SP-20AB MANUAL 0008A 960026-832 SP-20AB MANUAL Important Note: To obtain best results from this Furman Sound electronic product, please be sure to read this manual carefully before using it. Please fill out and return the Warranty Registration Card immediately to obtain full protection under the terms of the Limited Warranty, in case your ownership documents are lost. Please verify that the serial number shown on the Warranty Card matches the serial number on your unit. stereo, two channel mono, or single channel (bridged) mono operation. It is intended to power speakers or headphones with equal ease. The SP-20AB is fully protected against thermal overload and can withstand a short circuit on either or both outputs for an indefinite time without damage. Additionally, the SP-20AB's advanced toroidal transformer assures reduced electrical hum and mechanical noise from the unit itself. This minimizes leakage into other nearby sensitive equipment, such as mic preamps, video monitors, etc. The SP-20AB is expected to find application in recording studios (for driving small near field monitors and/or headphone systems), in distributed commercial sound installations, for powering high-frequency drivers in bi-amped or tri-amped PA systems, and wherever a requirement exists for compact, high quality, moderate power audio amplification. SP-20AB Features · · · · · · · 20 watts per channel in stereo mode XLR Balanced inputs May be bridged for 40 watt mono operation (requires load of 8 or more ohms) Front panel headphone jack with volume control Ideal for small speakers or headphone system Speaker on-off switch Overload and signal-present LED's for each channel Power-on indicator Ground lift switch Provision for remotely located headphone volume controls (Using the Furman HR-2 Remote headphone station) Description The SP-20AB Stereo Power Amplifier is a unique and economical 20 watt per channel stereo amplifier. It may be operated in any of · three modes as selected by a rear-panel switch: · normal stereo, two channel mono, or single · channel (bridged) mono. The latter mode allows a power output of 40 watts provided the load is 8 or more ohms. The SP-20AB is housed in a half single-space rackmount chassis. The SP-20AB can be Introduction mounted in a 19" rack by using the Furman HRKIT-1 rack mounting kit or side by side Congratulations on your purchase of a with another SP-20AB using the HRKIT-2 rack Furman Model SP-20AB you have chosen an mounting kit. extremely versatile general purpose power amplifier. The SP-20AB is a compact 20 watt per channel stereo amplifier capable of normal 1 SP-20AB MANUAL The SP-20AB's compact size and 20 watts per channel make it ideal for modular use in large commercial installations with multiple small speakers. Its power capacity is also just right for driving the small near field monitors used in most recording studios as a comparison with the main control room monitors - it can power them without overpowering them. The SP-20AB's output is available through either of two connectors: standard banana jack binding posts for speakers, or through a male XLR connector. The Satellite/Remote XLR output allows the unit to become a headphone driver, linking any number of `Furman HR-2 Headphone Remote Stations together via standard microphone cables. Each HR-2 station conveniently clips to a mic stand and provides individual volume controls for two sets of headphones. When used for overdubbing or rehearsal, this setup provides more than adequate loudness in all headphones (even older high-impedance models), and allows each musician to set his or her own comfortable volume level. When the overdubbing is complete and the musicians remove their headphones, the SP-20AB can also power the tape playback speakers through the banana jacks, as selected by pressing the SPEAKERS button on the front panel. An additional headset may be plugged directly into the SP-20AB's front panel. A volume control is provided for it. The SP-20AB has a convenient input level control on the left side of the front panel. A pair of yellow LED's - one for each channel - light up whenever signal is present (threshold -30 dBu). Another pair of red LED's show an overload condition in either channel. 