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Description :
The Parasound A23 amplifier is the ultimate combination of cutting edge technology, superb craftsmanship, and stunning industrial design. The Halo line represents a dramatic improvement in both appearance and performance for Parasound. It represents a departure from Parasound’s traditional black box styling and is clad in a silver brushed metal finish. Each component has a groove, forming an accent line across the bottom portion of each unit. With high current class A/AB amplification, smooth sounding MOSFET drivers, and balanced XLR inputs, this mighty amplifier will make any speaker sound better than ever before. The Parasound A23 power amp uses mostly discrete transistors, including three pairs of output devices per channel, with a large toroidal transformer giving near-dual-mono design. A choice of balanced and unbalanced inputs is given and the amp can be configured in bridged mode for massive (mono) output.

The Parasound A23's power supply begins with a 1kVA encapsulated toroidal transformer with independent secondary windings for each channel. This design has a hybrid circuit topology, utilizing JFETs, MOSFETs and bipolar transistor. Each stage of amplification is complementary, meaning half the transistors amplify the positive half of the musical waveform and half the negative side of the waveform. Differentially arranged JFETs are used for the input stage, taking advantage of their high impedance. MOSFETs are used in the driver stage, as they are known for generating less odd-order harmonic distortion than bipolar transistors. The output stage utilizes three pairs of bipolar transistors per channel. Bipolar transistors are better suited than MOSFETs for delivering large amounts of voltage and current, as they have a much larger safe operating area. The Parasound A23 has several protection devices, DC offset is maintained by a servo system that operates outside of the audio signal path, current sensing transistors and relays are also utilized in the protection scheme.

The overall impression of the Parasound A23 gives a very musical performance, involving and communicative, with perhaps a slightly underwhelming rhythmic drive. As such, it works better with some music than others. Midrange textures and timbre are nicely resolved, putting little in the way of what is musically essential. Detail is good, clear and unforced, and never verging into the 'dissected' sound that many associate with American high-end. Tonality is generally natural, although some concern is that piano sounded a little artificial through the amplifier. Voice is good, and harmonic-rich sounds such as violin and trumpet are nicely presented.

Perhaps the most impressive aspect of the Parasound A23's performance is its imaging. The system's lateral image is very wide, extending well beyond the outside edges of the speakers, although not razor sharp, it is well defined. The guitars and drums are well articulated and distinctly placed across the soundstage. While playing loud, the Parasound A23 will never sound strained, nor will the sonic picture loses coherence or take on unwanted coloration with the increased volume. Chamber music is presented with a real acoustic space; the ambient sounds of the recordings provide a real sense of place. The sound seems to come out of the box, out of the speakers and out of the room. There are clearly performers several yards behind the back wall of the listening room and their positions are stable in both dimensions across all the dynamic ebb and flow of the music.

Specifications :
Continuous Power Output.................Stereo: 2 x 125 watts RMS @ 8 ohms
                                     .................Stereo: 2 x 200 watts RMS @ 4 ohms
                                     .................Mono: 400 watts RMS @ 8 ohms
Current Capacity..............................45A peak per channel
Slew Rate.......................................>130V per us
Frequency Response.......................5Hz to 100kHz, +0/-3 dB at 1 watt
Total Harmonic Distortion..................<0.06% at full power
                                    ..................<0.03% at typical listening levels
Intermodulation Distortion.................<0.04%
Topical Immune Modulation...............Unmeasurable
Dynamic Headroom.........................>1.5dB
Interchannel Crosstalk......................>80dB at 1kHz
                                ......................>63dB at 20kHz
Input Impedance..............................33k ohms
Input Sensitivity...............................Balanced: 1V for 28.28V output into 8 ohms
                      ................................Unbalanced: 1V per leg for 28.28V output into 8 ohms
Loop Output Level............................Same as input level
Signal-to-Noise Ratio.......................>112dB, input shorted, IHF A-weighted
Damping Factor...............................>800 at 20Hz
DC Trigger Requirements..................+9 to +12 Vdc, 2mA
Audio Trigger Requirements..............50 to 200 mV AC
DC Trigger Output............................+12Vdc, 150mA
Power Requirement..........................Standby: 25 Watts
                            ..........................Full Power into 4 Ohm: 700 Watts
Dimensions(w x d x h)......................44 x 39 x 11 cm
Weight............................................12kg

Miscellaneous :
XLR Inputs.......................................Yes
Made By..........................................Parasound Products Inc San Francisco CA USA
Condition.........................................7/10 (Marks and scratches on the amplifier)

Product Information :
http://www.parasound.com/halo/a23.php (Manufacturer's Website)
http://www.parasound.com/pdfs/A23Manual.pdf (Manual)
http://www.parasound.com/pdfs/A23EBrochure.pdf (Brochure)

Reviews :
http://www.techradar.com/reviews/audio-visual/hi-fi-and-audio/amplifiers/parasound-p3-a23-704161/review
http://www.avrev.com/home-theater-power-amplifiers/stereo-amplifiers/parasound-halo-a-23-stereo-power-amplifier.html
http://www.goodsound.com/equipment/parasound_halo_p3_a23.htm
http://www.stereotimes.com/amp040803.shtml
http://www.audioreview.com/cat/amplification/amplifiers/parasound/halo-a-23/prd_136630_1583crx.aspx
http://www.audioasylum.com/reviews/Amplifier-SS/Parasound/A-23/amp/90617.html