Two Short Videos: 2) RPM

That RPM app is brilliant, I'd never have guessed it would exist, thanks for posting about it. FWIW, my $30 Amazon USB record player is only 1% off at 33-1/3, better than I would have expected... I suppose it might come down more to the supply used.

While I was watching, you started talking about an app and I immediately thought "how clever, use the phone's camera to watch the disc rotate and calculate speed based on the frame rate".. Might be a wiser approach for those slick 78s ;-)

Have you seen this Mat - looks like your sort of gadget, even it t does only work with a smart phone... <a href="https://www.indiegogo.com/projects/arrim-one-world-s-first-professional-ar-measuring-design?utm_content=campaigns_one_column4_hero_image&utm_source=sailthru&utm_medium=email&utm_campaign=" rel="nofollow noopener" target="_blank">https://www.indiegogo.com/projects/arrim-one-world-s-first-professional-ar-measuring-design?utm_content=campaigns_one_column4_hero_image&utm_source=sailthru&utm_medium=email&utm_campaign=</a>#/

The word of advice concerning LED lights and strobe discs is very true. I have both an LED-equipped floor lamp and an LED torch. Both have adjustable brightness which can be set by holding the power button which makes the lamp go through the possible brightness settings. I also have a servo-controlled Technics Direct Drive turntable which has strobe patterns on the side of the platter (which are lit by a red light built into the turntable so you can set the speed correctly). Now, when I go through the lamps' brightness settings, I can see how the strobe patterns on the turntable platter start to visibly "interact" with the light from the lamps. This is a clear sign that these LEDs are PWM-controlled. Maybe at some brightness, they will flash at 50/60 hz or at a whole multiple but you'd never be able to "hit" that setting reliably. I like the new format btw. Stuff like this or the wall radio is still fun to look at, even if it's not enough for a typical, ultra-thorough Techmoan episode :-)

2:32: "You put tape on a record you really don't care about" [puts on Chart Heat] Probably not an intended joke, but I chuckled.

Just used this app on my Thorens TD 190-2, an automatic belt drive turntable, just a couple of years old. At all 3 speeds it runs about 1% fast with w/f around 0.4% - neither of which deviations are noticeable to me. Mind you it is incredibly hot today, I wonder if the temperature affects belt drive turntables? I'd have thought if the belt stretches a little in the heat, then it would run slower than normal. I'll try to remember to check it in 6 months time!

The initial email got me REALLY curious as it said "Two Short Videos: 2 RPM". I thought you actually uncovered a record technology where the records actually ran that slow!

Dang, my Pioneer is a tad slow and I need to get the screwdriver out now to adjust... 🙀

An app to measure record player speed, thats pretty handy. Now find one for cassette players! :D

Thanks Matt - That's a neat app. I can see testing accuracy at 78 ... place the $500 iPhone on a shiny shellac disk, press start ... whoops, there goes the iPhone skidding off the record onto the floor!

Hm. Unless I'm missing a point of physics, the app can't be using the phone's accelerometer to measure RPM, because the reading from that should be constant (except for vibration or speed changes) under these conditions. It must be using the compass (magnetometer), or _possibly_ the front-facing camera. The accelerometer could, though, be used for wow/flutter measurement since that is a change in speed (and also in centripetal acceleration).

I imagine you donned a baseball glove and mask whilst running the tests at 78rpm...

Finally, something I already have! It’s a good app.

Man how technology changes!

Will certainly give this a try on my Aiwa PX-E850, I mean why wouldn't you? I don't even have the thing plugged in and I'm curious to know how it fares. I'm not surprised that the laser struggled, my understanding is that they're designed for much higher speeds and would then be more accurate.

Yes, nice little app. Does anyone know of a similar app for Android devices?

For Android users there is a free app called RPM Calculator. I tested it on my turntable that has a built in strobe light and it seemed decently accurate. Also if you don't have 45 converter that is tall enough, try using a plastic cup to rest the phone on.

Nice little app, never heard of it. Thanks!

Wow, brilliant, I’ll certainly be getting that App! Thanks, Mat. Great demo, too. I wonder if you can use it to check the spin speed in your washing machine? Joke!!

Did you ever try the app out on your Sound Burger? Mine runs a bit too fast, so I was curious to see if it’s the same flaw.

Very cool, had not considered that the phone sensors would be fast or accurate enough to pull this off. Clever!

Literally stopped this video to download and try out that app. Fantastic find!

I enjoyed both videos. The first one (wall radio) did feel fairly short, but I can see why. This one (RPM) seemed like a good length, and really interesting to see the variety of measurement methods. I’m surprised how accurate/repeatable the app is (but not that one exists). For very short items (eg shorter than the trailer) maybe put a few into a “variety act” kind of video? Ewen

That app is the weirdest thing I have seen all week. So clever.

That’s pretty amazing that our phones can do that. Would have never thought.