The first arm that the G. F. C. Hadcock company delivered was the Unipoise that was originally introduced in the latter half of the 60's and was a fairly simple Unipivot arm that got somewhat mixed reviews initially due to its basic build, somewhat varying construction quality and looks that where a bit DIY, but sold reasonably especially in the UK and the USA since it was fairly inexpensive and mated well with moving magnet pickups and low mass moving iron designs but at the time there were a few quality arms around that mated with MM’s and those who did like the KMAL Laboratory Arm had a tendency to be a lot more expensive than the Unipoise. It also went through a number of revisions each year, Unipoise was on “type III” (Mk3) by 1969, but that is a characteristic of all of the Hadcock products, at one point in time there were almost monthly updates to some arms, so much so that by the early 70’s the company stopped marking individual improvements unless there was a major design change.
The "garden shed" looks of the Unipose are no joke, we have seen a number of people claiming to have owned a Unipose "prototype", what they actually own is an early model of the arm that looks like a prototype but is a retail product ... It went through a number of revisions in the early 70’s, noticeably a fairly big changes came in 1971 and again in 72 and it gained a reputation of working well with the old MI Decca pickups pickups that were considered at the time to be good sounding but difficult to mate with quality arms. Note that the Unipoise does not have an armlift, but the company made and sold generic armlifts at this time.
Unipoise, BTW is an alternative name for an unipivot and was used by other companies, Pickering used it for all their unipivot arms until the 1980's (while Stanton used unipivot for the same arms released under their name), also earlier models of Hadcock tonearms interestingly enough appear to be more plentiful on the USA second hand market than in the UK, for whatever reason. The Unipoise was replaced with the Super Unipoise at the turn of 1975/6 and although it looks quite similar due to the one piece arm and headshell the Super is a redesigned version that shared some parts and geometry with the GH 228 and is much better suited to very low-mass cartridges and thus had to be supplied with an complete with an extra counterweight specifically designed for the Decca London, original RRP for the Super was 32.50 UKP in early 1976 but like its predecessor it came without an arm lift and the optional Uni-Lift MkIII was 6.75 UKP.
Because of their similar looks and names the Super Unipoise and the original Unipoise are often confused but they differ significantly in build and specs, the Super appears to have been only on the market for a couple of years, it had disappeared by the turn of the decade. The classic arm from the company though is the GH 228 that seems to have been introduced in 1974 or thereabouts, it was an almost complete redesign from the Unipoise and shared little of the basic specifications and build with it although they are in many ways similar, the 228 being a 9" unipivot with optional silicone dampening and replaceable low mass armtubes, an aluminium alloy shell and armtube coming standard with the arm but a steel armtube being available as an option and is understood to have been a better match with moving coil pickups, the original 228 mates extremely well with low mass MM carts.
The 228 was updated in 1976 with the GH 228 Super that had lots of small improvements, the headshell had now become detachable, the internal wiring was improved but the high capacitance of the original wiring had been complained about and in general it is recommended that any pre-Export tonearm from the company is re-wired but even the high end arms of the 80’s had cable capacitance of 120pF which is considered much too high in modern systems especially with low output pickups and the 70’s arms could get higher than 400pF, note though that the early 228 arms only had 3 internal wires, the 2 earth wires were combined to reduce twisting torque, you can find a review of the 228 Super model from Gramophone here.
The GH 228E version was introduced in early 1980 and featured various small improvement including Litz internal wire, an arm lift was now built into the arm and the counterweights better decoupled from the working part of the arm, it also seems that it was an upgrade option with a plain 228 and a 228E being sold concurrently at the least for a while and the plain of the period being similar to a 228 Super of a few years earlier in specification but I have not been able to nail that down, a review of the GH 228E version from 1981 is available online from Gramophone Magazine, overall very favourable too.
Some early variants of the 228 have a secondary sleeve that can be used to change the effective mass of the arm, but we have not been able to ascertain which models exactly, this feature is certainly gone by the time the Export model is released. Also early Hadcock models came with steel cinch plugs but around 80 the company started shipping gold plated ones. In the 80’s the company sold complete top-assemblies of the 228 arm for those that liked to play around with different pickups, the assembly simply lifted off its base complete with counterweights, these usually sold for half the price of a new arm or in the case of the Export and later around 70% of the price of a new arm, also note that the company stopped calling the arm optionally damped somewhere along the way, so use of the silicone damping fluid was now considered de-rigueur, in practice they always were, they will work without fluid but mis-tracking will cause a jump.
The 228 arm was redesigned again in 1982 and renamed GH 228 Export and it is that model that has been the basis of all the more recent arms from the company and its successors, it was noticeably simplified in parts which made setup easier and got a price reduction of over 20% along the way, the price reduction effectively made the 228 Export the entry level arm in the Hadcock line-up.
In response to the increased popularity of moving coil pick-up designs amongst the hi-fi fraternity in the late 70’s the company in 1981 introduced a standard gimballed 4 bearing design called GH 220 that was at that time about 5% more expensive than the GH 228 and was never as successful as the latter sales wise and got rather mixed reviews or in some publications was simply not reviewed, however a number of hi-fi magazines, notably Hi-Fi Choice, deemed the GH 200 arm to be both an excellent arm and good value moneywise, in fact considered it much better than the 228 and stated that the only reason that it was not given a full recommendation by them was that it like other Hadcock arms suffered from somewhat crude finishing that had no place on an arm that retailed at over 100 pounds.
Although the working part of the GH 220 is for obvious reasons considerably different to the GH 228 it nonetheless shares a number of design features and parts with the latter arm, the basic geometry, size and effective length of the 2 arms are the same so the same protractor can be used, so if you have an armboard for either they will simply slot in. Also the armtubes are the same, the difference being that the 220 came with a steel armtube as standard and an aluminium one as an option while it was the other way around on the 228 and the 220 had a silicone damped armtube which was not all that common at the time for gimballed arms.Spares & service : Even though the GH 228 arm has changed considerably since it was originally introduced some 40 years ago there is still quite a lot of commonality amongst parts especially with the post 1982 export versions and the Hadcock company should be able to help you with spares, in other cases the differences between versions are so small that a modern part may be used with a little bit of modification. The GH 220 is more problematic but some parts like armtubes and are interchangeable with the 228 and thus can still be had, the bearings in the 220 are standard commercial bearings and should be available from any good engineering stockist or catalogue retailer, do not be tempted to upgrade the bearings with better specified ones, the 220 is specifically engineered to use the bearings that came with it, better specs will almost certainly mean a worse sound.
Hadcock Unipoise Type III technical specifications
Hadcock Super Unipoise technical specifications
Hadcock GH 220 & Sound Tracer technical specifications
Hadcock GH 228 technical specifications
Hadcock GH 242 technical specifications