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The general consensus is triode for chamber music, vocal and jazz; ultralinear for symphonies and big band. With the Apogee Centaur Minor playing back Stokowski's Wagner Symphonic Syntheses conducted by Serebrier [Naxos 8.570293], that rule got broken. The Centaur Minor is very transparent and open. Stokowski's transcriptions cover a wide spectrum of orchestral moods and energy level. With this highly challenging repertoire, I found the Triode mode good enough for the richly scored orchestration like "Entry of the Gods into Valhalla" and "Ride of the Valkyries", yet at the same time, UL could be immaculately detailed even in the exquisite passages like "Liebesnacht from Tristan und Isolde". This was absolutely contrary to popular belief. But there was a catch - I had to adjust the NFB settings accordingly. If I left NFB unaltered:
  • Triode + Min NFB = wide deep soundstage and layering.
  • UL + Min NFB = swollen bloated images.

To salvage the latter when in ultralinear mode, NFB had to be set to or near max (naturally the output diminishes noticeably when doing so.) However, when I left NFB at max and flicked back to Triode, the soundstage would be so forward as to be intimidating and images flattened out. When I dialed down the NFB to minimum, things resumed to normal. In other words, I came full circle. My conclusion is that these user-adjustable settings are very functional tools for speaker matching. If your speakers require more power to drive, set the amps to UL + Max NFB. If your speakers prefer more resolution and refinement, set the amps to Triode + Min NFB.

Generally speaking, minimum NFB (0dB) will enhance airiness and ambience, therefore is often considered more musical. Maximum NFB (approximately -8dB) will improve damping factor, most useful for tightening up the bass response of larger speakers as well as for creating the illusion of a deeper soundstage in a large listening area.

Conclusion
So what did you just read - a suspense thriller? In a way. As all suspense should end up in a thriller, this review built up to a big thrilling climax in a most triumphant way. Peter's upgrade of the Pre-2 arrived in the nick of time and saved my day. It's a revelation. I have probably used fewer words than usual to describe the artifacts of sound in detail but that doesn't mean I'm unappreciative of what the Audio Space combo delivered in terms of sonic achievements. On the contrary, I am convinced that it does rather better than just deliver "sweet highs, accurate mids and powerful bass". It has gone beyond that and attained the even higher achievement of musical involvement. Don't bother to break up this combo to mate parts to other gear. This kit is designed to work in harmony. Together.

$6,000 buys a versatile tube system with enough output power (60wpc) to match a lot of speakers to taste. The many features like triode/ultralinear selection, negative feedback adjustments and bi-wire inputs provide you with further fine-tuning. The best part is that you have a better chance of molding the sound to your heart's content, then forget all about sonic fidelity and soak yourself full of music instead. Whether you crave an intimate tête-à-tête with a small chamber music ensemble or a full-scale tour-de-force Nibelungen epic, the Audio Space will deliver with spontaneous finesse or theatrical magnificence wherever appropriate, even with just stock tubes and cords. One valuable lesson I've learned from this evaluation is that when the equipment is done right, you don't need to fidget around with tweaking if you call yourself a music lover. This could just cure your audiophilia nervosa. After all, my justification is a wholly inferential affair...

Quality of packing: First class.
Reusability of packing: Be my guest.
Ease of unpacking/repacking: The stainless steel chassis and transformers are well protected with adhesive film for your own good. Just be a little patient.
Condition of component received: Immaculate.
Completeness of delivery: Included power cord, spare fuses, operation manual, chamois cloth and white cotton gloves.
Quality of owner's manual: Spiral-bound glossy paper high-quality printed document but the content is missing a few crucial points (on bias adjust and MM/MC settings – see text for details). No circuit diagram even though the manual mentions that it is subject to change without notice.
Website comments: Informative and professionally done.
Warranty: 12 months for the amp, 6 months for the tubes.
Global distribution: Asia, Europe and America.
Human interactions: Friendly yet untimely. A lot of technical questions directed at the manufacturer remain unanswered, for example: schematics, 6SN7 sockets, NFB calibrations in dB. However, readers are cautioned not to interpret this as after-sale example of their local importers. Only reviewers would ask so many technical questions.
Pricing: Hard to beat for this level of performance in this price range.
Application conditions: Float the ground of source equipment if you have hum. Be careful when mating Pre-2 to DC amps or hybrid bi-amping speakers with Nova M-34 and DC amps. Observe phono input sensitivity (0.3 to 1 mV) when using MC cartridge. See text for details.
Final comments & suggestions: Stick to the Audio Space preamp + power amp combo for the best performance. Probably the premier cure for audiophilia nervosa.
Audio Space website
Canadian importer's website