[HN Gopher] Show HN: I made a free app to calibrate your turntab...
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Show HN: I made a free app to calibrate your turntable by simply
playing a song
Hey there! I made a little app that lets you to calibrate your
turntable by putting on any record and tapping a button. It's
called Grooved and it uses your phone's microphone to see how fast
your platter is going, almost like magic. You can see what it
looks like in action here:
https://twitter.com/OKatBest/status/1795453042994680148 The app
itself is free without ads, subscriptions, or trackers. It's a tool
I built for myself, and I just thought someone else might want to
use it too. I have never seen this technology being used before,
all other apps require you to either print something and use the
camera, or to place your phone on the spinning platter and use the
accelerometer. You can grab it on the App Store, and I am working
on an Android version I hope to release at some point in June.
Would love to hear what you think about it! Ivan_
Author : okatbest
Score : 238 points
Date : 2024-05-28 14:23 UTC (8 hours ago)
(HTM) web link (grooved.okat.best)
(TXT) w3m dump (grooved.okat.best)
| gen3 wrote:
| Neat POC, are you doing a song fingerprint then comparing
| speed/stretch?
| KeplerBoy wrote:
| That really is a lot of copywriting for a bunch of FFTs, but
| nicely done.
| echelon wrote:
| 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?
| CaptainOfCoit wrote:
| > 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 another. I'm not sure how
| much value you'd get from an app like this that seems to be
| more "fire and forget" and not for on-the-fly matching.
|
| I'm guessing this app is for people who do their own
| maintenance, repairs and such of turntables, so they can easily
| verify their work.
| hnlmorg wrote:
| 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?
| CaptainOfCoit wrote:
| > 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?
| LM358 wrote:
| People who are serious about turntable repair have
| calibration records with sine waves for that purpose.
| beAbU wrote:
| Fancy record players have a trim setting where you can fine
| adjust the speed up or down a semitone. But all of them have a
| built in stroboscope/calibrator to help get the speed right. I
| think the drag of the needle impacts the speed, hence the
| desire to tune it per record.
|
| Audioplebs need not apply.
| yial wrote:
| 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 give a
| much better explanation along with other types of tuning. (Arm
| weights, needles, etc etc)
| echoangle wrote:
| Is the problem really the slip in the belt drive? I thought
| its just the motor driving it at a slightly wrong speed.
| yial wrote:
| 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.
| datpiff wrote:
| Models targeted at DJs will have variable speed adjustment on
| the front panel to allow beat-matching. Some turntables for
| home listening will have 2 or 3 speeds with a fine adjustment
| for calibration.
|
| Rates will be off due to manufacturing tolerance or mechanical
| wear (i.e. a loose belt slipping on a motor).
|
| Most people don't worry about it.
|
| It doesn't really vary album-to-album, unless you have some
| ridiculously heavy records that slow the motor.
| tpurves wrote:
| Yes, it turns out that it is rare for mass-produced mechanical
| devices like record players to spin at exactly the rate they
| are supposed to (eg 33.3 or 45). Or they can drift put of
| calibration over time. Often they will be a few % off or worse
| for really cheap players. Usually there is a way to adjust
| calibration by turning a small screw someplace on the machine.
| rufus_foreman wrote:
| DJ turn tables have a pitch fader and lights for calibration:
| https://www.youtube.com/watch?v=KbdK94vl_Bs.
| empath75 wrote:
| 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.
| recursive wrote:
| A DJ has no use for knowing if the turntable is calibrated
| correctly in an absolute sense. Only whether this song is
| calibrated with that song. And for that, good old fashion
| human ears will suffice.
| vel0city wrote:
| 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.
| okatbest wrote:
| 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!
| patrakov wrote:
| 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?
| franky47 wrote:
| A "properly tuned instrument" still requires a base frequency
| (usually defined for A4). Whether to use 440Hz or another
| slightly different frequency is a fun debate to get into.
| datpiff wrote:
| Older recordings on analog media also can have timing error
| at the recording stage or duplication stages.
| astral303 wrote:
| 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.
| netsharc wrote:
| I guess a phone's camera can be used to count the RPM, e.g.
| by filming the label and counting how many milliseconds it
| needs to do a full rotation (1818ms for a 33 RPM record)
| phreeza wrote:
| I tried to build a prototype of something like this with
| opencv once, didn't get it to work reliably though. I have
| a feeling there should be a relatively simple signal
| processing version of this, basically a spatiotemporal
| Fourier transform, that should solve it.
| stavros wrote:
| How can it use ShazamKit if it processes everything on-
| device?
|
| I'm really really curious how this is done now...
| pimlottc wrote:
| They don't claim everything is done on-device, just that
| the audio stream processing is.
|
| > Grooved does not collect any data, whatsoever. The audio
| stream is processed locally on your device and never
| recorded.
|
| Which is consistent with how ShazamKit works [0]:
|
| > Audio is not shared with Apple and audio signatures
| cannot be inverted, ensuring content remains secure and
| private.
