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****** Page 1 ****** Owner’s Manual Model BL2 INPUT CONTROLLER audio research HIGH DEFINITI O NO 5740 GREEN CIRCLE DRIVE / MINNETONKA, MINNESOTA 55343-4424 / PHONE 612/939-0600 FAX 612/939-0604

****** Page 2 ****** Contents Model BL2 Section Preface Introduction Warnings Packagings Page No, 1 1 1 1 Description of Controls 2 Connections 2 Installation Instructions Operating Procedure Muting Provisions Shut Down Servicing 4 Cleaning Warranty Terms and Conditions Warranty Outside the USA Specifications i

****** Page 3 ****** Model BL2 Description of Controls INPUT SELECTOR: Detents indicate selection of var- ious source material options: “Tuner” for AM/FM radio tuners; “Video” for audio input from HiFi video tapes, disks or broadcasts; “Phono” for phono pream- plifiers; “CD” for compact disc players or digital-to- analog processors; IJAux” for any additional high level source—tape, tuner, CD, video, etc. RECORD SELECTOR: Detents mark selection of the source to be routed to recording equipment. NOTE: See “Monitor/sourceii for primary tape recorder selection. POWER SWITCH: Supplies power from AC wall out- let to BL2 when in “Power” positiom Although not strictly necessary, it is nonetheless good practice to put the BL2 in “Mute” before turning on power for maximum protection of your power amplifier(s) and speakers. TAPE 1/ TAPE 2: With the “Source/Monitor” switch in the “monitor” position, this switch selects the out- put of either tape machine for playback. MONITOR/SOURCE: In “Monitor” position this con- trol selects the audio output of the primary tape recorder. “Source” accesses the input selector’s five high-level sources. PHONO MUTE/OPERATE SWITCH: In “Mute” position, shorts the main outputs of the line stage amplifier to allow listening interruptions for telephone answer- ing or other reasons. This switch should always be activated between listening uses or switching of inputs. This simple precaution will prevent inadver- tent misuse of your BL2 and help protect your power amplifier(s) and speakers from unexpected transient signal pulses. In “Operate” position, this switch allows the signal to pass normally to the outputs. POWER/MUTING CIRCUIT LED; Glows green to indicate unit is on and receiving power from the power supply. Note that for approximately 3 sec- onds after start-up or in “Mute” mode, this LED glow more dimly, indicating proper operation of the muting circuit. In the “Operate” mode (after warm- up) the LED brightens and your BL2 is ready for nor- mal operation. Connections INPUT CONNECTORS: All are clearly marked to indicate use. The inputs are 1.5 megohm impedance. MAIN OUTPUT CONNECTORS: There is one set of output connectors; They have (balanced) XLR type connectors. These should be connected to your Balanced-input Line Stage Amplifier.. PHONO VIDEO MODEL OL2 LINC 2 CD audio research MONITOR VitiCO TUNER MUTE Aug HIGH DEFINIT’0Nt SELECT INPUT CONVERTER

