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Arm & Cart xyz

Think of a tuning fork. If you strike the fork, it will resonate at a particular frequency. If you put the two ends of the fork into “goop” (silicon fluid), it will quickly go silent. So vibration is damped by the goop. That damping would apply to all frequencies though, not just to the resonant one, where it just happens to be more noticeable.

Similarly, vibration from the cartridge passes into the arm and it has to be got rid of (damped). The goop does that. Goop-less tonearms also have to dissipate that energy from the cartridge, but in just the one way, by sinking it into the turntable plinth via the arm mount. In both cases though, it’s all frequencies that have to be eliminated, not just the 10Hz “resonant” one (the frequency of the tuning fork). In fact, the main 10Hz resonance cannot be eliminated, so that’s a red herring. Lemma: the resonant peak is dictated by the effective mass of the arm, the mass of the cartridge and the compliance of its stylus cantilever.

I’m not familiar with the Mission 774 arm, so don’t know where the goop paddle is. From your description of the uneven bass, it sounds like the arm is damping certain frequencies more than others. That would apply to all cartridges though, not just to AT ones?

I know you don’t want to use a test record, but making a recording of pink (1/f) or white (flat) noise would allow you to plot a frequency response. You could see how different goop paddle sizes and goop thicknesses affected it. But of course, that’s just way too tiresome and the arm manufacturer would have done it already.
 
@Avon thanks so much for this. Now, unfortunately most of it is beyond my understanding. BUT. I can now see a little more in terms of vibrations going into the goop. That's a tiny step fwd.

Many things I still can't understand about this info though. I've seen the tuning fork analogy & tried to think how this is of use, but cannot transfer these 2 forks, across to my 1 stylus. 2 into 1. And my brain stops there.

Resonant frequency.. this I've painstakingly tried to comprehend, but eludes me. Linking turnings fork(s) + resonant frequency, is like me attempting Cantonese & Latvian at the same time. As to 10hz.. I think this is a note, or is it? Or is it an 'area' of possible notes? Linking mystery notes, to my two languages, is like adding a third. I'm totally lost.

I have tried to learn what a frequency response is, but get stuck on why dB are on one axis. I can't think why, so I'm stuck before I start with these curve shapes.

What I have to do, is simplify into almost childlike analogies. All I have currently 'banked', is the cantilever acting like a car suspension; & I know this is calibrated as 'compliance'. But why some 'levers are made less & some more though, I've no idea. I can fit my paddle corresponding to the compliance number fine, but I still have no idea why I'm doing it/ I can't understand how the suspension analogy, is continued, to include this hook thing, at this far end of the arm (if it included something springy.. I could likely imagine a "double suspension" situation).

Thanks, Capt
 
Helen Bach said:
The damping is to do with the low frequency resonance peak of cartridge/arm, ideally around 10 Hz. The 'paddle in goo' thing is the damper, a bit like shock dampers in a car/motor cycle.
The cartridge/arm have to move as one, there can be no compliant materials between the two (or, in fact between arm/cart and turntable platter) HTH.
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Hi Helen, I just cannot understand what a "low frequency resonant peak" is unfortunately though, let alone a figure ascociated with it.

I understand the cart & arm need to move as one, but can't envisage any situation, on any TT I've ever seen, whereby these two wouldn't be moving as one, if that is, one is bolted to the other & not loose. I can't understand why the coupling together of these two rigid items acting as one, can be decoupled, in even the tiniest way (let alone via a hook into goop in a trough).

And furthermore I can't link/ imagine the shock absorber analogy at the trough end. I can only imagine this picture/ analogy at the cantilever end.

So as simple as your kind reply is, so seemingly clearly put, actually every aspect of it is impossible for me to comprehend.

Thanks, Capt
 
@Avon yes the nub is, as you allude to, whether all cartridges on my 774 are acting the same boomy way.

No. It's only the 3 AT's. Plus the k9 as said, but to about 2/3rds as badly.

Goldring 1012, 1022gx, 1042, denon dl110, dl103, & my prior cart to my recent AT period, a Shelter 201.. none, nada, zilch.. emitted this infuriating bass boom. And furthermore I tried the Shelter back on midway through my AT period, just to 200 percent prove I wasn't going insane, or something on the arm had suddenly changed, & this boomy facet suddenly wasn't there. As I knew it wouldn't be.

So you see I had definitively linked it, without any shadow of doubt, to the AT's.

Thanks, Capt
 
cobbers said:
By putting damping material between the cartridge and headshell.
Click to expand...

Which is what I've never ever seen, & an idea I was wondering why (as it seems such a logical thing to add) is never seen either on the top of cartridges, or, on the underside of tonearm head shells... let alone as "page 1" an idea this seems in principle to me, as to lie not upon a bare wooden bed frame, but instead upon a soft mattress in between your body & the wooden bed frame.

Here, you are suggesting this -is- something that is done. I am therefore getting even more bewildered as a result.
 
I had a 774 for 4 years and never felt the need for the damping paddle so take it off. the AT cart bodies that you are using are the cheapest on the market ie. the AT95 series was an acceptable starter cart 35 years ago and it wont matter what stylus is on it its a £10 cart body. Go back to using a decent cart and stop messing with cheap rubbish.

Rgds
Stuart
 
The Captain said:
Oof. I can't get my head around this, apologies. But why wouldn't the arm automatically follow the cart body, if it's rigidly tethered to it-? I must be missing something in my imagining what you mean.
Click to expand...
It will, but you need the movement to stop. Imagine a weight on a spring without damping, once it starts bouncing it will go on forever. If you had undamped springs on a car it would be undriveable as once it but a bump it would boing away like Zebedee for ever. Then the next bump, then the next, you get the picture. So cars need dampers. So does a tonearm. It needs to move, but it needs to stop bouncing about. You are balancing total rigidity which is no good against total compliance, which is no good either because the tail starts wagging the dog.
 