|
| 0: https://developer.apple.com/shazamkit/
| pimlottc wrote:
| I love that everyone is guessing all these methods of
| detecting pitches or using the camera to count rotations, and
| it turns out that they're most likely literally just using a
| built-in API and displaying a return value [0].
|
| 0: https://developer.apple.com/documentation/shazamkit/shmatc
| he...
| tirthd wrote:
| Great copywriting. It's very rare that I read an entire paragraph
| without skipping a word.
| empath75 wrote:
| 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?
| turnsout wrote:
| Agreed--and it does feel like the Apple-inspired copywriting
| style the author is complaining about is feeling extremely
| (wait for it) played. Absolutely every site is like:
|
| "Lawn Order.
|
| _The X900 's diamond-tipped rotary blades cut your grass to
| within 50 microns of your desired length. Overkill? Absolutely.
| Because it's not just your lawn--it's our passion."_
| arytoriop wrote:
| This is really cool.
| shiandow wrote:
| This just tells you the speed, not the variation in speed over
| time?
| okatbest wrote:
| 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.
| gaudystead wrote:
| I'm just here to say that I enjoyed that intro you gave to the
| website, and although I hate unitaskers in the kitchen, that
| intro helped to remind me of the magical wonder of them in the
| early days of "The Modern Smartphone".
|
| Cool app and thanks for sharing! :D
| nickthegreek wrote:
| 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
| okatbest wrote:
| Hey that's awesome to hear, thanks for trying it out!
|
| This is exactly what I hoped for when building this app. Making
| a dead simple tool for people who want their records to sound
| better, but may not have the equipment or knowledge necessary
| to adjust it.
| kazinator wrote:
| 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.
| criddell wrote:
| 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.
| taylodl wrote:
| 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.
| criddell wrote:
| Do you happen to know of any tools for fixing pitch
| issues in music files?
| tharmas wrote:
| Anatares Auto-tune.
| 4gotunameagain wrote:
| Audacity.
|
| Free and open-source.
| cnasc wrote:
| I could swear the music video version of Evil by Interpol
| is faster than the album version, but it's just
| inconvenient enough to verify that I haven't bothered
| FelipeCortez wrote:
| hey, I have the same one and didn't know about these controls!
| I'll definitely try this out now
| tiborsaas wrote:
| > Now I have to figure out
|
| I'm glad it didn't continue with where you'll sleep tonight :)
| Severian wrote:
| Wow, I'm feeling lucky. I have the exact same turntable. Using
| a different app (since I use Android) I was able to
| gyroscopicly measure just 1.3% average difference.
|
| I have a sense of tone and it's always seemed fine to me.
| BuildTheRobots wrote:
| I'd be curious to know _why_ your wife felt it was playing too
| fast. Was it out of tune, out of tempo or something else?
| TylerE wrote:
| If it's a song you know well it's certainly possible. It just
| sounds _wrong_. I once pegged a friends turntable as well
| sharp (and it was) in just a few seconds.
| jiayo wrote:
| When US (NTSC) shows are aired in Europe (PAL), the framerate
| difference necessitates a small speed-up. It's barely
| noticeable, _except_ when music is playing, at which point it
| is very, very noticeable. Yes, it 's a little higher pitched,
| but it just feels wrong and is immediately noticeable. I
| think it's about 3% speed up, which is exactly what's being
| described here.
| nickthegreek wrote:
| She is musically inclined and she popped on a record I had
| recently gifted her of one of her favorite bands. She was in
| marching band her entire high school experience as well. She
| always finds stuff like this. She recognizes when it's a
| different recording or not the "proper version" from her
| childhood. It all sounds fine to me! As a visual person, the
| finer understandings of music might as well be magic to me.
| RRWagner wrote:
| good to know about the adjustment screws. I would have tried
| having the turntable straddle two piles of books or some such
| arrangement so that I could adjust the setting in real-time
| from below the turntable while getting the speed display from
| the phone.
| crazygringo wrote:
| 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?
| datpiff wrote:
| > 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.
| iaresee wrote:
| Every. Rolling. Stones. Album.
| sambeau wrote:
| My first thought was that it is listening to the scratches
| rather than the music, but I guess they speed up as the record
| gets played and the arm moves inwards. So, my second guess is
| that it's listening to the pitch of the notes being played. Of
| course, old albums (especially punk albums) are probably tuned
| to whatever worked on the day--maybe a tuning fork, possibly a
| piano, maybe just to one of the instruments.
| svantana wrote:
| Umm, no, scratches meet the needle once per revolution,
| regardless of the needle's position. So that would definitely
| be a possible method. But not all records have scratches, or
| they could be at an angle, which would give the wrong
| estimate. Also, actual sounds on the record could have
| scratch-like qualities.
| sambeau wrote:
| >scratches meet the needle once per revolution, regardless
| of the needle's position
|
| I need to go away and think about that :D
| kevincox wrote:
| The needle doesn't pass at a constant "ground speed"
| everywhere on the record. On the outside the needle
| "travels faster" and in theory you have more detail. Near
| the middle the needle travels over the record surface
| slower.