2 Options and Accessories · Model HR-2 Headphone Remote Station: The HR-2 is compact, unobtrusive box that clamps to a mike stand or belt, providing two headphone jacks, each with its own volume control. Any number of HR-2 stations may be connected to a SP-20AB using standard microphone cables. The HR-2 comes with snap-on, snap-off mike stand clamp. · HRKIT-1: The HRKIT-1 allows mounting of one SP20AB in a single rack space. Unit is centered in the space, which equally distributes the weight and allows room for user customizations such as additional selector switches, indicator lights, extra banana jacks, etc. · HRKIT-2: Allows side by side mounting of two SP20AB's in a single rack space or one SP-20AB in a standard half rack enclosure. LEFT / MONO I RIGHT INPU ON 120 VAC 60 Hz 130 Watts OFF LIFT SATELLITE / R STEREO BRIDGED SPEAKER LEFT RIGH S T USE FOR BRIDGED SP-20AB MANUAL 3 2 1 4 5 6 7 8 9 L OVERLOAD SIGNAL R OFF ON 3 2 1 4 5 6 7 8 9 0 10 INPUT LEVEL 20 WATTS / CHANNEL STEREO AMPLIFIER MODEL SP-20A 0 10 HEAD PHONE PWR SPEAKERS VOLUME Descriptions of Controls RIGHT INPUT Front Panel ON SATELLITE / REMOTE LEFT / MONO INPUT GND LIFT 60 Hz INPUT LEVEL: The Input Level control can be 130 Watts adjusted for maximum signal to noise and minimum clipping. The Input Level control is stereo - it affects both left and right channels simultaneously and affects all outputs. SIGNAL PRESENT LIGHTS: These yellow LED's turn on whenever a signal exceeding 125 millivolts RMS (40 dB below full power) is present at the SP-20AB's input jack. They will increase in brightness as the signal strength increases. This feature is very useful as a clue to where the fault may lie if the expected program is not heard at the outputs. OVERLOAD LIGHTS: These LED's glow red to indicate an overload in the SP-20AB. If the LED lights up, either the drive level to the unit should be reduced, or the setting of the Input Level control should be reduced until the LED remains off. The lights turn on when the signal level at either output is within 2 to 3dB of clipping. Once triggered, the lights will stay lit for a minimum of 50 milliseconds so they can be easily seen, even if the actual duration of the overload is much shorter. HEADPHONE JACK / HEADPHONE VOLUME: Any type of headphones wired with a standard 1/4" stereo phone plug may be used successfully. Note that the headphone 120 VAC OFF volume may be adjusted without affecting the speaker level or the level of any other headphones connected through HR-2 SPEAKERS Remote Stations. LEFT RIGHT SPEAKERS BUTTON: Depressing this button turns on the speakers connected to the SPEAKER banana jacks on the rear panel. This provides an easy way to mute the sound without changing the volume setting. POWER LIGHT: Glows red when unit is receiving power and the ON-OFF SWITCH is in the ON position. MONO USE FOR BRIDGED STEREO BRIDGED Rear Panel ON-OFF SWITCH: This switch turns the SP20AB on and off. For convenience, it is recommended that the SP-20AB and any other rack-mount equipment be powered through a switchable outlet box, such as the Furman Sound PL-8 or PL-PLUS Power Conditioner and Light Module. The PL-8 provides an easy way to power up the whole rack with one front-panel switch, and provides discreet illumination on dark stages and studios as well. If you do use a switchable outlet box, leave the SP-20AB's on-off switch in the ON position at all times. GROUND LIFT SWITCH: In many installations, hum-causing ground loops are formed by the common connection of various pieces of equipment to the power line ground, and by 3 3 2 1 4 6 7 8 9 L OVERLOAD SIGNAL R OFF ON 3 2 1 0 10 7 8 9 HEAD PHONE PWR SP-20ABLEVEL INPUT MANUAL 0 10 20 WATTS / CHANNEL STEREO AMPLIFIER MODEL SP-20A SPEAKERS VOLUME SATELLITE / REMOTE LEFT / MONO INPUT GND LIFT RIGHT INPUT MONO STEREO BRIDGED ON 120 VAC 60 Hz 130 Watts OFF SPEAKERS LEFT RIGHT contact between chassis, as in a rack with metal rails. Sliding the Ground Lift switch up completely isolates all signal grounds from the chassis, breaking any ground loops. The chassis always remains connected to the ground pin on the AC cord for safety and to provide shielding against RF interference. Try both positions of the Ground Lift switch, and leave the switch in the position that results in the least hum in your system. Note: The ground lift can