NAD 7220PE Stereo Receiver
NAD has always eschewed the bells, lights, and whistles approach to audio product design. Judging from its front panel, the 7220PE might well be characterized as the "plain Jane" of stereo receivers. Yet, when you look behind that rather drab front and begin to explore its innovative circuit design, solid construction, and consistently high-quality performance, you can't help but wonder how NAD is able to market this receiver at such a low, low price.
Circuit Description
Since circuit innovation is what makes this an outstanding performer, let's discuss that first. To begin with, don't be put off by the low continuous power rating of 20 watts per channel into 8-ohm loads. NAD had to specify that low power level to conform with FTC rules, but I know I don't listen to continuous steady-state tones and I'll bet you don't either. In the real world of musical listening, the 7220PE's unusual power supply, the heart of what NAD calls their Power Envelope circuit, can deliver short-term peaks that are 4.4 dB greater than the nominal continuous power rating. That would bring the total up to about 55 watts per channel. In fact, my measurements of dynamic headroom were even a bit better: 4.8 dB. In terms of power, that works out to be just a shade over 60 watts per channel!
Another feature of the receiver prompted me to reminisce about the time when vacuum tubes and output transformers were used in all audio amplifiers. In those days, the secondary windings of output transformers had taps at different impedances so that optimum impedance matches could be obtained for speaker loads of 4, 8, or 16 ohms. In somewhat similar fashion, NAD has provided an impedance switch on this receiver. In its 8-ohm position, maximum output voltage is provided for loudspeakers of 8 ohms or higher. In its alternate, 4-ohm setting, voltage is lowered but current capacity is correspondingly increased to allow driving lower impedance speakers or two pairs of speakers wired in parallel.
A "soft-clipping" circuit developed by NAD, when switched on, gently limits the waveform if the output transistors are driven into saturation. Those who believe "tube sound" is superior to "solid-state sound" will appreciate this feature-especially if they tend to play music at loud levels that might exceed the amplifier's short-term power output capacity.
Another enhancement found in the 7220PE is an infrasonic filter. Unlike most built-in subsonic "rumble" filters that have a shallow roll-off characteristic of 6 dB/octave, this one has a 24-dB/octave slope with a cutoff point of 15 Hz.
This receiver employs frequency-synthesis tuning, and the FM front-end uses a dual-gate MOS-FET which provides adequate sensitivity while resisting overload or cross-modulation distortion at high signal levels.
Control Layout
At the left of the matte black front panel is a green "Power" button, with a stereo headphone jack immediately to its right. A button labelled "Extra Speakers" follows.
NAD's approach here is to give the user only the option of turning a second set of speakers on and off-the system's primary speakers are always on. The owner's manual offers tips on how to connect a second set of speakers for "ambience recovery," should you want that kind of sound enhancement; of course, the second set of speakers can also be wired in the conventional manner for use as a stereo pair in another room. "Bass," "Treble," and channel "Balance" knobs, each with a center detent position, come next. After these are a "Tape Monitor" button (only one tape monitor loop is provided) and a cluster of five matching input selector buttons. In keeping with current trends, the two high-level inputs are identified as "CD" and "Video." These, of course, are nothing more than extra high-level audio inputs which can be used for any stereo program source you wish. The next pair of pushbuttons are for mono/stereo switching and turning on loudness compensation. A large rotary "Volume" control knob is at the extreme right of the panel; just above it is a momentary rocker switch for up and down tuning.
The upper center section of the panel houses the frequency display, five station preset buttons, "FM Stereo" and "Center Tune" indicator LEDs, an "Enter" button for memorizing up to five FM and five AM station frequencies, and a "Search" button. When "Search" is in its depressed position, touching the tuning bar causes the tuner to seek the next usable FM or AM signal.
As ergonomically ideal as the front panel of this receiver seems to be, it's clear that somebody wasn't thinking as carefully when they designed the back panel. The antenna terminals are, in my opinion, both poorly labelled and poorly configured. If your FM antenna's 300-ohm twin lead comes with handy spade lugs, you'll have to cut them off and strip the wires to feed them into the spring-loaded terminals provided for antenna connection. In all fairness to NAD, I should mention that the supplied twin-lead dipole antenna does have its leads stripped back at the connection point, so you won't need to use any tools if you choose to use it. Still, you'll have to be careful when you connect its two wires: One of them should go to the terminal for 300 ohms and the other to the adjacent terminal for 75 ohms-not to the terminal marked "G" for ground. On the other hand, if your FM antenna has a 75-ohm coaxial line, you'll have to cut off the standard F-type connector. Then you'll have to strip back and braid the cable's outer shield and strip some insulation from the inner conductor to fit into the 75-ohm and ground terminals. If you want to listen to AM, you must connect a wire to the "AM Antenna" terminal, as there is no built-in antenna. NAD does provide a length of wire for this purpose (which, in most instances, is all you'll need), but the omission of the usual loopstick is unusual.
The phono input jacks are at the extreme left end of the rear panel, with a ground terminal conveniently located nearby. The remaining sets of input jacks and tape output jacks are beneath the antenna terminals. Farther to the right are the "Soft Clipping" switch, two color-coded sets of spring-loaded speaker terminals (not unlike the antenna terminals), the previously discussed "Impedance" switch, and convenience a.c. receptacles (one switched and one unswitched).
Use and Listening Tests
The advantages of the Power Envelope design (large dynamic headroom) became immediately apparent when I hooked up the 7220PE to my low-efficiency reference speakers. While in truth I wasn't able to develop nearly as much sound power as I normally get when these speakers are hooked up to my reference (200 watt/channel) amplifier, the clean loudness levels that I did achieve were far more than I would ever have expected from a receiver whose "official" continuous power rating is only 20 watts per channel. In fact, when I substituted a somewhat more efficient pair of speakers that have a sensitivity rating of around 89 dB per watt at 1 meter, I was able to get as much SPL as I would reasonably ever want. Normally, these same speakers have required amplifiers whose power ratings were at least in the range of 60 to 75 watts. At all listening levels below clipping, I found the sound to be well balanced and reasonably transparent. With the receiver's soft-clipping switch turned on, even moderate amounts of overload seemed tolerable.
I missed having some sort of signal-strength indicator for the FM tuner section, but I did find that the center-tune indicator was completely accurate. I think you will appreciate the fact that the 7220PE's FM section tunes in increments of only 50 kHz. This will be useful if you pick up FM signals from a cable TV system which carries them at nonstandard frequencies. It may also prove helpful in dealing with adjacent-channel interference; if the desired signal is strong enough, off-tuning the set by 50 kHz may get rid of the adjacent-channel crosstalk (or other forms of interference) without causing severe distortion. Off-tuning worked in at least two cases in my metropolitan New York listening area, where radio stations seem to be stacked practically one on top of the other.
I sort of wish that some form of interstation muting had been provided too, since quite a bit of popping noise was generated as the tuner moved up and down the dial in manual or search tuning mode. I quickly learned to avoid this noise by reducing volume levels while tuning from one signal to another.
If I were to rate the 7220PE's sections in terms of performance and quality, I'd put the amplifier first and the preamplifier next. The tuner was only average in its performance. Although certainly adequate for most AM and FM listening environments, it is not as sensitive or selective as more expensive, separate tuners generally are.
For all my minor complaints, however, there's no denying that this receiver is attractively priced considering the performance it delivers. After all, many people pay as much or more for separate components that offer no more (and often less) than this all-in-one unit. If you're on a tight budget and are looking for great value in an audio receiver, I suggest that you have a look at-and a listen to-the NAD 7220PE.
