I guess thats what makes this a great hobby. Your own take on whats going to work for you, and exploring different approaches....
It would be interesting to know at what point the reduction in
weight of the arm becomes a detriment for what kind of cartridge.
Like I say, for $8 a wand with bearings included, I'll stock many,
in different configurations and weight combos for experimentation.
One of the reasons I built different types, was to try different carts and see how they react. For instance, I've tried the 440MLa and it is too compliant even for the lightest arm, but I kinda figured that would be the case. But maybe with some trial and error....I can come up with something that will work with a higher comp cart.
And as far as MC carts, that would be the next road to travel.
Good thing I'm employed....lol
It would be interesting to know at what point the reduction in
weight of the arm becomes a detriment for what kind of cartridge.
Like I say, for $8 a wand with bearings included, I'll stock many,
in different configurations and weight combos for experimentation.
One of the reasons I built different types, was to try different carts and see how they react. For instance, I've tried the 440MLa and it is too compliant even for the lightest arm, but I kinda figured that would be the case. But maybe with some trial and error....I can come up with something that will work with a higher comp cart.
And as far as MC carts, that would be the next road to travel.
Good thing I'm employed....lol
Hi Colin
thanks for your response on the bearings. You have described exactly what I did last night. Having had a Cantus I knew the bearings should be affiixed to the shaft rigidly-otherwise the whole carriage would slew around in use-as we know! Weight of whole carriage including cartridge is around 22g. Lashing up a 'first off' at the weekend. Will report back........
chris
thanks for your response on the bearings. You have described exactly what I did last night. Having had a Cantus I knew the bearings should be affiixed to the shaft rigidly-otherwise the whole carriage would slew around in use-as we know! Weight of whole carriage including cartridge is around 22g. Lashing up a 'first off' at the weekend. Will report back........
chris
I'll have to revisit the 440 Colin.....but the AT 13Ea works much better on my arm. The 440 is sitting on another table and I'm not pleased with it there
as well.....perhaps its a bad cart. I'm back home this weekend and I'll give it another go.
My bearings spin effortlessly, and ride the tube excellently.
I have a video made back in Nov of the first prototype sitting on the tubes,
the tubes moving back and forth, and the carriage staying for the most part
still, I'll try and dig it up and post it today if I have time.
Speaking of video.....any one else care to show their piece in action?
Would be worth a thousand words.....
as well.....perhaps its a bad cart. I'm back home this weekend and I'll give it another go.
My bearings spin effortlessly, and ride the tube excellently.
I have a video made back in Nov of the first prototype sitting on the tubes,
the tubes moving back and forth, and the carriage staying for the most part
still, I'll try and dig it up and post it today if I have time.
Speaking of video.....any one else care to show their piece in action?
Would be worth a thousand words.....
The carriage mass looks like a real balance of comprimise. Low mass for tracking. Higher mass for holding the cartridge more stablely at audio frequencies and higher armtube rigidity. I would be interested to know what the maximum mass you can make the carriage without tracking problems. A simple experiment of adding blutak or similar to the carriage until tracking becomes an issue
Sorry hit the wrong button and prematurely posted.
My calculations suggest that if bearing friction is negligible an ideal carriage mass would be about 50g for a cartridge with a 20um/mN compliance. If anyone fancies testing to see what the real world max mass is I would be most appreciated
Niffy
My calculations suggest that if bearing friction is negligible an ideal carriage mass would be about 50g for a cartridge with a 20um/mN compliance. If anyone fancies testing to see what the real world max mass is I would be most appreciated
Niffy
For a low mass carriage you need the mass distributed towards the ends of the wand to keep the effective mass high enough. Conversely to maximise rigidity and to push the resonant frequency as high as possible you want the mass concentrated at the centre of the wand. To push the rf and rigidity as high as possible whilst retaining correct effective mass requires a more massive carriage. Comprimise comprimise.
Niffy
Niffy
PDR,
I recall reading the 120 stylus sounded better than the 440 microline so this makes sense. At carts can be fussy for best setup, and require tracking weight above the recommended middle to align the magnets properly.
My apologies, don't mean to insult your bearings, I'm sure they run smooth. I was originally trying to lower the mass a lot, I found this was affecting the sound and thus began increasing it it 20grams plus. For what its means, Clearaudios arm wand weighs more than 30grams without cartridge.
Colin
I recall reading the 120 stylus sounded better than the 440 microline so this makes sense. At carts can be fussy for best setup, and require tracking weight above the recommended middle to align the magnets properly.
My apologies, don't mean to insult your bearings
, I'm sure they run smooth. I was originally trying to lower the mass a lot, I found this was affecting the sound and thus began increasing it it 20grams plus. For what its means, Clearaudios arm wand weighs more than 30grams without cartridge.Colin
PDR,
My apologies, don't mean to insult your bearings
Colin
No apologies needed...
