Stereo Amplifier

Review: Audiolab 8000S Stereo Amplifier

In since it was introduced the Audiolab 8000A integrated amplifier has won awards from all quarters and earned the appreciation of many contented users. Various changes have been made to the circuit over the years, amounting cumulatively to a substantial departure from the original.

Of course the R&D work has produced many additional ideas and a number of very significant innovations during the past decade and these have found their place in other models in the range. The 8000-range comprises two preamplifiers (8000C and 8000Q), a phono preamplifier for pickup cartridges (8000PPA), stereo and monoblock power amplifiers (8000P and 8000M), an FM/AM tuner (8000T), a cd-player (8000CD), a CD transport and a D/A converter (8000CDM and 8000DAC). The latest product was released is this 8000S “stereo amplifier”, described thus because it is “more than an integrated amplifier”. The design is novel in a number of important respects.

Reflecting the fact that many systems no longer require provision for the LP record, the 8000S omits the corresponding gain and equalization stages, substituting an extra line-level input. It also follows the widespread modern practice of dispensing with tone and balance controls. Like the 8000A it has six inputs, but the complement now includes facilities for three tape decks - labelled Tape 1 and 2 and Video (sound only). It retains the separate Input and Record selectors and has a fascia-mounted headphones socket. It is also rated at 60 watts per channel into 8 ohms. But physical appearance apart, there the resemblance ends.

The most unusual aspect of the 8000S is its ability to assume a number of roles. First it can be used as a normal integrated amplifier, with any of its six inputs amplified to conventional loudspeaker outputs. The second option brings into circuit two pairs of phono sockets on the rear panel. These carry the preamplifier outputs (the second pair duplicate the first). With the addition of a separate power amplifier this makes it an easy matter to use loudspeakers in bi-amplified mode, to add an active subwoofer perhaps, or H to add an additional amplifier and loudspeakers in another room.

The third option is to configure the 8000S as an electrically discrete preamplifier and power amplifier, with the two halves of the device operating independently (input phono sockets to the power amplifier section are now enabled). This could allow, for example, an external signal processor to be included in the chain (Dolby ProLogic or AC-3 surround sound decoders are obvious examples) with an additional power amplifiers) used to drive the multiple loudspeaker and subwoofer setup. Finally the 8000S can be used as a stand-alone preamplifier, with the power section disabled. Its twin line-level outputs have a low source impedance (100 ohms) which means it can drive long interconnecting cables if required.

The chosen configuration is set very simply by a five-position rotary switch on the fascia labelled Mode, the extra position being Mute, which is useful for silencing the system (e.g. when the telephone rings) without disturbing the volume or input selectors.

Input switching in the 8000S is handled by an array of encapsulated relays sited immediately behind the rear panel socketry. A dedicated microprocessor controls these under instruction from the front panel selectors, the circuit muting for a moment while the input is changed; there is some mechanical noise as the switch servo motor whirs and the relays click but electrically the switching is virtually silent - and foolproof. The six-position selector and the volume control are both motorized (high quality Alps devices) and can be operated by hand or by remote control from the supplied 34-button 8000RC infrared system handset.

The entire circuit is mounted on a single double-sided printed circuit board which occupies almost all of the chassis floor area. Only the large toroidal mains transformer and a small fascia-mounted pcb which carries the infra-red receiver and status LEDs are separate. The Digital Controller (microprocessor) is contained in a shielded box but again this is mounted directly on to the main pcb. The only flying leads are those which connect the transformer, the reservoir capacitors (which lie on their sides) and fascia pcb to the motherboard, and the output transistors to the rear panel terminals. All the line-level input and output sockets are board-mounted. Four pairs of loudspeaker terminals are fitted, to facilitate bi-wiring as described above. These are of a new type which will accept spade terminals or bare wire ends or 4mm plugs at a right-angle from above or below (to satisfy IEC requirements the outward-facing terminal ends are blanked). To accommodate the cable ends the two rows are staggered as viewed from above.

Virtually all of the audio circuit is made up from discrete solid-state devices. The preamplifier stages operate in Class A and the power amplifier is direct-coupled under DC servo control. The output devices are bolted to a substantial vaned heatsink which is located internally near the rear. The enclosed’ construction of this casting forms a ventilation shaft, with a cut-out in the pcb allowing the free passage of air via slots in the chassis floor and top cover. Locally regulated, "wide bandwidth" power supplies are employed and the output circuit is capable of delivering a peak current in excess of 25 amps. Widespread use of precision metal film resistors and low-loss plastic film capacitors is evident as is a standard of construction matched by very few rivals.

There are just five fascia controls in all, I have covered the Input and Mode selectors and the Volume control. Record is a second six-position rotary switch (manual only, not motorized) providing for independence between the auditioning and recording of sources (a very sensible arrangement) and Power is a simple mains on/off pushbutton. The record outlets are fed from a 1k ohm resistor, which means that the tape output source impedance equals this figure plus the output impedance of the selected source device (this does not present a problem with modern ancillary components). The rear panel sports 12 pairs of gold-plated phono sockets, a ground screw (not normally used but provided to establish a system ground if necessary when a separate phono gain/eq unit is employed), the eight loudspeaker terminals and a fused IEC mains input socket.


At switch-on the Audiolab 8000S remains muted for some 17 seconds to allow its circuits to stabilize fully, this condition indicated by the illumination of two red LEDs on tire fascia. The loudspeaker output protection relay opens after some seven seconds but the line-level muting relay stays dosed for the duration. A single LED is remains illuminated when the amplifier is ready to play.

A moderate level of output stage bias current is set, so the 8000S runs warm to the touch when it has been idling for a few hours. This is of no consequence other than to confirm the booklet’s caution that the amplifier be well ventilated and kept away from heat sources such as radiators and direct sunlight.

Routine bench tests revealed nothing untoward in any respect, an outcome entirely to be predicted with units of this pedigree. The frequency response was tighter than the ±05dB tolerance claimed and the crosstalk, separation and distortion figures were similarly as good as or better than specified.

Natural, unforced clarity and a sense of control were my first impressions upon connecting the 8000S up as a conventional integrated amplifier, driving my reference Quad ESL-63 loudspeakers -not the simplest load but without doubt one of the most most analytically revealing. The usual wide range of pre-recorded material was tried, current favourites that I know particularly well. None gave the 8000S the slightest difficulty or caused me a moment's hesitation. The material ranged from a simple (!) piano solo recording (Debussy's Eslampcs - “Pagodes” - from Ivan Moravec) to unaccompanied choir (John Tavener's Funeral Ikon from King’s College, Cambridge and Stephen Cleobury) to full orchestra (Sibelius's Fifth Symphony in the original 1915 version from the Lahti Symphony Orchestra under Osmo Vanska), it is all too easy to slip into the use of terms like coherence and stability in describing such ’by the book’ behaviour but I can think of no better way to convey my overriding impression that the Audiolab 8000S is in complete control.

Anyone seeking a high quality integrated amplifier at, or considerably above, this price level should certainly consider this beautifully constructed, substantially transparent unit. It can of course be partnered by ancillaries of any provenance, but as our previous reviews have demonstrated, its logical partners are other models in the 8000 range the tuner, CD transport and D/A converter, with the 8000PPA as well if your collection still includes LP records - it is a very superior phono equalizer. The addition of an Audiolab 8000P stereo power amplifier would be a logical upgrade for those with loudspeakers that benefit from bi-amplification. Then of course there is the plethora of other possible configurations as has been described.