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RPM's and Strobe

70.180.85.97
Posted on February 6, 2016 at 16:59:43
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 What do you think it means when the strobe indicates the speed is correct but, in actually counting the revolutions in one minute I came up with 30 more than once??? The music sounds fine I do not hear any pitch changes...

 

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RE: RPM's and Strobe, posted on February 6, 2016 at 17:09:48
Poinzy
 It either means your onboard strobe is ridiculously inaccurate, or you aren't counting the revs right. I don't know how you can NOT hear 10+% pitch variation.

 

RE: RPM's and Strobe, posted on February 6, 2016 at 17:17:53
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 How many different ways are there to count rev's???

 

RE: RPM's and Strobe, posted on February 6, 2016 at 17:19:22
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 Sorry should have said this is not and onboard strobe, and I am sure it is correct. I checked it against my SDS controller and it was correct...

 

RE: RPM's and Strobe, posted on February 6, 2016 at 17:22:29
Poinzy
 Well, apparently you know more than I. So I'll just move on.

 

RE: RPM's and Strobe, posted on February 6, 2016 at 17:29:31
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 If I knew more than anyone I wouldn't be asking, I am sorry if I sounded rude I just sat down and counted the rpm's for one minute. I thought that was the way to do it???

 

"counted the rpm's for one minute", posted on February 6, 2016 at 17:41:42
volunteer
Audiophile

Posts: 5666
Location: Louisville, KY
Joined: January 7, 2012
 If everything sounds as it should I suggest your manual method was highly inaccurate. He is right in that there is simply no way you would not hear a 10% difference in speed.


-Wendell

 

RE: RPM's and Strobe, posted on February 6, 2016 at 18:09:36
geezerrocket
 When all else fails, take a small piece of tissue and set it on the outside edge of the record while the needle is in the groove in the middle.of the record. Your count should be 100 for 3 minutes.



 

RE: the strobe is governed/regulated by mains frequency.., posted on February 6, 2016 at 18:09:41
user510
 Example; if mains frequency isn't perfectly accurate at exactly 60hz, but instead wavers throughout the day from 59hz to 60-1/2 hz, the strobe can only compare platter rpm against the mains frequency, whatever that may be.

Depending on the stability and accuracy of your mains frequency, the strobe may or may not be accurate.

Exceptions:
Electronic speed controllers that regenerate the frequency of the current that powers your turntable can potentially be more accurate than a turntable where the strobe depends upon the frequency of the power coming out of your wall socket.

-Steve

 

RE: RPM's and Strobe - Perry Mason, posted on February 6, 2016 at 18:16:10
escapist
Audiophile

Posts: 108
Joined: October 24, 2013
 Now Mr JC, you have stated that you have counted the number of revolutions per minute of your turntable platter. You have further stated that you performed this count in order to verify the strobe, which indicates that this same turntable is on pitch. Is this correct?

[Yes.]

Moreover, you say that you counted 30 revolutions in one minute when, as we all know, a properly operating turntable should make 33 and 1/3 revolutions per minute for a long play record. You then repeated your test and you again counted only 30 turns - roughly three turns less than there should be.

Have I described the events of your so-called 'test?'

[Yes.]

And yet the strobe would indicate no problem - no pitch problem. So I ask who - or what - are we to believe? It is well established that man is fallible - that a man may lose a train of thought, his mind may wander, he may tire. He may... lose track and miscount. You did miscount, didn't you? Is it not the case that you did miss a turn, one or more turns, and miscount? You BLINKED!! Isn't that true?

No further questions.

 

RE: RPM's and Strobe - Perry Mason, posted on February 6, 2016 at 18:36:59
escapist
Audiophile

Posts: 108
Joined: October 24, 2013
 Seriously, if you do a recount, maybe put a piece of tape on the edge of the platter (check the tape doesn't hit anything while platter turns). Use a pencil, for example, and tap for each revolution. The tapping occupies your attention - you are less likely to miss a turn.

If the count really is 30 rpm - can you adjust the pitch and then check your strobe?

 

RE: RPM's and Strobe - Perry Mason, posted on February 6, 2016 at 20:08:04
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 Well I shall count again tomorrow and pay the utmost attention!!!

 

I use a multimeter, posted on February 6, 2016 at 22:04:48
styx
Audiophile

Posts: 203
Location: Texas
Joined: August 27, 2004
 That is what I do.

- I Play a record with 3150 Hz.
- Then I use a multimeter, which is capable of measuring Hz, on the output of the phono preamp.
- Then I adjust the speed until it is close to 3150 Hz on the multimeter.
- For 45rpm I adjust to 4253 Hz. (45/33.33) x 3150



---
Comparing is the end of happiness and the beginning of discontent.

 

His attorney was Hamilton Berger, posted on February 7, 2016 at 10:05:21
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 No wonder he lost


ET
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: RPM's and Strobe - Perry Mason, posted on February 7, 2016 at 11:19:12
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 Ok my again I counted 30 rpms more than once this morning, and the strobe says that I am actually a lil fast???

 

RE: His attorney was Hamilton Berger, posted on February 7, 2016 at 11:22:25
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 Actually Hamilton Berger was the Prosecutor not the Defense Attorney!!!

 

RE: RPM's and Strobe , posted on February 7, 2016 at 11:56:08
Lakeshore Larry
Audiophile

Posts: 215
Joined: July 30, 2014
 What are you using as a light source for the strobe?

What are you using for the strobe disc (on the platter)?

How did you confirm the strobe system with the SDS?

If you get 30 revs in one minute, your platter is running slow. Either the light source is off or the printed strobe disc is off.

