In the early 90s, I was working for a company that sold professional audio. This company had a huge showroom that they used to demo lights and such, and all their speakers were powered by amplifiers like these, these solid JBL UREI power amplifiers. One thing I love about these amplifiers was the fact that they used only heatsinks, and they were bloody heavy. When we first got them, they were configured for volts.
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This banner text can have markup. Search the history of over billion web pages on the Internet. We have prepared this instruction manual to enable you to achieve optimum utility and performance from your new amplifier. We encourage you to read it and to make use of the material contained in this manual. We welcome your comments or suggestions on our products and on this manual. They are rugged and road-worthy, conservatively rated, and can handle reactive loads with ease. The engineering design approach stresses the optimization of each stage, allowing high slew rate and relatively low loop gain.
Overall feedback has been held to a minimum and is employed only to stabilize the gain and the operating point. This design approach results in amplifiers with excellent performance under the most demanding dynamic input and load conditions.
As evidence of the stress on dynamic rather than static or steady- state distortion mechanisms, transient intermodulation distortion measures less than 0.
The front panel and heat sinks of the amplifiers are made of heavy aluminum extrusions; the chassis is fabricated of heavy gauge steel. All internal components are easily accessible through removal of top and bottom panels.
Front panel graphic details are incorporated on the rear side of a polycarbonate laminate which is virtually indestructible. JBL amplifiers use multiple watt output devices in complementary configuration for high reliability and low distor- tion. The benefit is high reliability and long component life. Failsafe operation of these amplifiers is ensured through the following protection modes: Current is limited under improper load or drive conditions.
An output relay, with front panel LED indication, protects the loudspeaker load under cond- itions of DC offset or large low-frequency transients. The relay also provides power-up, power-down, and "brown out" muting to protect loudspeakers from AC power transients generated anywhere in the signal path. LED's on the front panel indicate the onset of clipping and standby mode. The JBL amplifiers may be operated in the normal stereo- phonic mode, dual monophonic mode, or bridged monophonic mode.
Rear panel switching sets these modes, obviating the need for patch cords, level matching, etc. Active differential input circuitry offers the benefits of balanced operation without the use of input transformers. The barrier strip has separate terminals for audio ground and chassis ground. Maximum total harmonic or intermodulation distortion measured at any power level from milliwatts to rated power is less than 0.
Short circuit protection is clean with no odd behavioral characteristics. The input amplif- iers are protected against excess input curr- ent. The loudspeakers are protected against any failure in the amplifier by an internal relay which disconnects the load from the amp- lifier output and connects it to ground. The relay also disconn- ects the load if excess DC voltage is detected at the output or upon failure of any of the amplifier power supplies. If the amplifier overheats due to a lack of ventilation the relay opens until the amplifier has begun to cool down.
Illum- inated rocker-type power switch. May be wired balanced or unbalanced. Nevertheless, we recommend careful examination of the shipping carton and its contents for any sign of physical damage which could have occurred in transit. Save the carton and packing in the unlikely event the unit must be returned for service; if you do not have a carton, call the factory for one before shipping the unit. If damage is evident, do not destroy any of the packing material or the carton, and immediately notify the carrier of a possible claim for damage.
Shipping claims must be made by the consignee. The shipment should include the Power Amplifier and the Instruction Manual this book. This presumes a free, unrestricted flow of cooling air to the rear mounted heatsink.
When the amplifier is mounted in a rack it is important to ensure that cool air is allowed to reach the heatsink, and that heated air is allowed to flow away from the amplifier. In most cases this will only require ventilation grills to be provided so cool air can enter the rack at the bottom and hot air can exhaust at the top through natural convection.
In some installations it may be necessary to provide forced air cooling to the amplifier and the space in which it is mounted. These amplifiers have thermo-protective circuits that will operate if the amplifier overheats.
This will happen for one or more of the following reasons: 1. Insufficient natural air flow. Average power and duty cycle of the program material too high. High ambient air temperature in which the amplifier is oper- ating.
It is not really possible to state exact requirements for air flow because of the number of variables, but in most cases fans with CFM will provide sufficient air flow. The rack, especially its mounting rails, should be capable of supp- orting the amplifier. When a rack is to be transported with a portable sound system, the amplifier also should be supported from below; a few pieces of angle iron secured to the sides of the rack will suffice.
It is further recommended that the amp- lifier be placed low in the rack to keep the center of gravity low and thus avoid any tendency for the rack to tip over. Amplifiers wired for operation on any other voltage are identified as such with a sticker on the rear panel and a tag attached to the amplifier power cord.
To comply with most electrical codes this amplifier is supplied with a three-conductor AC power cable, the grounding pin of which is connected to the chassis. In some installations this may create ground loop problems when an AC potential exists between conduit ground and audio ground.
