304 Headphone Amplifier
Contents
1. Declaration of Conformity We Symetrix Incorporated 14926 35th Ave West Lynnwood Washington USA declare under our sole responsibility that the product 304 Headphone Amplifier to which this declaration relates is in conformity with the following standards EN 60065 Safety requirements for mains operated electronic and related apparatus for household and similar general use EN 50081 1 Electromagnetic compatibility Generic emission standard Part 1 Residential commercial and light industry EN 50082 1 Electromagnetic compatibility Generic immunity standard Part 1 Residential commercial and light industry The technical construction file is maintained at Symetrix Inc 14926 35th Ave West Lynnwood WA 98037 2303 USA The authorized representative located within the European Community is World Marketing Associates P O Box 100 St Austell Cornwall PL26 6YU U K Date of issue October 31 1998 Place of issue Lynnwood Washington USA Authorized signature Dane Butcher President Symetrix Incorporated Symetrix Symetrix Symetrix Inc 14926 35th Ave West Lynnwood WA 98037 2303 USA Tel 425 787 3222 Fax 425 787 3211 Website http www symetrixaudio com Email symetrix symetrixaudio com2. Front amp Rear Panel Overview Chapter 4 INPUT HEADPHONE OUT HEADPHONE LEVEL LEVEL 1 LEVEL 2 LEVEL 3 LEVEL 4 304 MO OUTPUT1 OUTPUT2 _ 00013 OUTPUT4 HEADPHONE AMPLIFIER 15 0 Symetrix Input LEVEL Sets the input signal strength Fully counterclockwise no signal Fully clockwise input signals are boosted by 25 dB MONO STEREO Combines stereo or two mono input signals into one mono output signal fed equally to both left and right headphone outputs HEADPHONE OUTPUTS 1 4 stereo jacks for headphones The minimum impedance is 8 ohms see Table 1 for combined headphone impedances HEADPHONE LEVELS Volume controls set the signal strength at the corresponding output jack 1 4 Pwr Red LED indicates power on PASS THRU LINE INPUTS Symetrix MANUFACTURED BY SYMETRIX INC LYNNWOOD WA USA THRU 8 THRU A INPUT B INPUT POWER CONNECT TO INPUT SYMETRIX PS 3 OR PS 3E POWER CE SUPPLY ONLY THIS PRODUCT CONTAINS NO USER SERVICABLE PARTS METAK INC L FABRIQU AUX E U PAR SYI INC LYNNWOOD WASHINGTON REFEREZ TOUTE R PARATION UN TECHNICIEN QUALIFI 7 PIN DIN CONNECTOR Connect the 7 pin DIN plug end of a Symetrix PS 3 117V or PS 3E 230V here Connect the AC power connector end of the PS 3 or PS 3E to an AC power source that is of the correct voltage and frequency as marked on the PS 3 or PS 3E THRU A TRS jack connected i
3. including any dealer or sales representative to assume any liability or make any addi tional warranties or representation regarding this product information on behalf of Symetrix This limited warranty gives the buyer certain rights You may have additional rights provided by applicable law consequential damages including but not limited to damage for loss of revenue cost of capital claims of customers for service interruptions or failure to supply and costs and expenses incurred in connection with labor overhead transportation installation or removal of products or substitute facilities or supply houses Servicing the 304 If you have determined that your 304 requires repair services and you live outside of the United States please contact your local Symetrix dealer or distributor for instructions on how to obtain service If you reside in the U S then proceed as follows Before sending anything to Symetrix contact our Customer Service Department for a return authorization RA number The telephone number is 425 787 3222 Monday through Friday 8AM 0800 hours though 4 30 PM 1630 hours Pacific Time At the Symetrix factory Symetrix will perform in warranty or out of warranty service on any product it has manufactured for a period of five years from date of manufacture In warranty Repairs To get your 304 repaired under the terms of the warranty 1 Call us for an RA number 2 Pack the u
4. worth it Should you have any comments or questions please do not hesitate to contact us Your calls and e mail are always welcome Phone 425 787 3222 Fax 425 787 3211 Email symetrix symetrixaudio com Website www symetrixaudio com HEADPHONE OUT INPUT LEVEL MODE 12 AMPLIFIER MONO OUTPUT 1 OUTPUT2 OUTPUT3 OUTPUT4 304 m STEREO HEADPHONE 5 HEADPHONE LEVEL LEVEL 1 LeveL 2 LeveL 3 an 4 1 10 2 Front panel Symetrix MANUFACTURED BY SYMETRIX INC LYNNWOOD WA USA THRU B THIS PRODUCT CONTAINS NO USER SERVICABLE PARTS FABRIQU AUX E U PAR SYMETRIX INC LYNNWOOD WASHINGTON R F REZ TOUTE R PARATION UN TECHNICIEN QUALIFI Rear panel PASS THRU THRU A LINE INPUTS INPUT B INPUT A Symetrix Symetrix Operator Safety Summary The information in this summary is intended for persons who operate the equipment as well as repair personnel Specific warnings and cautions are found throughout this manual wherever they may apply The notational conventions used in this manual and on the equipment itself are described in the following paragraphs Equipment Markings CAUTION RISK OF ELECTRIC SHOCK DO NOT OPEN TO REDUCE THE RISK OF FIRE OR WARNING ELECTRIC SHOCK DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE AVI RISQUE DE CHOC ELECTRIQUE NE PAS OUVRIR SEE OWN
