NAD Electronics C420 User Manual download pdf (Page 4)

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

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

±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

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)

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 75µs

pre-emphasis and steep 16kHz LP

filter on the audio that is fed to

the FM signal generator, and the

75µs de-emphasis in the tuner

under test. Audio crosstalk perfor-

audioXpress June 2002 63

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.

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 (75

Ω

) 11dBf, 1

V (75

Ω

)

Stereo muting (Fixed) 40dBf

Stereo quieting @ 50dB 37.2dBf, 20

V (75

Ω

) 40dBf, 27

V (75

Ω

)

S/N, A-wtd, 65dBf, mono 74dB

S/N, A-wtd, 65dBf, stereo

74dB 68dB

Frequency response 30

−

15kHz,

1dB 20–15kHz,

−

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 600

Ω

, 1kHz

Output level 580mV, 1kHz

1 2 3 4 5

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NAD Electronics C420 User Manual Page 4

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