Jelco arm damping (Sumiko MMT)

[helma]

So I finally got around to testing the fluid damping feature of my Sumiko MMT. While I'm under the impression the Jelco 750D is a superior arm, outwardly they look pretty much identical and the damping system is exactly the same. I have two Lencos, other one has a Fidelity Research FR-54 for a tonearm, the other one has the Sumiko. In my past test (using the same cartridge on both) I preferred the FR-54 by slight margin. The Sumiko is a good arm but the FR-54 to my ears was a little step ahead, just generally a bit cleaner sounding.

Currently I have a AT15Sa mounted on the Sumiko and an Ortofon MC10 Supreme on the FR-54. Running these two cartridges head to head on the same arm, the AT15Sa always came up short to my ears. While it was always very clean sounding, it seemed a bit overly polite and not quite as transparent in the midrange especially. Yesterday I got a bottle of 10,000 cSt silicone oil (more on the viscosity later), did a "before" needledrop of a lead in groove + the first track, added few drops of the silicone oil into the damping well and redid the needledrop. I just wanted to get some objective info on what it does and that it's working. Doing a spectrum analysis of same portion of the lead in groove and it was clearly visible the cartridge resonance peak at 9Hz was diminished by a few dB. Also the 0-20Hz range was a bit clearer all around. What was surprising is that the peak after adding the silicone oil was actually more pronounced because everything around it was so much cleaner, but I was under the understanding damping should actually lessen the Q, spreading the resonance around with a less pronounced peak. So while the peak was about -3dB lower, it sort of stuck out more, because the surrounding frequencies were cleaned up to -6dB.

Anyway looking at the changes on spectrum analyzer, they didn't seem that big a deal (while cleaner, this stuff was already -50dB or so below actual music levels, except for the resonance peak wich was in the -30-40dB range) so I wasn't expecting much from actual listening. But the AT15Sa sounds sublime on that arm now. It's still not as "lively" as some other cartridges, but it sounds more dynamic now, because of the clarity of the music and the "emptiness" in soundstage is more empty now, making instruments stuck out more and the good qualities it always had are also emphasized, there's even better clarity and detail and the soundstaging seems more 3-dimensional now. It's hard to describe the changes, in a way they are subtle but also not, it's like a layer of extranous noise was removed from the sound(s) and only the music remained.

And now back to the viscosity, the RC car shop was low on stock on silicone oils and 10k was the closest I could get to 30k which is what I was planning on buying. The KABUSA damping kit for SL-1200 arm uses 60,000 cSt oil and on their website it says that is the thickest stuff that's still classified as "fluid" and also that less viscous stuff doesn't damp as effectively. I tried researching what Jelco ships with the arm, but couldn't find solid information, there was one Jelco email that stated 500cPs (which I understand should be very close to 500cSt) which is a lot more closer to water than even what I currently have and seems it can't simply be true, I don't think that would provide much damping at all. Other information I found suggested anything from 10k to 60k and even stating that the Jelco arms use same stuff for damping as for the cue levers, which also can't be right since the cue lever oils are usually in the range of 200k-500k or so - that stuff is more like a very thick grease.

I have 500k oil I got before for a cue lifter and I think I coud mix a tiny drop of that with the 10k stuff to get any viscosity between the two, so I might try that at some point, but I was wondering if anyone has experimented with different fluids and what worked best. Also how runny is the stuff that ships with the Jelco arms? The 10k is still clearly fluid, but it's approaching runny honey though I'd say it's more 'watery' than that.

Clearly the 10k works, it might not be optimal but at least subjectively the arm sounds way better now and I'm confident it's not overdamping but rather erring on the other side, which is good. I think with damping erring the side of too little is better than too much and certainly the sound didn't get killed with the 10k silicone oil, even though I used quite a lot of it (I kept adding it to see if there was better damping, but actually it seemed I already got past the optimal point so I might try to take some away - though I thought adding it would just be more and more damping, it seems from the spectrum analysis that my initial amount actually damped better??)

Fluid damping in arms is all new to me, but certainly seems a worthy thing to do, I might even try to put together a DIY damping trough for the FR-54 and see if I can make it work and if it would be an improvement. I could put the trough on top of the plinth under the counterweight and use somekind of paddle extending from the counterweight stub into the fluid. Not sure how effective that would be but I guess worth a try.

[blake]

Jelco Damping Oil

http://https://www.viparts.nl/product/jelco-spare-oil-damping-oil-do-01-for-the-sa-750-oil-damped-tone-arm/

[helma]

fr-damping.jpg

Ok I had the time and the curiosity, so I tried - FR-54 arm damping device in 15 minutes. It actually works, subjectively with similar (though a bit less pronounced) results as the Sumiko/Jelco above. Spectral analysis similar, about 3-4 dB reduction in cartridge resonance peak amplitude. Other subsonic resonances in the 0-15Hz range got flattened by similar amount or bit more. These figures are very much ball park, analyzing lead in groove, grabbing a just tiny bit different section of the groove the analysis can look quite a bit different, though the peak resonances are pretty reliable. And it's actual listening what matters anyway, but those lead in groove analyses are interesting in the sense they at least show SOMETHING is happening EDIT: also it's my understanding fluid damping actually works better at higher frequencies and nears zero damping the closer you get to 0Hz, so effects elsewhere might be more pronounced but I'm not sure there's an easy way I could try to figure those out.