****** Page 4 ****** Model BL2 Preface Please take the time to carefully read this instruction manual prior to installation or use of your BL2 Input Converter. Because it is a highly advanced electronic instrument, there are several facts and procedures you should know before you place it in operation. Introduction The Audio Research BL2 Balanced Line Driver Input Converter is designed to accomodate music lovers who wish to use single-ended (RCA Connector) input sources — digital or analog for the reproduction and enjoyment of music in their bal- anced-operation home audio systems. The advantages of balanced operation have long been known to the audio engineering community. They include: the ability to run long interconnects without interference from noise on the AC line or sources of noise in close proximity to the cables. (motors, electronic components, etc.) This occurs because the ground currents are carried on a sepa- rate drain wire, isolated from the signal-carrying hot and neutral conductors. Better and simpler amplifier and line amp circuits can thus be utilized without need for phase inverters (required to cope with two- pin RCA type connectors). The Audio Research BL2 balance Line Driver-Input Converter converts single-ended sources to true bal- anced operation. It uses innovative equal-path-length phase-splitter circuitry with the ability to accept up td five input sources, plus tape handling functions, Owners of Audio Research LS5 or LS2B Line Stage Amplifiers can thus continue to enjoy their existing single-ended sources (sounding their best driving the high 1.5 megohm input impedance of the BL2) and get tape handling convenience as well (listen to one source as you record from another). The BL2 is housed in a first-rate Audio Research mechanical package with a 31/2″ H. by 19″ W. face- plate. The BL2 is designed to stack neatly beneath the LS5 or LS2B, allowing easy connection with a single pair of half-meter balanced interconnects. Toggle switches control on-off manual muting, source/monitor and selection of Tape 1 or 2, while two rotary knobs control input source selection and, conversely, record output selection. Muting is auto- matic at turn-on and in brown-out conditions. The BL2 is a truly unique product in design and function, unlike any other currently available. Sonically, you will find it has the purity, openness and neutrality that have become the hallmark of Audio Research. Just as you would not purchase and attempt to oper- ate an expensive camera, computer system or high- performance automobile without first learning some- thing about performance parameters and correct operating procedures, so too your BL2 Input Converter requires some familiarization before you make it part of your music reproduction system. Your reward, in terms of maximum performance and a long services life, will be well worth the effort. Warnings 1. To prevent fire, or shock hazard, do not expose your BL2 to rain or moisture. 2. This unit contains voltages which can cause seri- ous injury or death. Do not operate with cover removed, Refer servicing to your authorized Audio Research dealer or other qualified personnel. 3. The power cord on your BL2 is equipped with a heavy gauge, 3-conductor cable and a standard three-prong grounding plug. For absolute protec- tion, do not defeat the ground power plug. This provides powerline grounding of the BL2 chassis to provide absolute protection from electrical shock. 4. For continued protection against fire hazard, replace the fuse only with the same type and rat- ing as specified at the fuse holder. packaging Save all packaging in a dry place away from fire haz- ard. Your BL2 Input Converter is a precision electron- ic instrument and should be properly cartoned any time shipment is made. You may not have occasion to return your unit to the factory for service, but if that should prove necessary, or other occasion requiring shipment occurs, the original packaging will protect your BL2 from unnecessary damage •Or delay. 1

****** Page 5 ****** Model BL2 NOTE: The XLR connector pin leads are as follows: I-shield; 2-positive; 3-negative. If used with a power amplifier which utilizes different pin leads for posi- tive, negative and/or shield, the signal being fed to the loudspeakers will be incorrect. Please consult your Audio Research dealer. At the performance level of the BL2, high-quality audio signal interconnect cables are critical to pre- serving maximum fidelity. Audio Research intercon- nect cables are highly recommended for connection to your power amplifier(s) and to other ancillary equipment. See your authorized Audio Research dealer for recommended lengths. TAPE OUTPUT CONNECTORS: The BL2’s Tape Outputs should be connected to your tape deck’s “REC” or “LINE” inputs. These outputs supply what- ever is selected by the Selector Control to the tape deck for recording. Level is non-variable and approx- imately the same as the selected input source. Installation Instructions While the BL2 does not dissipate an unusual amount of heat, it is important that it be provided with rea- sonable airflow to assure long, trouble-free opera- tion. In addition, the following installation guide- lines will help insure maximum sonic performance as well as reliable service. 1. Upright and horizontal mounting is suggested if extended operation (longer than one hour) is con- templated. 2. Do not “stack” the BL2 on top of a power amplifi- er: not only could this cause overheating, but “hum” may be introduced into the BL2 from the proximity of the amplifier’s power transformer. 3. Do not place or operate your BL2 on a soft or irregular surface such as a rug. This will prevent proper ventilation. 4. Do not operate your BL2 without the top and bot- tom covers installed. These are required both for safety as well as shielding from interference (except in service operations). 5. If rack mounting is employed, use Audio Research Rack Mount Ventilators (RMV-3) below and above your BL2. 6. If side-by-side mounting with other equipment is employed, place the BL2 to the left of the other chassis, so as to provide maximum spacing between the transformer of the BL2 and the other component. 3 “B aAIN ovrpt.m ooööoooöö MODEL BL-e TUNER VIDEO PHONO C-O TAPE’ RECI REC2 BALANCEO LINE DRIVER LEFT OUTPUT LEFT INPUTS BINNETONK.A. MINNESOTA MADE IN CAUTION 1 S WATTS MAX (9 3

