Price Paid:  $3000.00 from ex demo from G.T. Audio

Summary:
When I first sneaked these into my system my wife, who rarely takes any interest in the sonic progress of my audio, said it all with this very simple statement: 'Its like you're there'.
At the time of purchase I was at a cross-roads with my system: either high power complex or low power simple amplification with appropriate speaker sensitivity matching (I liked what could be achieved with the Celestion SL6000 set up) . I was keen to avoid masses of hard to find and difficult to match valves. Power amps don't come any simpler than Smart 845's, and good valves are cheap and plentiful.
I would go a stage further than the previous reviewers and say that the Smart 845's need speakers with a sensitivity higher than 90 dB. - the higher the better.
I use Posselt Albatross which have 92 dB. with which the system goes reasonably load but sometimes loses cohesion when things get very busy. Pre-owned Smart 845's are now fairly readily available in the UK at prices down to circa 2000 USD so the possibility of bi-amping becomes attractive.
The Smart 845 with Posselt combination was used to very good effect by Graham Tricker and others at a number of hi-fi shows and attracted very good reviewer comment.

Strengths:
Breathtaking midrange realism.

Weaknesses:
Lack of power; needs careful matching. Comparatively poor internal build quality.

Similar Products Used:
Mostly good vintage tubed gear. Leak TL10.1, TL12.1, Stereo 60; Radford; Quad 2; Michaelson and Austin (now Papworth Audio).

Summary:
I compared this amp with differnt devices like the Unison Research Simply 2, FM Acoustics 600, Mark Levinson 20.6. and the Naim 250.

The sonic signatur of the 845 is so unique, that a description is useless. Let me try with a metaphor instead: Lets have a look at a chessboard. It is made of black and white squares. If a chessboard would be made of marble and granite stones, perfectly polished and shaped, heavy and rocksolid, that would be a very good transitor amp. like A FM 600 or a Mark Levinson or a Naim amp for example.

The smart 845 "chessboard" would be all the same like the "transistor" chessboard, but the black and white squares would be made of solid ebony and ivory pieces instead of stones.

You can play chess on both boards, but you must decide which materials fit your taste, requirements and style.

Now some hints for the potential 845 buyer. If you like high SPL, do not consider this amp. 24 W are a lot, but not enough for disco SPL. The amp works fine with low sensitive loudspeakers like the Magneplanar 0.5(85 db) or the Audio Physics Step (84 db), but choose something around 87 db. The amp sounds "hard" when driven at its limit. The 845 dissipates a hell of heat, so you need a lot of "breathing" space over the amp.

I have directly compared this amp with a fully activ Naim installation. (sbl, fullactiv, 250 amps, one per side, the best Naim Preamp, cds 2. All components with seperate mains supply).

The Naim chain sounded breathtaiking with all materials, but had a distinct "electric" glare on all presented materials. The U.R. 845 could not match the Naim on high SPL, but on "normal" listening levels the U.R. was doubtless more musical without loosing out on any category the Naim was worldclass in - an that it is.

Strengths:
excellent tonal balance over the whole audiospectrum, transparent detailed. Punch combined with elegance.

Weaknesses:
output transformers need frequent demagnetisation, needs a very good support (Mana stands or equal), very sensitiv on microphonics, 845 needs long time to settel in (6 hours at least to be fully silent (no ringing or mechanical noises) etc., needs a worldclass preamp or a Passion Passiv Preamp if only line sources are used. Needs worldclass peripheric hardware (cd, tuner, analog turntable).

Similar Products Used:
nothing equal on this planet, not even the Unison R. Simply 845.

Summary:
For those of you who enjoy purity and truth of timbre, listen to the passive version of this amp, driven with a passive preamp (eg McCormack TLC-1). First, a brief description of the amp. It is a single-ended triode tube monoblock design with three tubes a side. Two are dual-triodes input tubes: the 12AX7 and 12AU7, driving a 845 power triode. The finish is first rate with nicely curved cherry wood panels on the front and sides.Give this pre-power combination the best signal you can get - I play CDs via a CEC TL2 belt drive transport through a Meridian 566DAC. Speakers are the Totem 1s. The sound is simply amazing. The speakers disappearing and the sound rising from a black background around speakers. The musical image is not flat, but three dimensional and full bodied and alive. And because its SE tubes, the midrange is real, with the sensation that the performers are in the room there with you.
I tweaked the system by using NOS input tubes and placed the amp on cones, which minimised vibrations. If you get you hands on those aluminium tube coolers, use them without the rubber band.
This amp is amoungst the Best I've come across.