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Old 14th January 2013, 03:08 AM   #31
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Quote:
Originally Posted by MrPig View Post
That's a popular misconception. The RB300 has two bearings, just like the RB250, and the bearing spindle is supported at both sides, just like the RB250. It's just that the dial-side bearing support is removable on the RB300.
I should have said that on the RB300 the vertical bearings are only supported on one side of the arm, and supported by the spring assembly on the other, which is a lot sloppier than the RB250...The RB250 is a lot more stable and superior on that regard, as bearings on both sides are secured on each side.

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Originally Posted by MrPig View Post
Maybe, but why then would they use a configuration that was less stable and less effective on their more costly arms when they have a better option that costs less? How does that make sense?
So that they could add an extra feature ie: the spring loaded VTF adjustment assembly (which 'rings like a bell' and adds distortion). Its just adding 'bells (forgive the pun) and whistles', with no real practical value...for the discerning audiophile who uses more precise measuring instruments.

I still like the RB300 arm, and have one and use it (modified) and am quite happy with it, but on inspecting the RB250, I believe it will be even better just considering the greater bearing housing stability....
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Old 14th January 2013, 09:47 AM   #32
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Originally Posted by sq225917 View Post
Rega have used 24v (currently) and 120v motors. So make sure if considering a Geddon you use the correct transformer for your needs. Here's my LP motor Geddon used on my Kuzma.

Click the image to open in full size.
I could easily make the Norton AirPower with 2 x 60/80v transformers @ 500VA each, or the Geddon with 1 x 1000 VA tranformer with 55vx2 secondaries..., at a similar price-point...

Which would work best? would there be a major difference?

I was previously thinking of just getting some copper or nickel plaited braiding, and putting shielding on a power cord and shrink tube over that; and earthing it...at some stage. I wonder if that might create a 'good enough' improvement???

Last edited by TigerScent; 14th January 2013 at 09:56 AM.
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Old 14th January 2013, 05:18 PM   #33
MrPig is offline MrPig  United Kingdom
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Originally Posted by TigerScent View Post
I should have said that on the RB300 the vertical bearings are only supported on one side of the arm
No, they're not. The removable plate on the dial side of the bearing boss supports the bearing shaft, just like the fixed side supports the other. What do you think the big nut in the middle does? I'm not saying that it's structurally better than the RB250 but it's not significantly worse either.

Also consider that for a few quid extra, at used prices, you're also getting a stainless steel pillar (brass on the RB250), a stainless steel counter-weight stub (plastic on the RB250) and, if you buy an early one, a tungsten counterweight (mild steel on the RB250). Someone said the cable is better too but I don't know that it is.

Like I said, I've tried disabling the spring tracking force and balancing the arm statically. I can't hear any significant difference. In stock form the RB300 is a good bit better than the RB250. The arm accounted for most of the sonic difference between the Planar 2 and three. The only other difference between the two decks was a couple of millimetres extra thickness on the plinth!

So you buy your RB250 and you need to spend how much just to get it up to the spec of the RB300? Fair enough if you want to mod the arm anyway and yes, of course it will sound better than an RB300 once you've rewired it, fitted a new stub and counterweight, stripped the tube etc but so it should as it will also have cost you a lot more!

Quote:
I was previously thinking of just getting some copper or nickel plaited braiding, and putting shielding on a power cord and shrink tube over that; and earthing it...at some stage. I wonder if that might create a 'good enough' improvement???
Why would it? I'd be very surprised if it did anything at all.
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Old 14th January 2013, 08:24 PM   #34
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Originally Posted by MrPig View Post
No, they're not. The removable plate on the dial side of the bearing boss supports the bearing shaft, just like the fixed side supports the other. What do you think the big nut in the middle does? I'm not saying that it's structurally better than the RB250 but it's not significantly worse either.

Also consider that for a few quid extra, at used prices, you're also getting a stainless steel pillar (brass on the RB250), a stainless steel counter-weight stub (plastic on the RB250) and, if you buy an early one, a tungsten counterweight (mild steel on the RB250). Someone said the cable is better too but I don't know that it is.

Like I said, I've tried disabling the spring tracking force and balancing the arm statically. I can't hear any significant difference. In stock form the RB300 is a good bit better than the RB250. The arm accounted for most of the sonic difference between the Planar 2 and three. The only other difference between the two decks was a couple of millimetres extra thickness on the plinth!

So you buy your RB250 and you need to spend how much just to get it up to the spec of the RB300? Fair enough if you want to mod the arm anyway and yes, of course it will sound better than an RB300 once you've rewired it, fitted a new stub and counterweight, stripped the tube etc but so it should as it will also have cost you a lot more!
Well, I took the thing apart - so I know; and clearly it is only supported securely on one side. The spring-loaded side is not a secure support in comparison, but is surprisingly basic and and nowhere near as secure as the RB250..., however it is also a commonly known fact stated in a number of reputable sources ie:

"Unlike the RB250, the RB300's vertical bearings are supported on just one side of the bearing housing to make room for the VTF adjuster on the opposite side. External wiring is slightly higher quality than that on the RB250. Internal wiring is identical." A Guide to Rega Tonearms | From RB250 to Michell TecnoArms | Vinyl Engine

In addition, one needs to properly 'dampen' the spring to stop it from ringing..., for if one taps on the RB300 with the stub against ones ear, one can hear it 'ring'. Setting it to 3 is not enough and does not stop the ringing. All these mods add up and make towards a better sounding tonearm once done.

