Why don't you use a strobe and neon light?
46 responses Add your response
I've been told that a very accurate way to measure the speed of a turntable is by using a test meter set to khz, placing the positive terminal into one of the outputs of the phono stage (or tape output), the other to the ground and then play a 1000hz test track of our a good quality test record... If the table speed is good, the reading should be very close to 1khz...
Nope! But I've been told that if you blink your eye 33 1/3 times per minute and if the revolving platter is somewhat stationary, then the speed is calibrated properly!
Okay, just kidding on the above. But if you are planning to keep your table or tables for a long time, the KAB Strobe is pretty handy and a worthwhile investment. Yes, it is $90 but money well spent since it gives you a peace of mind. I do own the KAB Strobe and Strobe disc. I attempted to DIY a strobe using old strobe parts and principle from broken Thorens and Technics tables, I would say I spent more than $90 easily and my efforts was a little short of what I was hoping to happen as a result.
It will work, but not be nearly as accurate as the KAB. If the light is locked to the incoming line frequency (50 or 60Hz), and the incoming line frequency shifts ever so slightly (which it does all the time, not by much of course (maybe +/- .2Hz)), but enough to be significant to a turntable's accuracy), you can see how the problem arises. You are now using your flourescent light (which may or may not be at the correct frequency corresponding to your strobe disc) to set the speed incorrectly. The power line is no place to look at as a point of reference!
The beauty of the KAB is that it operates off a battery - and it is easier to read than a garden variety "60Hz" strobe disc because of the higher operating frequency. All in all it is a very accurate device, and a worthwhile investment.
I never tried that method, but it sounds correct. I guess several HI FI test records have those test tones. So a test record could be found in used record bins. Since you feel confident in reading a meter, give it a shot and let us know.
The KAB is easier to do and work with while doing speed adjustment.
It all depends on money...What you have spent and what you intend to spend in the future. The KAB is one of the greatest inexpensive tweaks on the analog market. Anybody who is interested in analog can not be without a KAB. Analog is a comittment and part of that means you and what you will do to listen to the music, less pops and clicks and speed changes. All the best.
Whilst strobes of various kinds are good for measuring average speed, the advantage of the test tone approach is that it allows one to monitor speed stability over the shorter term. The simplest method is to set up a frequency counter with the shortest sample interval which gives acceptable precision.
A better method is to monitor the test tone waveform on a scope using a separate, stable wave as the timebase. The test tone will then walk back and forth across the screen at a rate which equals the frequency difference between the test tone and the stable wave. If the stable wave is indeed stable and the test tone was recorded at constant frequency then the variation is due to the speed of the table wandering.
Why cant a Dual strobe paper do it???? It has little bars for 50 hz on one side and 60 hz on the other. I adjust my TT till they dont move. Then I play a CD and record of the same song to check. Always worked for me and its only a couple of dollars. I think your using an elephant gun for a butterfly. If i am wrong, can someone tell me in down to earth terms why you must spend 90 some dollars for a strobe?????? Mike
The method suggested by the Acoustic Sounds turntable tech using a 1kHz test tone and a DMM is a very accurate way to calibrate the speed of your turntable. If you have a test LP with a 1kHz tone track and a DMM, you have everything you need. Laying out the money for a strobe won't buy you greater accuracy, but you might find the strobe to be a bit more convenient to use.
Why worry about $90 bucks when entry level carts cost $1,500 a pop to strain gauges $6G to $14G. Even if your a Grado moving iron type the KAB is easy to use with repeatable results. Should you be happy with your speed system so be it. Most of the time record care and reasonably good AC sources resolve most speed issues. Record care ? A clean recording spins well and has less grunge , a "mother's helper" to the ears.
"Reasonably good Ac sources" is to be understood as line controllers; VPI, ProJect, Walker,etc. "AC sources" also includes dedicated lines for analog, pre-amp , amp & speakers should they have active AC sources. In this situation one hand washes the other. If you are 'ol school and are agast at those recommendations, no problem. But turntable speed is a measure of many things , not soley lights and paper rings.
Given the relatively slow speed of a turntable, it may be difficult / expensive to find a tach that measures with enough resolution to give accurate readings. An alternative approach is to either buy or build a counter and measure the number of revolutions over a fixed, measured time - there are as many ways to do this as you can think of. Perusal of catalogs from companies like allied electronics will likely lead to an optical counter. If you can let the unit run for a measured extended time you will end up with an accurate average of the speed of the turntable. While this is a different measurement than the instantaneous result from a tach reading it is not necessarily a less informative result. Multiple tach readings and average readings would tell you more about the speed and stability of the unit. My guess is a little research will yield an inexpensive counter or the components to build one.
Just use a very cheap strobe disc and a flourescent bulb light source. The bulb flickers at a rate related to the 60Hz regulated frequency of the powerline. Even an incandescent bulb does this and can be used (though the image is not as clear). The frequency is so very close, any irregularity would be inconsequential.