....I wasnt implying.I have been trying to decrease the the mass. This weekend I'll experiment
with raising it in increments. Whats your/anyones thoughts on counter weight placement? Closer to the carriage the better?
More wands to build....sweet.
2.5hz is a bit low as it is nigh on impossible to isolate the turntable from environmental noise at this frequency. Even turntables with very compliant suspensions have the suspension resonant frequency at about 3hz, every thing below that gets through.
I reckon that a golden ratio above the suspensions rf is the target cantilever rf. For a 3hz suspension the target rf is about 4.85hz. For a 20um/nN cartridge this would equate to a required mass of about 50g.
The effective mass vertically needs to be less as significant warps occur up to about 6hz. So a cantilever resonance of 9.7hz and effective mass of 13.4g.
Don't worry about effective mass not being the same. On records low frequencies below 200hz are mono, lateral modulation only. Furthermore at audio frequencies lateral movements of the arm are very small, less than a couple of microns. If they weren't you'd really hear it. At audio frequencies the arm does not move straight side to side, rather it rotates about its centre of mass. A one micron movement at the cartridge on a 75mm arm twists the arm through less than a thousandth of a degree. No arm has less than that degree of play. Nature always take the lowest energy option. It takes less energy to ratate than to linear translate by the same distance at the cartridge. The effective masses when measured about the centre of mass of the carriage are going to be nearly the same.
Niffy
I reckon that a golden ratio above the suspensions rf is the target cantilever rf. For a 3hz suspension the target rf is about 4.85hz. For a 20um/nN cartridge this would equate to a required mass of about 50g.
The effective mass vertically needs to be less as significant warps occur up to about 6hz. So a cantilever resonance of 9.7hz and effective mass of 13.4g.
Don't worry about effective mass not being the same. On records low frequencies below 200hz are mono, lateral modulation only. Furthermore at audio frequencies lateral movements of the arm are very small, less than a couple of microns. If they weren't you'd really hear it. At audio frequencies the arm does not move straight side to side, rather it rotates about its centre of mass. A one micron movement at the cartridge on a 75mm arm twists the arm through less than a thousandth of a degree. No arm has less than that degree of play. Nature always take the lowest energy option. It takes less energy to ratate than to linear translate by the same distance at the cartridge. The effective masses when measured about the centre of mass of the carriage are going to be nearly the same.
Niffy
Counterweight placement
I have found counterweight placement to perform best further away from the carriage, doing this also increases dynamic vertical effective mass. Also this allows for a lighter configuration as a 10gram weight near pivot can be reduced to as little as 4 grams further away, but I have found ideally on these arms the weight should be the equivalent of the cartridge weight. Without cartridge or counterweight the carriage should balance out on its own, this has seemed to be a good engineering guide to shoot for.
Colin
I have found counterweight placement to perform best further away from the carriage, doing this also increases dynamic vertical effective mass. Also this allows for a lighter configuration as a 10gram weight near pivot can be reduced to as little as 4 grams further away, but I have found ideally on these arms the weight should be the equivalent of the cartridge weight. Without cartridge or counterweight the carriage should balance out on its own, this has seemed to be a good engineering guide to shoot for.
Colin
No apologies needed...
I have been trying to decrease the the mass. This weekend I'll experiment
with raising it in increments. Whats your/anyones thoughts on counter weight placement? Closer to the carriage the better?
More wands to build....sweet.
Hi All,
Need to get my tupenny in and give a small update. Got a new arm built with the two tubes mounted on an aluminum "L". Using all the previous mounting setup. Don't have a dust cap rigged yet. Pics coming soon. Did have to build a new carriage though, the old one didn't quite squeeze in. New one uses the "T" shape mount for the bearings and wand, and the wand is a birch dowel, 2.5" long, drilled out and finished. Something left over from old experiments. Whole thing weighs in at 14.5 grams cartridge, wires, counterweight included. While it tracks beautifully at 1.2 grams somehow there was something not quite right. To borrow a description of what an XLM sounds like from VinylEngine, that cart on the previous 2 tube lashup
has always sounded like an "open window at a concert hall". On the 14.5 gram carriage it was more like someone pulled the screens down. Next I put an extra 5 grams of putty (lacking BluTack) in a lump on the vertical carriage member, rebalanced for same tracking force and the window opened up again. Must do some more listening and weighing the old carriage from the single tube arm. It is way too early and too few samples but based on some previous tests of other configurations I suspect 14.5 grams is too light. I'm still wild about the XLM! and the LT. BTW XLM = extremely low mass.
rgds,
BillG
Hey Bill thanks for yor post and your efforts too. Wondering if you ever did a direct comparrison of a ZLM and an XLM or the XLM and the XLM ll/ I had the XLM for a long time Still have it packed away but it needs a stylus. tried a ZLM for a short while on a different table and arm thought it was ok but was not able to compare it to my XLM. I always likes the XLM and so I kept it after the tip was damaged and just never got it replaced for one reason or another. Good cartridge. Best regards Moray James.
