When can you see wow on a strobe?

[shimniok]

Saw another thread citing e.g., Music Hall MMF-5 having .15% wow/flutter and a Marantz having 0.03%. And how some people can hear 0.1% wow.

I don't know how much wow I can hear so I am wondering...

What degree of wow/flutter can you *see* on a strobe?

On one extreme, my Technics SL-QD33 -- I cannot really see or hear any variation in speed (0.025%). The other extreme, my BIC 980 -- I can definitely see and hear bothersome speed variations (I think it actually has a problem). In between these, my Realistic Lab-400 -- I can at times see a little tiny speed variation but cannot easily hear it, if I can hear it at all. (0.03% when new, but probably worse in current condition)

Maybe another way to get at the answer is to figure out a way to measure the actual speed of the platter, and thus I can measure wow/flutter directly. Naw, I don't need *another* project.

Michael

 

[dkelley]

wow will shift the strobe's apparent position over a tiny spec and then not move again.

So assuming your strobe doesn't move at all (perfect speed), if it suddenly moves and then stops again, that's some form of single period pitch deviation then returning to normal speed - IE, "Wow". it's called "wow" because the pitch goes down then back up again, sort of a "wow" sound if you make the sound right LoL.

it's completely audible if the source material has predictable enough pitch for the listener to hear something unexpected.

Wow is pretty nasty and shouldn't happen. IMHO on a turntable it means that either the lubrication is toast and needs to be redone asap, or the motor is in fact dying or it's power source isn't reliable causing intermittent power outages. If you think of the weight of a platter on a good TT (2 or 3 pounds up to several times that), also assuming very little friction (as in a well lubed vintage or new high quality turntable), powering off the motor should result in momentum keeping the platter rotating for a while at decreasing speed. if you power off the motor for a split second then back on, it results in a strong wow issue. or if you press your finger against it for a second while powered up then remove your finger, it's wow.

To have the TT create audible wow on it's own, something similar has to be happening inside it (extra friction unexpectedly and momentarily, or power source issues). In a DD turntable where the power source is custom built often, the power source can in fact be the problem. With a belt drive or rim drive, more often than not it's friction.

All, of course, just imho and ymmv and all that. It's mostly common sense I'm spewing out here, not experience with tons of turntables, although I'm a good engineer and certainly do have experience with a dozen or so TTs of my own over my life. But there are many here with a ton more knowledge than I, so if I'm wrong I accept it.

Sure sounds logical though LoL

cheers,
Don

 

[markd51]

I feel Platter Performance can go beyond just simple speed checks, and accuracy.

I noted an improvement on my own sound, on a VPI MK-IV Platter, which uses a 3-Pin Suspension, and the runout was not optimal. Meaning, I was seeing the Platter waver up and down in a vertical plane.

I decided to buy a Dial Indicator, and Vacuum Base Stand, from Harbor Freight, and then got to work. From a previous vertical runout of +- .012", I got the runout down to +- .003".
The sound did improve, and gained solidity, and steadiness. The $30, or so dollars spent was worth the cost, to zero out the Platter to the best of my abilities. Mark

 

[dkelley]

oh, and your question -- I never answered LoL

I don't know what degree you can see, but the strobe on my dual 604 is spec'd out for percentage accuracy, I suppose you would work it out from that. assuming the 0.1% is audible theory as fact. or work out the number of blocks on the 60hz/33.33 rpm strobe markers on your TT (unless you have the kind where the markers are the same for each speed and the lamp changes accordingly) and then do the math from there compared to a 33.33r RPM platter rotation speed.

In other words, I don't know the answer.

I can tell you though that I have a very good ear for pitch (classical violinist, not that classical violinists exclusively have great ears but it's sort of a requirement of the trade), and I can't hear it when my strobe moves a tiny spec briefly and then settles down again, something that happens a teeny bit once in a while on my dual.

I expect it's source dependent though. if I was listening to a perfect simple pure single unwavering tone for the length of the LP it would be a lot more obvious and maybe I could hear it in that case.

Classical piano music is a great test - there should be zero pitch deviation so W&F are both audible. Flutter doesn't normally happen much if at all audibly via turntables though, more of a tape thing.

 

[dkelley]

I feel Platter Performance can go beyond just simple speed checks, and accuracy.

I noted an improvement on my own sound, on a VPI MK-IV Platter, which uses a 3-Pin Suspension, and the runout was not optimal. Meaning, I was seeing the Platter waver up and down in a vertical plane.

