STOP the TECHIE 1200 Ringing !

[Audio Al]

playing devils advocate here but who taps or knocks there platter when playing records? does the resonance produced by tapping exist in real world use?

I was about to ask the same question

[Wakefield Turntables]

Some valid points, but bear in mind these measurements are relative, to prove to me that dampening the platter with a different material reduces the natural vibration of the platter and most importantly the decay time.

I think it is worthwhile to look at this as an energy issue, the new material is much better at absobing the energy created by the platter oscillation, probably at the end of the day as heat. We are looking at forces at play which in our norm are miniscule. But they all add up to become significant at the low levels of signal we are dealing with.( 30 millivolts MC)

Platter oscillation can be generated very easily at around 250 hz. No, we dont hit it when its playing records but other forces are at play. There will be noise from any bearing, where does that go, how is the energy dissipated ? The stylus running in a grove will generate forces at music frequencies. there will be a reaction to them by the record wanting to oppose them, where does that energy go, dissipated in a below record mat , passed on to the platter or just wear the record. Ignoring the effects of the tonearmat this point.
Platter oscillation induced at say 250 hz in this case will cause an unwanted 250 hz signal to be induced into the stylus and add or subtract to the wanted signal. While we have shown resonance at 250 hz, there will be effects at higher and lower frequencies. One has to think a little out of the box.
.

I have gone a little further today. I recently purchased a Denon 103r from Mike. He gave me a cover for it that snuggly fits over the body, it was supposed to improve the performance.
I took the cover off and installed some of our energy absober between the cover and my tone arm mounting . Wow the techie is rally singing Ive never had it as good.
My theory was to try and absorb the energy from the headshell.
No different from fitting a silicone damper to the arm, they work well which proves there must be vibration travelling up the arm
When I measured my first modded bearing, accurate measurements showed a decrease in noise of 8db over that obtained from a standard set up. We may be looking at a rejection of unwanted signals of few more db here. It all adds up

If I get time when this delving is finished, I will look at doing some more accurate noise figures. last time I used Arta software, I may have to look for a good soundcard for my PC

All excellent points. Anything subtracted from going through the platter to the cartridge must be a good thing.

[Audio Al]

The new 1200G has a brass and rubber sandwich bonded platter as std

https://www.technics.com/uk/products...-sl-1200g.html

[Ianmac]

Thanks for the link
Interesting changes to the platter design.
Im running with a very similar set with a SDs or copper top plate although not screwed to the platter.
Screwing to the platter would mean that the platter is finally machined after the plate has been attached by screws to ensure it is absolutely flat. What happens if the brass plate is ever removed (as will happen with some tweakers)
The Brass plate needs to be in contact with the aluminium base 100% no air pockets or distortions. This was one thing I found when testing silcon mats .There had to be 100% contact to the underside and the only way I could achieve that was with a top plate copper or SDS in my case. Left me thinking how with modern adhesives ?
Note their respose graph does not give a timescale.
I hope the underside rubber is not glued to the base in the same way as the 1200 and 100% contact is achieved
I cant afford one anyway !

[Pharos]

Yes Dennis, but not in a consistent way, no method of exact replication has been published, so until such evidence exists, the experiment is flawed and unreatable. All that's been proven is that by using Dynamat we can change measured decay time. Well, that's pretty much what the company relies on to sell it's product, so you could argue that this is an experiment proving something we already know. And if you want to be really pedantic we are not improving decay time, we are measuring changes and characteristics of measured resonance on a alloyed metallic structure with Dynamat application. But, hey, I'm not one for splitting hairs.

Not all experiments have to show an absolute final resolution or conclusion, some may be just qualitative and not quantitative.

I did not interpret what was done as a an absolute proof, or final dissertation for an award, rather a fairly rudimentary illustration of an effect.

I don't want to be pedantic or split hairs, but please do so if you wish.

[Wakefield Turntables]

Not all experiments have to show an absolute final resolution or conclusion, some may be just qualitative and not quantitative.

