When you first unpack the Blackbird, the key components are the arm-wand and the mounting pillar. These arrive separately and are connected together by pushing a small toggle on the end of each filament through a corresponding hole in either outer edge on the front face of the counter-weight box. For all those brought up on gimbal bearings and ABEC ratings, it might seem a bit Heath-Robinson, but it is (just like the rest of the arm) a simple, elegant and effective solution. Because the filaments attach to the outer edges of the counterweight box, the base of the triangle is around 5cms across. The two filaments pass through a narrow pipe at the top of the mounting pillar and each wrapped around an allen bolt. Turning those bolts allows incredibly precise adjustment of each filament individually, giving the user direct control of the arm-wand’s ride height and azimuth. In addition to the slots in the end of the arm-tube, overhang/effective length can also be fine-tuned by adjusting (screwing or unscrewing) the horizontal setting of the pivot-point, with an equivalent adjustment of the filament pipe.
Tracking force is set using a flat weight that attaches magnetically to the underside of the counterweight box. Three different weights are supplied, which can be used in combination if required: Adjustment is made by sliding the weight towards or away from the bearing, the magnetic fixing making smooth increments easy to achieve, although once again, there is no scale. Supatrac provide a simple see-saw balance to set VTF although I can’t comment on its effectiveness as I used my standard electronic stylus balance.
Bias is set using a falling weight system, a thread joined to the inner bearing filament activating a balance beam with a grub screw mounted in the far end. Once again, the absence of calibration means that you’ll be setting bias by ear – which is the only way to get it spot on. The balance beam’s travel (and weight) can be adjusted if necessary, to ensure that it delivers sufficient side force and is engaged when the arm is aligned with the lead in groove, but this involves threading the link through holes in the beam and tying it off: somebody used to sewing (or at least, someone with smaller fingers than me) might be a useful accomplice… Thankful this should only be necessary in the most extreme situations/cartridge pairings.
Which brings us at last, to the vexed question of VTA. No clever solutions here I’m afraid. The Blackbird uses the standard post and collar arrangement so beloved of UK tonearm builders. In this case, the post is a relatively loose fit, clamped at the desired height by a large diameter allen bolt with a nylon tip. Even so, DO NOT over-tighten the bolt! Doing so will risk scarring the aluminium surface of the mounting pillar and make fine adjustment all but impossible. Coming up with a way of fine-tuning VTA, preferably on the fly, would be a smart move. That oversight is down in part to the arm’s cultural background: bouncy decks like the LP12 (that still dominates the UK market) really don’t lend themselves to adjusting VTA in-play. Even so, adjusting the Blackbird’s VTA is worthy of considerable care. Loosen the set-screw and the arm pillar simply plummets through the mounting collar, so it’s important to fix (or adjust) the height with one hand while operating the set-screw with the other. Speaking to SupaTrac about this they acknowledge the issue and are already working on a simple solution (I’ve seen the Solidworks renderings), a threaded post that sits on the mounting collar, similar to the Alphason or Thales arrangements. That’s going to improve things dramatically, but I’d still dearly love to see an on the fly adjustment option for VTA applied to the Blackbird. Those who don’t want or feel the need for it can stick with the standard arrangement, but offering it as an effective option would elevate the Blackbird’s performance and increase its appeal and range of application significantly.