| taylodl wrote:
| That's one of the reasons you'd put your best song on
| side A, song 1 and your 2nd best song on side B, song 1 -
| you got the most detail on the outside track. I remember
| seeing an interview with Led Zeppelin quite a few years
| back where they were claiming they _knew_ they 'd have a
| smash hit with _Stairway to Heaven._ Which was funny,
| because I remembered then seeing an interview several
| years before where they said it was a track they never
| thought was going to go anywhere.
|
| Which is it? It's track position - 4th track on the A
| side, i.e. the last track, tells you how important they
| thought it was. Which is to say, it was a "throwaway"
| track that made it big. It happens.
|
| The other odd thing about that album is "When the Levee
| Breaks" is considered to be the 2nd-most popular song off
| of the album and it too was the _last_ track on the B
| side.
|
| What this tells me is the album's producer, one Jimmy
| Page, was out of touch with what Led Zeppelin fans liked
| most. Based off the sound of the next album, _Houses of
| the Holy_ , I'd say Mr. Page got the message loud and
| clear.
| tibbon wrote:
| Even pop albums aren't all 440hz. Def Leopard's Pyromania is
| about a 1/4 step off standard tuning, and there are many other
| examples of similar.
| kazinator wrote:
| People sometimes can't even make backing tracks for
| improvisation that are in tune.
| padenot wrote:
| ShazamKit, from that fetch the BPM, BPM detection from the mic,
| compare ?
| stavros wrote:
| It works offline, though.
| pimlottc wrote:
| Does it? I don't see that claim being made anywhere.
|
| They do say that the audio is processed locally, but that
| does not preclude them from making an API call to find a
| signature match.
|
| > The audio stream is processed locally on your device and
| never recorded.
| rmccue wrote:
| I just tested and a song that works fine normally failed as
| soon as I turned Airplane Mode on.
| dmd wrote:
| "Grooved does not use any third party library or API, just
| the built-in components provided by Apple."
| derefr wrote:
| 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 melody and/or
| harmony of the song is in.
|
| Then, you could either come up with a heuristic, or just train
| a Bayesian filter, using datasets of "real" and "erroneous"
| (key, BPM) pairs.
| fwip wrote:
| Are there really "standard" BPM? As far as I know, most music
| production is just "whatever tempo the band feels like
| playing." I haven't been in a recording studio, though, so
| maybe a use of a metronome is more common there?
| derefr wrote:
| I'm not in the music industry in any capacity myself, so
| take everything I say here with a grain of salt.
|
| And more specifically, to address your question, I don't
| know enough about the recording part of music production to
| say whether most performers get a click-track played into
| their monitors or not. (I know that I've seen at least
| _some_ performers using click-tracks for studio recording;
| but I 'm not sure if that's only given if they ask for it,
| or if it's the studio pushing it on performer to make their
| jobs easier. I imagine click-tracks would always be used
| for multi-performer async studio recording -- as otherwise
| you'd have performances that have _conflicting_ BPM. But
| maybe not for single-performer pop /EDM songs, where it's
| just a vocalist laying down a track, and then everything
| else is done in software?)
|
| The evidence I _can_ cite, is from the _outcome_ of the
| production process: I have a strong recollection from back
| in the late 2000s, of using some music library auto-tagging
| software that would, among other things, analyze the BPM of
| a song to populate the BPM ID3 field of MP3s. For at least
| the music I loaded into it, BPM did _appear to_ be (mostly)
| quantized to nice, round numbers. (And it wasn 't just the
| software being coarse-grained in its estimates; it _did_
| give weird numbers for unusually-produced songs.)
|
| I do know that for any modern "produced" music (i.e. music
| not recorded as a live ensemble session), even if the
| performers _did_ lay down their tracks at a weird BPM, the
| audio engineer is still going to be throwing their
| performances as separate tracks into a DAW. And one of the
| things you tell a DAW, when creating a project, is the BPM
| -- which creates a grid of bars that tracks /samples want
| to _snap_ onto. Even if you 're not trimming or speed-
| adjusting performances so as to snap the _ends_ of each
| track /sample to the DAW's grid, you're still likely
| snapping the _beginning_ of each track /sample to the grid
| -- you'd have to fight the DAW to not. Which means that, by
| default, if the song is "produced" enough -- tracks cut up
| and slid around, reused, etc -- then the output of this
| moving-and-snapping process will be a song that _reads_ as
| the project 's BPM.
|
| Separately, I know that people learning to play an
| instrument for classical/orchestra music, often practice
| their instrument using a metronome (at least at the early
| levels.) Which perhaps gives at least some of those people
| the speed equivalent of perfect pitch -- the ability to
| "lock into" certain BPMs; and to know if other performers
| are running fast/slow vs the "expected" BPM of the song.
