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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

#21

Post by vel0city »

echelon wrote: post #4

I'm not an expert on vinyl. The only record players I've interacted with have only had two speeds. Do most of them do variable spin rates? How frequently do the rates get out of sync? What causes it? Do they vary on an album by album basis?

Even a cheaper record player will often have some kind of adjustment on the motor itself. There is sometimes a small screw on the motor that can do some fine adjustments of the speed.

Belts age. Friction within the motor and the table's bearing will change over time. It is not necessarily a frequent thing that needs to be done, but usually the speed will change slightly over the life of the table.

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

#22

Post by okatbest »

echelon wrote: post #4

I'm not an expert on vinyl. The only record players I've interacted with have only had two speeds. Do most of them do variable spin rates? How frequently do the rates get out of sync? What causes it? Do they vary on an album by album basis?

So you have multiple speed settings (33.3RPM, 45RPM etc.), but most if not all players also have a little adjustment knob to tweak those settings more precisely.

Good players will have it on the front, and will have a strobe to help you adjust that (the little dots you see on the outside of the platter on fancy players). However, cheaper players may not have an easy way to adjust, and some (like mine) hide the knob under so it's a pain to adjust.

Cheaper players are more likely to come misconfigured from the factory. I asked a lot of friends (who are amateurs, not audiophiles) to test this app out and every single one had a turntable that required adjustment. Mine's running at 34.6 RPM which is just 3% off, but when listening to my favorite albums I can definitely tell that it's too fast and too high pitched.

The speed will also sometimes drift slowly over time, which is why it took me a while to notice my table was off.

If you have a turntable, you can try listening to the same song from a record and from a digital release, and see if you can hear a difference. If you do, I know just the app for you!

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

#23

Post by astral303 »

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 you one answer after listening, instead of a continuous gauge, which seems to corroborate song recognition. It probably won’t work with an obscure record that is not Shazamable. And so I don’t think it can measure wow & flutter as a result.

Still pretty cool for those that need to calibrate a turntable, or verify 33 vs 45 PRM for a record.

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

#24

Post by okatbest »

shiandow wrote: post #17

This just tells you the speed, not the variation in speed over time?

That's correct. The analysis takes a few seconds so even if I take more samples, it all gets averaged over time and won't be able to do instant read. If you're interested in measuring wow and flutter I think you'll need to look at more traditional calibration methods unfortunately.

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

#25

Post by nickthegreek »

Just put a record on yesterday and my wife said it was playing too fast. I thought she was wrong, then I see this post today! I grabbed the app and gave it a go, 3.5% too fast according to your app. Now I have to figure out how to adjust the damn thing. Really appreciate a free nonsense free app.

update: youtube to the rescue. pretty common affordable turntable( Audio-Technica LP60), so I figure I would put the vid link here for others who might want to know - https://www.youtube.com/watch?v=d3PdS2V8Jz0

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

#26

Post by crazygringo »

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 well the frequencies align to the well-tempered scale based on A 440 hZ.

Which then leads me to three questions:

1) Obviously this wouldn't work if you were playing a standup comedy album or something? Or the drum solo part of a song?

2) Are essentially all albums perfectly in tune with A 440 hZ? For example with classical music, I understand that 442 is also used, baroque is sometimes at 415, and 432 has been common as well? I don't know about pop but I can't help but wonder if some artists have intentionally chosen something other than 440 over the decades.

3) I assume this won't work if the turntable speed is off by more than 2.8%? Since the distance from A4 (440 hZ) to A-flat-4 (415.30 hZ) is a decrease of 5.6%, and so if the turntable is off by more than half of that you'd be trying to align to the wrong note?

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

#27

Post by empath75 »

rufus_foreman wrote: post #20
echelon wrote: post #4

I'm not an expert on vinyl. The only record players I've interacted with have only had two speeds. Do most of them do variable spin rates? How frequently do the rates get out of sync? What causes it? Do they vary on an album by album basis?

DJ turn tables have a pitch fader and lights for calibration: https://www.youtube.com/watch?v=KbdK94vl_Bs .

I used to DJ with vinyl at clubs and I don't think I ever knew a DJ that looked at those lights even once.

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

#28

Post by empath75 »

tirthd wrote: post #11

Great copywriting. It's very rare that I read an entire paragraph without skipping a word.

I actually disagree. There's a lot of extraneous stuff about app stores that's probably appealing to app developers but are developers the audience or audiophiles?

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

#29

Post by datpiff »

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…

> Are essentially all albums perfectly in tune with A 440 hZ? For example with classical music, I understand that 442 is also used, baroque is sometimes at 415, and 432 has been common as well? I don't know about pop but I can't help but wonder if some artists have intentionally chosen something other than 440 over the decades.

No they are not all tuned to 440Hz. This is really evident if you play an instrument and want to play along with an album.

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

#30

Post by CaptainOfCoit »

hnlmorg wrote: post #12
CaptainOfCoit wrote: post #6

Earlier quoted context omitted.

> I'm not an expert on vinyl. The only record players I've interacted with have only had two speeds. Do most of them do variable spin rates? Lots of turntables have variable speed, DJs can tell you more about it :) > How frequently do the rates get out of sync? What causes it? Do they vary on an album by album basis? When you're DJing, one of the main things you'd deal with, is making things be in sync, one way or an…

I don’t think this would be aimed at DJ turntables. It doesn’t matter if those things drift because you’re never playing anything locked in at a specific RPM. Plus DJ turntables tend to be direct drive, which should be pretty consistent. Where as consumer record players tend to be more belt drives. And I’m assuming those belts can stretch with time?

> I don’t think this would be aimed at DJ turntables

I agree :)

> Plus DJ turntables tend to be direct drive, which should be pretty consistent

Indeed, but once you start doing repairs and/or modifications, things can get fuzzy. Maybe the app would help those people?

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