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AAAVT P88i integrated amp

07.06.2011..
..

Aesthetics and functionality
The object of this review is a vacuum tube integrated amplifier with KT 88 output tubes that can be wired in ultra-linear or triode mode. The manufacturer is AAAVT, young but well-established Italian company based in Rome. The first thing to notice is its weight: about 30 kilos. Well, not very easy to move into your room! As soon as you have unpacked it, you immediately notice its mirror finish and its bulky KT88-98 tubes hidden behind a black and squared protection grid.
The thick front panel is finished in solid satin aluminium, tapered toward the lateral ends and refined with two deep vertical engravings. On the left side, positioned under the logo and the model type, are a blue led and the round on/off switch. On the right side, are two aluminium round knobs: the left for the volume and the right to select the four line inputs. Sober, clean and elegant, with just a minor fault: it is quite difficult to see from afar the notch that indicates the position of the volume. Anyway, the knob of the volume has a pleasant smooth movement. A little less "damped" is the input switch.
The sides are made of chromed mirrored metal and lodge the holes for the adjustment of the bias of the power tubes. Same material for the top panel where are the seats for the 8 tubes: 4 KT88-98 (external power tubes, Chinese) and 4 central (Russian). Two 15-79 Reflector NOS located in the front, two 6N8P Reflector NOS behind, just a bit higher. On the bottom, the expected two output transformers and one power transformer, all with a black lucid lid. The sample amp has some slight smears on the top, but fortunately, just on the back.

On the left side of the rear panel, are four double gold plated RCA pins for the inputs, quite close, I would say. In the middle the 4 and 8 Ohms connectors for the speakers, capable of accepting banana plugs. On the right the IEC socket. Centrally on the bottom panel, beneath the speaker terminals, is the triode/ultra-linear selector.
A basic design, classical but rational and pleasant, with some stylistic effects like the mirror plating and the wrought front panel. From the sound point of view, interesting is the possibility of commutate from triode to ultra-linear. A remark about the assembly of the KT88 tube sockets, considering that one is a little loose, at least in the model I have tested. Noteworthy is the air-wiring that is visible when the bottom panel is removed. This machine can also support the 6550, KT90, KT100 power tubes and the brand new KT120. As highlighted by the manufacturer, when using the KT90 or the KT120, you can get some more watts by increasing the bias.

 