|
| I would assume that even for rock performers with no
| classical training, the early-level "textbook" practice for
| drummers and rhythm guitarists also involves playing with a
| metronome. It might be a lot more _tenable_ to play a rock
| song at e.g. 117BPM, if everyone 's just playing on the
| down-beat of the drums; but these performers still don't
| want to have a sudden, unintended _shift_ in their BPM due
| to not being able to do a drum fill / complex chord change
| quickly enough; nor to start rushing as the song amps up,
| forcing everyone else into increasingly-stressful playing.
| In doing drills with a metronome to keep their BPM
| _constant_ , these performers are likely implicitly
| learning to lock into certain specific BPMs as well.
|
| My impression is that the one case where this probably _isn
| 't_ true, is in live jazz performance, and more
| specifically in live jazz improv "jam sessions." In those,
| the percussion (if any) isn't driving the performance, but
| rather is just another component of the harmony, following
| the (often wavering!) BPM of the lead performer.
|
| (Is this why the classic meme of classically-trained
| performers not getting along with jazz artists? Because the
| jazz artists won't stay on beat, and this irritates some
| perfect-pitch-like "out of tune" feeling in the classical
| musician?)
| nereye wrote:
| In some countries there are legal and illegal BPMs, e.g.
| according to [0] only the BPM range from 80 to 116 is legal
| in Chechnya.
|
| [0] https://www.npr.org/2024/04/09/1243632570/chechnya-
| music-ban...
| crazygringo wrote:
| That moment when you read the first half of a sentence
| and know it's clearly sarcasm, and then you finish the
| sentence and realize it's not... :(
| crazygringo wrote:
| 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.
| derefr wrote:
| But would a large-enough majority of songs be recorded with
| a multiple-of-5 BPM, that this app could _presume_ the
| first record you play has a multiple-of-5 BPM, and be right
| 80+% of the time?
|
| If so, then that _could_ still be how it was done here. It
| wouldn 't always work for the first record, but you'd be
| highly likely to get a "good reading" by at least the third
| one you try.
| crazygringo wrote:
| So I found some data and the answer is -- definitely not:
|
| https://assets-global.website-
| files.com/6188e55dd468b56ab674...
|
| from:
|
| https://blog.musiio.com/posts/which-musical-tempos-are-
| peopl...
|
| There are _plenty_ of songs ending in every integer.
| LeoPanthera wrote:
| It probably doesn't need to do an FFT, it just need to be able
| to count beats and have a database of BPM values for popular
| songs. You could use something like AcoustID/Chromaprint to
| identify the song you're playing.
|
| A very simple idea, as all the best ideas are.
| jerf wrote:
| I would expect:
|
| 1. Detect wow: https://www.youtube.com/watch?v=kCwRdrFtJuE
|
| 2. Time wow.
|
| 3. Round to nearest record speed and report delta.
|
| I'd also expect that armed with a normal FFT algorithm that Ye
| Olde Bash On Algorithme Until Functionale would be fairly
| likely to work with reasonable effort, without having to get
| too "signal processor-y" on the FFT output.
| mlyle wrote:
| Wow is wavering speed. A constant turntable speed error (that
| this helps you calibrate out) doesn't produce wow.
| jerf wrote:
| All turntables have wow. Wow is determined by the
| rotational speed. So if you measure 33.2326 wow
| oscillations per minute, you can know the turn table is a
| touch too fast. Wow would not be used to measure the error,
| it would be used to measure the absolute speed. Getting the
| error from that point is trivial.
| crazygringo wrote:
| I don't think you could use FFT or similar to reliably
| measure wow to anywhere near the accuracy necessary to
| produce a reliable amount of correction from just a few
| seconds of an arbitrary LP.
|
| If you were using an LP with a known pure 440 hZ sine
| wave that you could lock onto exactly, then sure. That's
| kind of how frequency modulation -- FM radio -- works.
|
| But I really don't see how you could do this with songs
| that are full of frequencies coming in and out and
| changing all over the place. If you analyzed the full
| side of the LP, you could probably get enough signal out
| of that.
|
| But trying to measure the precise wavelength of wow when
| you're only getting a few wavelengths' worth, from a
| _complex signal?_ I don 't see how.
| mlyle wrote:
| I understand what you're saying better, but I don't think
| you're going to be able to autocorrelate the frequency
| variation precisely at all from a few revolutions,
| especially since there are other non-periodic sources of
| frequency variability.
| adrianmonk wrote:
| It does if the hole in the record is not exactly in the
| center.
| okatbest wrote:
| Thank you so much! I spoke about why I'm not flat out saying
| how it works in another comment but let me answer your
| questions:
|
| 1) It actually might! Worth a shot I guess, but I don't have
| any comedy albums to try it out. I was able to get drum solos
| working fine
|
| 2) Was answered better by somebody else
|
| 3) I was able to get it to detect speed issues up to 9% off,
| beyond that it just stops working completely. Though that was
| in controlled environment so YMMV. If you see the sample vid I
| posted above, my player is roughly 4% off which is a lot but I
| genuinely believe a whole lot of people wouldn't notice that
| mkesper wrote:
| If you play an orchestra with an organ the organ sets the
| reference point. 440 Hz is a relatively young standard, many
| organs were built before that.
