et-2 damping trough-good idea or not?

phillippugh

is the trough a good idea ?

imo - the quick answer is it "depends" on how you have your ET2 setup, with what cartridge you are using.

Some history first
The first ET2's came out when MM's were popular. The same year CD's were introduced..... 8^0
Great timing - Still over 2500 out there. Imagine if digital was not around for another 5 years?
 
Anyway - So all early ET 2.0's had aluminum armwands. Bruce' tests with the damping trough reflect this armwand.

If you are using an aluminum wand, especially with later MC Carts, the damping trough is an improvement in resonances.
Years past I found the results very audible, and the amount of oil used directly effects how much damping is done.

The oil trough can be left on - you just turn the paddle screw in or out, so it is either touching or not touching the oil.

Note If someone has a Cat or Dog and or Pet, or other that sheds, the hairs, other floating material will find its way into the trough. The nature of the hobby. static, other, ensures this.  

Now,
Later advanced ET 2.0 and 2.5 setups use different Armwands (Carbon Fiber and Magnesium), and different Leaf spring setups so they match up well with the Cartridge being used. This is discussed in detail on the ET2 tonearm owners thread.

https://forum.audiogon.com/discussions/eminent-technology-et-2-tonearm-owners


This along with a properly isolated turntable, negates the need for a damping trough - imo.

My two cents. Hope this helps a bit.   Cheers

@rauliruegas

raulireugas
Dear @frogman : I’m not an expert with the ET-2 that I owned many many years ago.

frogman
On that point, we agree.

raulireugas
**** If that " damping " does not affects the normal and " free tonearm/cartridge movements ****

Frogman
It does.

From the damping trough manual

Please note that the tonearm now responds much more slowly due to fluid damping.

The ET2 maker designer and Frogman are telling you Raul that the tonearm movement is affected.

****************************
Getting philosophical now
One can only assume at this point that you hold such strong biases, that you refuse to believe the movement of the tonearm can be affected by the damping. This is not a pivot point in a tray that holds some oil.

Picture two people going across a lake on a canoe. Only the front person is paddling. Then the back person who has been enjoying the scenery chooses to just stick his paddle in the water and keep it still - will it affect the course of the canoe. Of course it will. The back paddle is the paddle in the trough of oil and it moves along with the air bearing spindle.

*****************************
You ask me about my experiences. I say dont be lazy.
go to - forum.audiogon.com on your computer/phone/tablet

place "Et2 damping" in the search field and you will find "114" responses.

Many are mine. Some are Frogmans, some are R Krebs, some Dover, etc....

God only knows what I have posted in the past. I do not give my family my name here. 8^0....lol

My virtual system shows pictures and details of my cartridges you request. Pic 31 shows the damping trough.
Good ? good....now

******************************************

raulireugas
I posted the true enemy that we have ( is a must to. ) to " figth against it and try to win in any analog rig are: generated resonace/vibration/developed distortion, named as you like or want it.

if this is really something you mean, then you owe it to yourself to set up an ET 2.o or 2.5 on one of your multiple tables with multiple tonearms showing in your virtual system, that house not ONE proper linear tracker. This shows to me a BIASED person. Now you can name your favorite cartridge and we can help - will instruct you on how to assemble it - ET 2 or 2.5, which armwand, which leaf spring. 3 things to consider. You see Raul - set up is three dimensional...... eh....8^0 ,,,think about it. Maybe you are not looking for new adventures ?

These days my priority is to get through as much of my music collection as I can through the winter months. In the Audiophile days and today still anyway - I am in the camp for the cleanest signal output from my turntable; then ....and this is the very important part.... the remaining chain components are selected and positioned to support THIS.
You see Raul, when your system kit has been set up in this fashion - the Q Resonance Bumps discussed here of my pivot arms owned became very obvious to anyone listening. Now, IMO if anyone’s gear - speakers/amp/ preamp have a harder time pressurizing their space - sometimes this Q resonance bump can be welcome; But it is not part of the music - it is equipment resonance - distortion. It wasn’t on the tape for one thing. I remember to this day when running with the Quad 57’s and two subs - that the subs for the FR64 tonearm needed a different subs setting than the ET 2.0 and R2R that was running in that room concurrently. The bass resonance with the FR64 was emphasized - Q resonance. I did not need it in that space. The VPI JMW 12 had similar characteristics.

