Fine tuning the Evolution (Vic's) Ladegaard type arm

301, 401, plinths and assorted idler stuff
Clive
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#1 Fine tuning the Evolution (Vic's) Ladegaard type arm

Post by Clive »

Sometimes with my 301 I find that the last third of an LP side can exhibit some ringing, mainly on piano and female vocals - notes take on a "warble". At first thought it was valve microphony but I think I've narrowed it down to the 301. I suppose the area where it starts is about half way between the platter edge and centre. So next I tried using my record puck, this seems to have improved things.

My theories so far are that either platter in ringing or that some records are slightly dished and the puck ensures good contact with the platter mat.

Does any of this ring true with anyone?.....
Last edited by Clive on Sun Dec 02, 2007 12:00 pm, edited 2 times in total.
Clive
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#2

Post by Clive »

I'm thinking now that the warbling sound is to do with the volume of air pumping into Vic's Evo arm. I'll report back when I've played some more.

Edit: Vic tells me it's too much air for the pump, I just need to turn it down. In the past too much air has resulted in a pumping sound from the subs, this seems to be a variation on that.
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#3

Post by Darren »

Hi Clive,

Read your post late last night and put some thought into it.

Nope, can't say I've experienced what you describe? Maybe you have the answer with the quantity of air. :?:
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#4

Post by Clive »

Maybe the pump inhaled some "wind"!
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Greg
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#5

Post by Greg »

Hi Clive,

Could this be a result of air delivery oscillation effecting the arm? Makes me wonder about further exploring the option of steady constant air delivery from a air cylinder through reducing regulators. What do you think?

Best wishes,

Greg
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#6

Post by Clive »

Hi Greg,

I reckon the bass pulsing I get when the air is turned up too high is due to air supply oscillation. The warbling effect is maybe the same or it is mis-tacking in some way. I'm sure a constant flow of air would make setup much easier and less likely to need tweaking when temp or other conditions change in that the arm will be less sensitive to the air supply in the first place.

Vic now runs his pump at max but has an air flow valve near the arm to reduce the supply. I've just bought a valve and will install it later today. I can imagine that running the pump at max and then restricting the flow could reduce oscillation but also put stress on the pump but maybe it just pressurises the reservoir better.
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#7

Post by Darren »

Hi Clive,
You might find two reservoirs give less pulsing?
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#8

Post by Clive »

There seem to be a couple of variables at play here. The setting for the air has become more sensitive since I placed the pump in the next room, the much longer air supply tube seems to be responsible. Yes a bigger reservoir seems like it should help but it may be that the length of tube on the output of the reservoir is a big factor.

I've just tried the valve close to the deck with the pump on max. So much easier to set, if only because the control valve is close to the deck. I just back off the air until the stylus skips and then increase air flow a little and its done. The warbling seems to be banished.
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#9

Post by Clive »

Greg,

My feeling now is that the pulsing when using high airflow is not pulsing from the oscillating pump but is instead due to the arm carrier being lifted by the air, which released the pressure so the carrier then drops and the cycle continues.

Cheers,
Clive
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Greg
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#10

Post by Greg »

Hi Clive,

Yes, I think I understand where you are coming from here. Are you therefore suggesting that the problem lies with the actual air delivery at the hovering armboard? It seems it is difficult to regulate the pump so that you have a consistancy of pressure under the armboard to allow it to float without any fluctuation. Of course, it might work better if you upgraded your pump to the later four output Sera 550R that Vic now supplies, however, given the audiofile level at which you are personally operating, I have some doubts about this. The other almost unthinkable consideration is that there is a design fault. I hope not.

Regardless, I still feel an air supply system which delivers at a constant pressure has to be the way to go. Modern regulators are a bit like modern batteries. They'll keep up the required delivery until the last minute when it'll suddenly drop and die. With a pressure gauge fitted at the first stage regulation from a compressed air cylinder, it would be easy to determin when you're reaching the run out stage and time to fit a new fully charged cylinder. In my view that would be a modern 300 Bar cylinder approaching a volume reading of 50 Bar. 1 Bar means 1 barometric pressure which is roughly 14.5 pounds per square inch. From that information it is easy to calculate the delivery capability of a charged compressed air cylinder. What is essential is understanding what volume of air Vics arm requires per minute/hour. I've only done this in theory but a fully charged 12 litre 300 Bar cylinder should have the capacity to provide over 6 hours playing/operating time. A cylinder refill works out I think at around £10. Seems a good deal to me.

