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Old 3rd Oct 2022, 11:18 am   #41
DMcMahon
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Default Re: Wow and Flutter Testing

First attempt at the Audacity Wow & Flutter Visualizer has given poor results.

For a quick easy way to get the signal into Audacity I used the 3kHz Ampex test tape in my Ion Express portable tape player connecting its USB output into my laptop.

The Wow and Flutter result is large, which it may well be, but also messy looking. Have not used Audacity for quite a while and am struggling how to change the x axis to stretch out the raw signal to be able to see what the 3kHz signal actually looks like.

David
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Old 3rd Oct 2022, 12:36 pm   #42
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Default Re: Wow and Flutter Testing

The visualiser shows you the raw peak to peak data, no weighting, Y axis is +/- 1%.

Click on the + magnifying glass icon to expand your capture.
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Old 3rd Oct 2022, 1:55 pm   #43
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Default Re: Wow and Flutter Testing

Thank you, I did eventually work out/remember it was the + magnifying glass (Zoom In icon).

After expanding the previous results from Post 41 the results look better (cleaner), the Wow & Flutter still high though, will later see what the Ion Tape Express measures on the Philips meter.

David
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Old 3rd Oct 2022, 5:17 pm   #44
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Default Re: Wow and Flutter Testing

What the earlier non expanded traces show agrees with your Philips meter, there is a large increase in the flutter levels every 4 seconds or so. That tends to point to a problem with the test tape.

The DIN wow and flutter readings are taken with a peak reading meter in the Philips, rather than the weighted rms type often quoted by manufacturers. A rough guide is that the DIN figure will be the square root of 2 (1.414) times the wrms figure. The numbers quoted for the RS-BX747 seem to have a worse DIN figure at +/-0.15% than would be expected for +/-0.05% wrms.

Hopefully someone who knows more about the subject can explain what is going on.

Paula
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Old 3rd Oct 2022, 5:29 pm   #45
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Default Re: Wow and Flutter Testing

Have you fast-forwarded the whole tape and rewound it before use, in case there's some mechanical issue with the evenness of the wound tape? It certainly sounds as though the spike follows the tape rather than being part of the machines under test.
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Old 3rd Oct 2022, 8:30 pm   #46
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Default Re: Wow and Flutter Testing

Yes the Ampex test cassette has been fast wound in both directions end to end previoulsy at least 3 times with no change to the symptom.

David
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Old 3rd Oct 2022, 8:39 pm   #47
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Default Re: Wow and Flutter Testing

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Originally Posted by frsimen View Post
What the earlier non expanded traces show agrees with your Philips meter, there is a large increase in the flutter levels every 4 seconds or so. That tends to point to a problem with the test tape.

The DIN wow and flutter readings are taken with a peak reading meter in the Philips, rather than the weighted rms type often quoted by manufacturers. A rough guide is that the DIN figure will be the square root of 2 (1.414) times the wrms figure. The numbers quoted for the RS-BX747 seem to have a worse DIN figure at +/-0.15% than would be expected for +/-0.05% wrms.

Hopefully someone who knows more about the subject can explain what is going on.

Paula
Thank you for that Paula. I think I have seen other cassette decks where the WRMS% quoted spec figure does not make much sense when comparing it to the quoted DIN % spec ?

David
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Old 3rd Oct 2022, 9:02 pm   #48
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Default Re: Wow and Flutter Testing

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Originally Posted by frsimen View Post

The DIN wow and flutter readings are taken with a peak reading meter in the Philips, rather than the weighted rms type often quoted by manufacturers.

Paula
The Philips manual references that with the internal filter selected the frequency response is "weighted" according to DIN standard 45 507 with a frequency response of 0.2 to 200Hz, this characteristic being adapted to the human ear response.

With the filter switched off the frequency response is 0.5 to 500Hz, this is described as unweighted. This unweighted signal can be monitored on a output BNC on the rear panel.

All the tests I have done have been with the filter switched on for the DIN weighted signal.

David
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Old 3rd Oct 2022, 11:50 pm   #49
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Default Re: Wow and Flutter Testing

The appelation "wrms" is a ghastly solecism perpetrated by advertising copywriters. It is a contraction of "Watts RMS", which, applied to amplifier output power, is misnomer enough, but is meaningless when applied to wow and flutter. There are no Watts involved. The simple percentage figure is, if anything, an average, for which "rms" is not a completely accurate label anyway.

Of course, there are also peak and weighted values for wow and flutter, but can we at least start by not perpetuating nonsense?
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Old 4th Oct 2022, 8:44 am   #50
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Default Re: Wow and Flutter Testing

Surely in this application it's an abbreviation of Weighted RMS?
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Old 4th Oct 2022, 9:04 am   #51
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Default Re: Wow and Flutter Testing

I thought the W may stand for "Weighted" but was far from confident.

If it is "Watts" then strange that they chose that erroneous nomenclature.

David
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Old 4th Oct 2022, 10:10 am   #52
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Default Re: Wow and Flutter Testing

From what I can make out, the Ebay W+F tape is beginning to look dubious. If two machines are both seeing the cyclic behaviour...

As I've written before (and I'm sure others such as Tim have also written), you need a test cassette that's been made on an adapted reel machine, recorded full track. By far, the best value I know of is obtained via Hanspeter Roth's tapes. You get a set of 6 for about 60 Euros. They are not 'perfect' - for example, my Teac tape gives O.03 RMS, but same deck gives 0.04 with the HPR. It's said that TDK D shells are excellent, so I intend to transfer my HPR tapes to them and see if things improve. You get a set of 6 tapes for less than 1 NOS Teac / Sony etc..(that will likely be rail-roaded).

