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Show HN: I made a free app to calibrate your turntable by simply playing a song

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Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#81

Post by crazygringo »

derefr wrote: post #47
crazygringo wrote: post #26

This seems really clever -- kudos! I'm curious how it actually works? At first I assumed you were comparing the vinyl track to the reference digital track from some streaming service and either analyzing the frequencies with FFT or the timing of peaks. But I watched your demo video and you don't need to tell it anything about the song. Which makes me think you're rather doing an FFT and simply trying to match how wel…

You can extract pitch information and compare it to a set of quantized reference pitches as an instrument tuning app does, sure. But you can also extract BPM info and compare that to a set of quantized reference BPMs that anyone would ever bother to use. And also, since you’re getting multiple pitches from multiple instruments in a time series, if you can isolate particular instruments, you can calculate the key the…

There aren't really reference BPM's.

Not everything is recorded with a click track, though a lot is.

But even so, while it will usually be an integer BPM, it's not always rounded to the nearest 5. 120 might be too fast while 115 is too slow, so you pick 118.

For an app that's trying to correct your turntable speed by e.g. 3%, it couldn't even begin to guess the "correct" BPM.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#82

Post by strongpigeon »

Nice work! This looks really good.

I'm not in the intended audience as I don't have a turntable, but if I had one I feel like I would be much more likely to use this if it was a web app. If I didn't know about this app beforehand, I'm pretty sure I'd be looking on Google rather than the App Store.

That being said, you made this app for yourself and it looks great. Congrats on shipping!

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#83

Post by taylodl »

criddell wrote: post #73
kazinator wrote: post #55

Earlier quoted context omitted.

3.5% is a lot! One semitone is a bit shy of 6 percent.s It's between 59 and 60 cents: more than a quarter semitone. Exact value: 1> (* 1200 (log2 1.035)) 59.5569212695205 So 59.6 to 3 sig figs. Someone with a good pitch memory of a tune (hearing in their head how it should sound) would spot such a difference. Especially if they heard the tune recently.

So many recordings (especially before 2000) seem to be sped up a little. I can’t tell by listening to the song but when you try to play along with a guitar, it sounds terrible. Sometimes it helps to find a live version on YouTube.

Correct. That was often done when mastering with tape. Record at one speed, playback at another to make it sound more "lively." There are songs that were sped up that way anywhere from 25 to 40 cents. It's another reason why live music so often doesn't sound like the recording.

When using digital mastering, you can also adjust the playback speed, but you can correct the shift. You get more "liveliness" without the shift change. That's why you're not hearing the pitch shift so much in more recent music.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#84

Post by okatbest »

peter_l_downs wrote: post #49

Strongly recommend updating your website to lead with some variation of "This is an offline iPhone app to help you calibrate your turntable's speed, all you need to do is play your records and the app will show you the current RPM" — wayyyyyyy too many words and other nonsense before I could figure out this is what it did. Embed the demo video (the tweet you linked) too! Looks great and if I still used records I woul…

That is fair criticism, I expected for the website itself to be polarizing. At the end of the day because this is a tiny free app I made for fun, I am willing to throw some people off of the sake of the joke, and judging by a lot of the comments I have succeeded!

Overall, my assumption is that by the time you make it to the website, you'll already know what the app does, and most people will link to the App Store directly (which is why the store listing is much clearer on what the app is/does). if not, my second assumption is that people will scroll right past that giant block of text and go to the last line which does explain what the app is in one sentence, because there isn't much more to say about it in my opinion.

If I made money off of the app I'd have a widely different approach, but in this case all I get paid with is strangers' attention and it is _very_ funny to me to spend that attention on a useless 2AM irrelevant tirade.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#85

Post by yial »

echoangle wrote: post #71
yial wrote: post #9

Earlier quoted context omitted.

