BeoloverRPM: Precise RPM Measurements on Beograms

An essential concern with turntables is their RPM accuracy and stability. Variations or inaccurate RPM can seriously diminish the listening experience. For this reason I developed the BeoloverRPM device that allows to qualify the RPM performance of Beograms for extended periods of time. This allows to verify if there are intermittent RPM issues etc..., which are notoriously difficult to diagnose and demonstrate just by listening to records.

The BeoloverRPM device is now available to other enthusiasts. If you are interested just send me an email or use the contact form on the right. This video gives an introduction to the capabilities of the BeoloverRPM unit (please, note that the design of the enclosure was recently updated - functionality and performance did not change, it still works exactly as shown in the video):

Here are a few more impressions of the device's applications. Scroll down for driver and download info:

The unit can be configured to either sit on the aluminum plate surrounding the platter, or clamped to the enclosure when the deck is in service position:

The display shows the current RPM value in 1 sec updates, i.e. is very convenient for adjusting the RPM on 400x units. It also shows the min and max values encountered during the entire time it is measuring. This allows a quick diagnosis if there are random RPM spikes due to motor or feedback malfunctions.

The BeoloverRPM also outputs an ASCII stream via its USB connection to any terminal program on a PC or Mac. This allows the measurement of the RPM performance over many hours. This is invaluable for the detection of sparsely and randomly occurring RPM deviations as they are characteristic for malfunctioning motors etc...Here is an example of what is possible:

This graph shows the progressively improving RPM performance during a Beolover restoration of a Beogram 4002 (5513) with DC motor. The curves were measured over approx. 24hrs with he BeoloverRPM device. The data was simply copy/pasted from the serial monitor into a spreadsheet of data-processing software and then graphed. The bottom graph shows the Beogram in original condition and the top spectrum is the perfect curve after the restoration was completed.

If you are interested in the design path I took for the BeoloverRPM, these are some 'historic' posts that I made while developing the concept:

1st iteration: BeoloverRPM: Beogram RPM Calibration Device

A more applied version for use on decks in service position: BeoloverRPM: The Shop Version

Then I added a OLED high resolution display: BeoloverRPM: Now with Display!

And added some key info to it: Beogram 4002 (5513): RPM Stability Test and an Updated Display on the BeoloverRPM Device

I confirmed its accuracy on a Beogram 8002: BeoloverRPM: RPM Measurements on a Beogram 8002

The enclosure was redesigned for better usability and 3D printability.

Downloads:

If you would like to take advantage of the RPM log stream that the BeoloverRPM sends through its USB port the USB driver of the device needs to be installed:

For Apple Macintosh go here and follow instructions.

For Windows PCs use this file.

Once the driver has been installed, any terminal software can be used on the Mac/PC for retrieving the log stream and save it to a text file or copy/paste it into Excel or similar for graphing.

Terminal Software:

For Apple Macintosh I tested CoolTerm. It can be downloaded here for free. Once it is open select "wchusbserial" under 'options' (for this to show the above driver needs to be installed prior to opening CoolTerm and the BeoloverRPM needs to be connected to a USB port) and 115200 baud rate. Then click 'connect'. The BeoloverRPM will then reset and then the serial stream should show in the CoolTerm window. To capture the stream for a longer period of time, please, use Connection/Capture to Text File.

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