Use and listening impressions
With the first set up, I have not had appreciable results. Probably the P88i does not like the match with the Magneplanar MMG speakers of my “garage” system, which need, considering their low efficiency, lots of power to perform satisfactorily. Consequently, the sound was rather disappointing: unbalanced, opaque, without any ambience. I thought it was a matter of warm-up, so I kept switching the system on and off for a couple of days. No changes. Then I controlled the “pre-calibrated” (as I was told) bias of the KT88 tubes. Eureka! In brief, the bias was out of tune! After the calibration, the sound was different as chalk and cheese. Actually, it is quite easy to realign the bias: just set a tester on 2 v of direct current and with a screwdriver turn the four potentiometers. I fixed the four KT88 at 450 millivolt, in ultra-linear mode and the sound literally flourished. It got depth, body, image, detail. Not bad for the 50w-8 ohms of the Maggies! However, I like better the reference sound of my “garage” system, which is more balanced from a tonal point of view and has a better image, as well as being capable of sharper and marked dynamical jerks. Clearly, the MMG appreciate a stronger driving.
To switch from the ultra-linear to the triode mode just move the selector placed on the lower part of the chassis. By decreasing the power the result was a shrinking of the sound, a stiffening in the harmonic built-up and a steaming in the brightness, which made me like best the ultra-linear circuitry. It is interesting to notice that, even with a 4 ohms load, the MMG speakers perform better if using the 8 ohms output.
Changing of room and system. With my home equipment things improved a lot as the ProAC Studio 125, with their 87 db of efficiency and an impedance not rough, offer what we can define an easy load. With these speakers, the amp performed to the highest degree, especially in the triode mode. A great sound, an ambience and presence never heard before with the Studio 125.
In ultra-linear, the sonic characteristics clearly shown, are: the bass range and an energetic and lively general setting, which privileges light dark colours. In triode – my favourite mode in this test - with some more volume, there is more refinement in the high range and a more balanced tone quality. The harmonics are richer with the possibility of recognise and appreciate all instruments and voices. The rhythmic is catching, thanks to the drum peels and their great resonances and decays, together with the broaden and articulate low range. Violins and cymbals generate multiple and bright harmonics, strings are given back accurately rough. Maybe the sound is a bit euphonic, but what a satisfaction hearing grace and power together! On one hand, as an example, we have the Reference Recordings performances showing a wide ambience firmly delineated in the horizontal, vertical and profundity planes, with a telluric low range (what a bass drums!) yet not prevailing and well amalgamate with the other sections. On the other hand, we have the female Chesky Records’ voices, notoriously difficult to master, with a body and a brightness fully enjoyable at last. Or the great Georg Gulyas classical guitar, a high rank marriage between playing and recording technique, with rich and potent strings. Then again, the incredible dynamic excursions of the Tonhalle-Orchester Zurich performing Beethoven’s Violin Concert. Or, last but not least, the romantic Ellis Marsalis’ piano accompanied by the sax of his son Branford and the cerebral but intense Bassini with his trio: both reproduced in an exemplary way, with an impressive sense of presence.
In comparison, my reference vacuum tube preamp with a 120 W solid state power amp performs stiffer and serious, with less harmonics, maybe it's more precise and analytic, but I have no doubt: the P88i amp conveys more emotions. Incidentally, the integrated amp is more silent.
Cables: Analogue Research Silver Raincoat main cable, which similar sonic characteristics go to the same sound direction of the amp and maybe accentuate some emphasis in the low range. Great marriage with a twisted custom cable provided with good ends. Even better the Wireworld Stratus: great spatiality and intelligibility. Speaker and interconnect cables by Stat Audio, very neutral and correct. For the MMG, 4 mm silver-plated copper Monitor PC power cables.
It is better placing the amp with its feet onto a solid and hard surface (marble or stone) or directly on the floor (with your wife’s permission!). For a better sound definition, I suggest using robust spikes and valves damper rings. The optimal levels of performances are attainable after 45 minutes, but just from the very start, the sound is good enough. Pay attention, as usual, to the correct electrical phase of the power supply.
Finally, some criticalities: there is no remote control, the mirror finish is easy to stain (but is also easy to clean with a microfiber cloth, when the tubes are cold and switched off, of course). The remarkable weight needs very strong and stiff supports, the quality of the tubes is medium-level (but you can reach a better sound by improving their quality and by calibrating the bias in the power tubes and by taking into account that matched quartets are not required).
I would like to add that it is very difficult to find at the same price (950.00 EUR, discounted) a similar product with the high sound quality of the P88i. You can be happy with it for a long time and - I confess – I am giving a little thought to this…

 

Music selection
Hi-Fi Spectacular!, CD Reference Recordings
24 hours of love, CD Chesky Records
Ana Caram: The other side of Jobim, Chesky Records
Georg Gulyas: Albeniz, Ponce, Tarrega, CD/SACD Proprius
J.S. Bach: “Concerti BWV 972, 973, 974, 975, 976, 978 e 981 per organo,” CD Fonè
Zinman, Tetzlaff: Beethoven Violin Concerto, Violin Romances, CD Arte Nova Classics
Hogwood, Consort Ancient Music: Handel, Water Music and Fireworks, 2CD Oyseau Lyre Decca
Ellis and Branford Marsalis: Loved ones, CD Sony BMG
Piero Bassini: Intensity, CD Red Records

 

Technical specification
Output power – ultralinear: 2 x 42W; triode: 2 x 26W
Frequency response: 20Hz ~ 30KHz ± 1.5dB
Input sensitivity: 0,5V
THD: <1, 5% (440 Hz maximum power headroom before clipping)
Output impedance: 4-8 ohms
Input impedance: 50k ohms
Tubes: KT88-98 x 4, 6N8P x 2, 15-79 x 2
General Power Voltage: 230V
Power consumption: 220W

S/N ratio: 90dB
Weight: 26 Kg
Size: 39W x 35D x 20H (cm)

Associated equipment: to Fabio "Puzzled" Barbato's system

 
by Fabio Barbato
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