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DC-300A
IM-9
S3P2-15-6
INSTRUCTION MANUAL
SERIAL NO
ISSUED
DC-300A
DUAL CHANNEL
LABORATORY AMPLIFIER
CROWN INTERNATIONAL, INC., BOX 1000, ELKHART, INDIANA 46514
`TOTAL PERFORM A N CE IS WHAT COUNTS"
CROWN test and check-out procedures reflect our basic design 4. Protection Test - This is a test with a 2 ohm load which
philosophy; we believe that reliability can be engineered into a determines the threshold at which the protection circuitry
product. As such, our check-out is designed to expose and will be activated. Sharp clipping should occur with no
correct a problem, before it happens. This testing begins when evidence of instability. The positive and negative limiters
operated independently and therefore may not be activated
the unit is still a pile of parts; grading and selection of
simultaneously.
components is standard. The final test-inspection is the culmina-
tion of this vigorous program, but our concern doesn't stop here. 5. Reliability Test - This test puts the output stages through
an extremely vigorous thermal cycling. The test is a very
Our products are backed by an extensive field service program,
low frequency input signal driving the output to full
and protected by a comprehensive warranty.
power across a short circuit for a predetermined period of
time.
A word about our testing procedure is in order. All our specifi-
cations are referenced to an AC input of 120 VAC. The high 6. 20KHz - This tests the amplifier at its rated power level.
current demand with high power tends to cause the line voltage We specify that at any frequency between 1Hz and
to sag, or the sinusoidal waveform to distort. With a distorted 2OKHz the DC-300A will produce 155 watts minimum
waveform (or lower line voltage) the peak voltage is lowered. rms (both channels operating) into an 8 ohm load, at a
Since it is the peaks that charge the filter capacitors in the sum total harmonic distortion of .05% or less. We choose
amplifier power supply, and thus determine the maximum power 20KHz as the test frequency because high frequencies
output, a line voltage problem reduces the maximum power produce more heat than lower frequencies. Thus, if the
output. CROWN uses a peak equivalent AC voltmeter which amplifier can safely pass the 20KHz test, it will operate
measures the peaks of any waveform and converts this to an safely at lower frequencies.
equivalent rms reading for a sinusoidal waveform. This way we 7. 10 KHz Square Wave - This test critically examines the
can vary or regulate the line voltage, no matter how distorted amplifier's frequency response and rise time. (How fast
the waveform, to an equivalent of a 120 VAC sinewave. We are the amplifier can follow rapid signal changes.) The output
square wave (with an 8 ohm load) should be clean and
then measuring a true maximum output power.
sharp, with no ringing or overshoot.
With regard to the precision load which we use for our testing, 8. Mono Operation - This is a check for proper operation of
we realize that a resistive load is quite different than a reactive the stereo mono switch. A signal is applied to channel 1
speaker. However, using readily available parts, a precision input only and the mono output is observed between the
resistive load is the easiest to duplicate, with respect to two red output terminals of the amplifier.
obtaining consistent results. We specify that the load must be IM D i s t o r t i o n T e s t - A t C R O W N w e f e e l t h a t I M
9.
resistive, having less than 10% reactive component at any distortion testing yields a truer picture of amplifier
frequency up to five times the highest test frequency. The performance than harmonic distortion testing. While a
resistance value should be maintained within 1%, at all power large amount of documentation supports this opinion,
levels. some of the reasons are apparent, even in layman's terms.
For example, a sinusoidal waveform (used in HD testing)
bears little resemblance to the complex waveforms
The following discussion examines each of the test procedures associated with actual program materials. IMD testing
listed on the facing page. This is an attempt to help you under-
uses such a complex waveform. Also, harmonic distortion
stand, in layman's terms, what the tests mean.
is not always aurally offensive. The human ear may
interpret such distortion as pleasing, but usually finds IM
distortion rather obnoxious. In order to support this
design philosophy, we designed and built our own IM
Quiescent Offset - This simply assures that your
analyzer with residual noise and distortion low enough to
amplifier's output is balanced with reference to its input.
test our amplifiers.
Thus the amplifier will not "bias" the program with a
dc component. To meet specifications, offset must be less 10. Hum and Noise - This test, in plain English, tells you how
than 10 mv. small a signal can be amplified without it becoming "lost
in the mud". The test is limited to the audio band width
1KHz - This test measures the power across an 8 ohm of 20Hz-20KHz, with a bandpass filter. Our specification
load at a frequency of 1 KHz with both channels operating. for the DC-300A is: hum and noise from 20Hz - 20KHz
This is a determination of how much power an amplifier will be at least 110db below the full power output of 155
can produce before a specified total harmonic distortion watts. This means that with a 155 watt output the noise
is reached. For the DC-300A, the power is 180 watts will be only .00155 micro watts. (That's 1.55 billionths
a t l e s s t h a n .1% T H D . of a watt )
4 Ohm Test - This is a critical examination of the DC-300's 11. Quiescent AC power Input at 120 VAC - This test
performance at impedances below that for which it is confirms that your amplifier is not drawing excessive
rated. We check the wave form for level (it must reach a power while "idling". If an amplifier exhibits a tendency
specified voltage before clipping) purity, and stability. toward instability, or oscillation, it may draw power with
no signal input. The DC-300A will draw 40 watts or less
at idle.
