Onkyo TX-SV7M A/V receiver Review

The Onkyo TX-SV7M includes a video tuner instead of just switching circuits for video sources. Along with the am and fm bands, the digital-synthesis tuner section receives the audio portions of the VHF band (Channels 2 to 13), and there is an MTS/SAP decoder for stereo TV programs as well as the Separate Audio Programs transmitted by many TV stations.

The TX-SV7M also includes a decoder for Dolby Surround sound in its basic, passive form, and there is a hall surround mode that uses the time-delay circuits of the Dolby system. Another enhancement mode, matrix, adds spaciousness to stereo programs without using time delay. There is also a simulated-stereo circuit for mono programs and a dynamic bass expander to enhance low-bass reproduction by a boost centered at 70 Hz, the amount of boost being proportional to the level of the program’s bass content.

The TX-SV7M provides four channels of amplification. The front-channel amplifiers, when used for normal stereo playback, are rated to deliver 100 watts per channel into 8 ohms from 20 to 20,000 Hz with no more than 0.04 percent total harmonic distortion. In a surround mode, their power rating is reduced to 90 watts per channel and the rear speakers are driven by a 20-watt-per-channel amplifier, which is rated at less than 0.08 percent distortion from 20 to 20,000 Hz. The front and rear preamplifier outputs and main-amplifier inputs, brought to separate connectors on the rear apron, are normally joined by connecting links. By removing the links, external amplifiers or signal-processing accessories can be inserted into the signal path while retaining the receiver’s full control capability and without sacrificing one of the tape-recording circuits.

The am and fm bands are tuned in increments of 50 and 10 kHz, respectively. Each of the twelve preset memories can be assigned to one am and one fm station; in the TV mode they are permanently assigned to the twelve vhf channels.

The front panel of the Onkyo TX-SV7M presents a clean, uncluttered appearance, with the large display window being its most prominent feature. A row of seven large pushbuttons selects the program source: TAPE-2, TAPE-1, VCR-2, VCR-1/VDP, tuner, phono, and CD. Smaller buttons select the speaker outputs, fm/tv muting and mono/stereo mode, and loudness compensation. The large volume-control knob, with an illuminated red index pointer, is at the right along with three small, center-detented knobs for the bass and treble tone controls and the balance control. The front panel also contains a headphone jack.

A large rectangular section below the input-selector buttons hinges downward to form a sloping control panel with a number of less often used buttons, including the twelve preset selectors, the fm/am/tv selector, and up/down tuning buttons for the radio bands, which combine manual and automatic-seek tuning functions. Four surround-mode buttons select Dolby, hall, matrix, and bypass modes (bypass also silences the rear-channel speakers). Smaller buttons switch the delay time sequentially to 15, 20, or 30 milliseconds (the Dolby mode always comes on initially at 20 milliseconds), turn the dynamic bass enhancer on and off, and select the simulated-stereo mode. The ANTENNA button connects the tuner input to either the regular or cable antenna connectors in the rear of the receiver. The mts button toggles between the main and subchannel programs of a stereo tv broadcast, and a tv fine tuning button, for use with CATV systems having nonstandard channel frequencies, allows the regular tuning buttons to shift the frequencies of preset TV channels over a ±2-mhz range in 50-kHz steps.

The display window is exceptionally complete, showing the status of every operating mode or feature. A tuning-information section shows the status of all tuner functions, including the preset station number or the tv channel.

The receiver’s rear apron has coaxial 75-ohm F connectors for an fm antenna, a tv antenna or cable-tv transmission line, and an output to the antenna input of an external tv receiver. There is also a coaxial output to a video monitor. The receiver includes a detachable, pivoted-loop am antenna and terminals for an AM wire antenna. The signal connectors include record and play jacks for two audio tape decks and two VCR’s (both audio and video circuits), inputs for a videodisc player and a CD player, and a phono input for a moving-magnet cartridge. There are insulated binding posts for two sets of front speakers and one pair of rear speakers. Two of the three AC convenience outlets are switched.

Finally, the Onkyo TX-SV7M comes with a full-system remote control, befitting the receiver’s status as a virtually complete A/v control center. The remote is considerably larger than the usual such unit, and its control panel is divided into two sections. The main portion, containing thirty-four buttons, is permanently programmed to duplicate most of the functions of the receiver’s front-panel controls, including power switching and volume-control, as well as the controls of compatible Onkyo turntables and CD players. The remaining twenty-one buttons can be programmed by the user to memorize the remote-control commands for any make of tv set, cable box, and vcr.

The remote’s audio-muting function (a 20-dB volume reduction) has no counterpart on the receiver itself. There is also a front/rear balance adjustment, critical to proper operation of a surround-sound system, that can only be made from the remote (the relative gain settings of front and rear channels are shown in the receiver’s display window). Although the remote control is rather bulky for normal hand-held use, its infrared output is strong enough that, in moderate-size rooms, it can be placed on a table and need not be pointed directly at the receiver.

The Onkyo TX-SV7M is a fairly large and heavy receiver. It measures 18-5/8 inches wide (including its woodgrain side panels), 16-7/8 inches deep, and 5-5/8 inches high, and it weighs 31 pounds, 5 ounces. The remote control is 8 inches long, 4 inches wide, and 1-1/2 inches thick. Price: $990 (including remote).

