Oxford Crystal Reference restoration

[peter]

Neil,

I know, I really liked my Oracle Alexandria too, one of the best audio buying decisions I ever made after my first bit of hi-fi (which was a PL12D).

I don't rate the experience a disaster at all! At the time it was a real opportunity to aquire some serious high end gear at cost price. I also always assumed that the hassle came with the territory, a bit like sports cars?

Never experienced such customer service before or since, which was nice.

The Air-Tangent has been squashed by a flying van propelled Oracle Delphi and rebuilt. It is cosmetically fine, albeit dusty. Not sure if it works yet. I have all the accessories. It would be fitting for it to adorn another Delphi.

I might consider exchanging it for an SME V, if you happen to have a spare one.



Seriously though, I need it to get the turntable to work, a tonearm exchange would be the only option for me.

[Snoopdog]

Found some more pics from my archives.

This shows the top of the 45kg sand-filled plinth/stand which sits on 4 x adjustable spikes for levelling. The void beneath the top plate houses the turntable power supply which is connected to the motor/speed switch via a DIn socket on the rear.



Next up, the top steel plate in position with the three sorbothane suspension housings which have inset threads and bolts to engage and support the three downward pointing spikes on the sub-chassis.



The top plinth with motor housing and speed switch is then bolted to the steel plate. Three holes allow the spikes on the sub-chassis to engage with the adjustable bolts on the suspension housings.



Views of the MDF/steel sub-chassis showing the inverted bearing housing and the underneath with the protruding spikes.




The component parts.



The assembled product playing a record (the 15kg phosphur bronze two-piece platter and weight buffs up nicely with some Solvol Autosol).

[Spectral Morn]

Neil,

I know, I really liked my Oracle Alexandria too, one of the best audio buying decisions I ever made after my first bit of hi-fi (which was a PL12D).

I don't rate the experience a disaster at all! At the time it was a real opportunity to aquire some serious high end gear at cost price. I also always assumed that the hassle came with the territory, a bit like sports cars?

Never experienced such customer service before or since, which was nice.

The Air-Tangent has been squashed by a flying van propelled Oracle Delphi and rebuilt. It is cosmetically fine, albeit dusty. Not sure if it works yet. I have all the accessories. It would be fitting for it to adorn another Delphi.

I might consider exchanging it for an SME V, if you happen to have a spare one.



Seriously though, I need it to get the turntable to work, a tonearm exchange would be the only option for me.

Hi Peter

Only arm I have sort of spare is a Graham 2.2 with spare ceramic arm wand.

Its on my Oracle at the moment as my SME 5 will be going onto a Technics 1200 as part of a wee experiment to see if the Technics is as good as many folks round here think. So far just with the standard arm it is showing huge bags of potential. What it will be like with a SME 5 on it I will just have to try to see.

I wonder what an Airtangent would be like on a Technics 1200 ?


Regards D S D L

[peter]

Steve,

Ah, you have a proper lid on yours, the one they made for me really lets the side down IMHO. I'd rather have an effective lid than a M.C. preamp frankly. Also a box or way of transporting it would have been good idea. You'd think this would be a prerequisite for dealers. They did seem to have an odd sense of priorities, but thoroughly decent fellows, absolutely.

I very much look forward to studying your setup docs and see if I can get this one going again. And some nice progress pics for this gallery, of course.

peter

[Snoopdog]

My Crystal Reference was serial number CR-052 and came with two packing boxes, one for the plinth/stand and the other for the platter and sub-chassis. I always keep all boxes (something I was advised to do many years ago) and was able to pack it securely when I sold it.

I never opted for the Oxford lid which was an odd-looking open plan acrylic design.

The one in the picture I bought from a firm on Ebay who manufactured to the customer's specific dimensions.

Your'e right about Jon and Fraser being decent guys. Jon even made the journey down to Basingstoke when I moved house in early 1989 to help me unpack and set up the turntable in it's new location.

I think that using three Stillpoints as the 'suspension' medium with their mini inverse risers on adjustable threaded rods replacing the spikes in the sub-chassis is worth exploring.

http://stillpoints.us/Stillpoints/applications.html

[peter]

Neil,

Of course the AT might be available for loan in the interests of such research.

To adress an earlier question. According to the mounting instructions you need to drill two 10mm holes through the mount of the TT spaced at 41mm apart. (the second hole is for the wires and airtube) the arm has spikes that keep it in place on the armboard even though it has only one mount hole.

