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DIY Air Bearing Linear Arm
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Old 9th June 2019, 05:57 AM   #401
MrKettle is offline MrKettle
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First thing to do if you are using the standard Terminator air pump (Sera 275) if you have an imbalance is to check that both sides of the air supply are working. The bellows develop splits over time and need to be replaced every year or so if the pump is left on constantly.
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Old 9th June 2019, 09:14 PM   #402
Stefanoo is offline Stefanoo  Italy
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Thanks for your comment but I donít think channel balance on the cartridge has much to do with the two sides of the airpump. However both sides of the pump work. I am not sure but even if one aide doesnít work all the tonearm cares is that sufficient pressure is being supplied
To the slider for the carrier to move freely and allow the cartridge to track.

Let me know in case I understood your comment incorrectly.
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Old 9th June 2019, 09:31 PM   #403
MrKettle is offline MrKettle
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Low airflow causes mistracking eventually, but a slight reduction can cause higher friction across the record which can lead to the generator not being in alignment (in my experience with a Cadenza Blue on a terminator).
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Old 10th June 2019, 07:08 AM   #404
niffy is offline niffy  England
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Theoretically open air bearing arms like the terminator should work at their best at the lowest possible air pressure, when there is only just enough to prevent the slider from fowling. The open type bearing is a constant pressure bearing, the air pressure in the gap is equal to the weight of the carriage divided by the area of the slider. Increasing supply pressure will make the gap bigger and reducing it makes the gap smaller. The air in the gap act like a spring. A shorter spring, of the same type, is stiffer than a longer one. Making the air gap smaller is the same as making a spring shorter. Therefore lower supply pressure results in a stiffer bearing. I think the general consensus among terminator users is that they sound at their best at low pressure, which is handy as low pressure pumps are cheaper and quieter than high pressure ones.
Low air pressure will only cause mistracking if the slider snags due to the air gap being too small.

Niffy
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Old 10th June 2019, 04:49 PM   #405
Stefanoo is offline Stefanoo  Italy
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Quote:
Originally Posted by niffy View Post
Theoretically open air bearing arms like the terminator should work at their best at the lowest possible air pressure, when there is only just enough to prevent the slider from fowling. The open type bearing is a constant pressure bearing, the air pressure in the gap is equal to the weight of the carriage divided by the area of the slider. Increasing supply pressure will make the gap bigger and reducing it makes the gap smaller. The air in the gap act like a spring. A shorter spring, of the same type, is stiffer than a longer one. Making the air gap smaller is the same as making a spring shorter. Therefore lower supply pressure results in a stiffer bearing. I think the general consensus among terminator users is that they sound at their best at low pressure, which is handy as low pressure pumps are cheaper and quieter than high pressure ones.
Low air pressure will only cause mistracking if the slider snags due to the air gap being too small.

Niffy
This is correct. The sound improves as you lower the airpressure for the same reasons you described.
However it is possible that the cartridge starts being misaligned before it even mistracks thus causing channel imbalance. I wonder if this is possible.
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Old 10th June 2019, 04:51 PM   #406
Stefanoo is offline Stefanoo  Italy
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Quote:
Originally Posted by MrKettle View Post
Low airflow causes mistracking eventually, but a slight reduction can cause higher friction across the record which can lead to the generator not being in alignment (in my experience with a Cadenza Blue on a terminator).
ok this is very, very interesting. Have you measured the misalignment in output imbalance or the image was getting skewed to one side?

I will try to measure using a much higher source of air pressure to see if there is any difference just as a curiosity.
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Old 9th July 2019, 03:59 AM   #407
Stefanoo is offline Stefanoo  Italy
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Sorry for my inactivity but I have been really busy trying to finish up other things and also to measure resonance frequencies in the current terminator arm to gather more info on what would be optimum to build for proper match with my cart..
In order to have a better understanding I have also acquired another test record: the ultimate analogue test to try to grasp what’s going on with my goldfinger and terminator arm. The vertical midulated test 10Hz-1khz sweeep I have detected a resonant frequency of 30hz which is extremely high.
Trackeability is ok but cannot track the torture track on the HiFi test record and he goldfinger accordingly to its specs can track 100um grooves.
However I have detected problem getting the azimuth right so I decided to switch from carbon fiber light armwand to the aluminum version and I have installed my other clearaudio titanium V2 which is almost half as heavy as the goldfinger.
With this cartridge I was able to achieve perfect azimuth using the hifi test track for azimuth and surprisingly I can track the inner torture track with very minor distortion equally distributed on both channels. Vertical resonance is now below 10hz and so is the lateral one.
But I have a question for people here about azimuth setup.
Using the test record HiFi test, the azimuth is within 0.1db between the two channels with the cartridge completely horizontal which would indicate a very accurate diamond installation for this unit. Nevertheless when I play other tracks in the same test record, for example the different tracking test tracks, one channel is always consistently higher than the other.
I can’t explain the reason for it other than L and R ch are mastered at different levels.
But the situation becomes even darker, in fact, if I use the two azimuth mono test tracks on the ultimate analogue test record, there is a difference of 1dB between the two channels on the same azimuth setting that produced less than 0.1db on the HiFi test record. Also the residual crosstalk using the mono tracks seem to be different on the two channels no matter how I set the azimuth for the cartridge in both directions.

Nevertheless when I play music I have very well centered image with most of the vinyls and fantastic stereo image on all theee dimensions.
I would like to understand why the two test records don’t seem to agree on the azimuth test.
Is anybody here that can help to guide me through this quest have been bugging me for the last few weeks to the point that I have sent my goldfinger back to clearaudio for inspection because I didn’t seem to be able to find proper azimuth setup.

Thank you in advance for your patient.
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Last edited by Stefanoo; 9th July 2019 at 04:06 AM.
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Old 10th July 2019, 01:39 PM   #408
super10018 is offline super10018  United States
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The track 2 and track 3 are for azimuth adjustment. You need to measure the leaks only if I remember it correctly. Adjusting azimuth to get minimum leaks.
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Old 10th July 2019, 04:49 PM   #409
Stefanoo is offline Stefanoo  Italy
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in theory track 2 and track 3 are meant to measure balance and crosstalk. Adjust should be perform to obtain perfect channel balance and minimum/symmetrical crosstalk.

In my case no matter the azimuth angle I set, the channel balance is off and crosstalk seems to be almost identical.
I haven't connected my spectrum analyzer to it, but visually on the scope they are very different in magnitude.

Nevertheless with the other test record "HiFi" I can achieve azimuth BUT the other test tracks on the same vinyl have asymmetrical amplitude.

This is very confusing to me and I wanted to know if anybody here had gone down to the same analysis detail using scope and the two test records mentioned here and can help me answer my questions.
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Old 10th July 2019, 05:51 PM   #410
Panayotis Kritidis is offline Panayotis Kritidis  Greece
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Quote:
Increasing supply pressure will make the gap bigger and reducing it makes the gap smaller. The air in the gap act like a spring. A shorter spring, of the same type, is stiffer than a longer one. Making the air gap smaller is the same as making a spring shorter. Therefore lower supply pressure results in a stiffer bearing.
Do you have some estimation about the magnitude of the variations of the gap during playback?
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