NAD C420 dimensions Inside the TDQ-150, MEASUREMENTS-NAD FM Section, ±12V DC to the circuitry

TABLE 2

PARASOUND TDQ-150 SPECIFICATIONS AND MEASURED RESULTS

FM SECTION SPECIFICATIONS	PARASOUND TDQ-150	MEASURED RESULTS
Usable sensitivity, mono		10dBf
Mono quieting @ 50dB	11.0dBf, 1∝V (75Ω)	11dBf, 1∝V (75Ω)
Stereo muting (Fixed)		40dBf
Stereo quieting @ 50dB	37.2dBf, 20∝V (75Ω)	40dBf, 27∝V (75Ω)
S/N, A-wtd, 65dBf, mono	>74dB	74dB
S/N, A-wtd, 65dBf, stereo		68dB
Frequency response	30−15kHz, ±1dB	20–15kHz, +0, −0.5dB
THD, 1kHz mono	0.08%	0.09%
THD, 1kHz stereo	0.20%	0.15%
THD, 100–10kHz, mono		0.28%
Separation, 1kHz	50dB	58dB
Separation, 100–10kHz	40dB
Alt. ch. selectivity, 400kHz	80dB
Capture ratio, 45dBf	<1.5dB
AM suppression	60dB
Auto search threshold		20dBf
Output impedance		600Ω, 1kHz
Output level		580mV, 1kHz

PC board behind the front panel. The compact double-sided epoxy tuner board occupies most of the chassis. A schematic was not fur- nished with the unit.

The display board connects to the tuner board through three Molex-style connectors, and the right side wiring loops through a toroidal ferrite core. The trans- former secondary is hard-wired to the PC board, where a pair of fuses deliver low-voltage AC to the power supply. The power trans- former primary remains energized when the tuner is plugged in. The front panel On-Off switch operates a power-supply relay that switches the low-voltage secondary. Linear regulators provide +5V DC and

transformer cases to the RF front- end shield. Parasound describes it as an ultra-wideband IF section for low distortion, flat response, and a wide dynamic range. Several audio transistors are located near the output jacks, so the TDQ-150 also appears to have a discrete audio output stage.

MEASUREMENTS—NAD FM SECTION

I did not run any tests on the AM sections of either tuner, except to make sure they were functional.

The C 420 does not invert polari- ty. The output impedance at 1kHz was 420Ω, delivering 550mV into a load of 100k.

The frequency response (Fig. 1)

eight individual wires. The shielded MOSFET RF front end sits just be- hind the two antenna connectors. A Sanyo LA7218 and LA1837 chip set handles PLL frequency synthe- sis and AM/FM tuning and RDS de- coding operations. The EEPROM preset storage memory chip is under the wide ribbon cable.

The FM tuner appears to have a

three-stage IF (intermediate fre- quency) section. A pair of emitter- follower audio transistors feed the audio jacks.

INSIDE THE TDQ-150

Photo 4 shows the interior of the TDQ-150 tuner. The power trans- former sits on the left side of the chassis, with the display/control

±12V DC to the circuitry.

The shielded MOSFET RF front end sits just behind the AM anten- na connector. A Sanyo LA3401 and LA1266 chip set handles PLL fre- quency synthesis and AM/FM tun- ing operations.

The FM tuner appears to have a two-stage IF section, with ground braid straps connecting the IF

was within +1.2, −0.5dB from 20Hz to 15kHz. The response curve above 10kHz may not be en- tirely accurate. In this area there are three filter responses: the 75∝s pre-emphasis and steep 16kHz LP filter on the audio that is fed to the FM signal generator, and the 75∝s de-emphasis in the tuner under test. Audio crosstalk perfor-

signals are changing—in a car, for example. Neither possibility holds true in a fixed installation in the U.S. (Only one station in our area broadcasts an RDS sig- nal.) Clearly the NAD is intended for European markets as well as the U.S. The C 420 has RDS capability and a multilingual manual, and it tunes in 0.05MHz incre- ments, requiring four steps between U.S. stations.