Can't trust this aluminum foil mess to not explode on me and leak silicone oil all over the place + it's very ugly. I'll spin some more vinyl with this hack in place tonight and if the results seems generally as favorable as this first disc, I'll definitely create a better solution some other day.

[Jazid]

... Interested to know how you are progressing with these damping experiments? I have an FR54 and am keen to find out how more can be got from it.

Sent from my GT-I9195 using Tapatalk

[helma]

I think it's a good arm as it is, between the FR, Sumiko MMT & Denon DA-305 I liked the FR-54 the best, though the Sumiko with fluid damping & FR-54 without, the Sumiko would come out top at least with some cartridges.

I've continued experimenting with the damping. I made a bit better version of the trough, though the paddle is still attached to the rotating counterweight stub which makes it a bit fiddly if you want to adjust tracking weight, but it should be possible to make the trough smaller and install it right by the arm pillar in which case the paddle wouldn't have to be installed to the counterweight stub. I'll try that at some point. The cartridge I'm using is an Ortofon MC10 Supreme, which is medium compliance (15cu). With the damping trough I'm finding it clears up the upper midrange and treble especially, making the sound a bit more focused and a bit less "lively". Whether this is an improvement or not I guess is subjective, but trying to be objective I'd say the presentation is more true to what's on record now. To me it sounds like before there was a layer of resonant energy on those frequencies which was removed, clearing up the sound. I'm not yet 100% on the bass range, sometimes I feel instruments like double bass were perhaps robbed some of their character, but I'm not sure if this is a result of "overdampening" or just getting rid of a coloration which emphasized the upper harmonics. I'm also still experimenting with the amount of fluid and the size/orientation of the paddle to get it just right. Interestingly too much fluid seemed to kill the sound while providing slightly worse damping in the 0-15Hz region. Not sure why it would work like that, but that's what seemed to happen. Anyway based on what I'm hearing, I'd say for anyone not afraid of a little DIY, fluid damping is definitely something to experiment with. Besides an hour or so of my time, the total cost of this experiment was 9,90 euros for the 60ml bottle of the silicon oil, and that would be enough damping fluid for something like 10 arms. Based on what I'm hearing I don't think I'm going back, but I'll need to get used to this arm with the fluid damping and then try it without.

[helma]

fr-damping2.jpg

Version #3 of the DIY fluid damper for FR-54. I like this, it doesn't stick out like a sore thumb, except for the paddle for which a more permanent and neater looking solution needs to be figured out. In the photo you can see a top of a match sticking out above the arm - that's the arm for the paddle, on the other end there's a piece of wire ending in a vertical paddle. I'm not sure if I want more damping of horizontal or vertical movement, currently vertical is more damped. Seeing the arm moves less/slower horizontally, maybe it should be the other way around, or similar amount of damping in both directions. I guess I should study up on the subject to understand better what happens with fluid damping. The good thing is it's not exactly difficult to make different paddles using this method and trying them out, though the positioning is a bit sensitive and fiddly to adjust with the blu-tack fastening...

As the damper is closer to pivot now, 10,000 cSt fluid wasn't doing much anymore. I kept mixing 500k goo into it until I got desired level of damping. While there's still room for optimizing the level of damping, I like it better with it than without as it is. Everything is just a tad better focused. What it sounds like to me is a layer of extranous 'sheen' and noise is removed, letting the actual musical information come through clearer. With some material the change is not big and subjectively on some discs it sounds a bit more 'dead' now, but I think that is more about those records benefitting from adding a bit of distortion in the form of resonances. Well recorded music with real instruments have better soundstaging and presence, plus especially instruments with a lot of energy in the high mids / treble area are clearer sounding. Things are just better separated across the spectrum with less "bleed through" of sounds, especially as things get loud and there's a lot going on.

EDIT: one thing I forgot to mention warped records play better now. I have a one offending record in particular with a bad warp, which used to cause flutter as the warp sent the resonance into oscillation, no such thing happening anymore. I used resist playing it for that severe and rather sharp warp, but now it's ok. Still don't feel too good about a record like that, but at least it's playable.

[helma]

I added some horizontal width to the paddle, but it seems it's more sensitive to changes in vertical damping. I think I got it where I want it now, more damping would seem it might be possibly overkill.

In terms of specral analysis, as it is resonance frequency peak was lessened by about 5.5dB compared to no damping at all. About 5dB change in 0-3Hz range. These are quite significant changes, don't know if they are the most meaningful ones, but it's what I can easily measure playing a silent groove. Also interestingly rumble @ 50 & 100Hz was also reduced by a couple dB. Doesn't really matter because the levels were so low to begin with, and that measurement isn't exactly reliable because how long the motor has been on, ambient temperature etc. might also affect it.

I think it's time to stop fiddling for now and leave it be for some time and just listen to music.