Arm resonance

[vince666]

The replacement carts for the Shure V15-VI such as Jico have the brush but apparently are only a sweep brush with no damping like the originals. I have one of each kicking around but I’m not home rn to compare the brush compliance...

Ah, nice to know! So, this is the reason why I read around the net that on such Jico replacements you have to add only 0,25 gr VTF when you use the brush, as opposed to adding 0,5 gr VTF with the original brush.


Regarding tonearm mass and compliances...
Shure carts are on the high compliance side then they work best with lightweight tonearms and, indeed, the S-shaped ones are mid mass ones.

My M97xE is mounted on a Pioneer PL-720 (exact same TT as PL-7 , save for the colour of the buttons) which has a lightweight arm and it works just NICELY without the brush at all, which should be the preferred situation unless there is another reason to use the brush.
In fact, I've read that the M97xE with the brush in use can still work OK on mid mass tonearms, just because of the damping effect of the brush... but, of course, on a lightweight tonearm you can choose if to use the brush or not (and setting VTF accordingly)...
And I do use the brush only when I have problematic warps... because with very light warps I have no problems even without the brush... then, maybe, this also puts in evidence that my cart-tonearm match is just very good?

 

[Makymak]

As I can understand, I have to live with this problem. My Stanton sounds very good to replace it with a more compatible cart. Maybe when the stylus wear out.

May excuse me one more question: the compliance of a given cartridge has to do with the suspension of the cantilever (and how freely travels up and down)?

 

[8991XJ]

Yes there is both dynamic and static compliance. The dynamic compliance, how springy the stylus is in the cartridge is the value we use to determine the resonant frequency.

I don't know that you are experiencing a problem with compliance and the warp but heavy arms and high compliance cartridges do result in low frequency resonances in the 5-7Hz range. Depending on the type of warp, that can also be an excitation in the 4-6 Hz range.

Since it is isolated to the first 7 grooves on the record, maybe something else is amiss but we can put it down to resonance for now since you say it happens even with there is no volume in the room which indicates it is a function of the playback device, not the system.

 

[Makymak]

THANK YOU!!!

Yes, what triggers the oscillation is purely mechanical and has to do with the system "platter - record - stylus - cart - tonearm". What I have understood from this topic, it's a bad compatibility of cart - tonearm, making the stylus bouncing off the record wrapping, and all this bounce induces a very low frequency but of high amplitude signals into the amp. These signals although not hearing, are of such an amplitude that make the recording amplifier of my decks to clip resulting in a bad recording on the tape.

What I also understand is altering the suspension characteristics will alter the compliance of the cart and the eigenfrequency of the system "cart-tonearm", right? So, theoretically, altering the stiffness of the suspension will change the resonant frequency.

 

[J!m]

That is correct but altering the suspension is not practical.

I work on watches and would hesitate to try it.

I suggest recording your first track at a lower level and then resetting your levels for successive tracks.

You could also try a high-pass filter. I can look into a stand-alone elliptic filter, which would remove the “warp” without effecting music.

 

[J!m]

I may be able to provide an elliptic filter as a stand-alone product. Place in line; probably with a bypass; possibly 9V battery powered...

This is happening real-time so it may take a week...

 

[Makymak]

I fixed it!!!

I watched carefully the stylus and found that the magnet was resting near it's tube wall. Applying the vtf, the magnet was forced further close to the tube wall, so it wasn't in it's center optimal position. Under big bouncing, there was the possibility the magnet could hit on the tube leading in sound distortion and tracking error. So, I repositioned the suspension's elastic ball and centered the magnet. It was quite a delicate job to do since there is a tension wire which locks the cantilever not to move outwards. Under some trials, I found the perfect position. Now I gain some highs (measurable) and more clarity and details (listenable).

Stanton 681EEE is indeed a great cart!!! I don't know if this cart can give something more but I'm totally grateful for what it gives me right now! Maybe under a different setup could give more but I'm just fine!

Thank you all for your help. I learned a lot from this thread!

Jim thank you for your kind offering! In first place I would like to let the signal chain as short as possible, considering my system isn't any top of the line. That's why I searched for a mechanical solution before applying any filtering. For now it looks it is fixed.

 

[vince666]

I fixed it!!!

I watched carefully the stylus and found that the magnet was resting near it's tube wall. Applying the vtf, the magnet was forced further close to the tube wall, so it wasn't in it's center optimal position. Under big bouncing, there was the possibility the magnet could hit on the tube leading in sound distortion and tracking error. So, I repositioned the suspension's elastic ball and centered the magnet. It was quite a delicate job to do since there is a tension wire which locks the cantilever not to move outwards. Under some trials, I found the perfect position. Now I gain some highs (measurable) and more clarity and details (listenable).