Raul you have inspired me to post another Yellow Sticky on the ET2 thread.

Hi Frogman/Raul - hope this helps a little. I needed the rehash. Let’s try to understand this better and hopefully in words that anyone reading this can understand.

So we know it’s a resonance, vibration hobby - playing records. As far as the tonearm/cartridge combination mechanics on their own - it’s a spring system, with a natural occurring frequency -Resonant Frequency. Thinking about a tuning fork helps. A stiff tuning fork resonates high. Like a stiff MC cart with its low compliance cantilever. A "less" stiff tuning fork resonates lower - like a less stiff MM high compliance cart.

This shiny piece of black vinyl record is not perfect as we know. Non-centered center holes that cause speed and other issues, warps, scratches..... but if we look closely when the record spins, surface irregularities exist. Bruce discusses this in the damping trough manual. These irregularities are not part of the cutting process, but the molding process in making the record. You can see the small ripples on the surface as the record turns. These ripples excite the "natural resonant frequency" of the tonearm/cart. combination being used.
We want these resonances (which are not in the recorded music) to remain well below 20 hz where we can’t hear them. When a tonearm and cart are badly matched - resonances will rise and could and do cause problems. if the system is resolving enough it will be heard.
Bruce did measurements and found most tonearm/cart combinations give rise to the frequency some as high as 8db with high Q. Ok this is technical. Applies to speakers also, and this number would not be tolerated there. Yet no one has ever discussed it with vinyl play. 8^0... Anyway, the result of this resonant rise, he called the "Effects" - and they can be subtle and sometimes not so subtle - reproduced on our systems.
The Effects can cause a phase shift. Put simply the time the low frequency signals come from the tonearm/cart, are slightly shifted from the mid-range frequencies within the audible range, and substantially shifted up to several periods of resonance. Bruce measured near perfect low frequency phase response when the original ET 2.0 was used with the damping trough.

************************************************

The first ET 2.0 with "aluminum" armwand came out when MM’s were popular. So.....1) aluminum armwand with 2) MM cartridge, and 3) single leaf spring. The three are a good match in resonant natural frequency. Then stiffer lower compliance higher resonant MC’s arrived, and the damping trough was introduced.

*************************************************

TAKEN FROM THE DAMPING TROUGH MANUAL
.

Please note that the tonearm now responds much more slowly due to fluid damping.

A low frequency sweep was performed twice on the tonearm, once without the damping trough and once with the damping trough. The cartridge used was of very low compliance and the tonearm was set up so that a high amplitude high Q resonance existed. The results of the test show a reduction in the amplitude of the resonance of about 8 dB (horizontal). Not shown is the vertical resonance which was 15Hz with this cartridge and was reduced about 2 dB.

https://photos.app.goo.gl/oWHujb7CygwLU8SC7

****************************************
In due course Bruce introduced the larger bored out ET 2.5 (lower resonant frequency air bearing manifold) with Carbon Fiber and Magnesium armwands were introduced, along with the double and triple leaf (stiffer leaf) springs to deal with stiffer higher resonant MC. So - Likewise the ET 2.5 with Magnesium wand mated with double or triple leaf spring, mated to a high compliance MM is a bad match.

***************************************
The first ET 2, the 2.0 version. with "aluminum armwand", and low compliance MC cart produces higher resonances - and is a bad match. Frogman confirmed this with his findings here.

****************************************

There are folks on the ET2 thread that are using an ET 2.0 with aluminum wand and MC and single leaf spring, and do not have a damping trough. Most have made other mods - either to the headshell or armwand to compensate. So anything is possible but we really do need details on gear setup here, when people give their opinions. For it to be helpful to other people. This is not plug and play. Vinyl never was in the higher end. 

Remember we have no idea what lies downstream of the turntable in peoples homes and how the rest of the audio chain matches up to what is before. This helps to explain the infinite opinions on this forum.
This link in the ET2 Tonearm Owners thread, shows the setup to be followed for MM and MC carts - endorsed by BruceThigpen.
We called it one of the yellow sticky guidelines

https://forum.audiogon.com/discussions/eminent-technology-et-2-tonearm-owners/post?highlight=yellow%...

@rauliruegas

Raul - firstly - what I like to keep in mind for myself. It helps me is this.
All around us are materials that have their own resonant frequency. Now when something is made - with multiple materials, like a tonearm or a cartridge, the resonant frequency becomes that of all the materials, and it depends on what percentages of each material that went into making that tonearm or cartridge. We then join those two - tonearm and cartridge - we get another resonant frequency, and then they interface with something - in this case the vinyl record.

