The short:   If you love single ended tube amps, and you have full range speakers (read "Lowthers"), you are going to love this amp.

Nelson Pass, of Pass Laboratories, has introduced a new current source (transconductance) amplifier, which is produced by First Watt.  www.FirstWatt.com  The F1 was a push-pull design putting out 10 watts into 8 ohms.  The F2 is a single ended version of a current source amp, with 5 watts into 8 ohms.

Typically lovers of single ended amps say that a push-pull amp sounds dry, and a single ended will sound fuller, or more liquid, in comparison. This is the old 2nd harmonic vs. 3rd harmonic battle. Taste counts here, many prefer push-pull amps.  But if you like a single ended system there are a few reasons to consider this amp.

It most regards the F2 sounds like a very high quality single ended tube amp.  There is not the mechanical signature of so many solid state designs.  Most single ended tube amps are distinctly inferior to the sound of this lovely baby.  A few very expensive amps will sound better in one or two regards.  This is a true challenger to any single ended amp in that it is capable of doing some things that no existing commercial tube amp can do.  Because it is a current source amp it effectively extends the response of Lowthers both up and down, and additionally will flatten some of the bumps in the response curve.  You get drivers that have better, more extended highs and deeper lows.  No other amp will do this.

From a pure technical standpoint the output of a cone speaker is related to it's acceleration.  Acceleration is related to current, not voltage.  The F2 is giving the speaker the ideal power source.  That being said, most multi-way speakers use a voltage dividing network, and therefore will not work well with a current source amp.

Low level detail, dynamics, speed and transparency are all superb.  One of the few amps that you can get the "you are there in the recording studio" sound from.  If you want to fault this amp it does not have the ability to create a soundstage outside of the speakers, which some can do.  But it does have very good imaging both in width and depth.  Personally I am not fanatical about imaging, and this amplifier presents a realistic presentation of the musical soundstage.  If you like points, make it an 8 or a 9. 

The real advantage of this over the F1 is that it simply plays more music.  The F1 would sound lean on source material that was lean.  The F2 will fill in lean recordings, adding body and weight to the music.  In my collection this usually occurred on CD's, not vinyl or SACD. If you can listen to and enjoy more music on an amp it is a winner.  This amp is a real winner.

They will produce 2.5 watts into 16 ohms, causing them to clip when driving 16 ohm drivers at increased volume levels.   With 98db/watt speakers you have to be cranking, but some music just requires cranking.  First Watt  will be coming out with an F3 designed for high impedance speakers in the near future.

Nitty gritty stuff:  Unbalanced RCA inputs only.  Standard binding post for output.  120V standard, I understand they can be built for 220V if requested. Pure class A, it runs hot.  Leave room for cooling.  Sounds good after a 5 minute warm-up, slightly better after a half hour. It does not require a power source cleaner in my area, yours may vary.  There is a slight smell during the first week that you play it - it is there only to scare you.

In summary,  with Lowthers, you need to hear one of these.  Cost is reasonable, quality is great.  Call in advance if you wish to listen to mine - I am just outside of Chicago.