Crown dc300a schematic

‘TOTAL PERFORMAN CE IS WHAT COUNTS"

CROWN test and check-out procedures reflect our basic design philosophy; we believe that reliability can be engineered into a product. As such, our check-out is designed to expose and

correct a problem, before it happens. This testing begins when

the unit is still a pile of parts; grading and selection of

components is		standard. The final test-inspection is the culmina-
tion of this vigorous program, but our concern doesn’t						stop here.
Our	products	are	backed by an extensive field		service program,
and	protected	by	a comprehensive	warranty.
A word about		our	testing procedure	is in order.	All	our specifi-

cations are referenced to an AC input of 120 VAC. The high

current demand with high power tends to cause the line voltage

to sag, or the sinusoidal waveform to distort. With a distorted waveform (or lower line voltage) the peak voltage is lowered. Since it is the peaks that charge the filter capacitors in the amplifier power supply, and thus determine the maximum power output, a line voltage problem reduces the maximum power output. CROWN uses a peak equivalent AC voltmeter which measures the peaks of any waveform and converts this to an

equivalent	rms reading	for	a	sinusoidal	waveform.	This	way we
can vary	or regulate	the	line	voltage,	no matter	how	distorted

the waveform, to an equivalent of a 120 VAC sinewave. We are then measuring a true maximum output power.

With regard to the precision load which we use for our testing,

we realize that a resistive load is quite different than a reactive speaker. However, using readily available parts, a precision resistive load is the easiest to duplicate, with respect to obtaining consistent results. We specify that the load must be resistive, having less than 10% reactive component at any frequency up to five times the highest test frequency. The

resistance value should be maintained within 1%, at all power levels.

The following discussion examines each of the test procedures listed on the facing page. This is an attempt to help you understand, in layman’s terms, what the tests mean.

Quiescent Offset - This simply assures t h a t y o u r

amplifier’s output is balanced with reference to its input.

Thus the amplifier will not “bias” the program with a

dc component. To meet specifications, offset must be less than 10 mv.

1KHz - This test measures the power across an 8 ohm load at a frequency of 1 KHz with both channels operating.

This is a determination of how	much	power	an amplifier
can produce before a specified	total	harmonic		distortion
is reached. For the DC-300A,	the	power	is	180 watts
at less than .1% T H D .

4 Ohm Test - This is a critical examination of the DC-300’s performance at impedances below that for which it is rated. We check the wave form for level (it must reach a specified voltage before clipping) purity, and stability.

4.Protection Test - This is a test with a 2 ohm load which

	determines		the	threshold at which the protection	circuitry
	will be activated. Sharp clipping should occur with no
	evidence of instability. The positive and negative limiters
	operated independently and therefore may not be activated
	simultaneously.
5.	Reliability		Test	- This test puts the output stages through
	an extremely vigorous thermal cycling. The test is a very
	low frequency input signal driving the output to full
	power across a short circuit for a predetermined period of
	time.
6.	20KHz -		This tests the amplifier at its rated power level.
	We specify that at any frequency between 1Hz and
	2OKHz	the DC-300A will produce 155 watts			minimum
	rms (both channels operating) into an 8 ohm load, at a
	sum total		harmonic distortion of .05% or less. We choose
	20KHz	as the		test frequency because high frequencies
	produce more heat than lower frequencies. Thus, if the
	amplifier can safely pass the 20KHz test, it will operate
	safely	at	lower	frequencies.

7.10 KHz Square Wave - This test critically examines the amplifier’s frequency response and rise time. (How fast the amplifier can follow rapid signal changes.) The output square wave (with an 8 ohm load) should be clean and

	sharp,		with no ringing			or	overshoot.
8.	Mono		Operation		- This is		a	check for proper operation		of
	the stereo mono switch. A signal is applied to channel 1
	input only and the mono output								is observed between	the
	two	red		output	terminals		of	the	amplifier.
9.	IM	Distortion			Test	- A t		C R O W N w e f e e l t h a t		I M
	distortion testing yields a truer picture of amplifier
	performance than harmonic distortion testing. While a
	large amount of documentation supports this opinion,
	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
	associated with actual program materials. IMD testing
	uses		such a complex			waveform.			Also, harmonic distortion
	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
	analyzer			with residual		noise		and	distortion low enough	to
	test	our		amplifiers.