****** Page 6 ****** Model BL2 Operating Procedure Start-Up: 1. Make sure Power switch is set to “Off” position; Mute switch should be in “Mute” position. 2. Secure all rear-panel connections between BL2, pre-amplifier and input sources. Note: Given the advanced performance capabilities of the BL2, it is extremely important that high-quality intercon- nects be used for connection to ancillary electron- ics.Audio Research brand interconnects, in either unshielded or RFI-shie1ded configurations, are strongly recommended. Your authorized Audio Research dealer can assist you in determining op- timal lengths for your system. 3. Plug 3-prong powerline cord from rear of BL2 into grounded AC wall receptacle. 4. Turn Power switch to “On.” Green LED will glow dimly for approximately 3 seconds while power supply stabilizes, indicating operation of automat- ic muting circuit. After this warm-up muting peri- od, the LED will brighten when “Operate” is se- lected, indicating that your BL2 is ready for opera- tion. Note: For superior sonic performance, a warm-up pe- riod of at least one hour is recommended. In addi- tion, your BL2 may be safely left “on” continuous- ly for maximum performance at all times. 5. Rotate input selector to source desired; set switch options to positions desired. 6. Activate input source, then deactivate Mute switch. Muting Provisions: The BL2 has several provisions to help protect against misuse of the exceptional dynamic range and wide bandwidth that it offers. It is not subject to damage itself, but some power amplifiers and speak- ers are more limited in their ability to withstand sig- 4 nal extremes. These provisions, both manual and au- tomatic, are designed not to interfere with a flawless listening experience of unprecedented realism, while giving reasonable protection against warm-up surges and power line interruptions. However, for absolute protection of associated equipment some operator understanding, and responsibility, is required. Initial “settling” time of all circuit parameters within the BL2 requires approximately 5 to 10 minutes. The automatic muting circuitry timer is adjusted for about 3 seconds. (This is because recurrent interrup- tion “settling” time is much less. You would not want to wait for 5 to 10 minutes each time such an interruption occurred.) The Mute/Operate Switch allows manual disabling of the BL2 outputs during the switching of equip- ment. Use of this switch will minimize stress on your amplifier even if it is “off”. It is also highly rec- ommended that manual muting be employed during the initial 3 second warm-up period as well as during turn-off for maximum protection. While it is true that the automatic muting will pro- vide reasonably adequate protection against speaker burnout during these periods, it has limitations. At the 3 second point the automatic timer “releases” the output. Although this is normally adequate protec- tion, utilization of the manual mute provision will completely avoid stress to your speakers, Some solid-state power amplifiers have a DC offset present at their input connections. (This, of course, should not be.) Operation of the manual muting switch with such an amplifier connected will result in a “click” or “pop” in your loudspeaker (commensu- rate in level with the amount of the offset) each time the switch is activated. Repair or replacement of such amplifiers is suggested.

