Restoring a Roksan Xerxes (original)... Wow!

[YNWaN]

One thing that concerns me though is that when I tap the top plinth of the turntable with my finger while a record is playing, I do hear the thump coming through the speakers. I wonder to what extent this is expected or whether I should try to remedy it. Does this mean that my tonearm and cartridge are not properly (acoustically) decoupled from the top plinth and this negatively influences the sound?

Could / should this be improved and if yes, how? I have put a rubber washer at the arm base, but it did not seem to make any real difference. I wonder whether the bearing is too tightly screwed on the top plinth...

Any advice from other Xerxes owners, please?

I'm not sure which component you are referring to when you say the 'top plinth' as I would say there is the outer plinth and the top plate or chassis. Either way it is inevitable that tapping them whilst playing a record will result in a thump sound coming through the speakers. As you know the outer chassis is only decoupled from the plinth by Roksan's rubber 'blobs' and this only offer a modicum of isolation. If tapping the top plate then one is, in essence, effectively tapping the chassis directly and as this is directly coupled to the arm base and the platter this is bound to be heard as transmitted vibration (vibration very much greater than the stylus is generating). I wouldn't recommend placing anything compliant between the arm base and the chassis either. Unfortunately, I also wouldn't recommend changing the AC motor for the DC Origin Live - but you've already done that .

[pankon]

I'm not sure which component you are referring to when you say the 'top plinth' as I would say there is the outer plinth and the top plate or chassis. Either way it is inevitable that tapping them whilst playing a record will result in a thump sound coming through the speakers. As you know the outer chassis is only decoupled from the plinth by Roksan's rubber 'blobs' and this only offer a modicum of isolation. If tapping the top plate then one is, in essence, effectively tapping the chassis directly and as this is directly coupled to the arm base and the platter this is bound to be heard as transmitted vibration (vibration very much greater than the stylus is generating). I wouldn't recommend placing anything compliant between the arm base and the chassis either. Unfortunately, I also wouldn't recommend changing the AC motor for the DC Origin Live - but you've already done that .

Hi Mark,

thanks for the feedback. As a matter of fact, with respect to the motor, I changed it more than 10 years ago, when the PSU of my Xerxes appeared unable to even start rotating the platter. It must have been a PSU problem, but at that time -living in Greece- I did not have too many options of fixing the PSU. Why are you saying that the Origin Live motor worse than the original AC motor?

I see where you are coming from with respect to the thump and it seems quite reasonable. By 'top plinth' I am referring to the top horizontal, where the main bearing and the platter are supported, not the outer wooden casing.

May I ask why you do not think that placing anything compliant between the area base and the chassis is not recommended? I have done it (can be reversed) and did not hear any improvement with respect to the thump issue, nor any degradation of the sound quality either.

Any suggestions for further improvement, if any, are definitely welcome.

[YNWaN]

Hi Panos, to be honest there are a whole bunch of potential issues.

With regard to the thump there's nothing you can do and nor is there any need to. If you were to tap the sub-chassis of any turntable during play you will hear some thump through the speakers (unless perhaps if it is extremely heavy and dense but that brings other issues). The chassis is supposed to be isolated from the outer plinth and the rest of the world, as such your tapping of the top plate is not an input it should see (unless you bypass the suspension by deliberately tapping on it ).

The motor issue is another matter. I'm afraid I'm not overly impressed with the OL speed controller and a friend who had one found its speed stability to be deeply questionable. Attaching it to the top plinth also means that all vibration is effectively coupled directly to the platter and arm. I realise you have added some rubber shims but that is unlikely to be having a significant effect I'm afraid. In addition, one of the primary design features of the Xerxes was the rotating motor and this has obviously been lost in your modification. Further, in general, I'm not convinced by the use of DC motors in turntables and after years of experimentation have settled on AC (but that's another long winded story).

The problem with adding compliance to the arm base is that if it is sufficiently compliant to reduce the transmission of vibration it will be decoupling the arm. The point of the chassis is to act as a drain for vibration emanating from the arm (from the cartridge originally) and adding a rubber washer will work against this. The rubber is also likely to create an uneven level of damping which is also undesirable.