 

RE: RPM's and Strobe , posted on February 7, 2016 at 12:37:49
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 I am using the KAB disc and strobe... I set my SDS unit a long time ago using the platter app and test record at 3150 hz, the sds has never been changed and the strobe and disc say it's dead on..

 

RE: RPM's and Strobe , posted on February 7, 2016 at 12:43:00
Lakeshore Larry
Audiophile

Posts: 215
Joined: July 30, 2014
 Strobes are pretty poor indicators of speed, although one would think it should show a 10% error. The test disc and platter speed are a better indicator.

What does your test disc and platter speed app show with the current set up (30 revs/minute)?

 

If you use an iphone..., posted on February 7, 2016 at 12:44:07
mbhcid
Audiophile

Posts: 224
Location: east coast
Joined: August 8, 2006
 try the free app mentioned in the link. I downloaded it last week and find it easy to use and very accurate.

 

RE: RPM's and Strobe , posted on February 7, 2016 at 13:36:47
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 That's the problem I don't have my test record right now, I lent it to a friend.

 

RE: RPM's and Strobe , posted on February 7, 2016 at 17:17:09
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002
 Do you have a simple strobe disk?

You would need either a incandescent or a neon light source, the newer fluorescent bulbs don't work very well.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: His attorney was Hamilton Berger, posted on February 7, 2016 at 17:55:25
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 Yes but he was an attorney and always faced Perry Mason.
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

RE: RPM's and Strobe , posted on February 7, 2016 at 19:43:42
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 Yes I am using the KAB strobe and disc now, also have the VPI disc.

 

RE: RPM's and Strobe , posted on February 7, 2016 at 21:03:06
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Are you using the battery powered strobe light with the KAB strobe?

Does the VPI strobe agree with the KAB strobe when using a florescent light to illuminate the VPI strobe?

How did you mark your turntable platter for counting revolutions?

I put a white dot on my platter when I used to count revolutions on my Sota Millennia Vacuum. However, I never encountered the problem you're having. My platter revolution counting always agreed with my strobe disc measurements. In fact, I would set the platter speed using the strobe disc before counting revolutions in order to get it very accurate to begin with. Then, I would time revolutions with the clock in my handheld calculator that also contained a special program I wrote to calculate percent deviation from perfect platter speed. Now, I use a Phoenix Engineering RoadRunner to maintain platter speed and I highly recommend the Phoenix Engineering products.

I would recommend replacing your SDS with the Phoenix Engineering Eagle power supply and RoadRunner tachometer. These components will automatically adjust your turntable for the correct platter speed each time you turn it on in addition to providing electronic switching between 33 and 45 rpm. Feedback from the RoadRunner to the Eagle will maintain exact platter speed during motor warm-up and you will always have a readout of your platter speed to an accuracy of 0.003%. Check out the YouTube video at the link below.

Best regards,
John Elison

 

RE: RPM's and Strobe, posted on February 8, 2016 at 04:58:58
Not Yet There
Audiophile

Posts: 538
Joined: April 8, 2006
 You can download a free app called iRPM for use with an iPhone. You place you iPhone on the platter and it calculates the rpm..

 

RE: RPM's and Strobe, posted on February 8, 2016 at 05:25:24
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 Don't have an iphone...

 

RE: RPM's and Strobe , posted on February 8, 2016 at 05:30:54
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 John,
I am not using the SDS unit on this TT, I have two tables the one in question is DC powered. Thanks anyway, I think I just figured out what's going on!!!

 

RE: RPM's and Strobe , posted on February 8, 2016 at 06:27:41
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 Okay! I thought you mentioned an SDS, but I guess not. Sorry!

So, are you going to tell us what you figured out?

Thanks,
John Elison

 

RE: RPM's and Strobe , posted on February 8, 2016 at 09:30:16
jcmusic
Audiophile

Posts: 1387
Location: New Orleans, La.
Joined: June 13, 2006
 I did mention an SDS that is on my other TT, anyway I feel like an idiot. When I was counting the rpms I was using the splice on the belt as a reference point (dumb ass) instead of putting a piece on the platter itself. So the speed is correct and agreeing with the strobe and disc now I feel better...

 

I've made similar mistakes..., posted on February 8, 2016 at 10:38:18
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 We've all done it. Such is life! ;-)

Anyway, it's always good to find out you don't have a problem.

Best regards,
John Elison

 

If you use Android, posted on February 8, 2016 at 11:01:57
kyle
Audiophile

Posts: 1839
Location: London Ontario
Joined: September 29, 1999
 You can now get the RPM Calculator app for Android.
The video on play store shows an iPhone on a Linn table running at 34.2 rpm. That is very similar to my old LP12.

 

It's Hamilton Burger, posted on February 8, 2016 at 19:30:07
Dave Pogue
Audiophile

Posts: 11689
Location: DC Area
Joined: October 9, 2001
 HamBurger, gettit? Early radio humor.

 

RE: If you use an iphone..., posted on February 9, 2016 at 02:13:13
Alex M
Audiophile

Posts: 924
Location: Hampshire
Joined: February 9, 2001
 RPM looks like a great app, but when I tried to install it on my 4S with IOS7 I was informed it is only available for IOS8 and 9. I need a new iPhone!

Alex

 

RPM, Vs Belt speed, posted on February 9, 2016 at 06:07:34
Penguin
Audiophile

Posts: 7116
Location: Delaware
Joined: August 5, 2001
 they are not the same. You can calculate how many times the belt goes around per minute :)


dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.

quote by Kurt Vonnegut

 

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