Eminent Technology ET-2 Tonearm Owners

I recently was returned to AMC (the analogue manic clinic.)
It started with staring at the cold black turntable and dust accumulating there on. We know that seeing dust & cleaning is dangerous to many in average predominantly female persons, leading to well known manic episodes. Where at some places undefined flying objects appear, in the latter case defined objects disappear in a flying mode. Including sometimes dear and important things. (I admit havin some messie traits).
The more serious part:
I had a fight with my London pony on the ET2.5 which has its damping trough inabled, but with moderate eddy current damping provided by a small magnet (far away from the wiring).
So I still intend.ed to model the complex spring mass interactions of the ET2 & ET2.5 and I asked Bruce Thigpen (once more) for the +/- precise masses involved with the ET2 & ET2.5, and quote his given data for completeness of infos on this board:

- original aluminum wand mass: 12 grams
- CF wand mass about: 19 grams
- magnesium wand mass about: 23 grams

- Joint insert into wand is 6.5 grams

- ET-2 spindle 23.5 grams
- ET-2.5 spindle about 30.5 grams.
(spindle figures are without wire or connectors)

From measurements, roughly:

the lowest vertical effective mass is

- about 12 gram, original wand with 7 gram cartridge,
- about 12 grams CF arm wand with 7 gram cartridge
- about 14 grams for mag arm with 7 gram cartridge.

- Vertical effective mass increases about +2 grams for the 2.5 spindle.

The lowest measured horizontal effective mass is

- about 30 grams, original wand and 7 gram cartridge
- about 38 grams, CF wand and 7 gram cartridge
- about 42 grams, magnesium wand and 7 gram cartridge
- Horizontal mass increases another +7 grams for the ET-2.5 spindle.

I try to let models follow, maybe some weeks from now.
The second part in my next post:

"Do the wrong thing!"
Having trouble with my London cartridges mechanical behaviour, having tried quite long, I concluded that I simply wasn’t able to apply enough damping, the thing was "meta-stable", although there were quite a few elements of greatness.
So, what do to do? I had as an interim replacement of my MC phono stage a Lehmann Black Cube SE in use for my London, set to MM cartridges. So staring into my not (...) empty cartridge drawer, I recognized a slightly dusty beauty lurking within:
A B&O MMC1, bought from a B&O dealer, seeing it’s lonesome place in a window, this was maybe beginning of the ’90s.
So out with London, in with B&O. Well... magnesium wand, ET2.5 spindle and whatever counterweight will be: "The wrong thing".
From time to time refusing correctness is indicated by your mental health officers: Yes, the horizontal resonance is around 3Hz, the vertical considerably higher but not visible. As you may have noticed in this thread, I have my counter-orthodox opinions in case of low horizontal resonance frequencies (not in case of vertical resonance).
Theories besides: This combo works absolutely *phantastical*, it digs deep into the grooves and is highly musical as well as very uncoloured and naturally liquid. It also has deep and quick bass. It stands out of the way in communicating the music and constantly bringing this amazing slightly shuddering feeling when you enter different worlds from LP to LP, hearing amazing musical, timbral, expressive nuances.
So my quintessence is: From time to time, try things that don’t work, as far as anybody knows. And be amazed by the unexpected joys of reality vs. correct thinking. It is indicated for mental health - and for sheer pleasure & guilt.
The MMC1 is one great cartridge – as probably the MMC2 is too - and it works in whatever ET combo, I have to assume.
This is probably thanks to the B&O engineers being *the* kings of precise engineering and damping in turntables/cartridges. Remember: The actual (eternally circulated) knowledge about optimal tracing and suspension tuning / damping of turntables comes from... the B&O stable. What great lab!
PS 1: Soundsmiths SMMC1 is the ca. successor of the MMC1, except that it uses a "massive" ruby cantilever instead of a small saphire tube (with superbly mounted paratrace diamond in the original MMC1).
PS 2: It "feels" to me like every cartridge with saphire cantilever has/had a very special quality I very much like: The Sumiko Talisman S, my "special" Jan Allerts MC 1Mk2 (and MC2 Finish) cartridges, as well as the MMC1. It is a grainless coherence and ultra-quickness through the whole range through midrange into upper treble. It’s a cantilever that kind of disappears from the mechanical formula.

pegasus
Having trouble with my London cartridges mechanical behaviour, having tried quite long, I concluded that I simply wasn’t able to apply enough damping, the thing was "meta-stable", although there were quite a few elements of greatness.

