Record Speed Measurement Idea

[jmad7474]

Hello collector friends!! I want to share with you all an idea I came up with about how to ensure the correct record playback speed if you have a phonograph that uses a knob screw for its speed adjustment. As someone blessed(?) with perfect pitch, this issue has come up several times before when I want to hear a record cut at a non-standard speed (say, 74 rpm) but can't easily do so without precisely adjusting the motor speed. In addition, I have dozens of great records cut at these unusual speeds, so the quantity of them I feel justifies the time spent on this project. Here's what I did:

Step 1: Calibrate your phono motor so it runs at exactly 78 rpm. Then, using a black permanent marker*, mark a perfectly vertical line spanning from the center of the knob to its circumference (see the photo with red arrow).

Step 2: Using a digital tachometer device, mark how much you need to turn the speed control knob to increase or decrease the speed by 1 RPM. This will vary for each phonograph, of course, but as a reference, it takes about one full turn of the knob on my Victrola to increase/decrease the speed by ±6 RPM.

Step 3 (optional): Make a graph chart showing what exact speed/RPM corresponds to the position of the speed control dial from its 78 RPM "home base" speed. (This can be any numeric range you need.) Since my slowest-playing record is a Fonotipia cut at 68 RPM, I used that as my slowest speed and since my fastest-playing record is a "Cinch" label foreign pressing cut at 88 RPM, I used a 21-point RPM range on the X axis and a range of ±2 knob turns on the Y axis.

Step 4: Play the non-standard record and increase/decrease the speed until it is correct. Note how many turns of the speed control knob it took to obtain this result.

Step 5: On the record sleeve or in a separate notepad, note via the graph which position of the knob the correct adjusted playing speed is for that particular record and return the knob to its original 78 RPM "home base" speed. Rinse and repeat Steps 4 and 5 for any other records you own which were cut at non-standard speeds.

*Marking the speed control knob will not damage it as the mark can be dissolved later if needed using rubbing alcohol.

I hope this helps other collectors affected by this issue! Thanks for reading and have a great day!

-Jason

[Frisco The Beagle]

jmad,
Love it - flash back (or PTSD) to algebra class!
You can probably easily develop the formula for this straight-line graph, plug in the RPM you want, and get the number of turns required.
What was the formula for a straight-line graph... y = mx+b?
Again - very cool!
Richard

[drh]

Alternatively, you can just measure the speed with your digital tachometer directly, adjusting the speed knob until correct, for each record. Note the correct speed on the sleeve or in your catalogue for future reference. If you play one record that is, say, at 76.5 (yes, Victor, this means you) and then the next one is at 80 and then the next one is at 90 (yes, Pathé, this means you) and then the next one is back to 76.5 and so on, you'll avoid lots of counting and calculations. If you don't want to put a strip of reflective tape directly on your turntable, you can apply it to the back of a dud/worn single-sided record or a cracked record of any sort and use that to do the settings. Use a small diameter record that you can set on top of another without obscuring all the playing area, like a Little Wonder, if you want to take your readings while the machine is playing to account for drag.

[emgcr]

I use an Apple iPhone App called RPM WOW which works well. It is necessary first to place a small diameter cylinder around the spindle to allow the phone a flat stable surface. This system can still allow for drag.

[CarlosV]

Hello collector friends!! I want to share with you all an idea I came up with about how to ensure the correct record playback speed if you have a phonograph that uses a knob screw for its speed adjustment. As someone blessed(?) with perfect pitch, this issue has come up several times before when I want to hear a record cut at a non-standard speed (say, 74 rpm) but can't easily do so without precisely adjusting the motor speed. In addition, I have dozens of great records cut at these unusual speeds, so the quantity of them I feel justifies the time spent on this project. Here's what I did:

Jason, the problem with your proposed method is that it assumes that the regulation system in a gramophone is stable. This is not the case for many, mostly due to age-related degradation of the parts, in particular the governor pads, or to poor design of the regulation mechanism. Therefore, after everything is calibrated, the reference speed will drift over time, and a recalibration will be required. The phone app mentioned above is the most practical method, I have been utilizing it for years in various different machines with no issues.

[Inigo]

That's true, but in my case, I'm lately using an HMV 127 tabletop whose speed is pretty stable, and so does the regulation mechanism, as I test it frequently with a strobo and it remains true...

[CarlosV]

That's true, but in my case, I'm lately using an HMV 127 tabletop whose speed is pretty stable, and so does the regulation mechanism, as I test it frequently with a strobo and it remains true...

Same with me, Iñigo, some of my machines have stable speeds since years, but with others - mainly the older ones - I need to adjust the speed frequently.