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Rega subplatter discussion-

xyyyy

xyyyy

pfm Member
On a U.S. audio forum, I recently posted the following in response to several posts stating the dramatic differences obtained from using of an aftermarket machined subplatter for the P3, P3-24 and P5 turntables.

"From reading some of these posts, one might be lead to believe that a subplatter upgrade on a Rega P3 or P3-24 is a must. I don't believe it is for the following reason: the stock phenolic resin sub platter's rigidity and low mass is well matched to the P3's glass platter, just as the machined aluminum Rega version is matched to their ceramic platters."

In reply, a well respected and influential forum member noted that the stock Rega subplatter was severely out of round in camparison to ____ subplatter.

Is this statement accurate? Despite compromises due to price points, I find it hard to believe that Gandy and Bateman would produce an out of round subplatter, if it impacted sonics.
 
It's true, it is out of round - whether or not it is severely out of round is a matter of interpretation. The Rega sub-platter is injection moulded and whilst this is reasonably accurate it would be more concentric if it were to be post machined (and more expensive).

I’m not sure how you conclude that the stock sub-platters “rigidity and low mass” are well matched to the glass platter (a reasonably high mass component); I’m not saying they are poorly matched, but in all honesty I wouldn’t say there is any real evidence either way.
 
I would not say it was a must, well not untill you have tried a groovetracer sub platter. The 'plastic' sub platter on my P25 was good, but it was shown to be not good enough when I fitted the groovetracer.
 
I can't speak for all Rega sub-platters, but when I had mine measured, on a big ass precision lathe using the short stub of the shaft under the cap as the mounting, it was shown to be both high and low.

Mine was measured as .04mm+ .02mm- .02mm+ and .02mm-, that's a significant variance. I'm guessing it's down to how fast/slow they cool in the mould tool.

Either way it was post machined down to the nearest 1/100th and sounded all the more even for it. Having the sub-platter machined was as large a jump as adding the Rega TT-psu.

The only way you can know for sure is be having it measured..
 
xyyyy said:
Is this statement accurate? Despite compromises due to price points, I find it On a U.S. audio forum, I recently posted the following in response to several posts stating the dramatic differences obtained from using of an aftermarket machined subplatter for the P3, P3-24 and P5 turntables.

"From reading some of these posts, one might be lead to believe that a subplatter upgrade on a Rega P3 or P3-24 is a must. I don't believe it is for the following reason: the stock phenolic resin sub platter's rigidity and low mass is well matched to the P3's glass platter, just as the machined aluminum Rega version is matched to their ceramic platters."

In reply, a well respected and influential forum member noted that the stock Rega subplatter was severely out of round in camparison to ____ subplatter.

hard to believe that Gandy and Bateman would produce an out of round subplatter, if it impacted sonics.
Click to expand...

The stock phenolic resin subplatter does indeed have a rigid support structure but the resin shrinks unequally (during manufacture) between these webbed support structures so you end up with an out of round circumference, or runout.

If you were able to rotate the subplatter about the shafts center of rotation and run a dial indicator on the circumference of the subplatter, you would find the indicator jumping all over the place.

You could actually place the indicator on the subplatter as it is running on the turntable. I have done this myself on several occassions and the best I could measure (on 6 samples) was runout of 0.2mm but keep in mind that the surface the belt rides on has both rise and fall. It is not a standard progressive runout feature on this phenolic resin structure.
I have a half dozen stock units in my shop. Whether this is important to you or not is your choice, but the fact remains that you will not achieve anything close to perfect pitch with the stock unit, not going to happen.
 
I've never been impressed with Rega build qual. My Rega deck wasn't even level, prob because when they drilled the hole there was some debris under the plinth and the op couldn't be bothered to sweep it clean each pass. Bloody precision engineering? Right.
 
It is'nt just the area the belt rides on, which actually is pretty concentric for something that is molded, not machined, it's also the little piece that the platter hole fits on and the spindle- this is a bigger culprit IMO because it makes the platter and record rotation off. This has the biggest variation of the many Rega subplatters I've seen, ranging from fairy well centered to hugely off. If your platter is rotating steady in both planes you got a good one. Some replace the sub platter and other parts, some just go up the Rega line, some buy another brand. The build quality and QC on the 3 series in particular is not what it used to be.
 