I pointed out in a previous post that the counterweight and wiring was better on the RB300, but once changed on the RB250, it was structurally superior and is most likely to have a better sound. In any case, I would advise changing the wiring on either arm, so its a moot point to the DIY'er. If dampening the arm, you need a heavier weight anyway to being it closer to the pivot point - which is advisable; and the Michell tecnoweight is a good option.

Last edited by TigerScent; 14th January 2013 at 08:38 PM.
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Old 14th January 2013, 08:58 PM   #35
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Originally Posted by MrPig View Post
Why would it? I'd be very surprised if it did anything at all.
Countering induced RF interference which may affect on some level the smoother possible running of the motor.

Used a fair bit in HiFi. Do a google search on it.

It may make a difference to some degree on a TT - with regards to the motor; and it may not. Just an idea...

Last edited by TigerScent; 14th January 2013 at 09:05 PM.
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Old 23rd January 2013, 05:04 PM   #36
MrPig is offline MrPig  United Kingdom
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Originally Posted by TigerScent View Post
"Unlike the RB250, the RB300's vertical bearings are supported on just one side of the bearing housing to make room for the VTF adjuster on the opposite side."
I have lost count of the number of times that I've seen this said despite knowing for a fact that it's wrong. I took the trouble of asking Paul Darwin at Rega to clarify. Here is what he said:

"I can state categorically that ALL Rega arms are supported on two sides, confusion may come in because of the spring tracking but it is still supported on both sides."

ALL Rega arms have two bearings for horizontal movement and ALL Rega arms support the bearing shaft at both sides. I can't reach the whole internet but I hope that at least on this forum people can get this simple fact right at last.
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Old 23rd January 2013, 06:01 PM   #37
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Tiger, IME you can shield the power cable all you like the improvement will be the absolute square root of SFA. If you want to improve on a simple phase shift capacitor network then a big traffo to clean higher mains frequency harmonics is a good way to do it. I'm not a fan of different voltages on different phases. All you are doing is weakening the drive torque of the motor at half of the poles, much better to use the correct phase cap values so that the drive isn't skewed, hint 0.22uf isn't the right value, and as motor windings vary it can be off by more than 10% and that's a difference you can feel in the palm of your hand.

I use the big traffo because that's what measured best looking at a series of Fm speed demodulations of test tones played via my deck. I do use very thick 'oil' in my deck which adds considerable drag, collapses the magnetic field in the motor and all but eliminates cogging artefacts in the process. You do trade a tiny bit of belt slippage and slow down if you go too viscous, but find the right value and it's all positives. (I'm not sure what 'oil' you could use on the Rega bearing that would add viscous drag, I use an LP12 bearing which has air bleed holes so is ideal for purpose.
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Old 23rd January 2013, 09:23 PM   #38
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Quote:
Originally Posted by MrPig View Post
I have lost count of the number of times that I've seen this said despite knowing for a fact that it's wrong. I took the trouble of asking Paul Darwin at Rega to clarify. Here is what he said:

"I can state categorically that ALL Rega arms are supported on two sides, confusion may come in because of the spring tracking but it is still supported on both sides."

ALL Rega arms have two bearings for horizontal movement and ALL Rega arms support the bearing shaft at both sides. I can't reach the whole internet but I hope that at least on this forum people can get this simple fact right at last.
Have you taken one apart? I can tell you that the support is not of the same standard on the spring assembly side, and one gets a strong impression there is only one bearing. Even though there are two, the secure and proper support for them is only on one side. The other sides support is nowhere near as secure nor precise and therefore not as stable as the RB250
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Old 23rd January 2013, 09:29 PM   #39
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Quote:
Originally Posted by sq225917 View Post
Tiger, IME you can shield the power cable all you like the improvement will be the absolute square root of SFA. If you want to improve on a simple phase shift capacitor network then a big traffo to clean higher mains frequency harmonics is a good way to do it. I'm not a fan of different voltages on different phases. All you are doing is weakening the drive torque of the motor at half of the poles, much better to use the correct phase cap values so that the drive isn't skewed, hint 0.22uf isn't the right value, and as motor windings vary it can be off by more than 10% and that's a difference you can feel in the palm of your hand.

I use the big traffo because that's what measured best looking at a series of Fm speed demodulations of test tones played via my deck. I do use very thick 'oil' in my deck which adds considerable drag, collapses the magnetic field in the motor and all but eliminates cogging artefacts in the process. You do trade a tiny bit of belt slippage and slow down if you go too viscous, but find the right value and it's all positives. (I'm not sure what 'oil' you could use on the Rega bearing that would add viscous drag, I use an LP12 bearing which has air bleed holes so is ideal for purpose.
Yeah, I was thinking the shielded cable would be most effective with regards to electronics....

Are you suggesting that the 'Geddon' single transformer as a 'large one' of about 1000 VA is preferrable to the Norton Air Power which uses 2 of differing voltages each 500 VA?

...and what would the more correct capacitor value be instead of 0.22uf ???

...also, on your 'Geddon', what values are the 'phase shift capacitors'? and what is the 'return' part of the ciruit - it must be the earth or ground wire ?

Last edited by TigerScent; 23rd January 2013 at 09:42 PM.
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Old 23rd January 2013, 09:41 PM   #40
MrPig is offline MrPig  United Kingdom
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Originally Posted by TigerScent View Post
Have you taken one apart?
Yes.

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one gets a strong impression there is only one bearing. Even though there are two
Brilliant mate, really :0)

Look, you can think what you want. I know how the arms are constructed and I gave you a quote from Rega telling you how they are constructed. I could explain it at length but that would just come across as patronising, and I really can't be bothered.
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