Sorry, it's all a bit negative - if you like it that's cool and all that matters. Unfortunately the Xerxes power supplies have gained rather a reputation for being a bit flaky in the long term so I quite understand why you abandoned it.

[rubber duck]

Looking at the last set of photos with three screws, and provided I've understood what you've done correctly, I think the three screws that now secure the arm board cutout to the top plate may nullify the purpose of the cutout to break up vibration to the arm from the top plate. I think there are several ways to fix the sagging plinth that preserve the design aim of the cutout, e.g. on pink fish.

[pankon]

Looking at the last set of photos with three screws, and provided I've understood what you've done correctly, I think the three screws that now secure the arm board cutout to the top plate may nullify the purpose of the cutout to break up vibration to the arm from the top plate. I think there are several ways to fix the sagging plinth that preserve the design aim of the cutout, e.g. on pink fish.

Thanks for the feedback. I searched on the Internet a few months ago and the only proposed solution I found was to bolt a metal shim below the top plinth and across the cut-out, to level the two parts and thus eliminate the sag. I did that initially, hence the six holes you can see on my deck. However then I realized that the horizontal screw across the two parts would provide less contact (and coupling) compared to the metal shim method.

Are you perhaps aware of any other method, which may be preferable?

Thanks for the feedback.

[pankon]

Hi Panos, to be honest there are a whole bunch of potential issues.

With regard to the thump there's nothing you can do and nor is there any need to. If you were to tap the sub-chassis of any turntable during play you will hear some thump through the speakers (unless perhaps if it is extremely heavy and dense but that brings other issues). The chassis is supposed to be isolated from the outer plinth and the rest of the world, as such your tapping of the top plate is not an input it should see (unless you bypass the suspension by deliberately tapping on it ).

The motor issue is another matter. I'm afraid I'm not overly impressed with the OL speed controller and a friend who had one found its speed stability to be deeply questionable. Attaching it to the top plinth also means that all vibration is effectively coupled directly to the platter and arm. I realise you have added some rubber shims but that is unlikely to be having a significant effect I'm afraid. In addition, one of the primary design features of the Xerxes was the rotating motor and this has obviously been lost in your modification. Further, in general, I'm not convinced by the use of DC motors in turntables and after years of experimentation have settled on AC (but that's another long winded story).

The problem with adding compliance to the arm base is that if it is sufficiently compliant to reduce the transmission of vibration it will be decoupling the arm. The point of the chassis is to act as a drain for vibration emanating from the arm (from the cartridge originally) and adding a rubber washer will work against this. The rubber is also likely to create an uneven level of damping which is also undesirable.

Sorry, it's all a bit negative - if you like it that's cool and all that matters. Unfortunately the Xerxes power supplies have gained rather a reputation for being a bit flaky in the long term so I quite understand why you abandoned it.

Matt, the point IMHO is not to be positive or negative. I do not mind that at all. It's about sharing experiences and helping each other to do better. So, I really appreciate your sincere feedback, as it highlights points you think could be improved on my deck. Quite right so.

I had at least two failures of the original Roksan Xerxes PSU and the repairs seemed to me rather costly at that time. That's why I decided to go for something else and I stumbled upon the OL DC motor. It was before 2000 when I replaced the motor, if I remember correctly. It seemed like a big improvement to me then. From a reliability point of view I had no issue at all. Recently I upgraded the controller unit with a new 'advanced' controller from OL again. It we me to be able to maintain a very constant speed. But I have used it only for a few tens of hours until now.

I have read also various opinions in favor of both DC and AC motors. I have no personal experience or knowledge on the issue, but the AC case locking on the power network's frequency (50 or 60 Hz) in order to keep rotational speed constant, seems pretty reasonable.

I wonder whether I could try alternative motor solutions on my Xerxes to see if they work better than the OL motor. Perhaps the recent ones from Roksan could be retrofitted to my Xerxes? In any case I am not eager to pay an arm and a leg just out of curiosity.in any case, Roksan's idea of the rotating motor seems rather strange to me. I would expect than at any point the stylus friction increases, the motor will just turn, instead of trying to overcome that friction and keep the speed constant. Am I getting something wrong here?

