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XA/B least expensive method to introduce speed control?

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XA/B least expensive method to introduce speed control?

Postby plexi » 11 Oct 2017 09:28

Is the music hall 2.0 the least pricey or even the only solution for making the old ARxa/b able to do speed control? or is anyone making a DIY controller for them? I'd like to keep my AR but the need to adjust speed between records is becoming essential. At the same time, I'd rather not spend hundreds to do this? any inexpensive options?

also, if a table is running slow, is there an issue with relying on the speed control to increase that speed or is a slow table (noticeably slow) indication of unhealthy motor? I have new pulley and oiled spindle - have not oiled motor as have not reearched the exact how to yet)

thanks
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Re: XA/B least expensive method to introduce speed control?

Postby snfrosten » 13 Oct 2017 02:10

The Music hall is the cheapest easiest way to control the speed and lets you select the 33/45 speed without changing the belt on the pulley.
Table shouldn't be running slow, the motor is set at the right speed. It is either the wrong belt or the platter bearing well is not letting the platter spin freely. Which motor and subchassis do you have? The stamped steel sub with the Delrin bearing are notorious for seizing up and causing the platter to slow down, platter should spin freely for at least a minute or two with no belt on.
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Re: XA/B least expensive method to introduce speed control?

Postby plexi » 13 Oct 2017 09:04

thanks for info. Does this tell whether either part is the one you mention? the only marking on the main silver motor says 6-520

Delrin is a kind of plastic no, the center sleeve appears to be metal?
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Re: XA/B least expensive method to introduce speed control?

Postby noisefreq » 13 Oct 2017 22:43

You have the later, metal bearing wells, which is good.
There is a delrin disc that is a round flat white plastic disc in the bottom of each bearing well.

These wells, the ball bearing under the tonearm and the discs should be cleaned and oiled properly.

The belt should be just tight enough to hold on the inner platter when in use. If you have to stretch it on, it's too tight.

Oiling the motor is just a matter letting a drop or two of oil soak into the top of the motor spindle as it's running.

Like you're thinking, I would sort out the slow rpm problem before I went and spent money on a speed control.
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Re: XA/B least expensive method to introduce speed control?

Postby derspankster » 14 Oct 2017 14:03

Good advice.

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Re: XA/B least expensive method to introduce speed control?

Postby plexi » 15 Oct 2017 00:55

the new belt was bought on ebay from a reputable AR dealer it seems..I once measured the belt against common wisdom I found on google and it was a match it seemed. It does feel a bit tight to my senses but I really don't have any reference of known tension, just a general feeling...
found this thread, and am reading to learn how to pry off covers and add motor oil. the silver motor on mine seems to be/have been soldered on?

viewtopic.php?f=34&t=64051&hilit=oil+motor
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Re: XA/B least expensive method to introduce speed control?

Postby derspankster » 15 Oct 2017 13:40

If the belt feels tight then I'd guess it is. Might be short or might be too thick - or both. My belts came from Vinyl Nirvana and are correct. I have no experience with 2 motor XA's. Both of mine are single motor. I added a drop or two of oil to the shaft of of one of mine because it was a bit noisy.

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Re: XA/B least expensive method to introduce speed control?

Postby plexi » 21 Oct 2017 01:14

loose belt 615mm


loose belt.jpg




tight belt 580mm
tight belt.jpg




so recleaned both belts and recleaned/lubed up the spindle and measured belts and speed using a tachometer rpm app. This is the fist time i've used a phone app for rpms so don't know how accurate these tend to be.

Interestingly before measuring with app, by ears only I could tell the oiling made it faster but still I thought i was hearing both belts a bit slow. but if the app is right, I was only 50% correct. But all in all it's amazing how fine tuned and close the ear can get to knowing correct speed.

but it's close now. I read on another post that ideal belt length is 600mm. So if that is true the two belts i have are on each end of that. The only thing I havent tried yet is talcum powder and not sure if that is supposed to speed up or slow down anything.....

Also looked into the music hall speed control on vinylnirvana and he only verified it worked with mid 80's tables and not the older XA. So I still don't know if that will work with the XA and/or if it's the only option we have to speed control the XA. I wonder why no one has DIY's and sold a speed control for this table as it would be popular no?
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Re: XA/B least expensive method to introduce speed control?

Postby snfrosten » 21 Oct 2017 02:17

I don't think those apps are that accurate. Also it would have to sit directly above the spindle to be more accurate.
The reason no one has built one is by the time you do it would probably cost the same as the music hall unit, time and materials. I have one and could have checked it on a two motor table, just built two but have already sent them to their new owners.
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Re: XA/B least expensive method to introduce speed control?

Postby plexi » 21 Oct 2017 22:00

so in your experience the music halls work on the single motor XA/b 's?
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Re: XA/B least expensive method to introduce speed control?

Postby snfrosten » 22 Oct 2017 00:33

Yes, the M H works on all the AR tables, just haven't tried it on the 2 motor table.
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Re: XA/B least expensive method to introduce speed control?

Postby plexi » 24 Oct 2017 05:32

....been thinking....I suspect the reason my AR sounds slow to me in actual listening is because of stylus drag. The phone app tests without any stylus and this in combo with the weak AR motor results in actual slow rpm in usage, so my ears are once again did not let me down. It's amazing to think the ear can pick up stylus drag effect but it can evidently (at least with small weak motors). Will continue to research because I really enjoy the musicality of the AR with stock arm.
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Re: XA/B least expensive method to introduce speed control?

Postby noisefreq » 24 Oct 2017 13:20

I believe you can train your ear to hear perfect speed just like you can train your ear to hear perfect pitch.

I know when I hear a top E string or middle C on a piano or 1000hz test tone.

I would recommend you download a stroboscope here from VE and use an incandescent light to check speed.
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Re: XA/B least expensive method to introduce speed control?

Postby plexi » 24 Oct 2017 23:41

Traditionally, speed testing of turntables has been done by viewing a series of bands on the turntable platter under mains lighting. The frequency of the mains supply (50Hz in Europe / 60Hz in the US) causes the bands to appear stationary at the desired speed

Unfortunately mains frequency drifts over time making conventional speed measurement inaccurate. To overcome this problem, companies such as KAB and Clearaudio have produced quartz locked illuminators which work independently of the mains supply to give highly accurate speed readings.


the above was taken from a diy strobe post. It is suggesting that 50/60hz mains freuency is not constant during the day and therefore it is not an accurate test method? If that is the case, doesn't this same phenomenon affect actual speed of the turntable? Perhaps at some times of the day a table will run correct and others not?

In any case, i found this in search of 'stroboscope'. If it is a printout that I would make and hold the incandescent light over it, wouldn'y this have to be done with no stylus running? because a paper template is on top of record.... and does this 50/60 hz fluctuation come into play as well?



Came across this post/mthod , which seems to allow a running stylus during....
the way I calibrate the speed is by playing a record with a 3150Hz testtone on it. The dr Feickert app for android can monitor the sound and an real-time graphical feedback of the speed and the deviation of it. Works like a charm



the method i've used in the past is 100 revolutions/3 mins. Set a timer from online and count revolutions. This can be done with stylus drag. I haven't tried that yet with my AR but I know it is/will measure slow because my ears tell me so...my problem is more how to get the AR speeded up rather than a testing method I think......that is the initial reason I made the post, thinking a speed controller could solve that problem while at the same time, give me some overall fine speed control as well.....
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