Set up for Naim Aro on Avid deck

Hi-Fi Corner
1

I recently swapped an Aro arm from an LP12 to an Avid Acutus SP. The arm wobbles while tracking the outer tracks of an LP, but steadies towards the centre, being pretty well dead still once on the last track(s) closer to the centre.

I don’t recall a pronounced wobble on the LP12.

A few details:

    1. Aro is mounted via an Avid Naim Slide
    1. The arm looks pretty well parallel to record surface, not sure I can eyeball it any flatter.
    1. Main chassis has integral spirit level, this is dead centred.*
    1. Naim spirit level that came with arm is dead centred when sitting in centre of platter.
    1. Cartridge is Ortophon Kontrapunkt B – no shims/spacers – full extent tracking weight with extra 0.5gram of blue tack as advised when I had mounted to LP12 by Audio T’s LP12/Naim experts that used to work there

Any advice would be much appreciated

2

Any slight wobble should cease almost immediately after the first few revolutions. Is the subchassis moving at all when it happens?

FWIW, I never rely on little round spirit levels or any that are integral. I always check and double check with a good quality straight spirit level. Worth doing, just to be sure.

Are you using the standard, heavyweight, or a 3rd party counterweight?

I would also check that the wiring is dressed so it’s not interfering in some way with the bearing during the play arc of the arm.

3

Thanks Richard. Yes, that’s how it was with the LP12, settling down after a few revolutions.

The sub chassis appears perfectly still.

I will try longer spirit levels.

I’m using the standard bias weight that came with the arm, on the furthest notch on the bias shaft, going by the tracking force recommended for the Kontrapunkt b.

I’d check wiring initially as I’d read about the position of the wiring connector on the Naim slide was on the outside and to be wary, but doesn’t appear to be touching anything from what I can see.

As mentioned, the wobbles ceases once tracking in the middle and inner grooves, but it wobbles constantly while tracking the outer third or so of an LP. Not sure if that would point to anything?

4

What about the counterweight? Is it the standard, heavy, or a 3rd party one?

5

It’s the standard counterweight, all just as supplied when new from Naim and completely standard, other than the little blob of bluetack.

The video below is a bit grainy, shot at night, but shows the issue, wobble on outer grooves, still on inner:

https://vimeo.com/489770530

6

Thanks. I see you have a lot of anti-skate bias on there with extra weight and also with it right out on the outside of the bar. Do you run with a lot of downforce? Even when I ran my arm with an SPU and the heavy counterweight, I added some extra mass to the bias weight but never needed it so far out on the bar. I’m wondering whether this is the problem?

Do you have an old LP you can try with no anti-skate bias?

7

Hi, I’d go back to basics if I were you.
First off, read Mark Dunn’s excellent Aro setup guide on this forum. It’s in a reply from him to a thread I created some months ago, sorry, can’t remember the name. I think a chap named Pieper was actively involved as well.
Agree with Richard, you need to check your deck levelling, in all planes, with a good quality (non bubble) level.
Check your arm levelling with the Naim supplied bulls eye level, on the Aro arm cup, with the cartridge placed on a (non rotating) old record.
Follow Marks advice! Again, agree with Richard, the setup of your VTF and bias looks all wrong to me.

8

Thanks for these suggestions.

I’ve just tried the bias weight without the the extra blue tack and makes no difference, still wobbles.

I also tried on every notch on the bias shaft, makes no difference and still wobbles.

I removed the bias weight completely so no longer attached at all, makes no difference and still wobbles.

I’ve used a long spirit level and all appears level.

9

Have you been in touch with Conrad at Avid? Assuming the only variable here between your LP12 set-up and this one being the Avid deck and Slide.

One more thing… does it do this on every LP? I do wonder whether there’s some kind of weird compliance issue at play here where the very low frequency groove noise is resonating and making the arm wobble. Have you tried it on a test disc such as the HFNRR one?

10

Thanks Matfff, I’ll have a dig around for that thread.

11

I had trouble setting up and mounting to the naim slide and they help advise on that. I have sent an email regarding the wobble and hoping to hear back.

It does it all LPs, tried quite a few. I don’t have a test disc but will have to invest, I guess it just worked without any problems before so never needed to.

Thanks again for the advice.

12

Just looking again at your video, it looks like the arm is rocking on the lift/lower platform. Is this an optical illusion? It might be an idea just to adjust the lift/lower mechanism so it sits a couple of mm lower just in case

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13

NP, just checked, the thread was called ‘in praise of a forum member’.
The fact that it doesn’t do it towards the spindle is a big clue to me. Could inner groove distortion (sometimes called end of side distortion) be stopping the ‘wobble’.

14

I wonder if it’s not a consequence of a wrapped lp. I had that on my past SME 20/ SME V. There was a record clamp, like you.
But if the lp was wrapped, not horizontal, the arm was dancing like that. But with an unipivot, it’s accentuated.

15

Is this happening on every LP you try?

Is the extra blue tack you put on the balance weight at the bottom of the weight ( it cannot be on top!!)

You seem to have way way too much antiskate in the video… definitely read Mr Dunn’s setup posts…it makes a huge difference

Lift the arm off the post…check the post turns freely and true…put the arm wand back on and make sure it has DEFINITELY sat back down on the cup correctly

16

Difficult to see the axis of wobble (!) but I think I’m with Richard here…

Edit - oh well… apparently not!

17

Hi, I reported your problem on the Audioflat forum, a place where a lot of TT/Aro expertise resides. I think their chief guru has the solution and I repeat verbatim;
“ Hmm… well there are a couple of potential issues evident from watching that video - but they interact. The first is that he has too much bias applied* - quite a bit too much in fact. The second is that the loop of the bias hanger is too low - this is a fault with the design of the Aro. I will try to explain; it is important that the bias line is parallel to the record surface between the point it leaves the bearing and the loop of the bias hanger. However, the only way of adjusting the height of the bias hanger is by bending it, whilst the bearing housing moves up and down as VTA is adjusted. You can see from the video that the line is not horizontal but slopes down toward the bias hanger. This means that a twisting motion is applied to the bearing. Add to that the fact that the bias weight has been increased by adding blu-tack and the greatest leverage point is being used then any eccentricity in the record (as most records have) will cause the arm to wobble. This will decrease in severity as the the record is played.

The user should; 1/ move the bias line to the groove closest to the bearing cup and, 2/ bend the bias hanger until the bias line is absolutely horizontal.

  • Presumably this has been decided upon by playing a blank disk or a test record. Alternatively is is due to a misunderstanding.”
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18

Just looking again at your video, it looks like the arm is rocking on the lift/lower platform. Is this an optical illusion? It might be an idea just to adjust the lift/lower mechanism so it sits a couple of mm lower just in case

This was really tricky to set up, but arm is definitely clear of the rest when playing, you can see clear space between them on video below:

https://vimeo.com/489880883

19

Thanks will read through

20

Thanks, LPs aren’t warped

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