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Crown DC-300A Instruction Manual

Dual channel laboratory amplifier
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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

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  • Page 1 DC-300A IM-9 crolun S3P2-15-6 INSTRUCTION MANUAL SERIAL NO ISSUED DC-300A DUAL CHANNEL LABORATORY AMPLIFIER CROWN INTERNATIONAL, INC., BOX 1000, ELKHART, INDIANA 46514...
  • Page 2 Proof of Performance Report DC-300A laboratory power amplifier Serial Number 1. Quies. offset of less than 1OmV 1 KHz 180 watts RMS minimum into 8 ohms, per channel, both channels operating, distortion 4 ohm test 4. Protection tests Reliability test 6.
  • Page 3 “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. This is a test with a 2 ohm load which...

  • Page 4: Table Of Contents

    - l l-2 DC-300A Performance Graphs I.M. Distortion ........................5 Harmonic Distortion .

  • Page 5: Output

    Table of Line Voltage Connections ... 2-10 Operating Controls ..Graph of VI Operating Range of DC-300A Output ... 20 Fuse Selector Nomograph For Loudspeaker Protection ... 22 Relay Controlled Protector with Overload Indicator ... 22 Turn-On-Transient Muter For Load Protection ...

  • Page 6: Section 1 Description

    1 .1 GENERAL 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 intermod- ulation 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.

  • Page 7: Specifications

    1.2 SPECIFICATIONS 1.2.1 STEREO SPECIFICATIONS 155 watts per channel minimum RMS (both channels oper- Output Power 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.
  • Page 8 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;...

  • Page 9: Phase Response

    1.2.3 GENERAL SPECIFICATIONS 110dB below rated output Hum and Noise (20Hz-20KHz) +0, - 1 5 ° Zero to 20KHz at 1 watt Phase Response 100K ohms at minimum gain, 10K ohms at maximum gain. Input Impedance Short, mismatch, and open circuit proof. Limiting is instantaneouswith noflyback pulses, thumps, Amplifier Output Protection cutout, etc.
  • Page 13 1OOK TO DC FREQUENCY (Hz) 1OOKHz 1KHz 1OKHz FREQUENCY (Hz)

  • Page 16: Normal Hi-Fi Installation

    Accessory Bag and Fig. 2-2. (Not needed with CROWN speakers.) 2. Since the DC-300A is a “basic amplifier,” the main outputs of the control-center or “preamplifier” must be connected via shielded audio-cables to the two jacks marked INPUT.

  • Page 17: Connecting Output Lines

    CONTROL CENTER 3 to 2 WIRE ADAPTER / SWITCHED OUTLET RIGHT SPEAKER POWER CABLE _ 2.4 CONNECTING OUTPUT LINES Input and output connectors are located on the back of the chassis as shown in Fig. 2-3. It is always wise to remove power from the unit and turn the input level controls off while making connections, REAR OF CHASSIS WITH OUTPUT COVERS REMOVED...

  • Page 18: Source Resistance And Damping Factor Vs. Length And Size Of Output Leads

    LOAD RESISTANCE (ohms) SOURCE RESISTANCE AND DAMPING FACTOR VS. LENGTH AND SIZE OF OUTPUT LEADS is provided for wire selection. For dynamic moving-coil loudspeakers the value of RL should preferably be that measured by an ohmmeter across the voice coil, rather than the manufacturer’s rating.

  • Page 19: Mono Operation

    CAUTION: Be certain that all equipment (meters, switches, etc.) connected to the Mono output lines is balanced. Both sides of the line must be totally isolated from the input grounds, to the DC-300A. If this is not ob- served, severe oscillation may result. st.r.0 Earphenor 2.5 CONNECTING INPUT LINES...

  • Page 20: Connecting Power

    effect of the size of the blocking capacitor on the frequency response. Only a low-leakage type paper, mylar, or tantalum capacitor should be used for this purpose. TABLE FOR SELECTION OF INPUT DC BLOCKING CAPACITOR If large amounts of ultrasonic or RF frequencies are found on the input, such as bias from tape recorders, etc., a low- pass filter should be placed on the input.

  • Page 21: Table Of Line Voltage Connections

    In order to change the voltage, it is first necessary to carefully detach the bottom cover from the unit. On the back of the board-mount subchassis a terminal stripwith solder- ALL VIEWS WITH BOTTOM PLATE REMOVED 1oov 120v See Note 2oov 220 v 2 4 0...

  • Page 22: Section 3 Operating Instructions

    OPERA TING CONTROLS 3 . 2 T H E P R O T E C T I O N The DC-300A is protected against all the common hazards which plague highpower amplifiers, including shorted, open, and mismatched loads; overloaded power supplies;...

  • Page 23: Graph Of Vi Operating Range Of Dc-300A Output

    A current limiter will yield to the load butwill sustain the constant current demands of the inductive load without flyback. Early amplifier designs frequently employed fixed current limiters but had serious difficulty with obtaining reliable low frequency output while being capable of full-voltage 4 ohm output.

