Nad 3140 Owners Manual
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REAR PANEL CONNECTIONS 1. PHON011NPUT. This input is designed for use with "high-output" moving-coil cartridges such as the NAD 9000, Dynavector (Ultimo) 10A and 10X, Satin M18 and M117, Adcom XC/LT, et al. This input may also be used with cartridges of other types which have lower-than-normal output voltage, such as the B&O MMC series and Audio-Technica models AT-22 through AT-25. The Phono 1 input has a standard input impédance (47K ohms résistance, 100 pF capacitance) but is 10 dB more sensitive than the Phono 2 input. Moving-coil pickups with low output voltage should be used with an external transformer or pre-preamp. The output from the step-up device may then be connected to either Phono 1 or Phono 2. CAUTION: Some step-up devices may produce a high enough output level to overload the Phono 1 input, yielding distortion; in case of doubt, use Phono 2. Heres one way to tell: if you find that the amplifier is driven to full power (as indicated by the peak-reading front-panel LED display) with a volume-control setting of 12 o'clock or lower, then you should switch to the less sensitive Phono 2 input. Conversely, if you must turn the volume control up beyond the 3 o'clock position in order to drive the amp to full peak power, then the extra gain of the Phono 1 input will be beneficial. 2. PHONO 2 INPUT. This input is intended for the majority of phono cartridges of the moving magnet, induced magnet, moving flux, and moving iron (variable reluctance) types. Plug the signal cables from your turntable into these jacks. If the cables or plugs are color-coded, refer to your turntable's in struction manual to learn which cable or plug is for the Left channel and which for the Right. Be careful to insert each plug fully into the socket so that the plug's metal skirt fits tightly over the exterior of the socket. If necessary, carefully crimp the plug's metal skirt slightly so as to obtain a tight fit with the socket. 3. CAPACITANCE SELECTOR. This switch selects the input capacitance for PHONO 2 on/y. It enables you to optimise the load capacitance for those cartridges whose frequency response is affected by this parameter. If you are using a low-inductance pickup (such as a Grado or Micro-Acoustics), or a moving-coil cartridge with a transformer or pre-preamp, then the setting of the Capacitance Selector is unimportant. But with many high-inductance magnetic pickups, the capacitance setting will audibly alter the sound of the pickup. In order to select the best value of preamp input capacitance you must first determine the total capacitance recommended for the cartridge. This will usually be included in the maker's specificat ions, and may also be mentioned in magazine reviews of the cartridge. Next, subtract the capacitance of your turntable's tone- arm wiring and signal cables. (Check the specifications supplied with the tonearm, or write to the manufacturer of the tonearm, or as a last resort assume a typical value of 150 pF.) After this subtraction, what remains is the desired value of preamp input capacitance. Set the Capacitance Selector to the nearest value. It is not necessary to match the computed value exactly : with most phono cartridges a variation of 50 pF one way or the other will produce only a very slight change in frequency response. Example: suppose you are using a Stanton 881S pickup car tridge in a Pioneer turntable. Stanton specifies a recommended load capacitance of 275 pF for the cartridge, and the Pioneer turn table has a cable capacitance of about 100 pF. 275 minus 100 equals 175 pF, so you should set the Capacitance Selector to the nearest value, 200 pF. It you prefer, you may simply set the Capacitance Selector by ear while listening to recordings which are strong in high-frequency overtones. Typically, when the capacitance is too low the upper-midrange (the soprano voice range) will be softened and the re-sponse at the highest frequencies will be peaky, leading to edgy violin tone and increased surface noise. Too high a value of capa- citance will bring the upper-midrange forward while rolling off the extreme highs. 4. GROUND. If your turntable is equipped with a grounding wire (usually a green wire terminating in a U-shaped spade lug), connect it to this terminal. Turn the thumb-nut counter-clockwise, place the spade lug under the nut, and tighten the thumb-nut clock-wise to secure the lug. If the grounding wire has no terminal lug, strip off a half-inch (1 to 2 cm) of insulation to expose the bare wire, twist the wire strands tightly together, insert the wire through the small hole in the shaft of the Ground terminal, and tighten the thumb-nut to fasten the wire in place. 