Use a stopwatch. Place a piece of masking tape on the platter at 6 oclock, and another piece at 6 oclock on the plinth, and yet another piece of tape at 1 oclock on the plinth. Put a record on, start the turntable, put the stylus in the groove. Start the stopwatch when the two pieces of tape line up at 6 oclock. At exactly 1 min and 40 sec the tape on the platter should line up with the tape at 1 oclock on the plinth. If it does not, you know what to do.
I haven't read the whole thread, but I could never get my speed set on my Bix with the KAB unit.
I sold my KAB strobe and bought the Digistrobo which claims my system is locked in perfectly and stays locked in rather tightly over time.
I wonder if the KAB strobe is much more sensitive/accurate or if it is too accurate; I could never dial in a stable speed with it...it was like trying to balance an egg on a razor when setting the speed.
The 'Digistrobo' looks alarmingly similar to laser tachs available on the ebay for a lot less than 150.00, such as this one http://cgi.ebay.com/Non-Contact-Digital-Photo-Laser-Tachometer-RPM-Rotation_W0QQitemZ160352588438QQcmdZViewItemQQptZMeters_Testers_Probes?hash=item2555c25296&_trksid=p3286.c0.m14 and many, many more.
After seeing the audiophile version in a catalog, I bought one of the ebay iterations to try-and it does seem to work as advertised-at least, it's accurate compared to my strobe disc. In fact, I made a little stand for it and it has a permanent spot on my tt plinth, ready at a moments notice to check stylus-in-place speed.
I've got a feeling-okay, I know- that this is just another case of audiophile product re-labeling, with the commensurate 6x price bump. Just like most electronic VTF scales.
I do have the KAB Strobe and disc. I am not 100% confident on its accuracy. I used Feickert's Adjust Pro + and his test record. When Adjust tells me I am dead on, KAB says otherwise by a significant amount.
I ended up using a Fluke DMM and measured the 3150hz tone on the Adjust test record after communicating with Feickert. He seems very confident on the accuracy of his test tone frequency.
It seems the old mentality of must spend lots of money in order to get good results has overcome logic again. Get real here. The powergrid line frequency is very tightly controlled to 60 Hz. Just google it and you can learn how accurate it is kept- to within 0.15 Hz. That is an error of just 0.25%. Probably less than the wow and flutter of many turntables.
Now go out and buy a cheap $100, give or take strobe light and tell me that it is accurate to within 0.25%? No way!
I laugh even more when I see someone looking at a digital readout and believe it to be accurate to the display's 2 decimal places.
OK, I have to speak up here as well. I pondered this same question a while back and found via the grape vine a great and cheap solution. I bought the Wally tools and tried the Cardas LP and frequency measuring via the test meter. My TT was running fast and I was trying to correct it via this approach. So, the problem was that the LP had a slight tendency to increase or decrease in the frequency tone due to a warp or LP pressing issue. So it was either right on or ever so slightly fast. I then contemplated buying into another method such as you. Then someone suggested buying a Digital Photo Laser Tachometer from Amazon. It worked great and cost $20, with an accuracy of +/- 0.05%. Plus you want you can play an LP for stylus drag while you measure. This is the only way to go!
"it worked great and cost $20, with an accuracy of +/- 0.05%. Plus you want you can play an LP for stylus drag while you measure. This is the only way to go!"
+/-0.05%? Unless it has a calibration sticker traceable back to the Bureau of Standards- no way. +/- 0.05% is the domain of very expensive laboratory grade equipment. A stobe-disc and fluorescent light is the most effective method. It leverages the Power Company's technology and accuracy- and it is dirt cheap. Plus, you can check the speed while playing a record.
Gerardff... how very interesting and simple.
Exceedingly dumb question (but I have to ask it anyway):
Does the accuracy of the measurement of a Digital Photo Laser Tachometer matter at to the placing of the reflective tape: whether the reflective tape is on the outer edge of the LP, toward the center, or somewhere in between?
Thanks & have an excellent new year's eve and new year.
I made my own strobe for pocket change, when I was making 3$/hr as a kid.
Used an NE-2 / socket and diode. changes AC to half wave and pulses the neon bulb on/off. Perfect 60hz. I scavanged a cord/plug from something and used a plastic tube for a mount. No exposed AC and worked fine. My TT at the time had 'barcode' circling the spindle for 45/33rpm at 50 or 60hz.
90$ for a strobe? nutty.
I had another idea.
Test tone CD and a test tone record.
Play them both, switch between them as you adjust TT speed until no pitch change between them.
If you have 2 systems available, you could even 'beat' the frequencies generated and get very close to perfect. Using that method you could even do drift checks.
Does anyone have any problem with CD pitch accuracy or repeatability?
Are there any speed variable CD players?