10.Hum and Noise - This test, in plain English, tells you how

small	a signal can be		amplified	without	it becoming “lost
in the	mud”. The	test	is limited	to the audio band width
of 20Hz-20KHz,		with a bandpass		filter.	Our specification

for the DC-300A is: hum and noise from 20Hz - 20KHz will be at least 110db below the full power output of 155

watts. This means that with		a 155	watt output	the noise
will	be only .00155 micro	watts.	(That’s 1.55	billionths
of a	watt )

11.Quiescent AC power Input at 120 VAC - This test

confirms that your amplifier is not drawing excessive power while “idling”. If an amplifier exhibits a tendency

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
			16
2.4.1	Mono Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. . . . . . . . . .
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
			21
3.3	Operating Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. . . . . . . . . .
3.4	Load Protection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. . . . . . . . . .21
3.5	Cleaning . . . . . . . .	. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . 22
Section 4	CIRCUITRY
4.1	Principles of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. . . . . . . . . .23
			24
4.2	Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. . . . . . . . . .
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

l - l l-2

		PAGE
DC-300A Pictorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . . .	. . . . . . . .1
DC-300A Performance Graphs		5
I.M. Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . . .
Harmonic Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . .	. . . . . . . .5
Frequency Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . .	. . . . . . . .6
Power Response		6
	. . . . . . . . . . . . . .	. . . . . . . .7
Phase Response
	. . . . . . . . . . . . . .	. . . . . . . .8
Noise Spectrum
	. . . . . . . . . . . . . .	. . . . . . . .8
Crossta Ik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..	_..............
Nominal Limits of V-l Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . .	. . . . . . . .9
Damping Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . .	. . . . . .10
Power Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . .	. . . . . .10
Input Impedance vs. Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . . . . . . . . . .	. . . . . .11

Section 1

DESCRIPTION

1 .1 GENERAL

DC-300A PICTORIAL

The DC-300A is a dual-channel high-power amplifier for precision amplification of frequencies from DC to 20KHz. The unit features extremely low harmonic and intermodulation distortion, very low noise, highest “damping factor,” and quality parts and workmanship. Because of the large output power, It is possible to obtain a monaural 70-volt balanced line without using an output transformer.

The DC-300A contains a new CROWN developed Signal Programmed Automatic Current Executor (SPACE control) electronic amplifier protection circuit which manifests no flyback pulses, thumps, or shut-down. At audio frequencies any impedance load including totally reactive loads may be driven with no adverse effects. Only maximum output power will be affected by variations in load impedance. At sub-sonic to DC frequencies the limiter acts as a VI limiter to provide optimum protection for the extremely rugged silicon hometaxial output devices (total of 16 for a total of 2400W dissipation).

A pair of thermal switches remove power from the unit if overheating occurs due to insufficient ventilation, The AC line is fused to protect the power supply.

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 of energy storage.

A total of 44 discrete transistors, 1 linear IC (dual op amp),

26 diodes, 1 bridge rectifier, and 3 zener diodes are used in the DC-3OOA circuitry. With the integrated circuit, the effective number of semiconductors is 60 transistors, 30 diodes, and 3 zener diodes.

The output devices, 8/channel, are conservatively employed, having a total peak current rating/channel of 120 amps in a circuit that is limited to a maximum of 28 amps. Among its unique features, the circuitry includes the CROWN-pioneered and patented AB+B output configuration.

The input operational amplifiers are powered by two voltage-regulated supplies. This results in complete channel-to-channel isolation and independence from line voltage variations.

Total direct coupling results in perfect, instantaneous, thump-free overload recovery even on non-symmetrical waveforms. This cannot be said for any AC-coupled amplifier presently in existence. Turn-on is instantaneous with no program delays.

Front-panel controls include two independent heavy-duty level controls and a power switch with an associated pilot light. DC balance controls, which never need adjustment 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 operating) 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				±0.1dB DC-20KHz		at 1 watt into 8 ohms; ±ldB DC-100KHz.
1 KHz Power				180 watts RMS into 8 ohms, per channel, both channels operating, 0.1% total harmonic distortion.
Harmonic			Distortion	Less than 0.001% from 20Hz-400Hz. and increasing linearly to 0.05% at 20KHzat 155watts RMS
				per channel into 8 ohms.
I.M.	Distortion			Less	than 0.05% from 0.01 watts to 0.25 watts and less than 0.01% from 0.25 watts to 155watts
(60Hz-7KHz 4:1)				into	8 ohms, per	channel.
Slewing		Rate		8 volts per microsecond (slewing rate			is the maximum value of the first derivative of the output
				signal, or the maximum slope of the output signal).
Damping			Factor	Greater than 750,		DC-400Hz into 8	ohms.
Output		Impedance		Less than 7 milliohms in series with			less than 3 microhenries.
Load	Impedance			Rated for 8 ohm usage; safely drives any load Including completely reactive loads.
Voltage		Gain		20.6±2% or 26.3±0.2dB at maximum			gain.
Input	Sensitivity			1.75 volts±2% for 155 watts into 8 ohms.
Output		Signal		Unbalanced, dual		channel.