5. TUNER. Connect the signal cable from a radio tuner to these jacks. As with ail of the other input/output jacks, the upper one in each pair is for the left channel and the lower jack is for the right channel. 6. AUX. These auxiliary input jacks are for any "line level" signal source-such as a spare tape player, a television sound tuner, the audio line output from a videocassette or videodisc player, or a child's record player containing a high-output ceramic pickup cartridge. 7. TAPE 1 REC/PLAY. Two types of connectors are provided for use with a stereo tape recorder: separate pairs of RECORD and PLAY phono jacks, and a five-pin DIN socket. If your recorder has only DIN-type plugs, use the DIN connecter. If your recorder has both a DIN plug and pairs of phono jacks, it is preferable to use the phono plug connections. (Do not use both the phono plugs and the DIN plug simultaneously.) The TAPE 1 connections may be used with tape recorders of ail types: cassette, micro-cassette, open-reel, eight-track, digital, etc. To make recordings, connect a stereo patch cord from the RECord jacks to the LINE or RADIO input jacks on the recorder (not to ils microphone inputs). To play back tapes, connect a stereo patch cord from the recorder's LINE output jacks to the amplifier's PLAY input jacks. 8. TAPE 2 REC/PLAY. These jacks enable connection of a second tape recorder of any type, and the amplifier is wired to permit copying tapes from one recorder to the other. Connect a cable from the RECord jacks to the tape deck's LINE or RADIO input jacks, and another cable from the amplifier's PLAY jacks to the recorder's LINE outputs. The upper jack is for the left channel and the lower jack for the right channel. The TAPE 2 jacks may be used for a signal-processing accessory instead of a second tape machine. Examples of such accessories include a dynamic range processor, a dynamic noise filter, an impulse noise ("tick and pop") suppressor, and any other processor whose operation depends on the setting of a signal threshold. Connect a patch cord from the REC jacks to the processor's inputs, and another patch cord from the PLAY jacks to the processor's outputs. Other signal processors, such as a graphic equalizer or the special equalizer supplied for use with some loudspeakers (e.g. Bose, Electro-Voice, KLM), may be connected either to the tape jacks or at the output of the preamp. The choice is a matter of convenience. 9. PRE-AMP OUT, NORMAL IN, LAB IN. Each channel of the amplifier is comprised of two independent sections or stages: the control preamplifier (including the phono preamp and most front-panel controls), and the power amplifier (which provides the power to drive loudspeakers). In normal operation the preamp and power amp are connected together via U-shaped metal jumpers; check to be sure that they are fully inserted into the jacks and that nothing is touching them. Two sets of power amp inputs are provided. The LAB inputs have wideband frequency response extending uniformly from low infrasonic to high ultrasonic frequencies, and may be used for laboratory tests and special applications. The NORMAL inputs are equipped with infrasonic and ultrasonic filters; these reject any
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interference which occurs outside of the audible frequency range, in order to prevent intermodulation distortion and preserve the amplifier's power for music. For conventional operation the PRE-AMP OUTjacks are connected to the NORMAL IN jacks by means of the metal jumpers. Removal of the jumpers (with the POWER switched OFF) enables various signal-processing accessories to be connected in the signal path between preamp and power amp: an equalizer, a time-delay ambience reproducer, a stereo image enhancer, etc. To use a signal processor, connect a stereo patch cord from the PRE AMP OUT jacks to the processor's line-level input jacks, and a second patch cord from the processor's output jacks to the amplifier's NORMAL IN jacks. (Note: any signal processor whose operation depends on the setting of a threshold, such as a dynamic noise filter or a DBX decoder, should be connected to one of the sets of TAPE REC/PLAY jacks-where the signal levels are unaffected by volume and tone controls-rather than to the PRE-AMP OUTjacks.) If you remove the metal jumpers, save them in case you may want to disconnect the signal processor and return to normal operation at a later time. If the jumpers should be lost, a conventional stereo patch cord can be used to connect PRE-AMP OUT to NOR MAL IN or LAB IN. The NAD 3140 can be used as the heart