  • Page 24: Warranty

    The fuse inherently protects the power supplies against overload. The AC line for 100, 120VAC is fused with a 1 OA 250V type A6 fuse (on 200, 220, 240VAC, 5A type MTH 250V). The use of any other size fuse will invalidate the warranty.

  • Page 25: Load Protection Methods

    Emmpl.: z:sn AllStir: --10 ” 2 ; .; ..14 y E ..16 g e-20 ..25 --30 --At3 FIG. 3-3 FUSE SELECTOR NOMOGRAPH FOR LOUDSPEAKER PROTECTION Another form of load protector is shown schematically in Fig. 3-4. Whenever the load is overdriven, a relay switches a lamp in series with the load, smoothly relieving the overload.

  • Page 26: Section 4 Circuitry

    This voltage is used in the amplifier’s driver circuit. The DC-300A represents nothing short of the highest quality in both circuitry and components. It should provide a lifetime of trouble-free service for the most discriminating users.
  • Page 27 4.2 TEST PROCEDURES The sole function of this section is to list precautions essential to obtaining accurate measurements when deal- ing with high-power, high-purityamplifierssuch astheDC- 300A. Use the proper line voltage, which is the one for which the amplifier is connected. The voltage should be measured throughout the testing with a peak reading meter, and adjusted to the RMS equivalent voltage (to compensate for line voltage regulation errors during...

  • Page 28: Application Notes

    APPLICATION NOTE NO. 1 V-l LIMITS OF A LOAD Evaluating the V-l (volt-ampere) needs of a load: Many loads exhibit large reactances which limits a power amplifier’s ability to deliver a maximum power. If a load stores energy, which in turn flows back into the amplifier, it is clear that the max- imum power efficiency of the system is not being achieved.
  • Page 29 The connections are made with the VFX-2 quickly and easily. If a balanced line is to be used with the unbalanced input of the DC-300A. the VFX-2 can serve asthe interface. While maintaining these functions the output can be shaped by selecting variable high-pass, lo-pass, or band- pass filters.
  • Page 30 APPLICATION NOTE NO. 3 WARNING POWER AMPLIFIER PROTECTION SYSTEMS PRO- TECTAMPLIFIERS BUT NOT SPEAKERS! YOU, AND/ OR YOUR SPEAKER MANUFACTURER ARE RESPON- SIBLE FOR SPEAKER PROTECTION! Except in unusual sets of circumstances, the circuitry in- cluded in power amplifiers designated as “protection”, whether made up of transistor limiters, circuit breakers, fuses, SCR’s, or whatever, is designed primarily to pro- tect the amplifier from damage and will only protect...
  • Page 31 PARTS LIST, DC-300A Page 1 Schematic Designation ClOO,...
  • Page 32 6.2K ohm l/4 watt 5% 3.9K ohm 1 watt 10% 2.7 ohm % watt 10% 75 ohm ‘A watt 5% Semiconductors 2N4125 0103,0203 Q119, cl219 Q12O.Q220 PARTS LIST, DC-300A Page 2 Crown Part # 2343 2877 3220 3620 3301 3300...

  • Page 33: Mounting

    Schematic Designation Description MPSA93 QlOO, Q200 0101, Q201 2N3859A (selected) Q102,0202 Q105,0205 NSDI 28 Q104,0204 RCA 61061 (selected) Q106.0206 0107,0207 2N4929 SS7304 PN4250A DlOO, D200 lN4148 DlOl, 0201 D102, 0202 D103, D203 D104, D204 D105, D205 D106, D206 D107, 0207 Dill, 0211 lN270 D108, D208...
  • Page 34 Transistors 0108,0208 2N3859A (selected) 0 1 0 9 , 0 2 0 9 TIP558 (selected) Q114, Q214 PARTS LIST, DC-300A Page 4 C r o w n Part # Other Information 3 6 3 6 Used to mount coil assy.
  • Page 35 Bright washer Carrier strip 25K ohm audio ZF3448 RlOO, R200 Rack ears SHIELD ASSY. Main board shield Brass shield spacer 8-32 x % THP screw PARTS LIST, DC-300A Page 5 Crown Part # 3937 3990 4039 407 1 2162 1823...
  • Page 36 Schematic Designation Description Brass tube 6-32 x 1 j/4 BHP screw G-6-G terminal strip 6-32 x % BHP screw 6-32 hex nut Added after G-6-G insulator SN A71 14 #6 internal star lockwasher l/4” expansion nut #8 x 5/e SMT hex screw Cl.
  • Page 37 R145, 245 1 ohm ‘/2 watt 10% Power cord 3 #18 male 8-32 hex nut 8-32 x 3/e RHS screw #lo solder lug SW-1 Power switch 250 faston flag PARTS LIST, DC-300A Page 7 Crown Part # 1823 1889 2176 4035...

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