| lukko wrote:
| This is cool - not sure if it's possible, but it would great if
| you could determine other things, like is the needle weight
| correct, or is the cartridge aligned properly (maybe left / right
| channel would be louder / softer??).
|
| I found the copy on the site a bit gross - I'm not sure something
| like this needs a critique of modern copywriting, and for me it
| gives that same weird sense of over familiarity ('we get you')
| that I think it's trying to criticise.
| mk_stjames wrote:
| So here's another method that doesn't rely on the song being
| detected or even a song at all:
|
| The gyroscope on your phone is accurate enough to measure RPM to
| about the first decimal place at 33 1/3 - 45 rpm's just by
| placing your phone on the turntable flat and letting it spin.
| sambeau wrote:
| Very cool. Great aesthetic and copy. No notes.
| gcp123 wrote:
| What a perfectly simple app! Going to try this out with my
| Technics SL1200 mk2 tonight. Thanks for sharing.
|
| P.S. Reading comments from a bunch of tech folks trying to wrap
| their heads around an app for calibrating analogue music playback
| device is very amusing. :-)
| bastardoperator wrote:
| I assume this is for belt driven turntables, not direct drive.
| I also have a pair of 1200's. Most mixers these days have BPM
| built in, and before that you had red micro bpm counters and
| headphone amps to validate BPM. Never once on my 1200's did it
| read something outside of the producers BPM count when pitch
| was locked.
| fmj wrote:
| My MK2 was off by about 3% when the pitch adjust was in the
| detent. To be fair, it had a rough life before it ended up in
| my hands. If you have a frequency counter they're pretty easy
| to calibrate the correct way though.
| plastic3169 wrote:
| Looks amazing and useful for me! The links don't take me to the
| app store on my iphone and the app name is not in the heading I
| need to scroll past the copy to find what to search for. Minor
| annoyance but for some reason annoyed me a lot. That annoyance
| led me to hate the copy as I was searching for the app name and
| tried to skim the text. This is probably the first time I write
| any feedback to internet. I am usually not one that does that
| kind of thing haha. Ok, now I will search and install the app. I
| bet it's great.
| okatbest wrote:
| Hey that's very odd, would you mind telling me which
| country/region you are located in?
|
| I actually released the app yesterday but didn't post about it
| til today because it wasn't being indexed properly on the App
| Store yet, it's possible that it's still not live everywhere. I
| have an image link to the listing in the first section of the
| web page and if on iPhone it should show you the classic "this
| website has an app" banner at the top.
|
| If you're searching for it, "Grooved" has many results but if
| you accept the suggestion of "Grooved: turntable calibration"
| it'll come up.
|
| This is a direct link to the store page:
| https://apps.apple.com/app/grooved-turntable-calibration/id6...
| Please let me know if it still doesn't work and I can take a
| look... Thanks!
| plastic3169 wrote:
| I figured that the site breaks with apple lockdown mode on. I
| think that appstore links usually work still, but might be
| that that's one of the lockdown mode protections. The
| spinning animation also was not there so I didn't see the app
| logo there.
| okatbest wrote:
| That's very good to know, I didn't even think to test it
| with lockdown mode! I'll see if I can add a fallback page
| if the content is missing. Thanks!
| kazinator wrote:
| I'm skeptical; you have no idea whether a random song from a
| record player is in tune or not, without a reference copy of that
| song from digital media.
|
| Is this zeroing in on traces of 60 cycle hum in the recording?
|
| Or else, won't it adjust an out-of-tune song to be in concert
| pitch? (Mind you, that would be extremely useful if you're
| playing along with the track and don't want to adjust your
| instrument, or cannot do so.)
|
| To get it to the correct speed, I would go through my record
| collection and find a tune with long, sustained notes. Find the
| same tune on Youtube and get a pitch reference for the note using
| a digital tuner. Then adjust the record player to match the pitch
| on that note, down to 1/10 of a Hz precision.
|
| (In the first place, why would you have a record player without a
| built-in strobe light for adjusting the speed in 2024, when this
| was a common item even in lower income households in 1984.)
| echoangle wrote:
| 60 cycle hum probably would not work, europe uses 50hz
| kazinator wrote:
| That's a big enough discrepancy that the program could have
| heuristics to figure it out, particularly if the record
| player is in the right ballpark.
|
| Also west Japan is 50, east 60.
|
| The main problem is: (1) there isn't a lot of hum on
| professionally produced records; (2) but there may be hum
| from the equpiment itself.
| okatbest wrote:
| Unfortunately a lot of mid-range tables nowadays don't have the
| strobe (mine included), most likely for aesthetic reasons...
| Even just looking at online shopping right now I only see a
| handful that do have it.
|
| As for being skeptical, good! That means I'm doing something
| great according to Clarke's third law.