of an elaborate audiophile sound System. For example the PRE-AMP OUT jacks may be connected via a stereo patch cord to any high-quality separate power amplifier. To use a separate high-power amplifier for one set of loudspeakers while continuing to use the NAD 3140's built-in power amp for headphones or another set of loudspeakers, simply install Y-connector adapters to split the signal from the PRE-AMP OUTjacks. The preamp stage is capable of driving several power amplifiers in parallel, or driving the long signal cables required to connect to power amps which are located near the speakers, or to "powered" loudspeakers with built-in power amps. The preamp output can also be fed to a time-delay ambience sys-tem, with the 3140's built-in power amp used to drive either the main stereo speakers or the time-delayed ambience speakers. In a bi-amplified System the preamp output is fed to the input of an electronic crossover; the low-frequency output of the crossover unit is fed to the amplifier which drives the woofers, while the high-frequency output of the crossover unit is fed to the 3140's NORMAL IN or LAB IN jacks, and the speakers' tweeters are connected directly to the 3140's SPEAKER terminals. 10. BRIDGING MODE SWITCH. This switch "bridges" the NAD 3140's two power amplifier channels to form a monophonic amplifier with more than double the output power. To convert to bridged operation, the following procedure should be followed. (1) Disconnect the metal jumper or signal cable from the left-channel input to the power amplifier section of the 3140. In the bridged (monophonic) mode the amplifier is driven through its right-channel input only (either the NORMAL or LAB input socket). If you need stereophony reproduction, the left-channel PRE-AMP OUT signal can be used to drive a second, separate power ampli fier and loudspeaker, (If another 3140 in bridged mode is used for the second channel, it too will be driven through its right channel power amp input regardless of whether it is used for the right or left speaker.) (2) Disconnect any speaker wires from both the SPEAKERS A and SPEAKERS B terminals. From the speaker which is to be driven by the 3140, connect its positive lead to the red R+ terminal, and its negative lead to the red L+ terminal, in the SPEAKERS A group of terminals. NOTE; do not connect any wires to the black (R- and L-) terminals. If you want to drive two speakers in parallel, connect the second speaker's leads to the red (R+ and L+) terminals in the SPEAKERS B group; make no connection to the black (R- and L-) terminals. NOTE: in the bridged monophonic mode, the loudspeaker's impedance appears to be halved as "seen" by the amplifier. An 8-ohm load looks like 4 ohms, a 4-ohm load looks like 2 ohms, and a pair of 4-ohm speakers operated in parallel will look Iikea1-ohm load. Driving a pair of such speakers to high levels may cause the amplifier to overheat, activating its protection circuits. CAUTION: In the bridged mode the speaker wires must be "floating" with respect to ground. Do NOT connect the speaker wires to anything which shares a common ground between stereo channels (such as a headphone adapter) nor a common ground with the 3140's inputs (such as a switching comparator or a distortion analyzer). (3) After the preceding conditions have been satisfied, use the bridging switch. It is normally covered by a metal bracket to prevent its accidental use. Loosen the screw which holds the bracket in place and swing it out of the way or remove it altogether. Press and release the BRIDGING button. The button has two settings: IN-normal stéréo mode OUT-bridged monophonic mode To return the 3140 to normal stereo operation at a later date, simply depress the BRIDGING button to engage the normal stereo mode, fasten the metal bracket in place over the button to prevent accidental re-setting of the switch, feed stereo signals into the left and right channel power amp inputs, and connect loudspeakers to the appropriate terminals as described below under SPEAKERS A and SPEAKERSB. 