Varying speed at start of record

[Kfeuerherm]

I recently acquired a new Dual CS 429 and had a few growing pains which I posted here. These are thankfully resolved with the help of forum members.

However, I’ve experienced something else, once on the first day—but I wondered whether I’d misheard (though my wife says she heard it too), and again, today.

When I started the record, the speed varied down and up a few times (like a stretched tape) before stabilizing… most peculiar. I mentioned it to Dual when I contacted them about the other issue, but they said they’d never heard of such a thing and couldn’t imagine it.

Any thoughts? This never happened in 30+ years with the previous Dual. Stress:it’s new. It has happened only twice, both times at the start, briefly.

I should mention that apparently the needle set down a bit far out (the other issue linked to above was on initial needle drop adjustment) and moved a bit abruptly inwards. That said, I don’t believe that was the case the first time, as the needle was then setting too far in. Just being through.

I’m still within the return period if I have to go that route, but not for long….

Tks

 

[jrtrent]

I recently acquired a new Dual CS 429 and had a few growing pains which I posted here. These are thankfully resolved with the help of forum members.

However, I’ve experienced something else, once on the first day—but I wondered whether I’d misheard (though my wife says she heard it too), and again, today.

When I started the record, the speed varied down and up a few times (like a stretched tape) before stabilizing… most peculiar. I mentioned it to Dual when I contacted them about the other issue, but they said they’d never heard of such a thing and couldn’t imagine it.

Any thoughts? This never happened in 30+ years with the previous Dual. Stress:it’s new. It has happened only twice, both times at the start, briefly.

I was reading avforum's review of your turntable, a highly complimentary one, that mentioned pitch changes when pressing the stop button, "Pitch stability is good (with the exception of when you hit the stop button when the pitch lurches as the arm release engages)." I am not at all mechanically inclined and far from a do-it-yourselfer, so my guess is likely wildly off-base, but I was wondering if whatever mechanism is involved in moving the arm might not have fully disengaged yet when you heard those brief speed variations at the start of a record. I know you've only heard it twice, but I was curious if it only happened when using auto start or if it also occurred when starting a record manually.

I just have Audio Technica's cheap little LP60X, and I find it more convenient to start it manually, but I love the auto return and shutoff. I fully agree with the reviewer's comment about how nice auto operation is. He wrote, "After a bit of time with Dual, it becomes second nature to listen to records at times you might not bother or when attending to tasks that would normally have you streaming. There’s a liberating aspect to the CS429 that I’ve appreciated more than I thought I would." I, too, find myself enjoying vinyl much more frequently than I did with a fully manual turntable simply because it can take care of itself at the end of a record side.

 

[Montycat]

What Jrtrent suggests above is likely the case. There's more demand on the motor during the automatic cycle and it doesn't have a lot of torque.

I doubt much can be done about when using the automatic start.

 

[Kfeuerherm]

Thanks, both. Given the rarity, hard to be sure, but I think it’s only on auto-start.

The theory makes sense, except that if it were a question of slow speed-up only, I’d jump on it. But it seems to go up and down briefly. Of course, I was taken by surprise both times so that’s hardly good data for analysis, maybe that’s not quite what I heard.

If this is right, then it means there’s not enough delay before setting the arm down, which would be a design flaw. The thing is, I never experienced such a thing with any turntable in the 70s with this feature (mostly Fusl also) so this feels (to me at least) very anomalous.

Perhaps I’ll ping Dual again and see what they say..

And if we’re right, the solution is to activate the cue lever, wait a moment, then set it down, effectively turning it into a semi-automatic. That would work… but I still think shouldn’t be necessary….

 

[Sleiven]

Your Dual it is a belt drive it can take some time before the speed is stable… check with a phone app and phone on a tape roll - centered above the spindle.

You can share the results here for more comments, anything below 0.2% variation is probably not audible. More than that indicates a problem

 

[Sleiven]

but they said they’d never heard of such a thing and couldn’t imagine it.

Very strange answer , it is not uncommon for a belt drive to need time to stabilise, with poor or faulty belt that is the premiere sign .

 

[Kfeuerherm]

Your Dual it is a belt drive it can take some time before the speed is stable… check with a phone app and phone on a tape roll - centered above the spindle.

You can share the results here for more comments, anything below 0.2% variation is probably not audible. More than that indicates a problem

Thanks. Not sure I understand the first part. But in any case the sound strikes me as fine except for the two two-second bits I mentioned above, which are clearly audible and then some.

I get that it takes time to stabilize. But 1) it should do so before dropping the arm (again, never experienced this before in 50 or so years) and 2 bad starts out of say 50 or 60 in the last few weeks presumably means something is rotten in Denmark?

Not that I’m suggesting I can fix it necessarily. I’m guessing no one else has experienced this sort of thing? (Guess that will take more reads of the thread.)

Meanwhile have pinged Dual again FWIW.

 

[Kfeuerherm]

Very strange answer , it is not uncommon for a belt drive to need time to stabilise, with poor or faulty belt that is the premiere sign .

The exact words, which to me beg the question: “Regarding your point 1; this I never heard before and generally we don't have issues with the speed during playback. It is a servo controlled motor installed and he will hold the speed constantly during playback.
Only if the start and stop process in function he will be disturbed.”

 

[Sleiven]

You probably got the reply from a clerk not an engineer .
Belt drive is inherently an oscillating system that takes time to stabilize , servo control or not. Speed issue during playback in not the same as start-up stabilization - the last is what is what you describe.