Lab Tests

The fm tuner section of the TX-SV7M equaled or surpassed the manufacturer’s ratings in all respects, within normal measurement tolerances. It had excellent sensitivity and distortion characteristics, with an 11.8-dBf usable sensitivity and typical distortion readings at a 65-dBf input level of about 0.1 and 0.15 percent in mono and stereo, respectively. The 1.1-dB capture ratio was also better than average, although the selectivity measurements (4.5 and 67 dB, respectively, for adjacent-channel and alternate-channel spacings) were average, and the 40-dB image rejection, which matched the published rating, was marginal for a receiver in this price range.

The frequency response was almost ruler-flat (+ 0.1, —0.3 dB) from 30 to 10,000 Hz, with a drop of just over 1 dB at 15,000 Hz. The channel separation was close to 50 dB at low to middle frequencies and better than 30 dB over almost the entire audio range. The signal-to-noise ratio was good, though not exceptional, measuring about 78 dB in mono and 72 to 75 dB in stereo (which required at least a 65-dBf input for full quieting). The am frequency response was down 6 dB at 60 and 2,600 Hz.

The tone controls had good characteristics, although the available bass boost of about 21 dB at 20 to 30 Hz should be used with discretion in view of the receiver’s considerable power capability. The loudness compensation boosted both low and high frequencies to a moderate degree (a maximum boost of 7 dB in the bass and 2.5 dB in the treble). The RIAA phono equalization was good, with a maximum error of ± 0.35 dB from 20 to 20,000 Hz. The phono input’s termination was 46,000 ohms in parallel with only 56 picofarads of capacitance, and it overloaded at an input level of about 162 millivolts over the full audio range.

Although the TX-SV7M’s power amplifiers are rated only for 8-ohm loads, a supplementary fact sheet from Onkyo indicates that the receiver can not only drive 4-ohm speakers but will not be damaged with two pairs of 4-ohm speakers operating at the same time. Its amplifiers and power supply are rather “robust,” in the manufacturer’s word, and are protected against excessive output current or overheating by a relay system. Our findings confirm those statements.

We preconditioned the receiver for 1 hour with each front channel delivering 33 watts into 8 ohms and each rear channel operating at about 7 watts. No part of the cabinet exterior became more than moderately warm to the touch. The front channels clipped at 120 watts (at 1,000 Hz) and the rear channels at 34 watts. We did not test the rear channels with less than 8 ohms, but the front channels delivered 175 watts per channel into 4 ohms. We also measured an impressive 200 watts into a 2-ohm load on one channel (the other had a 4-ohm load).

The amplifier distortion was unusually constant with frequency. At 100 watts into 8 ohms it measured about 0.02 percent from 20 to 6,000 Hz, rising to 0.046 percent at 20,000 Hz. At lower power levels the shape of the curve was similar but with lower readings (between 0.01 and 0.015 percent at 10 watts, for example). The rear channels, at their rated 20 watts, had very similar characteristics except for a rise above 4,000 Hz to a maximum of 0.15 percent at 20,000 Hz.

The 1,000-Hz distortion of the front channels reached 0.036 percent at the 120-watt clipping point into 8 ohms, 0.2 percent at 170 watts into 4 ohms, and 1 percent at 200 watts into 2 ohms. Based on the 90-watt surround-sound rating, the clipping headroom was 1.25 dB. In our dynamic power tests the front channels clipped at 156 watts into 8 ohms, 242 watts into 4 ohms, and 306 watts into 2 ohms. The dynamic headroom was 2.38 dB.

The slew factor of 3, reflecting the limited high-frequency power capability of the output transistors, was relatively low but still perfectly adequate. The waveform became triangular at about 60,000 Hz with a drive level of 100 watts into 8 ohms. Potentially more serious, the amplifier became unstable and oscillated at a high ultrasonic frequency (about 50,000 Hz) when it was loaded with a capacitance exceeding 0.035 microfarad. Although some speakers may present an appreciable capacitive load at certain frequencies, it is likely that most conventional (nonexotic) speakers will present a safe load to this receiver. We did not experience any problems with either the MB Quart 390 or the Allison IC20 speakers, both of which have rather uniform impedance characteristics. Some special high-capacitance speaker cables, or unusually long spans of ordinary speaker cable, should be avoided, however.

Comments

Clearly, the Onkyo TX-SV7M is a potent receiver, not only because of its many features but because of its performance in general. Little of importance seems to have been sacrificed in either its design or its construction.

In particular, its ability to deliver a high current when needed is impressive. Although high-current capability is now a feature of a number of other receivers as well, Onkyo seems to have carried this design approach further than one would expect in a four-channel receiver from a mass-market manufacturer. We confess to some concern regarding the ability of the amplifiers in this receiver to deliver their full performance into difficult loads. Obviously, it passed our tests with a qualification: If instability with

large capacitive loads is truly typical of the product, and not the result of some flaw in our test sample, some of the speakers that could benefit most from its large power reserves may be excluded from consideration. On the other hand, it is unlikely that the typical purchaser of an a/v receiver like the TX-SV7M would connect it to such a load.

The TX-SV7M had one other idiosyncrasy, which may also be a sample flaw: audible gear noise from the volume-control drive motor during remote operation. We heard a similar noise when balancing the front and rear channels; the control for this adjustment may use the same motor, though the front-panel volume knob does not turn during balancing.

The receiver’s surround-sound modes worked well, although we did not have the opportunity to judge the Dolby Surround circuits with properly encoded material. And we must admit that stereo TV programs played through its tuner and mts decoder sounded far better than what we are accustomed to hearing from TV receivers. Overall, the Onkyo TX-SV7M made a highly favorable impression. It does so much, so well, and with so little operating complexity that it should be considered by anyone in the market for an integrated audio/video receiver and control center.

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