Reed 5T Opinions

The 5a is based on a design like the Thales arm and so it has additional pivots to locate the arm.  That is not the case with the 5T.  With the 5T the arm’s motion is only restricted by conventional pivots.  When the arm is slightly out of tangent, a laser beam and sensor detects this condition and a servo motor slowly rotates base that the arm is on to reestablish proper geometry.  Other designs have used optical sensors and servos (like the B&O Beogram 4000), but, the slow rotation of the arm base is supposedly smoother and less likely to cause vibration.

bobbydd,

Thank you for this information.  The 5-T is basically a conventional arm located on a rotating base that allows for near perfect tangency and eliminates the offset angle which means no skating force.  It is good to know that the basic design of the arm is good.  

I saw the 5T at a show.  The base looks like it is too large for my Basis Debut.  What a relief, I won’t be tempted.  It is a thing of beauty, and the engineering appears to account for and mitigate all of the shortcomings of linear tracking design (except cost).  It works on the same principle as the Shroeder LT arm, except the rotating base is powered by a motor controlled by a laser sensor whereas the LT base moves from the drag of the stylus playing the groove and is controlled by magnets.  I wonder how these two arms compare in performance.

The Wallytools person I spoke to at a show said thar the $1250 microscope is used primarily to set VTA/SRA but that it is not useful for reading zenith. For that, you send your cartridge to them and they use an ultra expensive microscope and give you the zenith correction which you can make with another tool of theirs.  The representative said that none of the big makers of styli currently do a good job of accurately mounting styli as far as zenith is concerned, but they have said that they will look into this now that they have been shown data on this issue.  

I think you could do zenith with a regular USB by first aligning the cantilever horizontally or vertically in the field of view, and then changing the focus to look for the contact edge.  It would be even easier if the USB is capable of taking multiple images at different focal points and then integrating the images to get something that has a good depth of field, but, those scopes are about $1500 or more.  If you know the alignment of the cantilever, even if you cannot see it, you can see the stylus orientation and that would give you some idea about the zenith error.  I am sure an even fancier scope, would make this easier.

I sort of prefer not really knowing all of these things.  While I have a Fozgometer, I don't really use it that much.  I prefer to align the stylus visually to be perpendicular to the record surface.  If this is not electrically ideal with regard to crosstalk, I still rather do my records the kindness of having the stylus fit the groove properly.  VTA/SRA I set by leveling the cartridge and then listening to changes in the angle to find the right spot.  Basic alignment I do with a Smartractor.  This is more or less good enough for me.  I think record playing is robust enough to survive even rough alignment.

lewn,

True, even with perfect zenith alignment, only at the null point would the contact area of the cartridge along the line of tangency.  But, the maximum error at other points will still be relatively small, whereas, zenith error in manufacturer is much higher, typically, according to the Wallytools people, plus or minus five degrees.  Still, I am not inclined to open that can of worms with my setup.

mijostyn,

The dramatic difference in the inertial mass of air-bearing arms in the horizontal and vertical planes may be a problem or it may be a benefit.  There are some arms, like the Morch Anisotropic arm, that deliberately increases the horizontal mass by using outrigger weights on the vertical axis (to reduce impact on vertical mass) so that the arm resists swinging side to side when large horizontal groove movements (i.e., monophonic bass waves) are presented.  This preserves such bass information (a lot of deep bass is recorded monophonically (side to side movement) in order to reduce big changes in depth of the groove that stereophonic  recording would entail),  I've heard that arm and it DOES have impressive bass response.  Likewise, I've heard impressive bass response from air-bearing arms, like the ET-2, and the high horizontal effective mass might be the reason.  But, I do worry about whether such arms put a lot of strain on the cantilever when it has to drag the whole setup across the record--not only is the mass high, the lack of mechanical advantage of a pivot means a lot of force is needed to drag that arm linearly.  This high sideways resistance to movement also makes we wonder if that means the cantilever is never tangent to the groove.  Still, I've heard nice sound from all types of arms, so I don't know if any are inherently superior.