I decided to buy a Dial Indicator, and Vacuum Base Stand, from Harbor Freight, and then got to work. From a previous vertical runout of +- .012", I got the runout down to +- .003".
The sound did improve, and gained solidity, and steadiness. The $30, or so dollars spent was worth the cost, to zero out the Platter to the best of my abilities. Mark

true. cool by the way, how does that work exactly? I mean how does it adjust your platter? is it something that sits on top like a mat replacement and is adjustably uneven to compensate for such things? no, that wouldn't make sense I guess LoL. I won't guess, easier to sit back and learn.

I'm certain that verticle off-of-center issues (and even horizontal off of center issues I suppose) are legit things that we tend not to ever think about.

But I can't imagine that it's easily or at all adjustable in most turntables... so I'm at a loss how you could adjust/measure/fix it with a $30 tool.

Maybe I'll just have to buy one for myself LoL

 

[markd51]

true. cool by the way, how does that work exactly? I mean how does it adjust your platter? is it something that sits on top like a mat replacement and is adjustably uneven to compensate for such things? no, that wouldn't make sense I guess LoL. I won't guess, easier to sit back and learn.

I'm certain that verticle off-of-center issues (and even horizontal off of center issues I suppose) are legit things that we tend not to ever think about.

But I can't imagine that it's easily or at all adjustable in most turntables... so I'm at a loss how you could adjust/measure/fix it with a $30 tool.

Maybe I'll just have to buy one for myself LoL

The VPI Mk-IV/TNT Platter was sort of an odd animal, having three allen head machine screws centrated around the Spindle, and these 3 adjustable steel pins rested-rode upon the Bearing Shaft Flange at the underside of Platter.

VPI always warned not to mess with those adjustments, that they were Factory set, and if adjustment was needed, to send the Platter back to factory for adjustment.

The 3 Pins purportedly offered better isolatation of the Platter from the Bearing, and any possible transferred noise-vibration. For 30 years, Harry was an "Isolation Freak", with SAMA's, Idler pulleys, Firestone Air Bladder Feet (TNT), now it's just bolt everything together solidly, and call it a day! lol Mark

 

[dkelley]

cool, really interesting design.

I wonder though if the design also allowed for it to become off balance in the first place?

oh well, we'll never know

 

[Nat]

I've wondered about this issue myself. It does seem to me that some apparent variation in the strobe image (if that's the term) is psychological -- we suddenly notice when the bars get near a fixed object like the side of the strobe lamp, but they may have been moving at a very slow but steady pace all the time. Is this possible?

 

[shimniok]

oh, and your question -- I never answered LoL

I don't know what degree you can see, but the strobe on my dual 604 is spec'd out for percentage accuracy, I suppose you would work it out from that. ...

I can tell you though that I have a very good ear for pitch (classical violinist, ...
and I can't hear it when my strobe moves a tiny spec briefly and then settles down again, something that happens a teeny bit once in a while on my dual.

I couldn't ever hear my Dual although it did move a teeny bit, too.

It'd be interesting if there was some kind of demo audio file out there to 'test' one's ability to hear wow. I know some people on here say they are really sensitive to it and was somewhat curious if I am more or less sensitive than the normal person.

Michael

 

[midimaniac]

If you have a test record with a 3150Hz tone, it will reveal extremely small amounts of wow. I do know that Stereo Review's Stereo Test Record, Model SRT 14-A For Home And Laboratory Use has such a track. I would think that other frequencies close to that one should give good results also.

To check speed accuracy in a percentage you can download a strobe disc which has a radial line printed on it, then use a stopwatch and count 100 revolutions in 3 minutes. The strobe is actually a very small computer program which will run directly from any folder you put it in, using no linked files. You can vary the size of the disc. The program is two-part, the other half will print arc protractors according to Lofgren A/ Baerwald, Lofgren B and Stevenson null points. Inner and outer groove radii are adjustable, or you can just click on Typical, DIN, or IEC. There is a help tab and complete instructions. One of the coolest aspects of the protractor is that it even prints out 200mm reference lines which are used to verify your printer is printing precisely to scale. If not, you can easily correct for your printer. The readme appears initially to be just an update log, but please read the entire readme file- there is a TON of info and lots of tips there if you scroll down. IMO this strobe and protractor have no equals online. Find it here: http://conradhoffman.com/chsw.htm

 

[dkelley]

good info. as noted, I figured a test record with a solid tone would show wow more obviously, however most musical material hides wow so well that it's importance becomes smaller unless you're listening to sources that show it off better (long, solid tones, no use of vibrato)

 

[shimniok]

Hm, my Shure test record may have test tones, now that you mention it...