****** Page 7 ****** Model BL2 The automatic muting operates a follows: 1. The manual mute switch always disables both “main” outputs and overrides any automatic provi- sions, even when the BL2 is turned off (The “Op- erate” position of the manual mute switch is func- tional only when the unit is not in the automatic mute mode.) 2. The 3 second warm-up timer will restart automat- ically and the LED will dim if the power is tem- porarily interrupted for 0.1 second or more. Note: Power supply regulation of the BL2 is effective down to 100VAC without serious sonic degreda- tion. 3. The automatic muting of the BL2 is designed to be effective only against power line interruptions and power line failures. It will not mute against sub- sonic signal transmissions from your input source. Proper Fusing of speakers Is essential to protect against excessive audio level or power amplifier faults. Shut-Down: 1. Set “Mute” switch to “Mute” position. 2. Turn off power amplifier(s). 3. Turn off all input sources. 4, Set BL2 Power Switch to ‘Off” position. Servicing Because of its careful design and exacting standards of manufacture, your BL2 should normally require only minimal routine service to maintain its high level of performance. CAUTION: Your BL2 contains sufficient levels of voltage and current to be lethal. Do not tamper with a component or part inside the unit. Refer any need- ed service to your authorized Audio Research dealer or other qualified techniciam should service be necessary, please contact your Audio Research dealer, or Audio Research Customer Service (612) 939-0600 Cleaning To maintain the visual appearance of your BL2 line stage amplifier, occasionally wipe the front panel and top cover surfaces with a soft damp (not wet) cloth to remove dust* A mild, non-alkaline soap solu- tion may be used to remove fingerprints or similar smudges. Cleaners containing abrasives should not be used as they will damage the “brushed” grain of the front panel finish. 5

****** Page 8 ****** 3-Year Limited Warranty Terms and Conditions 1. LIMITED WARRANTY Audio Research warrants the product designated herein to be free ofmanufactUring defects in material and workmanship. sub- ject to the conditions hereinafter set forth. for a period of three (3) years from the date of purchase by the original purchaser or no later than five (5) years from the date of shipment to the authoriti?d Audio Research dealer, whichever comes first. excepe ing vacuum tubes which are warranted for 90 days only (See 6). 2. CONDITIONS This Warranty is subject to the following conditions and limita- tions. The Warranty is void and inapplicable if the product has been used or handled other than in accordance with the instruc- tions in the owner’s manual, abused, or misused, damaged by accident or neglect or in being transported, or the defect is due to the product being repaired or tampered with by anyone other than Audio Research or an authorized Audio Research repair center The product must be packed and returned to Audio Research or an authorized Audio Research repair center by the customer at his or her sole expense. Audio Research will pay return freight ofits choice. A RETURNED PRODUCT MUST BE ACCOMPANIED BY A WRITTEN DESCRIPTION OF THE DEFECT AND A PHOTOCOPY OF THE ORIGINAL PURCHASE RECEIPT. This receipt must clearly list model and serial number, the date ofpurchase, the name and address ofthe purchaser and authorized dealer and the price paid by the purchaser Audio Research reserves the right to modify the design of any product without obligation to purchasers of previously manufactured products and to change the prices or specifications ofany prod- uct without notice or obligation to any person. 3. REMEDY In the event the above product fails to meet the above Warranty and the above conditions have been met, the purchaser’s sole remedy under this Limited Warranty shall be to return the pro- ductto Audio Research or an authorized Audio Research repair center where the defect will be rectified without charge for parts or labor, except vacuum tubes (See 6). 4. LIMITED TO ORIGINAL PURCHASER This Warranty is for the sole benefit of the original purchaser of the covered product and shall not be transferred to a subsequent purchaser of the product. 5. DURATION OF WARRANTY This Warranty expires on the third anniversary ofthe date of pur- chase or no later than the fifth anniversary of the date of ship- mentto the authorized Audio Research dealer, whichever comes first. Warranty Outside the U.S.A. Audio Research has authorized distribution in many countries ofthe world. In each country, the authorized importing retailer or distributor has accepted the responsibility for warranty Ofour products. Warranty service should normally be obtained from the importing retailer or distributor from whom you purchased your product. 6 6. VACUUM TUBES Vacuum tubes are warranted for the original 90-day period only. 7. DEMONSTRATION EQUIPMENT Equipment used by an authorized dealer for demonstration pur- poses is warranted to be free of manufacturing defects in materials and workmanship for a period of three (3) years from the date of shipment to the dealec Vacuum tubes are warranted for 90 days. After the first year. demo equipment needing war- ranty service must be packed and returned to Audio Research by the dealer at his sole expense. Audio Research will pay return freight of its choice. A returned product must be accompanied by a written description of the defect on an AUDIO RESEARCH RETURNED GOODS AUTHORIZATION form. Dealer-owned demonstration equipment sold at retail within three (3) years of date of shipment to the dealer is warranted to the first retail customer to be free of manufacturing defects in materials and workmanship for the duration ofthe 3-Year Limited Warranty reu maining (as measured from the date of shipment of the equip- ment to the dealer). Vacuum tubes are not warranted for any period under these conditions Qfsale. Jn the event warranty ser- vice is needed under these conditions, the owner of the equip- ment must provide a copy of his purchase receipt. fulfilling the requirements described under “2. Conditions” above. The pro- duct must be packed and returned to Audio Research or an authorized Audio Research repair center by the customer at his or her sole expense. AudiO Research will pay return freight ofits choice. 8. MISCELLANEOUS ANY IMPLIED WARRANTIES RELATING TO THE ABOVE PRODUCT SHALL BE LIMITED TO THE DURATION OF THIS WARRANTY. THE WARRANTY DOES NOT EXTEND TO ANY INCIDENTAL OR CONSEQUENTIAL COSTS OR DAMAGES rro THE PURCHASER. Some states do not allow limitations on how long an implied warranty lasts or an exclusion or limitation of incidental or consequential damages, so the above limitations or exclusions may not apply to you. This Warranty gives you specific legal rights, and you may also have other rights which vary from state to state. 9. WARRANTOR Inquiries regarding the above Limited Warranty may be sent to the following address: Audio Research 5740 Green Circle Drive, Minnetonka. Minnesota 55343-4424. ATTN: Customer Services Jn the unlikely event of service required beyond the capability ofthe importer, Audio Research will fulfill the conditions of the warranty Such product must be returned at the owner’s expense to the Audio Research factory, together with a photocopy ofthe bill of sale for that product, a detailed description of the problem. and any information necessary for return shipment.

