DIY Air Bearing Linear Arm

Warrjon,

It is all right. Take your time.

I tested the tracking ability of my 1" air-bearing arm today again. The tracks are from CBS Test Record because I realized that there are two groups of tracks. One group is lateral and another group is vertical. Here are the results. The vertical trackings seem all fine.

Square Wave

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300 Hz lateral 6 dB

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300 Hz Lateral 9 dB

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300 Hz Lateral 12 dB

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300 Hz Lateral 15 dB

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300 Hz Vertical 6 dB

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300 Hz Vertical 9 dB

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300 Hz Vertical 12 dB

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From the test results, the mistracking happens in lateral tracking. It is understandable. The results also indicate that at 15 dB, the arm tacks one channel correctly the meantimes mistracks the other channel.

Jim
Hi Jim, i get a similar result with the tracking tests with my RTA. Nothing vertical of the three levels shows any trouble at all, the only test causing trouble is the highest level of horizontal, this has been the case all through the developments I have made. I have never put this on the scope, just done the conventional way by ear, I may try that as well. M
 
Mike,

I guess if an arm can trace the signal at 15 dB, it is an exceptional one. Since I haven't seen anyone publish such data, I can't get the correct evaluation of the performance of my arm. In fact, I saw you used Visual Analyser. It has a scope, too. If you have HiFi News test LP, it has only one 15 dB track. For CBS test LP, it has 6, 9, 12, and 15 dB tracks. But for CBS test LP, you are not supposed to use a phono with RIAA. But for this test, I am not sure if RIAA will make any difference.

Jim
 
Mike,

I guess if an arm can trace the signal at 15 dB, it is an exceptional one. Since I haven't seen anyone publish such data, I can't get the correct evaluation of the performance of my arm. In fact, I saw you used Visual Analyser. It has a scope, too. If you have HiFi News test LP, it has only one 15 dB track. For CBS test LP, it has 6, 9, 12, and 15 dB tracks. But for CBS test LP, you are not supposed to use a phono with RIAA. But for this test, I am not sure if RIAA will make any difference.

Jim
Hello Jim, I think you are correct about published data, there isn't much around, but I am sure it is clear from what I have seen that your arm is very good, that's probably why it interests me to explore openly the questions about the compliance or otherwise of the bearing with people like you responding and discussing!! - by the way you can see I recently made some improvements to coupling and results.
I use an old Hi Fi sound test disc, (cost £4.95 in 1981!!) and now prompted to look I find the Lateral modulation is slightly different, at 8, 11 and 14dB, anyway, the result is the same, it's the highest, 14 track that causes some problems. The vertical are lower levels. And yes, as you say I use VA so can probably put the scope on it, I have always used it in the traditional way by listening only, the only reason is that I have used the disc since way before VA existed!
I shall have a go with the scope and see what i can learn as well...........
 
Mike,

I just tried VA with an RIAA phono and CBS test LP. The trace is somewhat smoother but almost identical to the test result without RIAA. So, it doesn't matter probably if you use an RIAA phono or a microphone preamp for these particular test tracks. This is a 300 Hz 15 dB signal with an RIAA phono. I think your HiFi Sound Test LP is cut with RIAA.

Jim

VA 300 hz 15 db CBS with RIAA.png
 
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Mike,

I just tried VA with an RIAA phono and CBS test LP. The trace is somewhat smoother but almost identical to the test result without RIAA. So, it doesn't matter probably if you use an RIAA phono or a microphone preamp for these particular test tracks. This is a 300 Hz 15 dB signal with an RIAA phono. I think your HiFi Sound Test LP is cut with RIAA.

Jim

View attachment 1110898
 
I am a bit lost in this area Jim, however i will take a look over the coming days, meanwhile if I discern correctly you have both channels input to VA and one (A, L) shows a quite close representation of the wave but the other is distorted, is that what i am seeing please, and as its the 15dB torture test that's not surprising but why the difference between the two?
My disc description is in the pic below, i am not sure what this would look like at all........
 

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I am a bit lost in this area Jim, however i will take a look over the coming days, meanwhile if I discern correctly you have both channels input to VA and one (A, L) shows a quite close representation of the wave but the other is distorted, is that what i am seeing please, and as its the 15dB torture test that's not surprising but why the difference between the two?
My disc description is in the pic below, i am not sure what this would look like at all........
Mike,

The track you used looks like an intermodulation distortion signal, IMD. It has 4 kHz and 400 Hz. Usually, you may use IMD to test VTA. The Ultimate Analogue Test LP has an IMD signal, 4 kHz and 60 Hz. It can be used for testing VTA. I have another piece of software, Multi-Instrument. Here is a screenshot. You can see that I configured the software to test all parameters of tonearm adjustments. They are red-underlined in the image.

2022-11-18 15 22 47.png


For tracking tests here, the signal is actually a simple 300 Hz signal in the waveform at various levels. The high level of the signal is, the more difficult to trace it. If you have a 300 Hz signal, you may try it as well. However, you need to make sure of the level of that particular signal. Otherwise, it may not mean too much.

Here is an actual test for VTA. You can see f1 is 60 Hz and f2 is 4 kHz. IMD=4.95% for the left channel A and 4.10 for the right channel B.

vta test.png


Jim
 
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Guys I wouldn't worry about the 15dB test track very few cartridges will track this. A Stanton 881s will track it but this is special cartridge.

Jim that 15dB plot looks to me like the stylus is riding up the groove wall as the carriage is flung back and forth. If the arm can track 9dB I'd call that good there is not much on an LP that exceeds this. My pivoting arm and EPC-205 will track the 12dB if I increase antiskate and VTF but I never run this much antiskate and VTF. The Stanton 881s will track 15dB @ 1g VTF with just an increase in antiskate.
 
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