be rendered ineffective by 3 pin audio connectors that tie pin I (signal ground) to the metal shell of the connector (chassis ground). The connection from pin 1 to the shell is optional on all 3 pin connectors, and can be removed if present, by opening up the connector on the cable and disconnecting it. MODE SWITCH: This three position slide switch determines the SP-20AB's mode of operation The three choices are: MONO: This position is also referred to as "Dual Mono" because while both channels are operating separately (each driving its own speaker), there is only one input, which appears at both outputs. The input must be connected to the "Left/Mono Input" jack. STEREO: This position is for normal stereo operation, where there are two inputs (left and right) and two outputs. BRIDGED: This position should be used for straight mono operation, when there is only one input (plugged into the "Left/Mono Input" jack) and all the SP-20AB's power is to be concentrated into one output. Note that under some circumstances, this can amount to more than double the rated 20 watts pet channel for stereo .- to as much as 50 watts. Therefore, in bridged mode, for adequate protection, the speaker connected should be able to handle approximately 100 watts without damage. See "SPEAKER OUTPUTS" below for details of how to connect the speaker. SPEAKER OUTPUTS: These outputs should be used for driving speakers. The connections are via multiple-use terminals, which can accommodate either dual banana plugs, bare wires, or wires terminated in spade lugs. For stereo or dual mono operation, connect one speaker to the left pair of terminals and the other speaker to the right pair. Observe proper polarity - make sure that the wire connected to the top (red) terminal on the left channel connects to the red terminal of the left speaker, and that the wire connected to the top (red) terminal on the right channel connects to the red terminal of the right speaker. If the wires to one speaker are reversed, the speakers will be of opposite polarity (or "out of phase"), and a severe loss of low frequencies may, result. If Mono Bridged operation is desired, the single speaker must be connected to the 4 USE FOR BRIDGED SP-20AB MANUAL two top (red) terminals. In this case, nothing other applications. The HR-2 units are compact should be connected to the bottom (black) boxes which easily attach with a thumbscrew terminals. Positive polarity will be on the left to any microphone stand Each HR-2 has two channel (red) terminal. stereo volume controls and two headphone SATELLITE/REMOTE OUTPUT: This output jacks. There are also two XLR connectors, one is a single male XLR connector containing male and one female. These may be used to both the left and right channel outputs. It is "daisy chain" HR-2 boxes together with standard wired as follows: Pin 3 -left (high); Pin 2 - microphone cables. right (high); and Pin 1 - low, common to both Begin the chain at the SATELLITE/REMOTE channels. This output should be used as the connector on the rear of the SP-20AB, as shown starting point for a chain of HR-2 Remote in the above diagram. The SP-20AB connects to Stations (satellites). It necessary, it may also the first HR 2 box; another mic cable connects be used to connect a second set of speakers. the first HR-2 box to the second HR-2 box-, a This output is also turned on and off by the third mic cable connects the second HR-2 to SPEAKERS button. This output should not the third HR-2; and so on. If low impedance be used with HR-2 Stations when in Mono headphones are used, up to twelve HR-2's may Bridged mode. be in the chain. If medium or high impedance INPUTS: The SP-20AB is equipped with headphones are used, 25 or more Remote left and right balanced female XLR Stations may be chained. connectors. Balanced lines offer the If desired, the clip on an HR-2 box may be benefits of cancellation of hum, noise, and hung on a belt it no microphone stand is RF interference which may be picked up in convenient. the interconnecting cables. For balanced connections, shielded twisted pair cable must be used. The wiring is as follows: Pin 1-shield; Pin 2-signal positive; and Pin 3signal negative. Use of the HR-2 Headphone Remote Stations The HR-2 Remote Stations may be used to increase the ...