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Turntable Loudspeaker TubeONE Tracking Error Compensator
I built this Connoiseur BD1 turntable sometime in the 70's. It features an Audio Technica AT1005 arm, ADC magnesium headshell, Ortofon VMS30E cartridge, Microsorber feet and a Goldring Lenco lid. The sound was, and still is pretty good which is why parts of the combination are likely to form the basis of a complete new build.
(2013) The arm has now moved to another project where it serves as a second arm on a modified Dual CS505 chassis. The Dual arm is fairly limited in the cartridges it will take, the AT arm allows a greater range of cartridges to be used. In addition, the Dual arm allows semi auto operation. The chassis is used "floating" when using the attached Dual arm and clamped down, using the three knobs, when using the AT arm. This is because the AT arm is not attached to the floating chassis.
(2014) The turntable has now been installed in my media cabinet and it has gained an onboard pre amp/USB A to D Converter for converting vinyl to digital. The second arm is used for this, the setup being chosen as the second arm is better at tracking some older vinyl that has had a busy life.
A bit of a concept here. How to design a loudspeaker system where the drive units are mounted rigidly, front and rear radiations are isolated, there is no cabinet loading to reduce efficiency, there are no hard cabinet surfaces to cause reflections and no cabinet to store and release energy. Impossible? Well here is my solution. Has it been done already? I don't know. Does it work? In some areas yes. However, a lot of development would need to be done to worry the establishment.
I call this amplifier design tubeONE, not because it is a valve amp but because of its tubular design. The amp features on/off, volume and input selector controls arranged as three rings along the amp body and LED’s in the rings show power on and control position. The ends of the amp feature fluted heat sinks for the power transistors and the amp sits on two white marble cradles.
Tracking Error Compensator (1991):
A conventional turntable arm suffers from angular tracking errors between the stylus and the record groove. This is because the original cutting lathe cuts the groove following a straight line from the outside of the disk to the middle. The stylus in a conventional tonearm follows a curved path over the disk surface. This gives rise to tracking errors and thus distortion. The tracking error is normally zero at just two points on the arms path over the record surface and a graph of position on record surface against tracking error would look very similar to the figure below.
If you set the stylus down somewhere on a stationary disk surface, you could, if you were able, move the arm pivot point and adjust the tracking error at that point to zero. This is obviously impractical while playing a record, especially as the error changes as the record plays. What my compensator aims to do is to constantly adjust the arm pivot point to maintain tracking error close to zero. Basically the compensator consists of a sliding arm mount which is constantly adjusted during playback by a motorised cam. Cam profiles would be matched to arm parameters. Playing time is adjustable up to about 1 hour. Parallel tracking arms aim to eliminate tracking error also, but this system can be used with conventional arms.
Like so many of my other projects, a “work in progress” with “development needed”. Hopefully the rough prototype below gets the idea across though. A bit hi fi fringe I know but anyone still doing vinyl is considered a bit fringe anyway.
Further to the above, I have been thinking about the possibilty that a Technics type servo controlled system could be used for a conventional arm. This system was used by Technics on its parallel trackers of the early 1980's and reduced tracking error by driving the arm, and thus the stylus, across the disk on the same path that the cutting lathe would have taken. Arm misalignment was measured using an optical detector and this signal was used to drive a motor which moved the whole arm assembly across the record.
The big problem with a conventional tonearm is how to detect the arm misalignment without having to fit any measurement hardware to the arm. The front runner for this would appear to be some sort of optical system which would use a small piece of a reflective medium stuck onto the arm bearing housing which would reflect a light beam back onto a reflector.
Just an idea but, perhaps in the future, if I can source a suitable "spares or repair" Technics Linear Tracker, it might be an interesting project. For now it will have to remain just an idea....