Cheap upgrade for michell gyro

[gwernaffield]

hi bill the denso damp should help that , but i have seen a thread some where when the guy took the led weight off and then added the denso and put the weights back on , i think the design of the deck is that you will always get that microphone effect ,
after all every thing is connected to the chassis, Mr Moon and i are in the middle of finding out if we can use the rubber bobbins to put onto the chassis and then sit the arm board on them a bit like the old 3009 , that used rubber grommets and the bolts went through that ,
but we still think you will hear the microphone effect ,as it seems to get worse now as there is now where else for the vibration to go accept into the platter and picked up by the cartridge (microphone with a needle ) so the more you dampen one part the chassis the vibration needs to go some where else,
at this moment the chassis on the odyssey is fully dampened , which has made a difference , base has a bit more extension , along with the rest , but i think it is getting near that you just will lose all the musical feeling , to where a note is just a note, and the singer is just a singer with all the feeling kicked out , so for now the way the deck is i have no more to add,

[TAD12]

The only additional thing I can suggest is the tried and trusted Blutack. I use blobs of it to keep the feet from sliding. I have Sorbothane spheres supporting my Garrard 401 deck in its plinth. They do work. I have still to use the PTFE in between the cartridge and tonearm. I have slate flatbeds under my bass bins which are old REL 50's. I used 3cm thick slate slabs, they weigh a lot. I have a bamboo floor, with injected foam underlay, because it can go to Minus 40C here in Montreal during the winter!!!

The bins are mounted on spikes for good measure. I mentioned the spike feet in a previous note. I'll also try a blob of blutack in the spike recess to see if there's any improvement. Unfortunately it's one thing at a time. So granite base for the Odyssey first. ? Do I make it triangular or the same shape as the plastic base on which the odyssey frame sits. All comments welcomed.

Kind regards.

T.

[gwernaffield]

you would have to make the base the same thickness unless you are going to higher the motor housing , i looked into it but the cost was too much for me, and i like the fact i can close the lid to keep the dust off , instead i had 3 spare spiders and added them so now the base is 36mm and the top 2 spiders are 24mm , i had to add to the height of the motor with a bronze spacer and a bigger foot , it weighs 3kg , the microphone effect must be because the arm is bolted direct to the chassis, which we now no away around , ask Mr Moon , but if you have Granite lying around i would make it round , like this one https://www.youtube.com/watch?v=v9jD6sx7oaQ
the deck is 30+ years old, and has had a round base made , so it looks new but the motor is AC and the rest is just an old Gyro with the gold caps, board etc

[Pegwill]

Interesting observations about dampening the chassis. Alineswith much my own thoughts. I also guess that the instructions for adding the denso tape in that don’t fill the chassis completely also reenforces this. I don’t have enough skill or knowledge to understand the note we should be aiming for for bestsound. I suppose it’s really called resononce.

In my own situation I have Michell supplied acrylic base and as you are aware the pylon supports go right through the acrylic to the feet. I happen to have 3 isolation feet that I used another turntable I think I got them from Origin. They are rubber topped that go into a point and sit on brass footers. I have placed them in the opposite formation to the existing feet. This has lifted the feet off of the wooden isolation shelf that I use. I have unscrewed the feet and applied some Mortite to the remaining exposed studs. Quick and easy. Does it make a difference? I think so, massive no. It strikes me that on my setup the biggest problem I’d say is the pylon studs go through the base and therefore are connected to big expanse of acrylic that could do with dampening. Better still would be to remove the the studs through the base not sure if that is possible and then use some form of isolation to decouple the chassis from the the acrylic. Not sure if it’s possible. I need to keep it within the lidto keep the dust of but should be possible with just putting minimal isolation under the chassis.

Anyway just my thoughts, I would like to understand the resonance thing but it’s probably very scenitific and would need some sophisticated measuring equipment. As I said in my previous post in the middle of the front pylons the note is higher than aoround where the motor sits.

I did read an article where it mentions putting a thin layer of blue tack between the lead and the chassis it did say whether or not it made a difference. Anyway subjective as always I guess.

[AJSki2fly]

Anyway just my thoughts, I would like to understand the resonance thing but it’s probably very scenitific and would need some sophisticated measuring equipment. As I said in my previous post in the middle of the front pylons the note is higher than aoround where the motor sits.

I did read an article where it mentions putting a thin layer of blue tack between the lead and the chassis it did say whether or not it made a difference. Anyway subjective as always I guess.

To accurately work out what is going on you need one of these. https://www.bksv.com/en/products/tra...erometers/4374 The potentiometer can measure vibrations from 1 to 26Khz and they are very accurate. So with the plater turning you would mount the potentiometer in different positions on the chassis and at each observe through an oscilloscope the resonant frequencies, you could record these to tape as well for referencing back to. Then with the knowledge of what frequencies were the issue you could make changes to the chassis with sound deadening materials or physically to the chassis and then re-measure and see what effect this had. This would be a gradual and time laborious process ultimately with the aim of limiting the resonances as much as possible and also any that remained to be lowered in dB as much as possible.

It can be done and I have done it many years ago on several different objects when I worked at a sound and vibration laboratory, but never on a turntable.

[Pegwill]

Hi ASJki2fly

Yep as I suspected quite a bit of money just for the potentiometer alone on eBay is £114.00. Would it be possible to compare the note as this converts into a frequency. I have a clip on guitar tuner that works on vibration that I will try, although it needs to be within that range. Do you have any idea of the frequency I should be looking for? Not sure if it will work but in theory there’s nothing lost especially when the whole essence of this thread is improvements on the cheap.

Many thanks

[AJSki2fly]

Hi ASJki2fly

Yep as I suspected quite a bit of money just for the potentiometer alone on eBay is £114.00. Would it be possible to compare the note as this converts into a frequency. I have a clip on guitar tuner that works on vibration that I will try, although it needs to be within that range. Do you have any idea of the frequency I should be looking for? Not sure if it will work but in theory there’s nothing lost especially when the whole essence of this thread is improvements on the cheap.

Many thanks

Hi William

I could not even guess the frequency without at least hearing it and my ears are not that well musically trained I am afraid, even though I used to play guitar.

If you have a computer and a microphone for it and a a recording of the note then you can analysis it using REW software that is free. I have used it to do some basic measurement of speakers and to experiment with their position in the room and also my listening position. I did briefly play around with soft furnishings and there effect on the reverberation/acoustics of the room.

Have fun,

Adrian

[gwernaffield]

have a look at this if you want to go further, https://www.ebay.co.uk/itm/SMART-SEN...UAAOSwhUpcbldH

[Pegwill]

I did a bit more research on this and just asi suspected it is a lot more complex. The resonant frequency would appear to be between 5 - 8hz so that instrument will not measure low enough. This is not worth pursuing because of the likely costs. I will have a look at putting some extra dampening as you would if using the the denso from Michell. One interesting observation I did pick up is that it is obvious if you think about it is that there is more weight on the arm side and so it will be always out of balance with and need levelling with the pylons. Also the resonance on that side will be different due to the increased mass. As I said far to complicated to contemplate.

[AJSki2fly]

have a look at this if you want to go further, https://www.ebay.co.uk/itm/SMART-SEN...UAAOSwhUpcbldH

I doubt it is sensitive enough for the levels I think we would want/need to detect.