This will be evidenced by hum or buzz in the amplifier output. If this should occur please refer to Section 2. Proper grounding of the amplifier is important for both noise and safety reasons.
The switch may be actuated with a small screw- driver. The functions are as follows; Stereo; Input to Channel A. Output is on Channel A and level is controlled by Channel A level control. Input to Channel B. Output is on Channel B and level is controlled by Channel B level control. Input is to Channel A. Input B is not used. Bridged Mono: This mode makes the stereo amplifier into a single mono amplifier with the power of both channels combined.
Level control is by Channel A Level control and output is taken from the red binding posts of Channels A and B as described in Section 2. See Figures , and 2—3.
Since all three connect- ors are wired in parallel, however, only one should be used at a given time unless it is specifically desired to loop a signal through the amplifier input. The amplifier will not unbalance floating or balanced input sources since the input circuits consist of balanced diff- erential amplifiers. To use an unbalanced source, wire the signal carrying conductor of the cable from that source to XL- type pin 3 phone plug tip , and wire the shield to XL-type pin 1 phone plug sleeve.
The unused connector terminal, pin 2 ring , should also be connected to shield ground. Unbalanced connections are simplified by using two-conductor standard phone plugs because they automatically short the ring and sleeve together when inserted in the input jacks. Set the mode switch to Dual Mono. Do not apply signal to the Channel B input. That signal is applied "in phase" to Channel A, and, with inverted polarity, to Channel B. No signal should be applied to the Channel B input, and the Channel B level control should be turned all the way down fully counterclockwise.
See Figure The preferred connection method is to use a dual banana plug for each speaker cable. Simply insert each plug into the corres- ponding channel's red and black binding posts. In the absence of a dual banana plug or two single banana plugs , there are other alternatives.
To connect stranded speaker cable, loosen the plastic terminal nut, wrap the stripped and twisted wire end clockwise around the terminal, and secure it by tightening the nut. NOTE: It is preferable to tin the wire ends with solder to prevent unraveling; avoid excess solder as it can promote cable breakage. Smaller speaker cable could be pushed through the hole in the binding post shaft, but we recommend using heavier gauge cables that ought to be wrapped around the shaft.
If a lug is installed on the cable, loosen the terminal nut, push one "leg" of the lug through the hole in the shaft, and tighten the nut. Long audio transmission lines, like their video counterparts, must be properly sourced from and terminated in equipment which matches their characteristic impedance if optimum frequency response and noise rejection are to be achieved. However, transmission line theory and techniques are not only unnecessary but impractical within modern recording studios, broadcast studios and other local audio systems where transmiss- ion circuits are seldom more than several hundred feet in length.
The advent of negative feedback circuitry and solid-state elect- ronics has spawned modern audio amplifiers and other signal pro- cessing devices having source impedances of only a few ohms. They are essentially indifferent to load impedances and, by varying their output current inversely to changes in load impedance, maintain the same output voltage into any load impedance above a rated minimum, with no change in frequency response.
Modern audio systems, therefore, utilize amplifiers and other active devices which have very low output impedances and high lOK to 50K ohm input impedances. These products may thus be cascaded operated in series , or many inputs may be connected to a single output of a preceding device, without regard to impedance matching.
Switching and patching is simplified because double loads and unterminated bugaboos are essentially elimin- ated. Floating ungrounded transformer outputs minimize ground loop problems, and differential transformerless input circuitry or input transformers minimize common mode noise or interfer- ence which may be induced into the interconnecting wires or cables.
This amplifier has input impedances of 40, ohms when used in a balanced, differential input configuration, and 20, ohms when used unbalanced one side grounded. This makes the amp- lifier suitable for use with any normally encountered source impedance, low or high. Therefore, there are only two situations which will require an input load at the amplifier: 1 when the source requires a ohm load, such as a passive equalizer, older vacuum tube equipment, etc, 2 when the source is a transmission line such as a tele- phone line.
In some instances it may prove beneficial to treat the input feed to the power amplifier as a transmission line to lower its impedance and its susceptibility to noise pickup. The fuse value must be chosen with some care. Ideally, the value will be high enough that the fuse does not excessively reduce the capability of the loudspeaker to handle peak transients which are above its continuous power rating.
On the other hand, the fuse value must be low enough that the fuse can actually do its job. It takes some period of time to heat the fuse element enough to cause it to melt and break the circuit. If it takes too long, the loudspeaker may go first.
Images : Urei / Jbl 6260
Discussion in ' Solid State ' started by miscrms00 , Oct 21, Log in or Sign up. Messages: Location: Phoenix, AZ. Just thought I'd share my experience bringing an ebay bought JBL into service.
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