So really short description, you have 33, 45, and 78 rpm. Most record players are belt drive. Anything that is belt drive usually has some slip / variation (if more familiar to you, imagine the belt drive on a lawn tractor). Many have a finer adjustment to tune the spin rate. +- off of the selected rate. (Perhaps you selected 33 rpm but it’s really spinning at 32) I’m sure someone who knows much more then I do, could…

Is the problem really the slip in the belt drive? I thought its just the motor driving it at a slightly wrong speed.

That may be the case, my experience is with a limited number of record players.

I only commonly use a dual 1219, dual 1229, (both purchased for under $30), and a victor victrola from 1908 so my knowledge is severely limited despite having played with others it’s focused on those units.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#86

Post by hinkley »

egypturnash wrote: post #68

All the turntables in my life as a kid had built-in calibration, in the form of four rows of repeating black/silver squares on the side of the wheel, a light flickering at the mains frequency, and a little dial to adjust the turning speed until the row of squares corresponding to your current combination of 50/60 hz DC and 33/45 RPM appeared to stop moving. It was a very clever trick.

We have replaced a lot of stepper motors with a more refined version of this using stripes and a photoreceptor. Printers for instance. Surely there must be turntables doing the same thing?

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#87

Post by peter_l_downs »

okatbest wrote: post #84
peter_l_downs wrote: post #49

Strongly recommend updating your website to lead with some variation of "This is an offline iPhone app to help you calibrate your turntable's speed, all you need to do is play your records and the app will show you the current RPM" — wayyyyyyy too many words and other nonsense before I could figure out this is what it did. Embed the demo video (the tweet you linked) too! Looks great and if I still used records I woul…

That is fair criticism, I expected for the website itself to be polarizing. At the end of the day because this is a tiny free app I made for fun, I am willing to throw some people off of the sake of the joke, and judging by a lot of the comments I have succeeded! Overall, my assumption is that by the time you make it to the website, you'll already know what the app does, and most people will link to the App Store dir…

Fair enough, congratulations on your launch and I hope you see continued success!

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#88

Post by stavros »

astral303 wrote: post #23
patrakov wrote: post #5

Does it rely on the fact that music has a concept of notes with well-defined frequencies and that there is no such thing as 216 Hz (must be 207.6 or 220 Hz) when the music is played on a properly tuned instrument? Or does it use other heuristics?

I tried it out and the instructions have tips on what record to pick, they say to pick a well known version of a song (like not a live version etc), and preferably song with a beat, but it says it doesn’t use any 3rd party APIs or libraries, only Apple APIs. So my guess at to what it’s doing is using a ShazamKit recognition behind the scenes and looking at the frequencySkew value of the matched result. It also gives…

How can it use ShazamKit if it processes everything on-device?

I'm really really curious how this is done now...

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#89

Post by c5karl »

egypturnash wrote: post #68

All the turntables in my life as a kid had built-in calibration, in the form of four rows of repeating black/silver squares on the side of the wheel, a light flickering at the mains frequency, and a little dial to adjust the turning speed until the row of squares corresponding to your current combination of 50/60 hz DC and 33/45 RPM appeared to stop moving. It was a very clever trick.

I would think that any turntable that allows for adjustment of the speed of the motor would have this already (based on my limited experience with turntables from decades ago). So, nice little app, but if it shows you the error of a non-adjustable turntable, it won't have a lot of practical applications.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#90

Post by taylodl »

egypturnash wrote: post #68

All the turntables in my life as a kid had built-in calibration, in the form of four rows of repeating black/silver squares on the side of the wheel, a light flickering at the mains frequency, and a little dial to adjust the turning speed until the row of squares corresponding to your current combination of 50/60 hz DC and 33/45 RPM appeared to stop moving. It was a very clever trick.

You had access to nicer turntables as a kid! That was a distinguishing feature between the more "serious" music hobbyist and the person who just wanted to play some tunes.

I haven't messed around with a turntable in over 20 years but these days, only the supposed "serious" music hobbyist would be using a turntable and I'd think anyone making a turntable that didn't have this adjustment would be laughed out of the market. What are you going to tell me next - they're also using belt drive, a plastic needle, and a tone arm with a non-adjustable counterweight?! :)

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