Abbingdon Music Research ΑΜ-77 Integrated

[Κώστας Φ.]

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Dual-mono υβριδικός ολοκληρωμένος τάξης....Χ.
Με ενδιαφέρουσες σχεδιαστικές επιλογές, τιμή στα 6.000 ευρώ περίπου και βάρος 34 κιλά (ζωή να'χει).


Everything you always wanted to know about sex - single-ended class X...

Isn't it embarrassing how the sex word triggers hard-wired reflexes to get our instant attention? Mention integrated amplifiers to the average audiophile male and you'll get a yawn instead of a bulge. Abbingdon Music Research believes they've rediscovered the sex in this category with their new 75 lbs/34kg AM-77. It combines a 5687/6900 NOS valve voltage gain stage with a class A bipolar power buffer. There's patent-pending non NFB error correction. 48,000uF of per-channel capacitance. And a 1200VA custom dual C-core power transformer. These ingredients combine for 180wpc into 8/4 ohms (220/320 watts into 8/2+4 ohms mono strapped). Output impedance is 0.5 ohms and S/N a colossal 100dB or better. The touch-sensitive, auto-illuminating remote shifts volume in 1dB increments over a 71dB range. It also selects from 5 RCA inputs (one is shared with the balanced connectors, one with a 3.5mm iPod link).

For sexy mating -- who wants mismatches -- there's stereo, mono/mono or high-power mono mode. Unlimited sync'ing with multiple units. Integrated or power amp mode. A provision to adapt the XLR input to transformer-coupled sources. The above-mentioned USB port for an iPod-ish portable source with 5V DC power mounted into the right side edge of the fascia. Paralleled 5-way and SpeakOn speaker outputs. Home theater direct conversion to transform one input into a pass-thru bypassing the volume control. Input labeling from a stored list. Input level offsets for volume matching. Display brightness adjustments. Touch-sensitive chassis controls. And a 9-pin RS232 uplink port for future upgrades. Phew, quite the run-on gymnastics on the interface front.

For cosmic sex aka cosmetix, there are the champagne or Titanium finish options. For serious locker room envy, there are dimensions of 17.9" x 6.2" x 18.3" WxHxD (46cm x 16cm x 47cm). That's mondo big and heavy. For more boasts, there are IHF dynamic (i.e. short-term peak) ratings of 270 stereo watts, 380/480 mono watts into 8 and 4/2-ohm impedances. Flex that muscle.

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Class X

"In the AM-77, two stages are used for the OptiGain®circuit. First, the signal is amplified to the desired voltage using an NOS 5687 electron valve with linearity and drive without the need for a negative feedback loop. This solution is much more costly and difficult when compared with more ubiquitous and cheaper operational amplifiers (op-amps). In our view, this represents a very significant sonic improvement over a circuit with negative feedback.

"The second half of the OptiGain®circuit is the power buffer stage where solid-state technology is combined with a thermionic electron valve phase-separation circuit. The power buffer stage uses AMR's "Class X: Jikoda circuit" with bipolar output devices, which in real-time, simultaneously detects and cancels unwanted artifacts in the audio signal. None pass to effect the playback of music, exceeding the ability of even traditional well-regarded class A circuitry.

"In addition, making the power buffer stage balanced and by actively driving both terminals of the speaker (as opposed to connecting the negative terminal of the speaker to some ill-defined 'ground') will ensure that the amplifier remains in full and direct control of the attached speaker and that any noise or error signals impressed upon the power supply are suppressed.

"Of course, this requires in effect two complete power buffer stages for one channel of amplification instead of the more common use of just one power buffer stage. It is thus twice as costly but the extra cost is well justified by the superior sonic performance. Finally, having a balanced power stage allows the application of a very specific form of feed-forward error correction, a unique method of reducing nonlinearities that is far superior to the common use of so-called negative feedback in amplification devices.

"In the AMR circuit, the error between input and output signal in one of the two balanced phases is precisely extracted and applied in reverse polarity to the opposite phase section. As a result, the output is only left with two signals which are in opposite polarity to each other. With all the errors removed, the result is a perfect replica of the input signal driving the speaker's output. This feed-forward error correction in effect completely removes the 'solid-state' sonic signature of the power buffer stage. This leaves an amplifier that behaves sonically like an optimal, extremely high power (>160W) and very linear (0.09% THD @ 160W) single-ended triode amplifier with only two stages, which also has a constant high damping factor (over 15 from 1Hz to 100kHz)."

Περισσότερα: 6moons.com