It could be Blue. Like I mentioned cast products can vary depending on the Mfg process, environmental conditions etc. If the Mfg process is not well controlled you could get warping of the platters during and after molding. Also the platters may not be perfectly flat coming out of the mold so machining seems like it may be a necessary part of the Mfg process.
Some may remember my ongoing issues with my G platter. Technics tech support even came round my house 5 weeks ago to take measurements, and again waiting on Japan. I sent a stinky letter to Technics voicing my opinions that irrespective of whether it's within their tolerance, it is not what I would expect from a turntable that is advertised as having high precision. Who would buy a performance car and put up with a steering wheel that was bit wonky, or uneven stitching on the upholstery? Perhaps not the greatest analogy, but you get the point.
Just an update. Before and while I was posting here about what I though was a cosmetic issue, I was in talks with Technics to find out if this was normal or not. I have had quite a few emails back and forth with Technics Sr. Product Engineer and he also had a convo with the engineering team in Japan. The Business Development Engineer had this explanation. The dots are arranged in 4 rows, each designated to the four pitch variations. By design, their size and placement vary in a non-uniform pattern. These are not intended to be some sort of an aesthetic feature. The variations are required because this unit can operate at both 50 / 60 hz. Maybe they are misunderstanding me or what I read to understand is that each row is purposely non-uniform. It doesnt explain why other parts/design of the platter look uneven or non-uniform, that arent part of the speed pitch. Not trying to rehash this, I have come to accept this design flaw if thats what it is or purposely designed. I just figured some might find the response interesting.
They play the fool, as usual with customer service. I got the same lingo from a record mailing company when complained about their wrinkled sleeves: "they are dj, not collector intended records". Try again, explaining more specifically. First find an example of non-misaligned dots platter and show it to them.
Heard 1200G in anger today in a high end system and have to say it sounded very nice- bass especially.
definitely not a design issue- they didn't plan for this to happen. it is a part quality issue- the supplier of the platter made it out of spec, possibly from an older, worn tool.
Today, I wanted to calculate the resonance frequency of my setup. For this calculation I need to know the effective tonearm mass, without headshell/headshell wires. On the web I found that it's 12 grams according to some, others said that this includes the headshell weight. But 12 grams is the same as for the SL-1200MK2, which has an aluminium tonearm. I would expect a magnesium tonearm to be significantly lighter than an aluminium one, so does anyone know if 12 grams is correct for the SL-1200G?
Much easier to just measure it, record the output while lowering the stylus onto the record, don't even need to turn on the motor. May need to do it by hand if the cueing is highly damped, just drop it the last little bit to the record surface. Analyze the recording for spectrum and you should see a decaying resonance in your recording at around 10 Hz or so...
Thanks, but the point is that I want to calculate it for cartridges that I don't have, but where the compliance is given. Or is it possible to derive the effective mass from the measurement by doing the calculation in reverse?
Yes, you can calculate the tonearm effective mass with the resonant frequency measurement and cartridge compliance, but relying on manufacturer supplied cartridge compliance ratings can be a bit iffy, so the effective mass may not be accurate unless it is based on measurements with a few different cartridges, or using one with a known and tested value based on a 10Hz measurement. The tonearm effective mass in the measurement includes cartridge and hardware, so you would have to estimate that contribution to get the tonearm only value. Our friend @missan here has provided the details for a fairly accurate calculation methodology for tonearm effective mass, but it does require some data you don't yet have.
To comment on the issue with the strobe dots. Comparing the strobe dots on my Mk2 vs my GR. The dots on the mk2 are left how they were cast. The face of the cast dots on the GR have been machined. The wavering you are seeing is the variance between the casting/machining process. If the dots had not been machined (like on the mk2), you would likely never notice this. To me, this is purely cosmetic. Even the best casting process’s have error. I work as a Quality Engineer and deal with cast/machined parts daily, what I’m seeing is nothing abnormal even if it’s not pretty. I bet if I put a dial indicator on the black of the strobe strip on the mk2, and checked the runout/form, it would be similar to that of the GR.
I think the 12 grams is consistent for both, including headshell and screws. I know I read a reason why the magnesium would still be the same weight as the aluminum but it’s eluding me now.
Can you tell more on this? I don't really understand it. What is machined and is it additional process to the casting? Like the dots are "scraped" after being cast?
Yes, on the newer models (can’t speak for mk7 or 1500c) the face of the dots are being cut after they are cast. The dots on the older models were not.
Perhaps because of the polymer lining inside the magnesium tonearm tube for damping? Because the pre-2010 models had a bare aluminium tube (except the MK4 with titanium) with the wires in it, that’s all. Btw, that’s why I liked the Pioneer PLX-1000 over the old Technics models; it also has polymer tonearm lining for damping. But I don’t remember it to be heavy.
Like "shaved off" to desired length? If that is correct understanding, why would that process misalign the dots? Their alignment is set on the mould, isn't it?
It wouldn’t “misalign” the dots per se. But make some dots taller than others relative to the consistency of the casting. I am not sure why they decided to cut this surface when they hadn’t in the past. Somebody had to make that decision for any number of reasons. Maybe for a cleaner look? My best guess is that the cast finish of the dots was not very good to begin with, and they tried to clean it up.
Does anyone have any thoughts/experiences with a Koetsu Black MC cart on a 1200GR. I have a lead on a pretty decent price on a used cart, and it's through a dealer, so I can return it if it doesn't work out. I'm thinking it'd be a good way to get a taste of a higher-end cart for not a huge (or at least not completely absurd) outlay. But if it's a bad match with the Technics arms, I might skip it. Most of my reading/research thus far suggests it might work okay, though I certainly don't see it as a commonly recommended cart for the GR. I've also got an ART-9 I'll be trying out.
I could swear the platter is slightly warped rather than dodgy dots and playing warped discs may help create an optical illusion.