My subplatter replacement was machined better, which I guess you would expect given the price.

But the bearing was noticeably better. The standard glass platter would spin so freely compared to the original.

It is inevitable Rega have to employ value engineering on all but their high end products. Perhaps a phenolic resin represents a decent compromise at the right price on a mid-budget deck ?
 
stevec67 said:
I've never been impressed with Rega build qual. My Rega deck wasn't even level, prob because when they drilled the hole there was some debris under the plinth and the op couldn't be bothered to sweep it clean each pass. Bloody precision engineering? Right.
Click to expand...

That's a pretty serious fault for a TT so i hope you returned it for a replacement.

I've had a Planar2, two Planar 3s and a P9.
Nothing obviously amiss. Not built to SME precision fit and finish but then they cost a lot less.

Mass producing a £300-£500 TT (including arm) is clearly going to involve some hard decisions on where to focus the costly high precision parts of the build. No different to any other company in that regard.

I suppose Rega could employ an army of Chinese workers on subsidence pay and whip them until they deliver perfection.

Frank_S said:
I have a half dozen stock units in my shop. Whether this is important to you or not is your choice, but the fact remains that you will not achieve anything close to perfect pitch with the stock unit, not going to happen.
Click to expand...

Nevertheless the crunch measurement has to be with platter in place and the stylus playing the disc. Just as PSU related noise doesn't always make it through to the end of a circuit, so small speed errors need to be examined at the end of the mechanical chain - the stylus tip.

The only way to ensure perfect pitch is to use perfectly flat, concentric records, on perfect turntables using cartridges with zero compliance :)


kabayiri said:
It is inevitable Rega have to employ value engineering on all but their high end products. Perhaps a phenolic resin represents a decent compromise at the right price on a mid-budget deck ?
Click to expand...

Yes it likely does.
Remember that for years the Rega Planar 3 along with a certain other belt drive TT was regarded as sounding superior to most rivals at their respective price point in the area of PRaT.
Therefore probably not quite the issue a raw measurement of an unloaded sub platter might indicate.
 
I worked in a value engineering subteam on a commercial product some time back. (Not hifi but still relatively mass market).

I remember long hard discussions on things where the superior item cost mere pennies more than the cheaper item. Even so, the decision was often made to go with cheaper to hit the price target. Small amounts at production and build stage can add up to much bigger differences at retail.

I read an article once which portrayed Roy Gandy as someone who focussed on manufacturing just as much as product design and development. They must be doing something right, to still be in business decades after they started.
 
kabayiri said:
I worked in a value engineering subteam on a commercial product some time back. (Not hifi but still relatively mass market).

I remember long hard discussions on things where the superior item cost mere pennies more than the cheaper item. Even so, the decision was often made to go with cheaper to hit the price target. Small amounts at production and build stage can add up to much bigger differences at retail.

I read an article once which portrayed Roy Gandy as someone who focussed on manufacturing just as much as product design and development. They must be doing something right, to still be in business decades after they started.
Click to expand...

The June 2013 Stereophile magazine has a nice interview of Roy Gandy where he discusses turntable design. Quite interesting!
 
I feel there needs to be more quality control on the subplatter as in my experience there are a few that are well off spec and appear warped you only need to spin the glass platter on the offenders to see this .I had one replaced and the 2nd was totally fine a couple of friends also had a similar problem ,both quickly sorted by their dealers and we are all pleased with our regas but shame it happened in the first place !
 
Frank_S said:
If you were able to rotate the subplatter about the shafts center of rotation and run a dial indicator on the circumference of the subplatter, you would find the indicator jumping all over the place.
Click to expand...

I've done this using my thumbnail as a makeshift substitute for the dial indicator, and it did seem uneven.
 
I skimmed the sub-platter on my old P5, it made a big difference to speed stability. I'm not sure what other sub-platters are like but mine had two symmetrical high and low points and it was out at these points by nearly 2/10mm, (so .4mm overall deviation). it might not sound like much, but the difference was most apparent.
 
I have nothing to add, but would like to say this is the most reasonable discussion I've ever read about Rega sublatters. Kudos.
 
I bet they could improve them if they just reduced the cycling time on the injection molded.
 
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