|
| You can see me testing out the app on multiple records here:
| https://twitter.com/OKatBest/status/1795453042994680148
|
| The results aren't 100% perfect, and they definitely won't be
| as good as matching specific frequencies, but it'll get you
| very close to the ideal RPM.
| ssl-3 wrote:
| Building a "strobe" is just a matter of putting an LED, some
| diodes, a resistor, and (optionally) a transformer together.
|
| The idea is that the LED reaches peak brightness (and
| darkness) at twice the line frequency, just as ye olde
| fluorescent tubes did. (Or: Skip the extra diodes and have it
| work at 1x line frequency. I'm not your boss.)
|
| After that, just print a strobe disc and use it.
| shudza wrote:
| I've used to use an app (there are many) which measures angular
| velocity using accelerometer and displays RPM (you place the
| phone on the turntable). I can't see why would anyone need
| something other than that.
| hobofan wrote:
| Complete noob here, but wouldn't the phones weight (especially
| with how big phones are nowadays) have a significant impact on
| the RPM by slowing it down?
| svantana wrote:
| It's very possible, increased weight will increase friction
| in the bearing. However my iphone SE weighs almost the same
| as a 12-inch record (150g). BUT it is also more difficult to
| place symmetrically on the turntable, which also could affect
| friction.
| peter_l_downs wrote:
| 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 would try it out!
| Congratulations on the launch.
|
| EDIT: keep the rest of the writing if you'd like, I have no
| objection to it and I thought it was funny. But _lead_ with what
| the app is and what it does!
| gamegod wrote:
| Yeah, but he gets great time-on-site engagement numbers by
| doing that. Somebody give this guy a job in Silicon Valley!
| berkes wrote:
| Maybe they already changed it, but there's a chapter "As easy
| as 1-2-3."
|
| I'd personally move that way up. I had to scroll across all
| sorts of fluff and effects. I was sold by this (edit: this
| chapter, not the fluff)
|
| Maybe I'd personally even research how to make the entire
| website just that. Where maybe step 0 is "install the app" :D
|
| The (promised) simplicity of the app doesn't show in the
| communication of the website at least.
| joebergeron wrote:
| I thought the copy was fun and don't mind a good soapbox every
| once in a while, but yeah, wouldn't hurt to slip in a few words
| about what exactly the product does earlier on.
|
| I'll definitely be trying this out on my decks before my next
| set :)
| peter_l_downs wrote:
| Updated my comment for clarification, agreed the extra copy
| is fun.
|
| Also hi joe :^)
| gchamonlive wrote:
| > Let's be real, if this charade of a website was an actual
| startup, we'd probably wear t-shirts that say...
|
| It's intentional. The app is free. There is a statement about
| this whole corp mission mindset.
|
| This is the way it is. If people don't like it or push it away
| from the product, they are not the target audience.
|
| I think this is brilliant. I understood immediately what the
| app does and kudos for the courage in setting the website the
| way it is. Was also impressed with the aesthetic of the site.
|
| If only I had a turntable...
| peter_l_downs wrote:
| This is a Show HN, so I replied with my feedback. The author
| explicitly invited this, too, by writing:
|
| > Would love to hear what you think about it!
| gchamonlive wrote:
| An this is hn, where you post comments and people reply.
| Doesn't change the fact that I think the original comment
| misses the purpose of the website. Doesn't matter the
| downvotes I'm taking, I stand by my comment and I think
| there are better ways to critique the work other than to
| bash on an obviously conscious aesthetic choice.
| okatbest wrote:
| 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.
| peter_l_downs wrote:
| Fair enough, congratulations on your launch and I hope you
| see continued success!
| PascLeRasc wrote:
| Don't throw away the "this is off the record, player" line.
| That's gold.
| miah_ wrote:
| This is a neat idea. I don't know why it needs to be an app on a
| phone though. I guess you "know" a phone has a microphone and the
| setup is minimal and you have a api for everything? It being a
| phone app leads me to believe the 'no data collected' bit is
| temporary as all phone apps eventually gobble data to sell.
|
| I have an Android so I can't try this out, as its in 'private
| beta' on Android currently.
|
| Would love to see this as a open source project that I can
| install on Windows or Linux though.
| okatbest wrote:
| Probably a smart idea to be suspicious of new apps, though I
| will say I am someone who care deeply about privacy. You can
| take a look at my previous project Boop (
| https://boop.okat.best/ ), which is open source and has been on
| the App Store for 6 years, yet I still don't have any analytics
| or data collection in it. I have no clue how many people use it
| beyond download figures I get from Apple.
|
| I have considered making this app open source, and it may still
| happen in the future, but I do want to release the Android
| version first. I'm worried that somebody will see my code,
| repackage it with a new name, beat me with better SEO (which
| would be easy considering how dumb the copy is on my website)
| and sell it for profit before I have a chance to reach a wider
| audience. This is something that did happen with Boop, not a
| hypothetical.