I really want to do some work on this but my time is so tied up with my mother as I've already explained privately. If you want to pursue the option, I suggest the place to start is your local BOC (British Oxygen Corporation) depot and take advise from there. They can be a bit basic on this sort of thing and if you get no joy, come back to me and I may be able to point you towards other firms that can help. As said privately before, you should be able to set up a well regulated constant pressure air supply with sufficient volume for several hours playing before needing to change the resevoir cylinder.

I hope that helps you think further. Please feel free to share this with Vic.

Best wishes,

Greg
Last edited by Greg on Mon Nov 12, 2007 10:57 pm, edited 1 time in total.
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pre65
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#11

Post by pre65 »

Hi-had you thought of using the pressure from an inflated car tyre to power the arm ?

I was thinking about the brake bleeding kit that was similarly operated.

Very simple to top up (pump up) and need not cost a lot as the condition (tread wise) of the tyre is unimportant.

You would need some form of regulator,but it would be cheaper than renting a bottle from BOC and paying for a refill each time.

I have no idea how long a tyre full would last though.
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G-Popz THE easy listening connoisseur. (Philip)
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Greg
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#12

Post by Greg »

Hi Phil,

What a lovely bloke you are :D

Yes, we could try your suggestion or a car tyre inner tube as a resevior. Trouble is, we'll be constantly foot pumping away as the music plays. Lets be honest 30 odd PSI ain't going far........could be a new approach to dancing though :shock:

Realistically, I believe a constant pressure system based on a charged air cylinder with a capacity for about 6 hours playing could be safely set up for about £300. Given the obvious significant potential of Vic's arm to produce excellent sound, in terms of hi-fi upgrade at the level we all now like to listen to, this surely is not an out of reach price. Certainly not if we compare what in ignorance we all previously might have pass over the counter at the local dealers.

I think this option is well worth pursuing and also expect it to turn out cost effective.

Best wishes,

Greg
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#13

Post by Clive »

Hi Greg,

The arm is now working a treat. It does seem that increasing the length of tube between pump and deck makes setup more finicky. I suppose the pump has to drive a larger column of air and there must be resistance in air tube of some sort. Running the pump at max and then throttling the air back near deck does work well and it's easy to adjust. Your larger pump should be even more effective and able to drive longer air tube.

When the air setup isn't right this happens:


Too little air - the arm doesn't move but the stylus skips a groove

Way too much air - the arm carrier jumps up and down as air pressure builds quickly under it, the arm carrier lifts to provide a release for the air, you can hear this very easily as the sound comes from the arm itself.

Too much air but less now - similar to above but you only hear a pulsing through the bass speakers, this is very low frequency and low level, I put my hands on the woofers to check if the pumping is occurring.

Just a little too much air - still some form of pumping but only audible as a warbling in the mid-range.


The constant air supply you advocate is interesting for two reasons:

1 a constant, non-oscillating air supply seems like a good idea to see if it works better than a smoothing tank.

2 a constant air supply that is silent is great for those who can't position the pump out of earshot.


It seems the air supply is working well in my situation with the pump remotely positioned. Also I therefore don't have a noise issue. I don't feel the need to experiment with air cylinders as it's all working in my situation. I realise that you will have a noise issue so the air cylinder is worth exploring, and you know about Scuba equipment too. My time will become a very scare resource from the end of the month due to my taking a new position at work. Realistically I'll have little time to experiment, like you but for less noble reasons. In the next couple of weeks I should have enough time to review Vic's arm vs an OL Encounter mkIII but that's as much as I can do.

Clive
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#14

Post by Nick »

I would also guess that the length of air in the tube would alter the resonant frequency of the system, the air will act as a spring. Maybe if the resonant frequency of the air conincides with that of the arm system then the problem will be worst. Maybe its possible to install filters in the tube to act as dampers?
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#15

Post by Darren »

Clive,

I suggested before a second reserve tank, the pump would feed the 1st tank, this would then feed the second tank with much reduced pulses.

Similar effect to your longer line, but much bigger/better results I would think.
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