If you are serious about this cassette malarkey, I recommend hitting up Hans before he decides we are a bunch of curmudgeons and no longer wants to supply us. You will be introduced to the delights of azimuth* and Dolby level setting.

* Hans' tapes are not bang-on due to shell alignment. Methinks the right shell will yield perfect results. You can't blame him for not having forensic-grade shells, seeing as they haven't been made for 20+ years... Hans' tapes will get the machines shown here to factory spec. I am splitting hairs about the shells for aligning, as if I don't, someone will come along and say 'my azimuth HPR tape isn't perfect'. Unless you have a mint Dragon (most really aren't), it'll be perfect.

edit - you need to Google 'Hanspeter Roth tapes'. I haven't provided a direct link as I don't want to infringe forum rule (even though I very much doubt Hans is doing this to pay for his retirement to Monte Carlo!).
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Old 4th Oct 2022, 11:26 am   #53
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Default Re: Wow and Flutter Testing

Quote:
Originally Posted by wd40addict View Post
Surely in this application it's an abbreviation of Weighted RMS?
I very much doubt it - if the adverts were in that class they usually stated the weighting standard, DIN for example ("DIN weighted"). Lots of the figures quoted in hi fi advertising of the boom period (70s-80s) were determined by copywriters' herd activity than by measurement, certainly in the lower price bracket.
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Old 4th Oct 2022, 12:38 pm   #54
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Default Re: Wow and Flutter Testing

Thank you knobtwiddler for the tape information I will check those out.

For me personally the Wow & Flutter tests are just an interesting exercise to understand the measuring process better. I do not have any high end cassette decks and am not really worried about the actual Wow & Flutter results accuracy, so do not want to spend a fortune on lab standard reference tapes, but agree the tapes you reference sound very good value for money.

David
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Old 4th Oct 2022, 12:55 pm   #55
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Default Re: Wow and Flutter Testing

Quote:
Originally Posted by knobtwiddler View Post
my Teac tape gives O.03 RMS, but same deck gives 0.04 with the HPR.
How are you measuring your RMS Wow and Flutter %, equipment wise ?

David
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Old 4th Oct 2022, 2:24 pm   #56
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Default Re: Wow and Flutter Testing

I get perfect results with the free W+F GUI program: http://www.ant-audio.co.uk/index.php...st&qry=library

I use a MOTU M4 if I need accuracy, and the input on my laptop for when I don't need perfect audio performance (it gives same result for W+F).

I also have a rather lovely Lindos LA100 for W+F. The bunch of high-end analysers I have at work (AP, R+S, Prism etc.) do NOT measure W+F... By the time they came out, it was considered old hat. I dream of finding the AP W+F daughter-card, but it's rare and expensive. It would only be for geeking out, as the WF Gui is just as accurate, even with the internal audio input!

NB - from a value perspective, I really do recommend HPR's tapes. They are cheaper than Ebay offerings that are made on cassette decks, but they are made on an A80. I plan to get a second set in case he sells out.
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Old 4th Oct 2022, 7:43 pm   #57
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Default Re: Wow and Flutter Testing

Did a quick first test of the wfgui software application using my Ion Express Tape player.

Still need to work out how to drive it fully, it has 4 operating modes "DIN", "Unweighted", "Wow" and "Flutter" but it seems like once you select an operating mode and Start the application running, it then is impossible to change to a different mode without first shutting down and restarting the application.

There were some high flying peaks but they appeared random, i.e., not at the normal regular 4 -5 seconds period.

David
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Old 4th Oct 2022, 10:55 pm   #58
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Default Re: Wow and Flutter Testing

Made a 3kHz test tape using signal generator signal into my Uher CG 310 Stereo cassette deck.

I wanted to check out the CG 310 because a few weeks back had a mini disaster where I was up in the loft trying to find something and knocked into a pile of reel to reel lids, one of which (Philips) fell out of the loft and landed on the landing floor, I think the lid would have been OK but somehow the CG 310 also went tumbling out of the loft and landed on the Philips lid. The CG 310 visually looked OK but the Philips lid was virtually split into 2 halves.

Went to play the test tape but after a few seconds playing the tape transport totally stopped working, so something else to fix !

David
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Old 5th Oct 2022, 12:37 am   #59
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Default Re: Wow and Flutter Testing

Most of the studies over the years have tended to suggest that over 0.1% W+F RMS is audible. Of course, source material will be a component, i.e. sustained piano notes and the like will make it more audible than minimal Techno.

If you're using a home-made tape, the values will be a lot higher than one that's made to a standard such as the HPR. Regardless, 0.3% RMS is well below what budget decks from the '90s were capable of (for example, a cheap deck like a Denon DRM-710 can get below 0.05% if in good condition).

For me, the fun of restoring a deck isn't getting earth-shattering W+F values, but seeing if you can get it to the OEM's book spec. Sometimes you can get them to exceed OEM spec. I'm not sure what the Uher spec is, but it ought to be fun to see if you can achieve it. You may need to try a handful of belts, and invest in some PDP65 oil and the like. The condition of the rollers will be paramount. Stripping, degreasing and reassembling will need to done carefully.
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Old 5th Oct 2022, 12:37 pm   #60
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Default Re: Wow and Flutter Testing

Have ordered a set of the 6 recommended test tapes, was slightly hesitant because one review on tapeheads had some not so good comments as well as good ones.

David
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