RSA-F33EX integrated amplifier is SPEC CORPORATION top-of-the-range model. It is made as it could be expected from a product manufactured by a small Japanese firm that has the right technology. It has a double housing made of a steel chassis that also constitutes a screen for the impulse circuit inside and from thick aluminum panels. The bottom has been reinforced and decoupled using a wooden oak plate with three wooden feet (two at the front, one at the back).
The heart of the device is the PWM International Rectifier IRAUDAMP4 DB modulator. Analog input signal is fed into it and modulated impulses come out of it. It was developed together by Mr. Yazaki and his friend, an engineer working for International Rectifier, Mr. Honda (a younger colleague from Pioneer). It controls FET transistors operating in a bridge. An analog low-pass filter has to be installed on the output of D-class amplifiers, consisting of two elements: a coil and a capacitor—it is an especially sensitive element of the structure. The SPEC company uses sophisticated oil capacitors manufactured by Arizona Capacitors there. These are exact replicas of the WEST-CAP CPV09 0.47 μF/600 V “Hermetic-seal” capacitors, originally manufactured for the American army in 1967.
Finally, the amplifier itself: classic D-class amps are powered by impulse circuits that are easy to connect to the amp’s circuit in order to optimize their performance. Still, however, an old and reliable line amplifier with a large transformer has its advantages that are hard to copy in an impulse circuit. And here we have such an amp, with an enormous R-core transformer. In its basic configuration, the RSA-F33EX does not have a remote control, any tone color adjustment, digital inputs, a phono input, or a headphone output. It is a classic product with a “twist” inside. It costs a lot, but I know from my experience that SPEC is one of few manufacturers that propose sound which is very close to the sound of tube amplifiers, but without tubes and with a much higher power at a fraction of the price.
An amplifier is a musical instrument
The top of a violin is made of spruce.
The back and ribs are made of maple.
Because an amplifier which has high gain is sensitive to rigidity and vibration, wooden structure provides suitable vibrational damping property. Like a musical instrument maker , we select materials and consider grounding method. As a result, the bottom plate is made of spruce, and the insulator is made of maple with hickory embedded in the center. They are the same as the material used for a violin.They vibrate with music and bring out the beautiful sound. This is why we say “the amplifier is a musical instrument”.
The parts made of natural materials play a natural sound
The parts made of natural materials play the sound which is gentle to listen and fine textured.
These PAPER-OIL-CAPACITORS have been tuned exclusively by SPEC. It’s a CAPACITOR for the MUSICALITY. Inner KRAFT PAPER brings completely beautiful tone.
PAPER-OIL-CAPACITORS
Mica capacitoers used in SPEC amplifiers are made of highest quality ruby mica.It is produced only at the foothills of the Himalayas. It is made by orogeny of the Himalayas.Mica of high purity is a great benefit from Himalayan orogeny movement and we can hear a profound silence.
PMICA CAPACITORS
Capacitor blending
We blend several capacitors to obtein the sound with MUSICALITY.
And,EMC coating absorbs internal noise reflections to offer especially transparent sound playback. As a result,the sound is warm,smooth and exceptionally creamy while keeping details.
SPEC sticks to the R-core transformer.
R-core transformer plays a dynamic and powerful sound.
Class-D doesn’t generate heat at all
Because Class D system is using switching technology, the power stage doesn’t generate heat at all. Therefore, HEAT SINK is not required.
In addition,you can’t find any cooling hole on the amplifiers. This SEALING STRUCTURE prevents entering of the dust to the inside of an amplifier.
No heat and no dust mean long life with clean environment.From circuit point of view, small size circuit will playback highspeed and detailed signal as it is.It is most important for the Musical expressions.
It’s an “ANALOG” amplifier
The myth that a “CLASS D” is a DIGITAL AMPLIFIER is incorrect. SPEC CORP. has adopted “Pulse Width Modulation” in our “CLASS D”. This “PWM” converts “signal amplitude” to “duration switching” through “ANALOG PROCESSING”. This system doesn’t digitize the audio signal. This is in fact type of analog amplifier because magnitude resolution is infinite. “CLASS D” with PWM contributes to bring you beautiful acoustical sound. In the past, some audio makers adopted delta sigma modulation for “CLASS D” . This is quite simply “1bit digital” modulation. Combination of switching technology and analog technology makes the sound realistic and beautiful.
RSA-F33EX appearance
| Maximum output | 120 W × 2 (4Ω), 90 W × 2 (6Ω), 60 W × 2 (8Ω) |
|---|---|
| Frequency response | 10 Hz – 30 kHz ±1dB (6Ω, 1W) |
| Harmonic distortion ratio | 0.02% (at 1 kHz, 80% output) |
| Input sensitivity, gain | 300 mVrms, 37.3 dB (at MAX volume, 6Ω, 1kHz, unbalanced input) |
| Line input terminals | XLR input: 1 RCA inputs: 3 |
| Speaker terminal | 1 |
| Power supply, other | |
| Power voltage | 220 V AC, 50 Hz |
| Electrical consumption | With no signal: 15 W, during maximum output: 215 W (8 Ω, 100 Hz) |
| External dimensions | 450 mm (width) × 130 mm (height) × 422 mm (depth) |
| Weight | 20 kg |