11. SPEAKER LEAD COMPENSATOR (SLC™*). When a speaker is connected to an amplifier through a length of wire, the résistance of the wire will affect the signal reaching the speaker terminals. If the wire is sufficiently short or sufficiently large in diameter, its résistance will be negligible. As a general rule, 18- gauge or heavier wire should be used for lengths of up to 20 feet (6 meters) and 16-gauge or heavier wire for lengths of up to 30 feet (10 meters). But if you use thinner wire, or greater lengths, the wire résistance may have a directly audible effect on the speaker's sound-especially with low-impedance speakers, or pairs of speakers wired in parallel. This effect is of four kinds: (1) Some power is dissipated in the wires, and the signal delive red to the speaker is slightly reduced in level. (2) Since the speaker's impedance varies with frequency, the reduction in signal level varies in proportion; i.e. the tonal balance of the signal is altered. (3) Typical speaker impedances are complex, varying with signal level (for example, the voice-coil inductance varies as the coil moves in and out of the magnet gap), and may become non-linear at high volume levels. The resulting non-linear current flow produces a non-linear (i.e. distorted) voltage across the résistance of the speaker leads. Thus the audio signal may be completely distortion-free at the amplifier's output terminals, yet exhibit sev eral percent of distortion at the far end of the leads where they connect to the speaker terminals. (4) Finally, the wire résistance reduces the amplifier's damping factor. The Speaker Lead Compensator (SLC) cancels the effects of the wire résistance, eliminating the distortion and restoring the performance which would be obtained if the wire had no résistance. The SLC is calibrated for a specific amount of wire résistance, corresponding to the following lengths of standard wire sizes: GAUGE FEET METERS 30 19 12 7 5 4 3 2 14 1618202224 26 97 61 38 24 15 1 2 10
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FRONT PANEL CONTROLS 1. POWER. Depress to switch on the amplifier and any other equipment plugged into the SWITCHED convenience outlet on the rear panel. To switch off the power, depress the button again and release it. If you prefer, you may leave the 3140's POWER switch per- manently engaged and use an external switch (such as a clock timer) to turn the power on and off. 2. PHONES. Plug stereo headphones in here. The circuit will provide proper drive signals for ail conventional stereo head phones regardless of their impedance, with just one exception: electrostatic headphones usually are supplied with an adapter unit which must be connected directly to the speaker terminals on the rear panel. Before plugging conventional headphones into the PHONES Jack, turn down the VOLUME control for safety. And when you are not listening to the headphones it is wise to unplug them from the PHONES jack. Otherwise, when listening to loudspeakers you might turn up the volume to a level which would feed excessively strong signals to the headphones and damage them. You may freely use headphone extension cables. If you want to use a headphone Y-connector to drive two headsets simultaneously, they should be identical models. Connecting together two headphones which differ widely in impedance usually will produce a substantial loss of volume in the headset having the higher imp edance (or in both). 3. SPEAKER SELECTOR. When this switch is set to "A", sound is heard only from the speakers connected to the SPEAKERS A terminals on the rear panel of the 3140. When the switch is set to "B" the SPEAKERS A terminals are shut off and sound is heard only from the speakers connected to the SPEAKERS B terminals. At the "A+B" setting the amplifier's output power is fed to both sets of speakers; they are wired in parallel by the switch. At the "OFF" setting, both sets of speakers are shut off. Thus if you have your main stereo speakers wired to the "A" terminals and a set of extension speakers wired to the "B" terminals, you can choose to hear only the main speakers (A), only the extension speakers (B), or you can activate both (A+B). The amplifier's output signal is present at the PHONES jack at ail settings of the SPEAKER SELECTOR switch. When using headphones it normally is advisable to switch OFF the loudspeakers; then the VOLUME control may freely be used to adjust the loudness level in the headphones with no fear of overdriving the speakers or disturbing neighbors. If you have connected the adapter unit for electrostatic head- phones to the SPEAKERS B terminals, you can use the SPEAKER SELECTOR to switch between your main stereo speakers (A) and the headphones (B). If you have connected speakers wired for "ambience recovery" to the SPEAKERS B terminals, you can use the SPEAKER SELEC TOR to listen to conventional stereo (A), to switch off the main speakers and listen to only the stereo L-minus-R "difference" signal in the rear speakers (B), or to listen to spatially-enhanced stereo (A+B). You will find that the stereo difference signal is usually lacking in bass. If the difference signal is very weak, the recording lacks stereo separation. 