Strange subsonic rumble problem?

That's strange. I would put the Koetsu back on that arm. If it there is no problem after that, then at least you know it's not the arm. Could be that the Ikeda Kai has a problem. Try it out on another table.

Is this the first time you had the Kai with the FR? Rumble is usually caused with arm and cartridge mismatch causing the cartridge to resonate. If you have a test record with that test track it will verify this. I found this out the hard way after blowing woofers!

I used the Kai with FR 64s in the past with no problem but never tried it with 66s. After I put the Koetsu back on, the rumble was still there also. Koetsu/Ikeda was connected to
Audio Tekne SUT into Asthetix Io. Using resonance evaluator on vinyl engine, resonance is somewhere between 8-9 Hz with effective mass 38g for FR 66s so it should be ok though.

That resonance is on the low side close to record warp frequency! Nine times out of ten this will cause woofer pumping. You should get a good test record so you can see this for yourself.
I use Shure ERA 1V TTR115 test record, it is invaluable for this test.
You can find them on Ebay for about $20.00. It would be a wise purchase for someone like you who is into vinyl.

Maybe that arm/cart combo does not like that record? Does it do it on other records? If so, you may have a problem with the arm.

have you checked if your FR66s arm is properly grounded?

Sarcher, it happened with every LP and Reed/Lyra did not have any problem with rumble on any of those LPs. Anyhow, for some reasons, the rumbles all disappeared today. All I did was taken out the phono cables from Audio Tekne and and plugged it directly into my Thoeress phono instead (mainly because it was a lot faster to turn on and off and I don't have to wait as long in between while I tried to fidget with the arm/headshells etc. Go figure, don't know what is going on but will try to plug it back into AT SUT/Aesthetix later.

11flat6, not sure what you mean by teh arm properly grounded? As in the ground lead on phono cable?

Yogiboy, I do have a few test records, if the prolem recurs, I will verify it with a test record, thanks.

Hmm. I guess it's just a bad connection. I would not think that would cause woofer pumping. Could be something is causing the preamp to go into oscillation? Maybe someone with more technical background could elaborate?

Combination of an arm/cart mismatch that excites a room mode.

Hmmm.... when I reconnected FR/Koetsu to Audio Tekne SUT/Aesthetix Io, rumble came back again :(
This is getting rather strange. I assume it means something downstream from the arm that is now the culprit. Bad tubes in Aesthetix? The sound seems fine though.

It could be tubes. I would contact Glenn at Aesthetix, and explain the issue. I'm sure he can help you figure it out.

Could it be the combo of the Audio Tekne transformer and the Aesthetix Io? Have you tried the Io alone with another cart.
Most users with Io owners use it without a transformer from what I have read. I understand why you are using it that way since the Ikeda output is so low.

I agree with 11flat. It could be a grounding problem with the FR66s.
First try the 66 not grounded and see if it is the same problem.
Checking from then can be difficult if the issue is around the tonearm itself.

I am not sure what do you mean by grounding problem? I assume it is the ground lead from phono cable or is there something else? The FR has no problem when connecting through Thoeress preamp though so if it is a problem in the arm itself, I assume that the problem would occur with either phono.
In my Aesthetix Io Eclipse, I only have tubes in first 2 gain stages and not in the third so it gives about 50 dB of gain plus Audio Tekne SUT which gives just the right amount of gain for Ikeda. This combination works great with Ikeda on my
FR 64s for many months. I tried replacing Audio Tekne with Ikeda SUT and the problem is still there.

Will have to find tubes to put in the third stage and bypass SUT completely and see what happen.

Bad tubes are probably less likely as well as rumble occurs in both channels. Chance of tubes failing in the same way in both channels at the same time probably is pretty low.

I talked to my Aesthetix dealer and they will get back to me.

Suteetat

Well you have ruled out the Tekne SUT with the Aesthetix since it works with your other arm.

Perhaps the ground lead has come undone inside the arm. Check continuity with a meter.

Hmmm.. I think it is definitely the phono unit that is causing the problem. Ground on FR66s seems to be fine.
Today, I tried Reed/Lyra with Aesthetix and rumble occurs again (neither FR or Reed had rumble with Thoeress phono).
I put Kinetic Wave footers under Aesthetix and that seemed to reduce rumble a bit as woofers are not pumping as much but rumbles are still there (may be I am only imagining this). My Aesthetix dealer (also distributer) unfortunately left for CES a day after I talked to him so will have to wait until he comes back in a couple of weeks... oh well.