I did not interpret what was done as a an absolute proof, or final dissertation for an award, rather a fairly rudimentary illustration of an effect.

I don't want to be pedantic or split hairs, but please do so if you wish.

Dennis,

Firstly great reply! I'm afraid I'm a dye'd in the blood quantitative scientist so you could call me a little narrow minded, perhaps I like to see a black or white answers and maybe a little less accepting of the various shades of grey that exist. I'm afraid I can't split any more hairs as I only have a few left! Anyway I think Ian's experiments are excellent.

ATB

A

[Pharos]

Much science today is done on a quantitative basis, that is, measurement of something which has already been established.

But new phenomena are suspected, and concepts are put forward, often by radical thinkers, and then tentatively tested for plausibility. Once some validity is established, further work to validate and then determine relevant parameters is done, and then quantification occurs.

What we so often see is the latter, done on a routine basis, and much science today requires a great deal of capital investment in hardware, this precluding the individual from doing his own 'basement' science, unlike a few hundred years ago when the children of the wealthy were financed as individuals.

[Ianmac]

Chapter 3.
I have modified both platters I have.
It is easily identified why the platter is not well damped. The rubber is only glued to about 50% of the platter base and edge leaving large areas undamped and full of air.
The photo shows this clearly as the glue is not spread but looks like its a nozzle application with the pressure from the instalation of the rubber base left to spread the glue.

[IMG][/IMG]

Removing the rubber is time consuming, I took 4 hrs with my first attempt, 2 hrs for my second. First time round I tried to remove the rubber as one piece with a view to use it as a template for the new damping, trying to get a starting point wasted a lot of time.
There is no need for a template, measure - compass and good steel ruler is all thats needed.- the damping cuts easily.
The rubber fits into a groove in the platter casting around the edge, leave this to last.
Cut through the rubber at the circumferene of the base and platter edge vertical. Cut a few radius lines, search for a piece that has not been glued, lift it and work from there. I found a slicing action with a craft knife ( with break off blade sections ) the best tool.
Cut deep into the edge moulding on the verticals, then an angular cut and it will be moveable.
Slow small slices between rubber and aluminium and patience. On the final stages with thin deposits of rubber ,I used some cellulose thiners and it helped.
I finised with thiners and a kitchen scouring pad to get a sound base for the damping

[IMG][/IMG]

Fitting the damping is relatively easy. It cuts cleanly with craft knife or scissors. Ensure you fill the platter edge. I put a U channel of damping into the groove with a narrow top piece place on after the U was firmly pressed into place. Wooden or metal rollers are usefull to ensure the damping is pressed firmly to the base. I didnt experiens any problems with air bubbles but if you do a, pin into the bubble will help the air out .The damping will self seal

[IMG][/IMG]

Ill report back if needed on any issue I find but so far its ++ on both my decks

Good £20 upgrade, I doubt if you will beat it for sound for your pound.

[SiT4]

Thanks for doing all the hard work for the rest of us Ian, thats really useful info !

How would you describe the sonic benefits once the platter is dampened ?

Best

Simon

[Ianmac]

I'm getting more detail and much better dynamics on both my Decks. (One MC the other MM.)

Another level of "unwanted effects" has been removed.

I have reduced all the rubber /silicone mats,copper and SDS plates to one 2mm silicone mat and a layer of IKEA STOPP. Im still playing in this area trying to find out more about the "hardness" of silicon and where I can get softer more flexible grades

Remember any descriptive comments by anyone on techies must take into account the status of their deck, but this in my book, is a basic fundamental weakness in the technics platter construction, largely due to the way it was assembled in manufacture. One can clearly see from the photos how the rubber was not doing the job it was intended to do. I do respect the vintage of the original techie design and the price it was produced for.
In todays world there are many materials that claim to have excellent sound dampening properties. Dynamat is one and it is easy to use DIY.
Of all the mods Ive done to my decks this is one that should be done. At circa £10-£20 its a no brainer.