SOUND JUDGMENTS

Given an adequate antenna, all three tuners pro- duced a completely acceptable sound. One small ex- ception: all three grated on us occasionally during operatic soprano solos, but we ascribed this effect to the listeners’ taste rather than to the tuners. None of the tuners bested our reference SACD player (Sony SCD C333ES) sonically, a not-unexpected result.

Although all three tuners sounded pleasant, each had a distinct sonic signature. The sound of the NAD could best be characterized as inoffensive: most de- fects in reproduction were subtractive rather than ad- ditive. The midbass response of the NAD was slightly loose or boomy; this effect was especially apparent on rock recordings. The NAD’s response seemed a bit re- cessed at both frequency extremes, but this effect was small and may have been due to the source material.

The NAD presented a good soundstage, extending from speaker to speaker, but the images within this stage were not particularly well defined. The NAD’s sound seemed slightly compressed, even more com- pressed than the source material. This effect was es- pecially noticeable when we listened to classical music stations, which tend to transmit less com- pressed signals.

The Parasound produced a precise, detailed sound. I characterized it as having detail and clarity, while

Duncan saw it as having a slight high-frequency em- phasis. In any event, the high-frequency response was clean, extended, and never fatiguing.

The Parasound’s imaging was sharp and well-de- fined. Its soundstage was similar to the NAD’s; howev- er, the detail and clarity of the Parasound extended to the spatial characteristics as well. With well-recorded material the images of individual instruments were well separated and sized appropriately. The Parasound seemed capable of reproducing as much dynamic in- formation as was transmitted.

In comparison, the ADCOM presented a smooth, natural sound. No frequency region was missing or particularly emphasized. The soundstage was very wide, occasionally extending beyond the speakers. The ADCOM’s imaging was somewhat smeared: each in- strument appeared to originate from a space several feet across rather than a single location.

The dynamics produced by the ADCOM were good without being obtrusive. Again, with this tuner we had the impression that the dynamic range was limited more by the transmitted signal than by the tuner.

FINAL THOUGHTS

NM: All three tuners had a pleasant sound; none pro- duced fatigue even after hours of listening. To choose among them, focus on which specific charac- teristics mean most to you. If looks are your top pri- ority, buy the NAD. If you plan to make extensive modifications, pick the NAD or the ADCOM—you’ll have more working room. If you want a spare, precise sound with good imaging and good dynamics, go for the Parasound. If you prefer a fuller sound, again with good dynamics, look for the ADCOM on the used-equipment market.

DM: As with most decisions, the choice of “best” tuner in this group depends on which features are most important to the buyer. Both the NAD and the Parasound are currently available; you would need to purchase a used ADCOM. Both newer tuners have automation features (remote control, DC switching, and so on) that are not available on the ADCOM. The ADCOM was designed as a stand-alone stereo tuner, while both the NAD and the Parasound seemed in- tended to be part of a home theater system.

Both the NAD and the Parasound are visually inter- esting, although in different ways. I like the small size of the Parasound, but this same size would make it less appropriate in a stack of 17″ components (unless you pair it with Parasound’s matching preamp, ampli- fier, or phono preamp.) The ADCOM is supremely easy to use but lacks some features in comparison with its remote-controlled brethren. (If you purchase the NAD, I strongly recommend buying the optional remote con- trol—use of the presets, in particular, is arcane when using the front-panel controls.)

Sonically each tuner offers a different picture. De- pending on the program material, I alternately pre- ferred the sound of either the Parasound or the ADCOM. The Parasound possesses good imaging and a very detailed sound. It works well in a tube-based sys- tem, such as ours, which has a smooth high-frequency response and no need of additional bass emphasis.

The ADCOM is fuller and arguably more natural but lacks some detail when compared to the Parasound. Although the NAD didn’t match well with our system, it might be better matched to a solid-state system that could use a bit more bloom in the lower midrange.

audioXpress June 2002 63