I will continue experimenting. The method is quite clear. Trial and error... -))

[Pete The Cat]

Aside from Roksan's own under-platter shim, the other conventional solution to plinth sag is the so-called "Gene Rubin fix" (named after a US retailer, I believe) which involves screwing a small plate underneath the upper plinth, bridging the gap at about 12.30 o'clock - ie supporting the sagging side with the opposite side. This does seem to defeat the object of the decoupling principle that the gap is intended to provide though.

The other hitch with the original Xerxes is the PSU, which seems to be unusually fault-prone albeit they are rather old now. Mine was fine at 33 1/3rd but didn't like singles... I still rate the Xerxes nonetheless.

Pete

[legb4rsk]

Hi,I have an original Xerxes as well.Purchased new back in the early '90's.I also had problems with the old PSU & have the new smaller XPS 7 which has been ok for many years now.I always 'kick start' the platter when spinning up as it is very heavy.The original motor is mounted on the sub-chassis so was completely decoupled from the platter/arm board and the belt drive poked through a hole in that board.I have replaced the main spindle bearing with a TMS one as it has finer tolerances.
I always remove the old lubricant using alcohol & a cotton bud before adding the new.It's surprising how black & gungy the old stuff gets.I used a short nut & bolt with large washers inserted in the cut out slot to remove the sag.I was drawn to the Xerxes as it has a sense of precision that appeals to me.I still havn't heard a TT that would persuade me to spend a lot of money to replace it.I am using the original Tabriz arm & a 2M Black............must count as my best buy after giving such great service after all these years.My one is the ash black look.I have removed the outer box & added a chrome strip around the lower plinth.I will post some pics when I get the chance.

[pankon]

Hi,I have an original Xerxes as well.Purchased new back in the early '90's.I also had problems with the old PSU & have the new smaller XPS 7 which has been ok for many years now.I always 'kick start' the platter when spinning up as it is very heavy.The original motor is mounted on the sub-chassis so was completely decoupled from the platter/arm board and the belt drive poked through a hole in that board.I have replaced the main spindle bearing with a TMS one as it has finer tolerances.
I always remove the old lubricant using alcohol & a cotton bud before adding the new.It's surprising how black & gungy the old stuff gets.I used a short nut & bolt with large washers inserted in the cut out slot to remove the sag.I was drawn to the Xerxes as it has a sense of precision that appeals to me.I still havn't heard a TT that would persuade me to spend a lot of money to replace it.I am using the original Tabriz arm & a 2M Black............must count as my best buy after giving such great service after all these years.My one is the ash black look.I have removed the outer box & added a chrome strip around the lower plinth.I will post some pics when I get the chance.

Yes, it seems that many of the older PSUs were rather unreliable due to excessive heat build up, which could not be dissipated. I understand that newer generation PSUs do not have that problem.

In any case, I am still wondering about the theoretical benefits that the spring-loaded motor placement can bring. The purpose of the motor is to keep the rotational speed constant even at more demanding moments, such as when the cartridge friction ('stylus drag') peaks. At such moments the speed should not be affected and the motor should be there to overcome such resistance, not turn around its axis. From a theoretical perspective I am rather cautious. I wonder whether any one has tried to eliminate this axial self-rotation of the motor and provide an opinion about the improvement/deterioration observed...

Furthermore, it's clear that placing the motor on the bottom plinth provides decoupling from the tonearm and cartridge. However, the possible relative motion of the two plinths makes me think that the motor pull may cause minute horizontal motions of the top plinth, which may end up in audible speed variations. Just my two pence...

[legb4rsk]

Hi,the motor only spins on it's axis when the platters spins up apparently to compensate for the torque needed to start up the very heavy plater. Once up too speed it stabalises & remains in place.If you put the outer platter on upside down,which Roksan have provided the lip cut-out on the underside exactly for this purpose,you can see the motor spin to it's maximum extent & then gradually return to it's original position, assisted by the return spring, as the platter reaches a stable speed.With the platter on upside down you can also check that the belt is running true.Quite a neat solution.

Apologies if seeming to tell you what you already know but may be of benefit for others less well acquainted with the idiosyncrasies of this design.