OMG! I sort of get scared by simply reading about what you did there!
For sure, I wouldn't be brave enough to even try to make such a thing myself.

EXCELLENT work!

 

[Makymak]

@vince666 I wasn't scared as long as I discovered the fault. I had nothing to lose, the stylus was one way or another, practically useless... It was quite good luck that it survived and more importantly, it was fixed. What bothers me, is why this happened, at first place. I bought the stylus brand new. I think it was bad batch.

One more problem, now: I have to re-record all my vinyl copies!!! That is what you call scaring!!!

 

[8991XJ]

That is why I recommended a reset of everything on the tonearm. I didn't expect it to include diving into the stylus and adjusting the position of the magnet.


more info on the resonance issue
Because the resonance of the arm/cartridge system is one that needs to avoid the frequencies of record warp, 0-3 or so and of the lowest notes on records, 16Hz and up the ideal resonant frequency is seen as 8-11 but in reality a cartridge will be able to play records even if the resonant frequency is much closer to either of those limits. I'm comfortable with a 6Hz-13Hz range with my systems. I see people making more of this than needed. The fact that your cartridges work on your turntable when you use proper styli is an indication that worrying about the exact resonant frequency is going a bit too far.

Your description of the issue only at the outer grooves led me to believe it was not arm cartridge interaction and something else was amiss. I don't know if I would have found that issue in the stylus but glad you did and got the nail sounding good.

 

[J!m]

The beauty of the elliptic filter is the way it works. It does not detract any musical information at all. The same filtering technique is utilized on cutting lathes.

I'm going to press forward on a stand-alone, because any playback chain can benefit from this gizmo. I really like it to use an internal 9V battery (or two) and therefore have no chance to add any A/C byproducts to the signal.

 

[Makymak]

glad you did and got the nail sounding good

Beginner's luck!!!

Thank you for your contribution!!!

 

[Bob Boyer]

...I'm going to press forward on a stand-alone, because any playback chain can benefit from this gizmo. I really like it to use an internal 9V battery (or two) and therefore have no chance to add any A/C byproducts to the signal.

Keep me posted on progress; I might be interested in a finished product.

 

[J!m]

circuit and board art exist; I just have to see if I can get boards, or if I have to do another run of boards. Really keen on going battery power too, but not certain that'll work yet.

Another crazy option is the battery power when on and batteries charge back up when the unit is off via A/C power.

 

[laatsch55]

Same thing my Coherence does.

 

[J!m]

Possibly where I got the idea from, but I'm not sure.

 

[vince666]

@vince666 I wasn't scared as long as I discovered the fault. I had nothing to lose, the stylus was one way or another, practically useless... It was quite good luck that it survived and more importantly, it was fixed. What bothers me, is why this happened, at first place. I bought the stylus brand new. I think it was bad batch.

One more problem, now: I have to re-record all my vinyl copies!!! That is what you call scaring!!!

Yes, it's clear... with nothing to lose, the fear of ruining a "just useless" stylus went away by itself.
And since if worked fine, that's just great... and maybe from now on, if you meet a similar problem again, you'd be more relaxed in doing the same kind of work again.
Actually, I'd be curious to learn handling issues like that... must make some practice on a couple old/worn-out cheap ones I have here and see if it's a suitable work for me or not... what scares me the most is the risk of damaging the delicate cantilever tube.

Anyways, I've got to be more familian in handling and relapping cassette deck magnetic heads... but, for sure, first time I had tried to lap a head I wasn't relaxed at all... but after a few years and several heads relapped successfully, I am a lot more relaxed now while doing this kind of work.

Well... but re-recording your vinyl copies, now that you know that they will all sound better than before, is going to be a true pleasure, IMO.

 

[borchee]

All things the same, adding mass to the cartridge will increase the resonant frequency of the arm.cartridge combo.

Yes...but adjusting/changing VTF by moving the counterweight closer/farther to the pivot, alters the effective mass as well. BTW, the vertical tracking force, or any force for that matter, is not measured in gramms, but newtons. Vince, take it from here.

 

[J!m]

I find their weight to be too inconsistent to use as a measurement standard.

 

[vince666]

BTW, the vertical tracking force, or any force for that matter, is not measured in gramms, but newtons. Vince, take it from here.

but on cartdridge's specs they mention grams and our scales usually work with grams.

anyways, since we're using our TT here on planet earth, the weight in grams is nicely proportional to the mass in newton, via the "g" constant, being the weight in grams equal to the mass * g constant. ( g = about 9.81 on earth )

and, hey, if for some reason "g" stops being the usual constant we know on planet earth, I'd say that how we set VTF on turntables would be the very last of our problems. LOL