Here is my belt drive start-up compared to a direct drive. It takes 5-7 seconds for the speed to reach stable rpm. Direct drive to the right is much faster.

Depending on the condition ( belt quality, temperature, humidity whatever ) this stability may take long or short time. It could be a number of reasons for speed stability to fail. The servo control may control the rpm once per revolution or many times per rev. It is like a cruise control in a car, not always perfect if you start to climb a hill..

I think maybe you are expecting too much… a few seconds delay for stable speed in 2% of the starts does not seem as a problem, as long as it keeps stable beyond that.

It can be useful to be able to check speed with a phone app, google it or look at YouTube. But bear in mind that the apps do not show absolutely correct speed, they deviate. Correct speed is best set with a strobedisk and strobe light.

Getting more advanced , and much more challenging is to use test records, but that is for nerds..test below is not made under same conditions as above, so results deviates

 

[Kfeuerherm]

I think maybe you are expecting too much… a few seconds delay for stable speed in 2% of the starts does not seem as a problem, as long as it keeps stable beyond that.

Very helpful details, thanks. Makes sense now.

But I can’t agree with you on this particular point above. I don’t have an issue with the thing requiring time to stabilize, that makes perfect sense. But I do have an issue with the tonearm setting down before that has reasonably finished. Who wants to listen to a warbling first track? Especially as it’s the only time I’ve experienced this in 50 years, now twice in two weeks. To me that suggests a flaw—specially as it’s inconsistent behaviour.

But I guess my options are limited

Just before this, I tried a Pioneer PLX-500, which was direct drive, in part to obviate the stabilization issue as you describe. Unfortunately, it didn’t cue properly and the support was next to nil. So that leaves me thinking that maybe where my expectations are too high is to expect the same standards of quality these days as in the 70s (2 duds for 2?). Sigh. Do I sound old or what? lol

 

[Kfeuerherm]

Additional info: I had occasion to push Stop in the middle of the track… and the sound slowed in the same way as discussed above. This suggests to me that the arm servinis stealing power from the platter rotation. That shouldn’t be (at least the three Dual predecessors didn’t) so two questions. 1. Is this a design flaw which occurs across all units? 2. Regardless, why does it happen only sometimes?

 

[jrtrent]

Additional info: I had occasion to push Stop in the middle of the track… and the sound slowed in the same way as discussed above. This suggests to me that the arm servinis stealing power from the platter rotation. That shouldn’t be (at least the three Dual predecessors didn’t) so two questions. 1. Is this a design flaw which occurs across all units? 2. Regardless, why does it happen only sometimes?

The sound slowing when Stop is pressed doesn't strike me as a design flaw. My AT does the same thing, and I really don't recall what my other automatic turntables did as that was over 40 years ago. But it can't be normal for speed not to be stable when the stylus sets down at the beginning of a record. It will be interesting to find out what Dual has to say after your follow-up to them.

 

[Kfeuerherm]

The sound slowing when Stop is pressed doesn't strike me as a design flaw. My AT does the same thing, and I really don't recall what my other automatic turntables did as that was over 40 years ago. But it can't be normal for speed not to be stable when the stylus sets down at the beginning of a record. It will be interesting to find out what Dual has to say after your follow-up to them.

Well, ok, it’s not a big deal when stopping, though it doesn’t match my past experience; fair enough.

 

[Sleiven]

I see, the problem is that the automatic lowers stylus to platter before speed is stable. Can’t you override the lever? My belt drive is all manual so I decide when to lower arm manually… my DD has a button to lift/keep the arm up.

I think if you explain the problem more exact to Dual once more Dual may better help you on the issue . Maybe you have an off spec belt? It may help to clean belt and platter contact. A trick I use is to put the belt in a plastic bag with talcum , shake it , and shake off excess talcum, it makes my belt drive run smoother, but will probably give an even longer start up time…


If you record the start up sequence with the Phyphox app ( I have IPhone , maybe android work too) and share with Dual they me investigate better

 

[Kfeuerherm]

So… yes, I can override with the cuing lever, certainly; but I paid extra because my wife wanted autostart (she has balance issues so it’s important).

Here’s what Dual said: “
Well noted your explanation, thank you.
However, I can't offer much help remotely without seeing the device.
Maybe you need to double check again the settings of the counterweight as well as antiskating!
We are having some video files for all the settings and adjustments, here: Videos - DUAL

For me it would be also helpful if you could send me a video file showing the start procedure of the unit, maybe I can find then some specific issue?”.

Am I missing something? How is any of that likely to be relevant? I’m on the road today, soonest I can jump through hoops will be tomorrow.

 

[jrtrent]

So… yes, I can override with the cuing lever, certainly; but I paid extra because my wife wanted autostart (she has balance issues so it’s important).

Here’s what Dual said: “
Well noted your explanation, thank you.
However, I can't offer much help remotely without seeing the device.
Maybe you need to double check again the settings of the counterweight as well as antiskating!
We are having some video files for all the settings and adjustments, here: Videos - DUAL

For me it would be also helpful if you could send me a video file showing the start procedure of the unit, maybe I can find then some specific issue?”.

Am I missing something? How is any of that likely to be relevant? I’m on the road today, soonest I can jump through hoops will be tomorrow.

I don't understand how vtf and antiskate would affect your speed issues, either, but I'm curious to know if you went ahead and jumped through the hoops, including sending them a video, and if there's been any resolution to the problem.

 

[Kfeuerherm]

I’ve been on the road, so not yet. Hope to son and will certainly post an update when there is news. I did ask, no response, but Easter weekend may be to blame.