence in all con-
ventional arrangements. There are no circuit breakers,
speaker fuses, or other resettable devices to impede the use
of the Stereo 120 under any reasonable conditions of use
or abuse. This is achieved by using novel circuits (on
which patents are pending) which automatically and in-
stantly protect the amplifier.
The components in the Stereo 120 are of the highest
quality to protect against failure, both now and for many
years in the future. All parts are used conservatively with
OPERATING INSTRUCTIONS
Connection from preamplifier or other signal source
Since the Stereo 120 is a basic stereo power amplifier,
it has no operating controls; it should be supplied with an
audio signal from a stereo preamplifier or similar signal
source (such as a multiplex tuner or a stereo tape player
with a volume control). Most preamplifiers can supply the
required 1.5 volt signal and can operate into the 100,000
ohm input impedance of the Stereo 120. In particular, the
Dynaco PAS-3X (or PAS-2X) is recommended with the
Stereo 120, as well as the solid state PAT-4 preamplifier.
With earlier Dynaco preamplifiers such as the PAS-2,
PAS-3 or a pair of PAM-1s, a simple change of a resistor
on each channel will provide the proper match for the
Stereo 120. The installation of this resistor in the preamp-
lifier is described in a later section of this manual. Earlier
Dynaco preamps which have been modified by adding the
TC-3X tone control kit are directly useable.
If the Stereo 120 is being used with another make of
preamplifier, tuner or tape recorder, you should check
with the manufacturer of the equipment to see if it is suit-
able for 100,000 ohm load impedance.
From the preamplifier, or other source, conventional
single-conductor shielded cables with standard “phono”
plugs should be connected to the inputs of the Stereo 120.
Make certain that the plugs are pushed fully into the
sockets, and that the outer ground connections on the plugs
are gripping the sockets tightly at each end. The maximum
length of these shielded cables is determined by the output
impedance of the preamplifier and can generally be as much
as 25 feet if the Stereo 120 is to be remotely installed.
close tolerances to assure proper operation, and etched
circuit modules are pretested under actual use conditions to
ensure that every unit, after assembly, will meet the speci-
fications normally associated with laboratory prototypes.
The specifications of the Stereo 120 speak for themselves.
The distortion at low levels is comparable to that of the finest
tube designs, while the high power distortion remains in-
audible. Specifications do not reveal all the facets of sound
quality, however. In use with varying program material,
the Stereo 120 justifies its design efforts to have quali-
ties of ease and naturalness always sought and rarely
achieved in solid state designs. There is no extra bright-
ness or stridency which is unfortunately sometimes attri-
buted to high fidelity sound, but rather there is an impres-
sion of limitless range and effortless handling of the highest
power peaks.
Like any precision equipment, the superior capabilities
of the Stereo 120 will best be obtained when it is utilized
properly. Therefore, read these instructions, and make the
specified connections to the input audio source and to the
loudspeakers before connecting the amplifier to a source
of AC power.
Connection to loudspeakers
The Stereo 120 is supplied with two pairs of different
color binding posts, one pair for each channel output. The
“common” terminal is black, and the “hot” connection is
red. The two black posts are electrically connected intern-
ally, and are also connected to the chassis, so that the
amplifier may be used with special output connections
which require common grounds if desired. You must be
certain that the polarity of such output connections 1s
never reversed, and that the “hot” sides are never acci-
dentally connected together in accessory equipment.
The binding posts accept single “banana plugs”, double
“banana plugs” (such as the General Radio type 274-MB),
spade lugs, or simply stranded wire. If stranded wire is
used (as from lamp cord) the wire ends preferably should
be “tinned” with solder first to avoid fraying. To connect
the wire, unscrew the cap until the horizontal hole in the
metal shaft is uncovered, push the wire end through the
hole and tighten the cap. Make certain that no wire strands
are touching another post or the chassis. The banana plugs
are inserted into the ends of the posts. These plugs are
available from any radio parts distributor.
Quality loudspeakers whose rated impedances are be-
tween 4 and 16 ohms can be connected directly to the
binding posts. For short distances (25 feet or less) ordi-
nary #18 lamp cord can be used. For longer distances, it is
suggested that heavier cable (#16 or #14) be used.
The terminals on loudspeakers are marked in different
ways, and sometimes are left unidentified. They may be
(+) and (=), (1) and (2), or (С) and (8 ohms) for
3