TABLE OF CONTENTS
PAGE
Section 1 DESCRIPTION
1 .1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 4, 5
1 .3 Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 12
Section 2 INSTALLATION
2.1 Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
.
2.2 Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 13
2.3 Normal Hi-Fi Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.4 Connecting Output Lines ................................................................................................, 14
2.4.1 Mono Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
2.5 Connecting Input Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.6 Connecting Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Section 3 OPERATING INSTRUCTIONS
3.1 Controls and Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2 The Protection Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.3 Operating Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
3.4 Load Protection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
3.5 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Section 4 CIRCUITRY
4.1 Principles of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
4.2 Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
4.3 Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...... 24
Section 5 APPLICATION NOTES
Application Note No. 1 - V-l Limits of a Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Application Note No. 2 - VFX-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Application Note No. 3 - Speaker Protection . . . . . . . . ....................................................... 29
LIST OF ILLUSTRATIONS
TITLE PAGE
l - l DC-300A Pictorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
l-2 DC-300A Performance Graphs
I.M. Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Harmonic Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Power Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Phase Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Noise Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Crossta Ik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._.............. 8
Nominal Limits of V-l Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Damping Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Power Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Input Impedance vs. Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Maximum Output vs. Load Impedance ............................................................................ 11
output (Z) ............................................................................................................................ 12
output IL I.. ........... . .............................................................................................................. 12
2-l Mounting Dimensions ....................................................................................................... 13
2-2 Normal Hi-Fi Hook-up ........... ............................................................................................. 14
2-3 Rear View of Chassis ...... .................................................................................................. 14
2-4 Source Resistance and Damping Factor vs. Length and Size of Output Leads ............ 15
2-5 Schematic For Full Range Electrostatic Speaker Connections ...................................... 15
2-6 Schematic of Earphone Pad .............................................................................................. 16
2-7 DC-3ODA Mono Hook-up ................................................................................................... 16
2-8 Table For Selection of Input DC Blocking Capacitor ....................................................... 17
2-9 Low-Pass Filter For Severe RF At Inputs ......................................................................... 17
2-10 Table of Line Voltage Connections ................................................................................... 18
3-l Operating Controls ........ ..................................................................................................... 19
3-2 Graph of VI Operating Range of DC-300A Output ......................................................... 20
3-3 Fuse Selector Nomograph For Loudspeaker Protection .................................................. 22
3-4 Relay Controlled Protector with Overload Indicator ........................................................ 22
3-5 Turn-On-Transient Muter For Load Protection ................................................................ 22
Section 1
DESCRIPTION
1 .1 GENERAL
DC-300A PICTORIAL
The DC-300A is a dual-channel high-power amplifier for 26 diodes, 1 bridge rectifier, and 3 zener diodes are used in
precision amplification of frequencies from DC to 20KHz. the DC-3OOA circuitry. With the integrated circuit, the
The unit features extremely low harmonic and intermod- effective number of semiconductors is 60 transistors, 30
ulation distortion, very low noise, highest "damping diodes, and 3 zener diodes.
factor," and quality parts and workmanship. Because of
the large output power, It is possible to obtain a monaural
The output devices, 8/channel, are conservatively em-
70-volt balanced line without using an output transformer.
ployed, having a total peak current rating/channel of 120
The DC-300A contains a new CROWN developed Signal amps in a circuit that is limited to a maximum of 28
Programmed Automatic Current Executor (SPACE amps. Among its unique features, the circuitry includes
control) electronic amplifier protection circuit which the CROWN-pioneered and patented AB+B output con-
manifests no flyback pulses, thumps, or shut-down. At figuration.
audio frequencies any impedance load including totally
reactive loads may be driven with no adverse effects. The input operational amplifiers are powered by two
Only maximum output power will be affected by varia- voltage-regulated supplies. This results in complete
tions in load impedance. At sub-sonic to DC frequencies channel-to-channel isolation and independence from line
the limiter acts as a VI limiter to provide optimum pro- voltage variations.
tection for the extremely rugged silicon hometaxial
output devices (total of 16 for a total of 2400W dissipation).
Total direct coupling results in perfect, instantaneous,
A pair of thermal switches remove power from the unit thump-free overload recovery even on non-symmetrical
if overheating occurs due to insufficient ventilation, The waveforms. This cannot be said for any AC-coupled
AC line is fused to protect the power supply. amplifier presently in existence. Turn-on is instantaneous
with no program delays.
See Section 3.2 for a description of the protective systems.
The power supply features a 1 KW transformer and large
computer-grade filter capacitors giving over 48 joules Front-panel controls include two independent heavy-duty
of energy storage. level controls and a power switch with an associated pilot
light. DC balance controls, which never need adjustment
A total of 44 discrete transistors, 1 linear IC (dual op amp), in normal operation, are located behind the front-panel.
1.2 SPECIFICATIONS
1.2.1 STEREO SPECIFICATIONS
Output Power 155 watts per channel minimum RMS (both channels oper-
ating) into an 8 ohm load over a bandwidth of 1 Hz-20KHz at
a rated RMS sum total harmonic distortion of 0.05% of the
fundamental output voltage.
Frequency Response