5. 304 Headphone Amplifier User s Guide Symetrix Table of Contents Chapter 1 Introduction 1 Chapter 2 Operator Safety Summary 2 Chapter 3 Fast Setup 3 Chapter Front amp Rear Panel Overview Chapter 5 Using the 304 5 Chapter 6 Applications 6 Chapter 7 Block Diagram 7 Chapter 8 Troubleshooting 8 Chapter 9 Specifications 9 Chapter 10 Warranty and Service 10 Chapter 11 Declaration of Conformity 13 Rev A 31 October 1998 Symetrix part number 53304 0A00 Subject to change without notice 1998 Symetrix Inc All right reserved Symetrix is a registered trademark of Symetrix Inc 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 manual may be Symetrix reproduced or transmitted in any form or by any 14926 35th Ave West means electronic or mechanical including photo Lynnwood WA 98037 USA copying scanning recording or by any information Tel 425 787 3222 storage and retrieval system without permission in Fax 425 787 3211 S tri writing from Symetrix Inc Email symetrix symetrixaudio com Chapter 1 Symetrix 304 Headphone Amplifier is 1 4 out amplifier designed to drive multiple headphones of any impedance Symetrix proprietary high voltage d
6. ERS MANUAL VOIR CAHIER D INSTRUCTIONS No user serviceable parts inside Refer servicing to qualified service personnel ll ne se trouve a l interieur aucune piece pourvant entre repar e l usager S adresser a un reparateur comp tent The lightning flash with arrowhead symbol within an equilateral triangle is intended to alert the user of the presence of uninsulated dangerous voltage within the product s enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons The exclamation point within an equilateral triangle is intended to alert the user of the presence of important operating and mainte nance servicing instructions in the literature accompanying the 304 i e this manual Caution prevent electric shock do not use the polarized plug supplied with the 304 with any extension cord receptacle or other outlet unless the blades can be fully inserted Terms Several notational conventions are used in this manual Some paragraphs may use Note Caution or Warning as a heading Certain typefaces and capitalization are used to identify certain words These are Note Identifies information that needs extra emphasis A Note generally supplies extra information to help you to better use the 304 Chapter 2 Caution Identifies information that if not heeded may cause damage to the 304 or other equipment in your system Warning Identifies information that if ignored may be ha
7. in the range of 8 ohms to 2000 ohms The output source impedance shall be 100 ohms Specifications Input Output Input Type Bridging Balanced or Unbalanced Maximum Input Level 18dBu Balanced Maximum Output Level 21dBm 600 Ohm load gt 6VRMS 200 Ohm load Input Impedance 20k Ohms Balanced 10k Ohms Unbalanced Output Impedance 100 Ohms Performance Data Frequency Response 20Hz to 20kHz 0 1 dB THD Noise 01 102 OdBm 600 Ohms 02 102 20dBm 600 Ohms Signal to Noise Ratio 9508 Maximum Gain 2508 Connections Input 1 4 TRS Output 1 4 TRS 7 DIN Physical Size hwd rack unit 1 75 8 5 6 5 in 4 445 21 59 x 15 875 cm Shipping Weight 4 5 Ibs Electrical Power Requirements 117V nominal 95 to 130V AC 50 to 60 Hz 230V nominal 207 to 253V AC 50 Hz In the interest of continuous product improvement Symetrix Inc reserves the right to alter change or modify these specifications without prior notice 1998 Symetrix Inc All rights reserved The headphone amplifier shall be capable of delivering 35 volts peak to peak into a 2000 ohm load or greater The unit shall be capable of operating by means of a Symetrix PS 3 or PS 3E external power supply connected to 117V nominal AC 95 to 130V 50 60 Hz or 230V nominal AC 207 to 253V AC 50 Hz where applicable The unit shall be a Symetrix Inc model 304 Headphone Amplifier Symetrix o Symetri
8. n parallel with Input A jack Use this jack to connect to other 304 s or other audio equipment It s a built in wye cord THRU TRS jack connected in parallel with Input jack Use this jack to connect to other 304 s or other audio equipment It s a built in wye cord Input A Leftchannel 3 conductor 1 4 jack for line level balanced or unbalanced input signals Tip high Ring low Sleeve ground Input Right channel 3 conductor 1 4 jack for line level balanced or unbalanced input signals Tip high Ring low Sleeve ground Symetrix Chapter 5 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 head phones to maximum levels because the amplifiers are capable of very high output voltage swing However to get a l
9. nit in its original packaging materials 3 Include your name address daytime telephone number and a brief statement of the problem 4 Write the RA number on the outside of the box 25 Ship the unit to Symetrix freight prepaid We do not accept freight collect shipments Repairs made in warranty will cost you only one way freight charges We ll prepay the return surface freight If you send us your product in substandard packaging we will charge you for factory shipping materials If you don t have the factory packaging materials please use an oversized carton wrap the unit in a plastic bag and surround it with bubble wrap Pack the box full of Styrofoam peanuts Be sure there is enough clearance in the carton to protect the rack ears you wouldn t believe how many units are returned with bent ears We will return the unit in Symetrix packaging Of course if the repair is due to operator error parts and labor will be charged In any event if there are charges for the repair costs you will pay for the return freight All charges will be COD unless you have made other arrangements prepaid Visa or Mastercard Out of warranty Repairs If the warranty period has passed you ll be billed for all necessary parts labor packaging materials and freight charges Please remember you must call for an RA number before sending the unit to Symetrix Symetrix Symetrix Chapter 11 Declaration of Conformity