When they are put against a moving vinyl record which is not perfect, and has imperfections I discussed previously - like the ripples; these imperfections, since this is a vibration resonance activity - EXCITE - the resonances. You can see how much in the graph.

That could affects in some way the freely cartridge stylus ridding the recorded LP surface but for forgman " overdamps " with the other wands but aluminum where is an improvement

Look at the graph in my previous post. It describes this scenario. That was a low compliance cartridge set up to produce a lot of resonance with the aluminum armwand. The oil trough smoothed out the resonances. It helped. Now if the carbon fiber or magnesium wand was used instead with the trough, because of these armwands lower frequencies the damping trough would probably have been too much. The results would not have been good and I believe this is what Frogman experienced.
Maybe Frogman can elaborate here if what I am saying is off.

Raul - while acknowledging your experience using damping troughs with pivot arms, you need to recognize that the ET 2.0 and ET 2.5 are unlike any pivot arm, especially when discussing resonances, damping troughs and their effect on Q. They are unique among air bearing linear trackers as well.
Bruce Thigpen has done extensive measurements not just on the ET 2.0 and 2.5 but including many pivot tonearms.

*****************************************

Mass from different wands changes the resonance frequency, but
has very little effect on Q, (the sharpness of a rise in response). A pivoted arm sums the vertical and horizontal resonance frequencies (because of the pivot, they are the same value). The typical rise at the resonant frequency of a pivoted arm will be 12-18dB. Audio Magazine published these figures when they tested tonearms from around 1965 until they ceased publication in 2000.

The ET-2 or 2.5 by comparison splits the resonance into two
different frequencies, one for vertical and one for horizontal, (the
math and discussion are in the tonearm manual) so they do not sum and
the rise is usually about 6-8dB which is much better. This results in a lower wow and flutter figure (about half) when you compare an ET-2 with any pivoted tonearm on the same turntable.

-brucet

*******************************************

So Audio Magazine published these figures when they tested
tonearms from around 1965 until they ceased publication in 2000.
Would you or anyone else reading this - have magazines from that period that show results ?

Anyway Raul, if interested to come up to speed on the ET 2 and 2.5, a good start is with the technical section of the manual. Then I would recommend doing a search on yellow stickies in the ET 2 thread.

The decision for an ET2 owner on whether to use the trough is like having your cake and eating it to. It’s not a this or that scenario, but both. As discussed in this thread already, the oil trough paddle - is a screw design and can be raised to dis-engage and lowered to engage the oil.

It does add 18 gms so putting it on a lightly sprung table like a Linn needs to be considered. 


Cheers Chris

Raul - what are you trying to gain from this thread ?
I thought it was to learn about ET2 damping, which means to me, learning about how resonances affect the tonearm, and how it deals with them. Apparently not from your response.
The OP of the thread got his answer a long time ago.
So whats your objective here ?

@rauliruegas 

no one is at fault Raul when we are in learn mode.  the forum mode here makes discussion challenging sometimes. Especially when I am not able to link pictures from my virtual system into a forum thread. I am forced to add a picture to my external google account and link it.  

I mentioned that this is a 3 dimensional setup - meaning 3 aspects need to be considered. 

1) armwand which you reference. 

2) leafs springs on the I beam that hold the weights. these are small flat leaf springs that we attach to the I beam that holds the weights. We match the spring compliance to the cantilever compliance  SO - 1 leaf is the most springy / compliant-  for MM carts.  2 or 3 leafs joined together become firmer and match well to MC carts with stiffer cantilevers.  
.  
3) ET 2.0 and 2.5 - the air bearing manifold in the 2.5 holds a larger diameter air bearing spindle. It resonates lower. think of hitting two hollow pipes -  one is 1/2 inch the other one inch. The one inch pipe will resonate lower and it matches better to MC carts as they are stiffer than MM and resonate higher. We need to bring their resonances down.  

I will be posting an ET2 Damping Yellow Sticky on the ET2  thread soon and leave open discussion questions there as well.  

I am hoping that you liked my Tale of the Canoe ride going across the lake. It was trying to show what the trough paddle is doing. See picture 31 of my virtual system for a visual of this picture.