In December 2004, UK distributor HiAudio sent me a sample of Graham Slee’s Solo headphone amplifier for review in Hi-Fi News. The copy I submitted to Steve Harris coincided with his replacement as editor by Steve Fairclough – after several reminders it became apparent to me that he had no intention of publishing the piece, although in November 2005 the Slee Era Gold phono stage won a category award in the magazine and in the following year’s awards issue, in combination with the Elevator EXP it was also ‘highly recommended’..
Howard has very generously allowed me to log an updated text on his website, for anyone who for whatever reason prefers a moving coil headphone to the Stax electrostatics!
Andrew Harrison’s November 2004 Hi-Fi News review of the GSP wideband cartridge pre-amplifier system, the Era Gold V and Elevator EXP, suggested that audio designer Graham Slee was capable of something rather special. And there is plenty of appreciative comment on his products to be found on the internet. I was delighted, then, to receive that Christmas his Solo Monitor Class headphone amplifier and it was put into almost every day use for many subsequent months.
I rather enjoy headphone listening (though not closed-back moving coils!) and the ones I use, the BeyerDynamic 990PROs, are a good tonal match with my main speakers, the original Quads. I have also seen these in studio use, for master tape monitoring. Sadly, this model is no longer imported and none of the company’s domestic-range alternatives are as good, in my view.
The Solo is available with a more basic wall-plug power supply module, the Solo Intro, at £333.49, or (as tested) supplied with the high grade PSU1 at a total of £480.00. This has a 1.5m captive DC lead with figure-of-eight termination. Uncommonly, the unit runs virtually silently.
Housed within a 107 x 164 x 45mm simple clamshell casing, the Solo is a Class A device based on theAD823AN op-amp. The circuit layout is minimalist. Slee’s current drive output is designed to produce the same power irrespective of headphone impedance., It is suited to a 20-600 ohm headphone impedance range and may be switched between two inputs – the fascia toggle also has a centre mute position.
Rear connections are via gold plated phonos (inputs are specified at 30kOhm impedance/325mV sensitivity); there is no facility for source signal out to the main amplifier/room speakers and you can only have one headphone connected (Jalco socket diameter 6.5mm). The casework has a silver anodised, sheeny finish which, if necessary, can be wiped with damp kitchen paper to remove any finger marks.
The Solo is equally suited to direct CD replay or low level sources and the ALPS volume control has a fine, smooth travel allowing tiny changes – just as well, given the wide range at which CDs seem to be mastered nowadays.
For best results, the Solo should be powered at all times (it has no on/off switch). From new, and with repeat play for a couple of days, my unit clearly improved further over a fortnight’s or more use. Indeed, even when left connected on standby I find it sounds best after around 20 minutes’ continuous listening.
This is certainly the most revealing device of its kind I have heard, apart from DNM’s new 3D pre-amp at fifteen times the cost! Its timing is excellent, whilst instrument locations within the soundstage are held in sharp focus at all dynamic levels. The Solo is particularly well defined in the lower registers – during a Bartók piano concerto recording on DG one loud bass drum entry literally startled me! The lack of coloration meant that cable or input differences (e.g. those between my Meridian 508-18 and -24bit players) were easily identifiable. The case underside is fitted with four small pliable hemispherical feet; I did not find that accessory feet or any special isolation platforms significantly enhanced the performance.
I tried various other BeyerDynamic models and the well regarded Sennheiser HD650 (which I wrote about in HFN Sept 2004): their sonic characteristics were always evident and subjective rankings remained constant, although with perhaps greater appreciation of their musical capabilities. I also enjoyed comparing CD and LP transfers of the same recordings at matched levels (by setting the pickup output gain from my main pre-amplifier and taking the signal to the alternative Solo input) and start-points – analogue was invariably preferred!
With the caveat that you might find the Solo almost too revealing (e.g., of close microphone setup, etc), a true audiophile product. My only reservation is that the green fascia LED is rather too bright!
See also: www.gspaudio.co.uk.