10. oudness equivalent to that of low impedance 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 impedance should be used on the same channel This allows each listener to properly adjust loudness without regard to the impedance and sensi tivity 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 1 16 2 32 4 100 10 200 20 400 40 600 60 Note 1 The quantities given above reflect usage with typical wide range musical signals If you are driving low impedance headphones 16 ohms or lower actual impedance and you intend to drive them to the brink of amplifier clipping then you should revise the number of headphones possible per 304
11. r 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 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 Does your console have an anemic headphone amplifier The 304 will make it roar 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 Here s how to use the 304 as a one in four out balanced line amplifier Make a wye 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 wye cable s input Connect each of your balanced loads to the tip ring sleeve output connectors The tip connection is hot Chapter 7 Block Diagram 22 CHANNEL 4 CHANNEL 3 CHANNEL 2 CHANNEL 1 MASTER VOLUME j STEREO MONO V 4 V 9 o CHANNEL 0 0 OUTPUT NPUT B lt t i V Symetrix Troubleshoo
12. rive technology gives the 304 the ability to drive high imped ance headphones with the equivalent output voltage of a much larger power amplifier yet provides more than ample current for low impedance phones The four stereo outputs automatically adjust output power to match the load impedance Controls provided are input level output level for each individual amplifier and a stereo mono switch The STEREO MONO switch allows the amplifier to be used several ways As a normal stereo amplifier with four outputs the left and right inputs are used for stereo signals which feed the left and right outputs Switching to mono with a stereo input provides a quick check of the mono compatibility of a stereo mix For that matter you may want to monitor in mono As amono amplifier one signal fed to either input will feed both outputs Also in mono mode when two different mono signals are fed to the left and right inputs they will be mixed to feed both the left and right outputs Introduction The inputs are electronically balanced but will operate normally in an unbalanced configura tion when 2 conductor 1 4 plugs are inserted The outputs are 1 4 stereo connectors Do you hate reading manuals Chapter 3 of this manual was written just for you Pleeeeeze Skip the rest of this and just read Chapter 3 It will get you up and running with minimum reading and minimum pain Try to read the rest of the manual later It s
13. rst Time Setup This section is dedicated to users who hate to read manuals The 304 is a four output headphone amplifier A stereo input drives all four headphone amplifiers Each amplifier has an independent level control There is an overall master level control and an overall STEREO MONO switch Wiring To install the 304 D Plug the PS 3 power supply s DIN connector into the 304 Plug the PS 3 into suitable source of AC power Refer to the labelling on the PS 3 to determine what is suitable Connect your source to the 304 s tip ring sleeve input jacks The inputs are balanced They will work with either balanced or unbalanced sources Connect your headphones to the four output jacks The 304 can handle headphone impedances ranging from 8 ohms to over 2000 ohms 60 ohm headphones are optimal they get the loudest It is not necessary for each set of headphones to be the same although it might help if they were Go Set the individual level controls to minimum max rotation Set the master level control to the halfway position 12 noon Set the stereo mono switch as appropriate With the source signal active adjust the individual level controls for comfortable listening levels 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 Symetrix
14. ting Chapter 8 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 Symetrix Chapter 9 Specifications Architects and Engineers Specifications The headphone amplifier shall have a single stereo input and four stereo outputs Each output shall have its own amplifier and volume control An overall volume control master shall also be provided There shall be an overall stereo mono switch All inputs are balanced bridging inputs Outputs shall be suitable for driving head phones