|
| The reality is that this app cannot collect anything valuable
| either way. It's a simple serving app that only uses your
| microphone for a couple of seconds at a time, and I assume most
| people will delete it once it serves its purpose. If I wanted
| to monetize it, the best way would be to add a "Pro" version
| with a subscription or to add ads, but I have no interest in
| doing either. This is a fun side project/portfolio piece, and
| I'd rather collect internet love distributing a ton of free
| copies, rather than sell a small fraction of that number of
| paid copies for $0.99 and have to deal with things like
| marketing, taxes, and customer support.
| dmd wrote:
| Funny, I have the exact opposite intuition as you. It being a
| totally-sandboxed phone app means I _can_ trust it not to
| collect any data without my knowledge, _without_ me having to
| spend hours looking through the source code for some trick I
| might miss.
| thekegsi wrote:
| You can get apps where you place your phone on the turn table and
| it directly measures the turntable speed using either gyroscope
| or compass
| https://play.google.com/store/apps/details?id=com.vinylrpm&h...
| zamadatix wrote:
| Here I was thinking it'd be smart to have the app use the
| camera to figure out how fast the middle label is spinning
| around but this seems way simpler now that you mention it.
| okatbest wrote:
| This is how this project started! I thought I was super smart
| figuring out I could do that, then I realized there are many
| apps that already do the same thing. Eventually I decided to
| see if I could find a novel, more user-friendly approach that
| doesn't require you to put a thousand-dollars phone on a fast
| moving spinning thingie, and that's how Grooved came to be.
| egypturnash wrote:
| 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.
| crazygringo wrote:
| I never knew what the heck those squares were for!
|
| Just thought they were some funny aesthetic choice from the
| 70's and 80's.
|
| Thanks for giving me the definitive answer for something that
| has always seemed odd to me.
| hinkley wrote:
| 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?
| c5karl wrote:
| 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.
| taylodl wrote:
| 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?! :)
| egypturnash wrote:
| My dad was a recording engineer, so he knew where to go to
| find the sweet spot between "this sounds great" and "this
| sounds insanely fabulous but requires a second mortgage".
|
| And yeah honestly I'm surprised you can _get_ a turntable
| that isn 't made for the audiophile market any more, but the
| one shown in the video for this app sure does lack any fine
| speed adjustment. Just a little button labeled 33/45.
| derefr wrote:
| > And yeah honestly I'm surprised you can get a turntable
| that isn't made for the audiophile market any more
|
| It's because of the _other_ re-emerged market for vinyl:
| the "not-so-enthusiastic" collectors, who just want the
| album "on vinyl" to say they have the album "on vinyl" or
| maybe "in every possible format"; or because they love the
| band and the vinyl is just what you happen to get when you
| buy the special collector's edition box-set; or because
| they want to display the vinyl album cover somewhere
| visible in their house as if it were a poster print; or
| because they consider "a vinyl collection" to be an
| aesthetic decor item, like some people consider a full
| bookshelf to be an aesthetic decor item.
|
| A lot of these are people in their teens/20s who don't
| actually think that vinyl sounds better, so don't have much
| enthusiasm for actually _listening_ to the vinyl release
| (as they 're mostly buying _new_ vinyl, and these tend to
| come with a code for a digital copy as well.) So if they
| bother to buy a turntable, it 's the $30 one they say at
| Urban Outfitters. They _know_ they 're just listening to
| the vinyl as a novelty experience, something they're only
| going to be doing a few times -- and so they don't want to
| waste too much money on it.
| ssl-3 wrote:
| And for those that don't have that, a strobe disc can be
| downloaded and printed.
| dmd wrote:
| I've tried this on a dozen or so records and all I get is "Please
| made sure your device can hear the music, and that you're using a
| modern song with a clearly defined beat."
|
| (There is definitely a very well defined beat.)
| okatbest wrote:
| That's odd, could you share an example of a record you use? Are
| those fairly popular/common records?
|
| Also, do you see the little disk outline moving during the
| analysis? This would confirm that your phone can hear the sound
| coming out of your record player (just to be safe: you need to
| play the song out loud)
| dmd wrote:
| I've tried the White Album, Tiffany (I think we're alone
| now), and a bunch of songs on Cake Comfort Eagle.
|
| No, the disk is not moving at all! It's turned up pretty
| loud.
| okatbest wrote:
| That's super odd. So it's not even rotating? There might be
| an issue that occurs before the analysis starts.
|
| If you don't mind, do you have any special setting on?
| Lockdown mode or something? Are you able to play the music
| back if you use the Voice Memo app to record a bit of it?
|
| Sorry about all that, hopefully we can figure out what's
| wrong!
| dmd wrote:
| Yep, voice memo works fine, not on lockdown (not sure
| what that is).
| Omni5cience wrote:
| Basically it's a setting for people who are concerned
| about being targeted by 0days.
|
| > Lockdown Mode is an optional, extreme protection that's
| designed for the very few individuals who, because of who
| they are or what they do, might be personally targeted by
| some of the most sophisticated digital threats.