4. SPEAKER EQ. The lowest octaves of deep bass sound are seldom experienced at their full level in stereo playback, for three reasons: (1) Most loudspeakers are designed for uniform response down to a planned System resonance frequency (usually in the 40-70 Hz range) and roll off rapidly in response below that frequency. (2) The low bass is often rolled off by filters when records are made in order to limit groove-modulation levels and increase playing times. (3) Standing waves bias the distribution of low-frequency energy in listening rooms, weakening the low bass and reinforcing the mid-bass at typical listening positions. The NAD SPEAKER EQUALIZER compensates for these losses by providing a 12 dB/octave boost below either 45 Hz or 70 Hz. Since ail closed-box (acoustic-suspension and infinite-baffle) loudspeaker Systems roll off in response at 12 dB/octave below the woofer/cabinet resonance, the NAD SPEAKER EQUALIZER precisely compensates this rolloff and extends the useful response of the speaker a full octave lower in frequency. Note: while the SPEAKER EQ can be used with "vented" speakers (bass-reflex, tuned-port. auxiliary bass radiator, et al.), these designs usually exhibit a much more rapid rolloff below the system's planned cutoff (typically either 18 or 24 dB/octave); consequently the SPEAKER EQ will not produce the same dramatic benefit with these designs as it does with acoustic-suspension Systems. If you have full-size speakers with strong response down to the 40-50 Hz range, the 45 Hz setting of the SPEAKER EQ is theoretically "correct." Nevertheless you should feel free to use the 70 Hz setting (instead of the BASS control) to bring up the rolled-off bass in recordings to a satisfying level; let your ears be your guide. Three CAUTIONS should be observed in using the SPEAKER EQ: (1) This circuit is intended for use with loudspeakers having woofers eight inches (20 cm) or larger in diameter, preferably those with "long-throw" voice-coils and acoustic-suspension enclosures. It is not recommended for use with small "mini" speakers having woofers smaller than six inches; in most cases they are not designed to accept high power input at low frequencies and will only distort or suffer damage as a result. (2) Be prepared to reduce or switch off the equalization when playing recordings (especially digitally-mastered ones) which contain unusually potent recorded bass. The SPEAKER EQ boosts deep bass levels by 12 dB (i.e. by a factor of 16 in power). A bass- heavy input signal may Overdrive the amplifier into clipping and Overdrive your woofers beyond their safe excursion limits causing the voice-coils to clatter against their magnet back-plates. As long as it sounds good it probably is OK; but distorted or unmusical sounds are a sign of distress in a woofer. (3) We recommend that you use the Infrasonic Filter, in order to avoid amplifying inaudible frequencies below 20 Hz, and to preserve the amplifier power and available woofer excursion capacity for the genuine bass energy in the music. 5. BASS. The Bass control adjusts the relative level of the low frequencies in the sound. The electrical response of the amplifier is flattest when the control is set in the detent at the 12 o'clock position. Rotation of the knob to the right (clockwise) increases the level of low-frequency sounds, and rotation counter-clockwise decreases their level. Adjust it to achieve the tonal balance which sounds most natural to you. You will note that at moderate rotations the effect of the Bass control usually is subtle because its action is confined to the lowest audible frequencies. Only at large rotations away from center is there a substantial boost or cut at the mid-bass frequencies which are prevalent in music. 6. TREBLE. The Treble control adjusts the relative level of the high frequencies in the sound. The electrical response of the amplifier is flattest when the control is set in the detent at the 12 o'clock position. Rotation of the knob to the right (clockwise) increases the level of high-frequency sounds, and rotation counter-clockwise decreases their level. Adjust it to achieve the tonal balance which sounds most natural to you. You will note that boosting the Treble increases the brilliance and clarity of details in the sound, but also makes any noise more prominent. Cutting the treble makes the sound mellower and suppresses hiss and record surface noise, but too much Treble cut will make the sound dull. 7. INFRASONIC FILTER. The signal from a record player usually contains strong infrasonic energy (due to disc warps, tone arm resonance, and vibrations reaching the turntable) which, if amplified at full strength, will waste amplifier power and produce excessive woofer cone excursions, muddying the sound. This