15. to 2 8 ohm headphones or 4 16 ohm headphones for the 8 ohm case you ll have two amplifier channels that aren t doing anything It is OK to use any remaining amplifier channels with higher impedance phones 50 ohms or higher For maximum output with all channels driven try to restrict the lowest combined load impedance to 50 ohms per channel Lower impedance loads simply reduce the maximum output possible Note 2 Many headphones are spec d as being suitable for eight ohm outputs They are but this does not mean that their actual impedance is 8 ohms In most cases the actual impedance is substantially higher This is good rather than bad For whatever it s worth most decent headphones have actual impedances ranging from 50 ohms and up Note 3 When multiple headphones are required with each output use headphone type Y cords or a breakout box A breakout box may have as many paralleled 1 4 stereo jacks as necessary as long as the numbers in Table 1 are not exceeded Symetrix Symetrix Applications Chapter 6 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 BROADCAST LIVE SOUND HOUSE OF WORSHIP BALANCED LINE DRIVER 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 mixe
16. written express implied or statutory Symetrix Limitation of Liability The total liability of Symetrix on any claim whether in contract tort including negli gence or otherwise arising out of connected with or resulting from the manufacture sale delivery resale repair replacement or use of any product will not exceed the price allocable to the product or any part thereof which gives rise to the claim In no event will Symetrix be liable for any incidental or 10 Chapter 10 Inc expressly disclaims any IMPLIED warranties including fitness for a par ticular purpose or merchantability Symetrix s warranty obligation and buyer s remedies hereunder are SOLELY and exclusively as stated herein This Symetrix product is designed and manufactured for use in professional and studio audio systems and is not intended for other usage With respect to products purchased by consumers for personal family or household use Symetrix ex pressly disclaims all implied warranties including but not limited to warranties of merchantability and fitness for a particu lar purpose This limited warranty with all terms conditions and disclaimers set forth herein shall extend to the original purchaser and anyone who purchases the product within the specified warranty period Warranty Registration must be completed and mailed to Symetrix within thirty 30 days of the date of purchase Symetrix does not authorize any third party
17. x Warranty and Service 304 Limited Warranty Symetrix Inc expressly warrants that the product will be free from defects in material and workmanship for one 1 year Symetrix s obligations under this warranty will be limited to repairing or replacing at Symetrix s option the part or parts of the product which prove defective in material or workmanship within one 1 year from date of purchase provided that the Buyer gives Symetrix prompt notice of any defect or failure and satisfactory proof thereof Products may be returned by Buyer only after a Return Authorization number RA has been obtained from Symetrix Buyer will prepay all freight charges to return the product to the Symetrix factory Symetrix reserves the right to inspect any products which may be the subject of any warranty claim before repair or replacement is carried out Symetrix may at its option require proof of the original date of purchase dated copy of original retail dealer s invoice Final determination of warranty coverage lies solely with Symetrix Products repaired under warranty will be returned freight prepaid by Symetrix via United Parcel Service surface to any location within the Continental United States At Buyer s request the shipment may be returned via airfreight at Buyer s expense Outside the Continental United States products will be returned freight collect The foregoing warranties are in lieu of all other warranties whether oral
18. zardous to your health or that of others CAPITALS Controls switches or other markings on the 304 s chassis Boldface Strong emphasis Power source This product is intended to operate from a power source that does not apply more than 255Vrms between the power supply conductors or between either power supply conductor and ground A protective ground connection by way of the grounding conductor in the power cord is essential for safe operation Danger from loss of ground If the protec tive ground connection is lost all accessible conductive parts including knobs and controls that may appear to be insulated can render an electric shock In line power supply This product receives its operating power from the Symetrix PS 3 or PS 3E power supply This is the only power supply approved for use with the product Do not connect the product to any other in line or plug in transformer The use of other power sources may cause damage to the equipment or present a shock hazard to the operator Operating location Do not operate this equipment under any of the following condi tions explosive atmospheres in wet locations in inclement weather improper or unknown AC mains voltage or if improperly fused Stay out of the box To avoid personal injury or injury to others do not remove the product covers or panels Do not operate the product without the covers and panels properly installed Chapter 3 Fast Setup Fast Fi
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