Captain, could you get someone to help you with this, or maybe you could take it to a dealer? Never transport a turntable with the platter attached of course. The AT-VM95ML cartridge you're using is superb.
 
stuwils said:
I had a 774 for 4 years and never felt the need for the damping paddle so take it off. the AT cart bodies that you are using are the cheapest on the market ie. the AT95 series was an acceptable starter cart 35 years ago and it wont matter what stylus is on it its a £10 cart body. Go back to using a decent cart and stop messing with cheap rubbish.

Rgds
Stuart
Click to expand...

Hi Stuart, know what I'm completely on board tbh. I think I will step off the AT bus now. I was hoping for an upgrade you see, simply this, from a Shelter 201. But it's turned out to be far from straightforward, with too many caveats/ things I miss about the 201, really fundamentally. So I can only go back to this cart, again (as there are no affordable 'next step up' stylus's available). I've only put 3 hrs on the ATSH.. but that bloomin bass, just ain't gonna change & is exactly similar to both other well broken-in ATML's. I'll break in & give it every chance, then it & the k9 will be up FS.

So just back to trying to understand cart/ arm basics then, even being the struggle this is proving to be.

Thanks, Capt
 
Avon said:
Captain, could you get someone to help you with this, or maybe you could take it to a dealer? Never transport a turntable with the platter attached of course. The AT-VM95ML cartridge you're using is superb.
Click to expand...

Hi Avon, thanks/ thoughtful, but really no need to take to a dealer; if I can strip & set up an Lp12 fine (& build guitar amps, modify preamps & speakers) it's not the tactile skills I lack, but understanding the "physics" of an arm/ cart.

I don't agree about the 95ML, the most obvious flaw is it's clinical quite hard sound. It's impressive in it's detail retrieval no doubt at all.. but it's just not right to me, at all. It's too fast for another page 1 thing.

Detail retrieval shouldn't be the principle goal of a cart. Connecting you with the music should be. That sums up my PoV on the 95ML. And that also sums up my view on why TT's are the best source, by far.

Thanks, Capt
 
Avon said:
OK and good luck. There must be something wrong with the 95ML I'm using then!
Click to expand...

Doesn't sound like it at all Avon if you think it's great. It's an entirely subjective thing after all. The 95SH btw, I'm using now is much better to me, the timing's right (not frantic-fast) & all organic-sounding & enticing. My boom thing is -really- bad on this though unfortunately.

You should try a 540ML.. it really is much better than the 95 & many things about it I think fantastic tbh. I'd very much like to hear the 740ML I admit just in case my boom issue -is- awol with the better body. The 740 SH.. would likely almost be the perfect cart I'd think, for me, unless this infernal boom thing happens with that too.

Thanks for your input anyway. Capt
 
This seems to predict what you describe. In other words, if something were loose "The arm is designed to direct couple the cartridge assembly to the turntable mass. This is essential in that if the tonearm suffers free play, it will inevitably set itself in motion independent of record modulations thereby adding to and subtracting from information retrieved by the stylus tip."

https://www.vinylengine.com/library/mission/774-(original).shtml

That also implies that decoupling the cartridge from the headshell could lead to undesirable results. It's another source of compliance to make another resonant frequency. However, such devices do exist:

https://jaguaraudio.com/experience-the-smooth-function-of-houdini-cartridge-isolator-by-funk-firm/
 
Avon said:
This seems to predict what you describe. In other words, if something were loose "The arm is designed to direct couple the cartridge assembly to the turntable mass. This is essential in that if the tonearm suffers free play, it will inevitably set itself in motion independent of record modulations thereby adding to and subtracting from information retrieved by the stylus tip."

https://www.vinylengine.com/library/mission/774-(original).shtml

That also implies that decoupling the cartridge from the headshell could lead to undesirable results. It's another source of compliance to make another resonant frequency. However, such devices do exist:

https://jaguaraudio.com/experience-the-smooth-function-of-houdini-cartridge-isolator-by-funk-firm/
Click to expand...

Hi Avon, interesting then that my 'theory' of a sorbothane shim or suchlike, actually has credence. As to why a -rigid, yet dampening- shim isn't par for the course for cart mfrs to add in for eg, I guess we'll never know.

[This junction an entirely separate thing from my boom issue (& AT woes) which is best dismissed from this thread as it's already veered off from my list of Q's.. apologies].

Another Q, no. 4) I get groundy-buzzing when I touch the metal arm lift. Quite prominent, like a staticy buzz sound. Never known this before. And just here too, but it's nowhere near any of the 4 diddy wires. Any ideas?

Thanks chaps, Capt
 
The buzz means the tonearm isn't attached to 0V. Does it have a separate "grounding" wire?
 
I did actually notice my one (blue) ground wire which has the single extra earth wire added, I think set up on the blue pin for my Shelter 201 before my AT recent adventures.. was perhaps wrong for the 540ML: I noticed a tiny single grounding plate on the -green- pin on this cart (presumably also the right place for the 95's, & the k9 possibly too). I didn't notice any sonic groundy noises at all though whilst listening though/ all seemed fine.

Would this one extra wire have made any difference shifted over onto the green pin I wonder?

It's the tiniest wire & a tricky solder job to move over, or I'd do it & see if the cueing arm (sorry finger lift was incorrect, it's the cueing arm which is buzzy to touch) issue is solved.
 
There should be a yellow wire on the 774 which is connected to the head block.

Grounding issues can be a nightmare to solve if there are problems (on all arms).
 
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