The distance of the mount hole from the spindle varies such that the arm is neatly perpendicular to the edges of the TT, I think that you can use an existing hole if you are prepared to have the arm at a radical angle to the edges, and in some cases on smaller units you have no choice IIRC.

peter.

[Spectral Morn]

Neil,

Of course the AT might be available for loan in the interests of such research.

To adress an earlier question. According to the mounting instructions you need to drill two 10mm holes through the mount of the TT spaced at 41mm apart. (the second hole is for the wires and airtube) the arm has spikes that keep it in place on the armboard even though it has only one mount hole.

The distance of the mount hole from the spindle varies such that the arm is neatly perpendicular to the edges of the TT, I think that you can use an existing hole if you are prepared to have the arm at a radical angle to the edges, and in some cases on smaller units you have no choice IIRC.

peter.

That is a very kind offer that I may well take you up on.

Thank you

Regards D S D L

[Snoopdog]

Neil,

Of course the AT might be available for loan in the interests of such research.

To adress an earlier question. According to the mounting instructions you need to drill two 10mm holes through the mount of the TT spaced at 41mm apart. (the second hole is for the wires and airtube) the arm has spikes that keep it in place on the armboard even though it has only one mount hole.

The distance of the mount hole from the spindle varies such that the arm is neatly perpendicular to the edges of the TT, I think that you can use an existing hole if you are prepared to have the arm at a radical angle to the edges, and in some cases on smaller units you have no choice IIRC.

peter.

Peter

As your picture shows, a nice touch by Oxford Acoustics was to mount a bespoke control switch on the front right hand side of the deck for the Air Tangent arm.

As to your reference about the 'gap' between phosphur bronze platter and bearing housing, it was my understanding that this was intentional and part of the design in avoiding transmission of vibration from the bearing to the platter. I know Jon always was very careful to align the reference markings on the top of the bearing and inside the hole in the platter and then lower the assembly carefully so that the slight gap was equal around the seated bearing housing. Another design consideration in reducing vibration transmission to the record/stylus was the detachable phosphur bronze spindle with sorbothane film contacting the bearing housing.

[peter]

Actually the gap I was referring to was between the platters, we are talking about a cigarette paper passing freely. A Tesco till receipt will go with a little encouragement. The first top platter resulted in a platter/platter gap that would acommodate 3 sheets of photocopy paper at some points before I complained.

I now hazily recall the bronze platter gap. I think I once saw Jon turn the bronze platter over the bearing until it hit a pin of some kind, but I don't see any pin in your pics.

To be clear, there is no gap and no play between the acrylic platter and the bearing housing on my unit.

So, did your turntable wobble at all?

The arm switch was a very good idea that sadly wasn't supported on the Mk1 AT. The arm lift is particularly frightning on a large TT when you can't rest your hand on anything and the lift arm is as rigid as a length of spagetti. takes a while to find the right action.

[Snoopdog]

The junction between the two part phosphur bronze and acrylic platters on my Oxford deck were closely coupled and no gap of the kind you describe existed. My platter did not wobble at all and speed stability was exemplary.

athe idea behind the two part platter and record weight was down to impedance matching of the materials. Oxford Acoustics argument was that acrylic was a better impedance match for the vinyl LP and so this material comprised the top of the platter and the corresponding bottom of the applied record weight. The phosphur bronze provided mass to create a flywheel effect for speed stability.

As I recall, the gap between phosphur bronze sub-platter and bearing housing was intentional and when fitting, two reference lines in pencil were aligned. There was no 'pin' of any kind on my turntable.

The acrylic platter was a close fit to the bearing housing and there was no intention to create a gap at this point.

I have given some thought to your wobbling issue and suggest that the inverted bearing be examined.

When the outer housing is removed (lift off carefully) it will reveal a lubricated stem which has tiny ball bearing sitting in a recess at the top. It is very easy to dislodge the ball bearing during disassembly so it is worth checking that this is still in place.

The ball bearing contacts a PTFE thrust pad located inside the inverted bearing housing. Again, it is worth checking to see if this is seated correctly and not worn.

I discovered during routine maintenance and refurbishment of the oil (I used a good oil of the correct consistancy obtained from Audio Origami) that the bearing housing can be pivotted slightly but when the mass of the platter is applied, the bearing is centered and sits straight without any lateral movement.

If you require a new drive cord, the one supplied by Mitchell for the Gyrodeck was recommended by Oxford Acoustics.