1 . 2 . 2 MONAURAL SPECIFICATIONS

Output Power	310 watts minimum RMS into a 16 ohm load over a
	bandwidth of 1 Hz-20KHz at a rated RMS sum total har-
	monic distortion of 0.05% of the fundamental output
	voltage.
Frequency Response	±0.15dB, DC-20KHz at 1 watt into 16 ohms; ±1 dB, DC-6OKHz at 1 watt into 16 ohms.
1 KHz Power	360 watts RMS into 16 ohms.
Harmonic Distortion	Less than 0.001% from 20Hz-400Hz and increasing linearly to 0.05% at 20KHz at 310 watts into
	16 ohms.
I.M. Distortion	Less than 0.05% from 0.01 watts to 0.25 watts and less than 0.01% from 0.25 watts to 310 watts
	into 16 ohms.
S l e w i n g R a t e	16 volts per microsecond.
Damping Factor	Greater than 700, DC-400Hz into 16 ohms.
Output impedance	Less than 15 milliohms in series with less than 6 microhenries.
Load Impedance	Rated for 16 ohm usage; safely, drives any load including completely reactive loads.
Voltage Gain	41.2±2% or 32.3±0.2dB at maximum gain.
Input Sensitivity	1.75 volts for 310 watts into 16 ohms.
Output Signal	Balanced, single channel.

4

1.2.3 GENERAL SPECIFICATIONS

Hum and Noise

(20Hz-20KHz)

Phase Response

Input Impedance

Amplifier Output

Protection

Overall Protection

Turn-on

Circuit

Power Supply

Power Requirements

Heat Sinking

Chassis

Controls

Connectors

Dimensions

Weight

Finish

110dB below rated output

+0, - 1 5 ° Zero to 20KHz at 1 watt

100K ohms at minimum gain, 10K ohms at maximum gain.

Short, mismatch, and open circuit proof. Limiting is instantaneouswith noflyback pulses, thumps, cutout, etc. No premature limiting on transients.

AC line fused. Thermal switch in AC line protects against overheating caused by insufficient ventilation. Controlled slewing rate voltage amplifiers protect overall amplifier against RF burnouts. Input overload protection is furnished by internal resistance at inputs of amp.

instantaneous, with minimum thumps and no program delay.

Wideband multiple feedback loop design utilizing one linear IC (dual op-amp). Total equivalent of 60 transistors, 30 signal diodes, 3 zeners and 6 rectifier diodes.

1 kilowatt transformer with massive computer-grade filter capacitors storing over 48 joules of energy. Two regulated supplies for complete isolation and stability.

Requires 50-4OOHz AC with selectable taps for 100, 120, 200, 220 and 240V ±10% operation. Draws 40 watts or less on idle, 500 watts at 300 watts total output.

Massive black-anodized heat sinks are thermally joined with the chassis, thereby utilizing the entire amplifier as a heat sink.

All aluminum construction for maximum heat conduction and minimum weight. Heavy aluminum front panel is a single extrusion.

Independent input level controls are on front panel. Power switch, with integral pilot light is on front panel. Non-interacting DC balance controls are mounted behind front panel. A mono-stereo switch is located above the input jacks on the rear panel.

Input - ¼ inch phone jack

Output - Color coded binding posts

AC Line - Three-wire (grounded) male connector on 5 ft. min. cable

19 inch standard rack mount (W.E. hole spacing), 7 inches high, 9 ¾ inches deep (from mounting surface).

45 pounds

Satinized aluminum front panel, with gray suede Lexan insert.

10

TO DC

10

100

1K

10K

1OOK

FREQUENCY (Hz)

6 0

10

100

1KHz

1OKHz

1OOKHz

FREQUENCY (Hz)