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- Page 1 User’s Guide 304 Headphone Amplifier...
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Page 3: Headphone Amplifier
User’s Guide 304 Headphone Amplifier Before You Begin What Ships in the Box Important Safety Instructions. or plug cord is damaged, liquid has been spilled or objects have fallen 1. Read these instructions. A 304 hardware unit. into the apparatus, the apparatus has 2. Keep these instructions. One PS-3 (117 VAC), PS-3E (230 been exposed to rain or moisture, VAC), or PS-3J (100 VAC) power 3. Heed all warnings. does not operate normally, or has supply. been dropped. 4. Follow all instructions. This User’s Guide. 5. Do not use this apparatus near CAUTION water. This apparatus shall not be RISK OF ELECTRIC SHOCK... -
Page 4: Fast First Time Setup
Caution The 304 is capable of driving many headphones past the threshold of pain. This can also result in hearing| damage. For your own hearing health, monitor at the lowest SPL that you can use and still get the job done. -
Page 5: Front & Rear Panel Overview
Volume controls set the signal strength at the corresponding output jack (1-4). eadpHone eveLS Red LED indicates power “on”. Rear Panel PASS THRU LINE INPUTS WWW.SYMETRIXAUDIO.COM MANUFACTURED BY SYMETRIX INC. MOUNTLAKE TERRACE, WA USA FABRIQUE PAR SYMETRIX INC. THRU B THRU A INPUT B INPUT A POWER CONNECT TO INPUT SYMETRIX PS-3 SERIES... -
Page 6: Impedance, Sensitivity, Loudness
User’s Guide 304 Headphone Amplifier Using the 304 Impedance, Sensitivity, Loudness Loudness is directly related to the impedance and sensitivity of the headphones. Impedance determines how much power the headphones will draw, while sensitivity indicates how much of the electrical signal delivered to the headphones is converted into sound. Because low impedance headphones draw more power from the amplifier they will sound louder, at the same control settings, than high impedance headphones. Also, headphones of higher sensitivity will sound louder than those of lower sensitivity. Check the manufacturer’s spec sheet for impedance and sensitivity information. Proprietary high voltage driver technology allows the 304 to drive even high impedance headphones to maximum levels, be- cause the amplifiers are capable of very high output voltage swing. However, to get a loudness equivalent to that of low imped- ance headphones, the controls will have to be set to higher settings when using high impedance headphones. This is normal. If low and high impedance headphones are combined on the same channel, the low impedance headphones will be much louder. As a result, when a combination of high impedance and low impedance headphones is used, only those of like imped- ance should be used on the same channel. This allows each listener to properly adjust loudness, without regard to the imped- ance and sensitivity of the other headphones. (It’s ok to mix impedances on the same amplifier, it’s just not optimum. You won’t hurt anything.) Maximum Amplifier Load The minimum operating impedance, or maximum load, for each output of the 304 is 8 ohms. Use as many pairs of headphones as desired, as long as the total combined impedance (per output) does not fall below 8 ohms. Table 1 shows how many headphones of various impedances may be used with each output of the 304. Table 1 - Combined Impedance Values (approx. 8:) Impedance of Headphones Maximum Number/Channel 8 (see note 1) 100 200 400 600 Note 1: The quantities given above reflect usage with typical wide-range musical signals. If you are driving low-impedance... - Page 7 User’s Guide 304 Headphone Amplifier Applications The 304 can be used in the following applications. Please note that this list is far from comprehensive and your imagination may create new uses that we haven’t listed here. ProjeCt StuDIo Let the 304 expand your mixer’s headphone capacity. You can drive it via a tip-ring-sleeve to dual tip-sleeve cable from your mixer’s headphone jack, or from one or two of your mixer’s aux sends. If you only use one aux send, then press the stereo/mono switch to route the signal to both channels. BroaDCaSt Use the 304 to drive the guest headphones in your studio. Does your console have an anemic headphone amplifier? The 304 will make it roar. LIve SouND Does your console have an anemic headphone amplifier? The 304 will make it roar. HouSe of WorSHIP Create assistive listening stations at several pews. Drive the 304 with a mixture of the sound reinforcement signal and a room microphone. No, this isn’t as sophisticated as one of the RF or infrared systems, but it doesn’t cost like they do either! BaLaNCeD Here’s how to use the 304 as a one-in, four out balanced line amplifier. LINe DrIver Make a “Y” cable so that you can drive both inputs in parallel. Wire the plug for the right-channel input so that it is reverse polarity from the left-channel input. Connect your source to the “Y” cable’s input. Connect each of your balanced loads to the tip-ring-sleeve output connectors. The tip connection is hot.