****** Page 9 ****** Specification Model BL2 FREQUENCY RESPONSE: dc to 500kHz. (-3dB point.) DISTORTION: Less than .01% at 2V RMS output. (Typically less than .002% at 1 kHz.) GAIN: 6dB. INPUT IMPEDANCE: 1.5 Megohms. OUTPUT IMPEDANCE: 60 ohms balanced. OUTPUT DC OFFSET: Less than 2mV dc. OUTPUT BEFORE CLIP: 18V RMS out balanced (9V RMS input) 16V RMS into 600 ohm balanced load. NOISE: Less than 18 uv RMS balanced IHF weighted. INPUTS: Tuner, Video, Phono, CD, Aux, Tape 1, Tape 2 OUTPUTS: Main (Balanced); Record 1, Record 2 (unbalanced). SWITCHES: Record Select, Input Select, On/Off, Tape 1/2, Monitor/Source, Mute/Operate. POWER REQUIREMENTS: 100-135VAC 60Hz (200- 270VAC 50/60Hz) 1 5 watts maximum. DIMENSIONS: 19″ (48 crn) W x 31/2″ (8.9 cm) H (standard rack panel) x 113/4″ (29.8 cm) D Handles ex- tend 11/2″ (3.8 cm) forward of the front panel. Rear chassis fittings extend 9/1611 (1.4 cm). WEIGHT: 9.0 lbs. (4.1 kg) Net; 19.0 lbs. (8.6 kg) Shipping. Specifications subject to change without notice. 01993 Audio Research Corporation. 7


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