|
| https://support.apple.com/en-us/105120
| strongpigeon wrote:
| 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!
| virskyfan wrote:
| Great! In the past I've used the app that measures the turntable
| speed through its accelerometer...it's somewhat uncomfortable and
| weird to set the mobile on the turntable, start and stop once and
| again. Would love to see a comparison of measurements taken with
| your app and the one using the accelerometer...calibration is a
| huge thing in engineering.
| okatbest wrote:
| I'm gonna be honest, using the accelerometer will definitely be
| more accurate because you can take more samples over a longer
| period of time. That's how this project started, but I also
| felt uncomfortable putting my brand new phone on a fragile
| player and even more so asking other people to do the same.
|
| Grooved is still very accurate, especially if you run multiple
| measurements to confirm on multiple songs/records. The
| threshold for "perfection" in the app is 0.01%, which to me
| anything beyond that is a rounding error and I could not tell
| the difference in my tests. This is equal to a drift of about a
| third of a second over an hour of listening.
| chriscjcj wrote:
| So is this just a test to see if it's playing records at the
| right speed? Does it do anything else? Is it comparing it to a
| known-good recording of the song or is it measuring how many
| cents the song deviates from a natural key? If it's the latter, I
| can say that I have many many records don't play back in a
| natural key.
|
| I have several records (45's) in my collection whose hole is not
| punched perfectly in the center and the pitch wavers up and down
| as the record rotates. How would this app react to that and what
| suggestion might it make to mitigate?
| nomel wrote:
| Oh, you could probably solve that concentricity error by
| looking at the subtle repetitive wobbles in the spectrum.
| Period of the wobble would be related to the radius from the
| center, and the amplitude of the spectral shift would be
| relative to the radius and the concentricity error.
|
| I suspect modern direct drive could handle the modulation of
| their speed. I suspect this has been done already.
| verelo wrote:
| So this is super cool but i am questioning its reliability after
| playing a song from Spotify on my Sonos and then letting the app
| listen: the result was 0.1% too slow? I guess that's a very small
| difference, what's the degree of error to expect here?
| nickthegreek wrote:
| I just played Bad Religion - Incomplete on YT Music through
| Sonos, app said "That's pretty much perfect". Played the same
| track on vinyl, app reported 3.5% too fast. Dev answered
| elsewhere on the post that .01% is required for the perfect
| message.
| okatbest wrote:
| So this is an excellent question, because no joke I have
| noticed the same thing testing with Spotify. Apple Music does
| not have that issue.
|
| Makes me wonder: do different streaming services get different
| masters? Or, is Spotify having playback issues? To the app,
| they both should sound the same. I intend to do some research
| with that when the fog clears out a bit and the Android version
| is out.
| kernal wrote:
| Made with Flutter?
| Balgair wrote:
| Great idea! Thank you!
|
| However, I don't think I'll ever use it.
|
| My turntable doesn't have an adjustment for speed outside of 45s.
| So, if I find out that my table is too fast or slow, that's just
| going to bug me forever. So, I'd rather not know, seeing as I'm
| enjoying the music just fine as is.
|
| If you can, try selling this out to an adjustable turntable
| manufacturer in stock options, so that when all the people find
| out their turntable doesn't spin quite right and then go spend to
| buy a new one they can adjust, you'll make even more money.
| ThomasBb wrote:
| Very nifty; thanks for building this. Great excuse to put a
| record on my player. Mine was 0.2% slow apparently...
| Object0541 wrote:
| It would be exciting to try your app, cause I have 2 turntables
| to calibrate, but I don't use google play store. Could you make
| it available on f-droid?
| criddell wrote:
| I wonder if this would work playing The Shaggs' _Philosophy of
| the World_ record? It 's notorious for having untuned guitars and
| the drummer doesn't seem to be following any kind of pattern.
| Animats wrote:
| You can get test records which have a constant tone recorded.
| That's the right tool for this. Not only can you measure speed,
| you can see small speed variations - wow, flutter, etc.
| czottmann wrote:
| I have zero use for this app (I own no turntable), but I
| absolutely dig the website. Well done on what you wrote, how you
| wrote it, and how good it all looks!
| sans_souse wrote:
| thank you Ivan looking forward to an android version!
| drewbeck wrote:
| This is cool although it very confidently asserted that a 45 rpm
| 12" single was a perfect! 33 1/3 rpm.
|
| Which suggests this is using song recognition and not discovering
| some underlying truth of the spinning platter.
| Lio wrote:
| Neat idea.
|
| For some reason I thought this might be for calibrating cartridge
| alignment. If someone can come up with an easier way to correct
| that it would be amazing.
| coloneltcb wrote:
| this is very cool! Just tried this on my TT (Pro-Ject Carbon
| Debut EVO) and got a perfect 33 1/3 and had to brag
|
| thanks for making this, and in general I love digital experiences
| that match with analog media, please keep making more and lmk if
| you want any free ideas
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(page generated 2024-05-28 23:00 UTC)