NAD 3225PE
A 25-watt integrated that shares its service manual, its board layout, and most of its parts list with the 3020i.
Overview
The 3225PE hides its ambitions in a spec sheet. Twenty-five watts per channel into 8 ohms is the headline number, and anyone shopping on wattage alone will skip right past it. The manual's power-amplifier table puts that 25W right next to the 3020i's 20W, and the interesting part is what happens above the continuous rating. Clipping power is listed at 40W. IHF dynamic headroom at 8 ohms is +4 dB. IHF dynamic power is 60W into 8 ohms, 85W into 4 ohms, and 90W into 2 ohms. That last one is the number to look at. The amp is rated for 25W continuous and will deliver roughly 3.6 times that on short-term peaks into a 2-ohm load. That's a power supply and output stage built to favor transient behavior over steady-state numbers, and it's why these amps have a reputation for driving real speakers rather than bench resistors.
The PE suffix means something here, and the manual confirms it. The rear panel has a dedicated Soft Clipping switch, one of the features NAD used to set the PE line apart from the base models. When the amp runs out of voltage swing, soft clipping rounds the waveform instead of squaring it off, which is easier on the tweeters and on the ears. Whether you engage it is a matter of taste. It's switchable rather than fixed.
The full power-amp spec set, per the service documentation: continuous average power is quoted as minimum power per channel, 20 Hz - 20 kHz, both channels driven, with no more than 0.03% THD. Slew factor is greater than 50. Slew rate is 15 V/µsec. Damping factor is greater than 40 referenced to 8 ohms at 50 Hz. Input impedance is 20 kOhm with 820 pF of capacitance, noticeably higher than the 3020i's 470 pF, which changes how the input stage loads a source a little. Voltage gain is ×14, or 23 dB. Frequency response is listed as 6 Hz to 60 kHz, +0/−3 dB. Signal-to-noise is 100 dB A-weighted referenced to 1W, and 114 dB referenced to rated power. THD across 20 Hz - 20 kHz from 250 mW to rated output is under 0.03%, and the same figure holds for SMPTE IM (60 Hz + 7 kHz, 4:1) and IHF IM (19 + 20 kHz at rated output).
Those distortion numbers say a lot. A 25W amplifier that holds under 0.03% THD from a quarter-watt to full rated output, across the whole audio band, and does the same for two different intermodulation tests, is not a budget circuit. It's an over-built small amplifier. The 3020i is well known for punching above its weight class, and the 3225PE is the same architecture with a bit more grunt on tap.
The preamp section is just as complete. Moving-magnet phono input impedance is 47 kOhm + 300 pF, with input sensitivity of 0.52 mV for 1W and 2.5 mV for 25W at 1 kHz. Input overload at 20 Hz is 20 mV, at 1 kHz is 200 mV, and at 20 kHz is 1.7V. RIAA accuracy is ±0.5 dB. Signal-to-noise with a cartridge connected is 75 dB A-weighted referenced to 5 mV in. The overload figure at 20 kHz, 1.7V, matters if you run a high-output cartridge or a step-up into this input. It's a lot of headroom for a phono stage in an integrated of this class.
Line-level inputs (CD, Video, Tape) are specified at 40 kOhm + 440 pF. The rear panel has Phono, CD/Aux, Tuner, and Tape in/out, plus Preamp Out / Main In jacks that let you split the preamp from the power amp or insert a processor. There's a phono ground terminal, two sets of speaker outputs, and AC outlets on the back, though the manual notes those outlets are absent on the UK version. The front panel is the standard NAD layout of the period: power, phones, bass, treble, balance, input selector, tape monitor, mono, low level, and volume. Six push buttons plus a power button, four rubber feet, and a top and bottom cover held on with self-tapping screws.
What's genuinely useful about the 3225PE from an ownership standpoint is that the service manual is thorough. The alignment procedure is spelled out: set the speaker impedance switch to 8 ohms, connect a DC millivoltmeter to the left channel output, and adjust R411 (470 ohm) to 0V ±30 mV. Repeat on the right channel with R412. Then for idling current, remove the solder short across R455 and R456, connect the meter across R455 (1 ohm), and adjust R443 for 26–30 mV. Repeat with R444 across R456. Leave the power on for at least five minutes, then re-check center voltage and re-adjust idling current to 30 mV with R443 and R444. After alignment, R455 and R456 get shorted again with solder. That's a real, followable procedure — not a "return to factory" dodge — and it's the kind of documentation that keeps forty-year-old gear alive.
The parts list is just as specific. The main board is 531-1054. The headphone board is 531-9016, the external speaker board 531-9015, the external preamp board 531-2201, the fuse board 531-V001. The power transformer is an EI 67 × 55 mm unit, part 521-167AMV501. The volume pot is a 10K C-taper (D) without switch, part 507-3103C21. There's a separate 20K W-taper pot (507-3203W11-T) and a 50K B-taper pot (507-3503B21). The power LED board is 531-7049. RCA jacks are listed as 4-position (527-441101, three of them) and 2-position (527-421201).
On reception: the magazine chunks available for this model are index pages and car-stereo advertisements from HiFi-Stereo/Stereo Review issues in 1990 and 1991. They don't contain review text for the 3225PE itself, so there's no period verdict to cite here. The documentation does establish that the 3225PE was sold alongside the 3020i as a matched pair in NAD's integrated lineup, sharing a service manual, a PCB layout section, a parts list, and an exploded view. The 3020i is the more famous of the two. The 3225PE has more headroom and a slightly different input stage. Period coverage of the NAD lineup placed the brand's integrateds alongside car-stereo and mail-order advertising in the pages of HiFi-Stereo (November 1990, p.182) and HiFi-Stereo (January 1991, p.135).
Collectors and technicians who work on these note a few recurring themes. The solder-shorted idling-current resistors (R455, R456) are a service convenience that becomes a hazard if someone forgets to re-short them after adjustment. The amp will run, but the bias will drift. The soft-clipping switch is a wear item on some units, and the push-button switches in general (Alps 21212IS and 252S types, per the parts list) are the most likely mechanical failure points. The volume pot is a C-taper 10K, which is an unusual taper and not a drop-in replacement from generic stock. If it goes noisy, you're either cleaning it or sourcing a correct part.
What the 3225PE is, in the end, is a small integrated amplifier that was designed by people who understood that 25 watts is plenty if the 25 watts are honest and the transient behavior is good. The +4 dB dynamic headroom, the 90W into 2 ohms, the 0.03% THD held across the full band and both IM protocols, the 1.7V phono overload at 20 kHz — these are the numbers of an amplifier that was built to a standard, not to a price point. It shares its DNA with the 3020i, which means parts and knowledge are shared too, and that's the difference between a collectible and a doorstop.
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