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Page 8: Block Diagram
User’s Guide 304 Headphone Amplifier Block Diagram HIGH VOLTAGE HEADPHONE HEAD- OUTPUT 1 PHONE LEVEL 1 HIGH VOLTAGE HIGH VOLTAGE LINE FILTER HEADPHONE HEAD- INPUT A CIRCUITRY OUTPUT 2 PHONE LEVEL 2 HIGH VOLTAGE MODE PASS MONO/STEREO INPUT THRU A... -
Page 9: Troubleshooting Chart
User’s Guide 304 Headphone Amplifier Troubleshooting Troubleshooting Chart SyMPtoM ProBaBLe CauSe No output Check cables and connections. Are inputs driven by outputs, and outputs driving inputs? Verify cables, source and load. Check for AC power presence. Hum or buzz in output Check input and output connector wiring. Ground loop: check related system equipment grounding. Are all system components on the same AC ground? Distortion Check input signal. Is it too hot, or is it already distorted? Check the output loading. Is something else clipping? Noise (hiss) Check input signal levels. The 304 is intended to operate at or near “line” level (+4dBu is nominal). Make sure that the signal you are feeding to the 304 is a line level signal, not mic level. Make sure that all systems components are on the same AC ground. Check gain settings on upstream equipment. The system gain structure should be such that the 304 receives +4dBu nominal signal. Is the input signal already noisy? No LeD display Is the unit plugged in? Is the AC outlet OK? Notes... -
Page 10: Specifications And Declaration Of Conformity
117V nominal, 95 to 130V AC, 50 to 60 Hz 230V nominal, 207 to 253V AC, 50 Hz Symetrix, Inc. 6408 216th St. SW In the interest of continuous product improvement, Symetrix, Inc. reserves the right to alter, change, or modify these specifications Mountlake Terrace, WA, 98043 USA without prior notice. -
Page 11: Warranty And Service
The Symetrix Limited Warranty exceed the price allocatable to the product or any part thereof which gives rise to the claim. In no event will Symetrix be liable Symetrix, Inc. expressly warrants that the product will be free for any incidental or consequential damages including but not from defects in material and workmanship for eighteen (18) limited to damage for loss of revenue, cost of capital, claims months from the date the product is shipped from the factory. of customers for service interruptions or failure to supply, Symetrix's obligations under this warranty will be limited to and costs and expenses incurred in connection with labor, repairing or replacing, at Symetrix's option, the part or parts overhead, transportation, installation or removal of products, of the product which prove defective in material or workman- substitute facilities or supply houses. ship within eighteen (18) months from the date the product is shipped from the factory, provided that the Buyer gives Servicing the 304 Headphone Amplifier Symetrix prompt notice of any defect or failure and satisfactory If you have determined that your 304 Headphone Amplifier proof thereof. Products may be returned by Buyer only after requires repair services and you live outside of the United a Return Authorization number (RA) has been obtained from States please contact your local SymNet dealer or distributor Symetrix. Buyer will prepay all freight charges to return the for instructions on how to obtain service. If you reside in the product to the Symetrix factory. Symetrix reserves the right to U.S. then proceed as follows. inspect any products which may be the subject of any warranty Return authorization claim before repair or replacement is carried out. Symetrix At the Symetrix factory, Symetrix will perform in-warranty or may, at its option, require proof of the original date of purchase out-of-warranty service on any product it has manufactured for (dated copy of original retail dealer's invoice). Final determina-... - Page 12 6408 216th St. SW, Mountlake Terrace, WA, USA • Tel +1 (425) 778-7728 • Fax +1 (425) 778-7727 • Web www.symetrixaudio.com © 2006, Symetrix, Inc. All rights reserved. Printed in the United States of America. Symetrix Part Number 53304-1A02. The information in this User’s Guide is subject to change without notice. Symetrix, Inc. shall not be liable for technical or editorial errors or omissions contained herein; nor is it liable for incidental or consequential damages resulting from the furnishing, performance, or use of this material. Mention of third-party products is for informational purposes only and constitutes neither an endorsement nor a recommendation. Symetrix assumes no responsibility with regard to the performance or use of these products. Under copyright laws, no part of this User’s Guide may be reproduced or transmitted in any form or by any...
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