@pegasus
Without more detail, the carts "mechanical behavior" we know - is greatly influenced by the I -Beam counter weight set up,

Are you using a single, double or triple leaf spring ?

Long or Short I Beam, and are you set up for the highest vertical inertia ?

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https://www.needledoctor.com/brand/London-Decca

Decca
• Output impedance: 2k ohms
• Dynamic compliance: 15x10-6cm/Dyne
• Channel separation @ 1kHz: >25dB
• Load impedance: 47k ohms

I don’t own a London cart. The Decca’s have medium compliance so just by the numbers alone they straddle between the ET 2.0 and 2.5 at 15 x 10-6cm/Dyne. Carbon Fiber or Magnesium armtube. I would set up on the Long I Beam. Double leaf spring set to the highest vertical inertia**. **Least amount of weights furthest out on the I Beam.
Try with no damping trough first. .

Hi Chris - thanks for your thoughts!
As you might remember I already owned the ET One and bought the ET2 about when it came out, and the physics behind interest me and I try to understand, master & use them since a long time... and I actually like to adjust & optimize the arm :-)

The London cartridge has a very uncommon combination of very high horizontal vs. very low vertical compliance. (ca. 40cu or more, vertical is below 10 cu). With conventional arms this leads to a one octave separation between horizontal and vertical resonance.
So, the cartridge does somehow the same "thing" with normal arms as the ET2 / ET2.5 or other tangential arm do with normal cartridges, (air bearing or mechanical passive arms) or the Moerch DP8 or the Dynavector arms: They split the resonance frequencies (of "normal" cartridges) too.
With such cartridges, I think Supexes were similar, you end up with two times the stretch of resonance frequencies - which is critical.
It results in an optimistic 12 Hz vertical resonance and 3 Hz or even lower horizontal resonance.
My London cartridge was restored and optimized by a swiss guy who learned / was trained & worked for Garrot Brothers. It has an even higher horizontal compliance than the usual Deccas (leading to lower VTF)

The lack of damping in the suspension (which provides a highly linear and probably also frequency-independent spring force) makes damping IMO a necessety. My small magnet is simply not enough, though it works very well in normal situations.

It sounded very good in pressings that worked. 
I use.d the new long i-beam, single spring, lowest counterweight far out (to bring this stiff vertical compliance to a rel. higher vertical mass).
And no it was not the low resonance of the i-beam / counterweight that made the thing slightly instable. And neither do I see a real indication that the low resonance frequency in itself was the problem:
The MMC1 has a similarly low horizontal resonance (ca. 3Hz) on my ET2.5 combo.
My feeling is also that other cartridges work more linear with wide excursions: They are more bullet proof, and "behave" better or / and are implicitely more damped.

It is BTW principally by no way easy to tune a tt suspension to fit / isolate a highly untamed vertical resonance of not far above or around 10 Hz from floorbourne vibrations.

@pegasus
(if you are disenchanted with your London) - Send it to me I will mount it and report my findings here. I have been curious about that cartridge for a long time. A good winter project and winter has come early here. 20 degrees Cel. below where we should be this time of year. So much for global warming. 8^0

@frogman
I think Frogman has one , an older version/ from what I remember? had grounding issues due to the common ground pin (3 pin) arrangement ? If he sees this maybe he can comment on the mechanical setup/tracking ability achieved - aside from the noise issues common to the older ones.

Is the damping trough a nice to have or absolute necessity with this cart. As we know the damping trough - slows - things down.