Onkyo TX-35 Stereo Receiver Review

Onkyo TX-35
Onkyo TX-35

Onkyo's TX-35 AM/FM stereo receiver is what in the movie or record business is called a "sleeper." It is rated to deliver 45 watts per channel (into 8-ohm loads, no more than 0.04 per cent THD from 20 to 20,000 Hz), but its actual performance is something else again.

Even the tuner section is unusual. It incorporates an "automatic precision Reception" (APR) system. This circuit automatically switches the reception mode (mono/stereo), antenna-input attenuation (distant/ local), and stereo high-frequency blend circuits (on/off) in accordance with FM signal strength and overall reception quality. In most respects the APR system operates without user control, but the FM muting-level switch on the front panel determines the signal level at which the tuner switches between stereo and mono operation.

The TX-35's front panel features an unusually complete and colorful status display window. It includes various APR indicators that show the status of the hi-blend, mono/ stereo, and DX/local functions as well as whether auto or manual tuning is in use (as controlled by a pair of front-panel buttons). In auto, a touch on one of the tuning buttons causes the tuner to scan until it finds a signal. In manual tuning the front-panel up/down buttons step one tuning increment per touch, or rapidly if held in.

Also displayed on the front panel are illuminated numbers matching those on the preset station buttons, so that one always knows which of the memory presets is being tuned. The visual contrast-against an allblack panel-of the display section with its pale blue, yellow-green, orange, red, and white markings and indicators is striking but somehow not garish. The multitude of tuner-section indicators, however, stay illuminated whether the tuner is being used or not.

When any of the tuner controls next to the display area is touched, a "Key Tone Touch" feature emits a gentle but quite audible "beep" (which also occurs whenever the tuner changes frequency in either tuning mode). The effect can be amusing for a while, but a switch on the rear panel of the TX-35 shuts off the tone for those who might prefer a more discreetly discrete digital tuning process.

The TX-35 measures 16-1/2 x 13-3/8 x 4-1/2 inches, and it weighs 18-1/4 pounds. Price: $345.

LAB TESTS

We observed some interesting effects of the APR system on the tuner's performance. The transition between hi-blend and full stereo separation took place around 45 dBf (100 microvolts, or μV). Within a narrow range of increasing signal levels, the noise and distortion first increased slightly and then dropped appreciably. Because of the narrow range of antenna input level (about 2 dB) through which this happened, it should never be audible in normal use. The automatic DX/local switching (consisting of a considerable attenuation of antenna input signal level to prevent overload of the tuning circuits) took place around 95 dBf (30,000 μV), and probably would never occur unless the receiver were located close to a powerful FM transmitter.

Unlike conventional FM interstation muting, the "muting" system used in the TX-35 does not eliminate background hiss in the absence of a signal. Instead, we found that it controls the operation of the tuning system, preventing the receiver from stopping its scanning action and unmuting until a signal of sufficient strength is received. Once this condition is met, the signal strength can be reduced to zero, and the program will be smoothly replaced by noise as though there were no muting at all.

Most of the key performance parameters of the Onkyo TX-35's FM tuner section were satisfactory or better. The capture ratio (better than 1 dB) was exceptionally good, but AM rejection and image rejection were marginal.

The audio amplifier had the most accurate RIAA equalization we have ever measured, differing from our precision pre-emphasis network by no more then 0.1 dB from 20 to 20,000 Hz. Phono response was not affected by cartridge inductance.

The power ratings of the TX-35 apply only to 8-ohm operation, and Onkyo warns against using it with a load of less than 4 ohms. In view of these cautions, it was a pleasant surprise to find that its amplifier apparently has little or no output current limiting and depends on its two internal 4-amp speaker fuses to protect the output transistors. As a result, not only did the 4-ohm clipping output power comfortably exceed the maximum 8-ohm output, but even into 2 ohms the amplifier delivered far more than its 8-ohm clipping power (although we did blow a fuse during this measurement). These effects were even more dramatic when using the tone-burst signal of the dynamic power measurement.