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Old 30th Jul 2022, 11:25 am   #21
mitajohn
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Default Re: Wow and Flutter Testing

Googling I found this one:

https://www.discogs.com/release/4322...-Demonstration
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Old 3rd Aug 2022, 10:04 am   #22
DMcMahon
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Default Re: Wow and Flutter Testing

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Originally Posted by wd40addict View Post

Some time ago I wrote an audacity plugin which allows you to visualise the wow and flutter components, see:

https://www.vintage-radio.net/forum/...d.php?t=127882

Note input file must be mono.
Sounds very interesting, I have never used a plugin with Audacity, I will have to have a go at this.

David
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Old 30th Sep 2022, 8:32 pm   #23
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Default Re: Wow and Flutter Testing

Did some Wow & Flutter tests on my Telefunken C2200 Stereo cassette deck using the Philips PM 6307 Wow & Flutter test meter, first time I have used the meter and the first time I have ever done any Wow & Flutter measurements.

The PM 6307 is a nice compact easy to use meter that I purchased from a Forum member quite some time ago, I think I paid £5 for it, it appears to work so was a good buy.

The meter measures and displays 2 values namely, % Drift which is the tape speed error and Wow & Flutter +/- %.

Internally it has a crystal-controlled oscillator at 4.032 MHz which is divided down to produce 2 switchable test frequencies of 3.00KHz or 3.15kHz (DIN 45 507 standard).

The test frequencies can be monitored on rear panel output BNC, they are 1V peak to peak, very clean and stable square waves, spot on the correct frequencies when measured on a frequency counter.

I used an Ampex C20 Studio Audio speed test cassette which has 10 minutes of 3kHz 0dB sinewave on both channels, recorded on a Technics RS-747. Purchased from eBay so not a certified reference tape, but adequate for the purpose of understanding the W & F test process.

I took the test signal from the cassette deck Phono/Radio line output DIN via DIN to Phono cable.

The signal when monitored on a scope was quite noisy/unstable (same on both channels) although listening on headphones sounded OK. Measuring the signal frequency on a frequency counter showed some variation in the frequency and sometimes it measured above 3kHz and sometimes below. The PM 6307 meter concurred with the counter measurements, i.e. when counter showed frequency below 3kHz the PM 6307 indicated a -ve % drift and when counter showed frequency above 3kHz the PM 6307 indicated a +ve % drift.

The average Wow & Flutter reading was around +/- 0.15 to 0.2%, 0.2% being the spec for the cassette deck. However around every 4 - 5 seconds the Wow & Flutter reading would quickly pulse/spike up to around +/- 0.45% and then quickly drop back down (only occurs when test tape playing and signal connected).

This pulsing effect could not really be seen on the scope or heard on headphones, so not sure if a real effect from tape signal or an effect from the PM 6307 electronics.

Need to check some other machines to see how they fare.

David
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Old 30th Sep 2022, 8:50 pm   #24
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Default Re: Wow and Flutter Testing

4-5 seconds could be long enough for a belt or drive error to come round again. Could it be mechanical in some such way? I guess you need to check another machine as you say, in case it's a bizarre quirk of the measurement rather than the source.
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Old 30th Sep 2022, 10:36 pm   #25
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Default Re: Wow and Flutter Testing

If possible mark the tape at the peak intervals (or every 5 seconds- so you have visual markers, a pain I know) with a wax/chinagraph pencil and try to work out where this relates to what happens on the travel in the mechanism inside.
You will have to be quick on the stop/pause and work out how long the internals take to make that journey- and then you could track it down, if indeed that is a problem, firstly, measure compare to another machine or two to be certain of course.
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Old 1st Oct 2022, 12:51 am   #26
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Default Re: Wow and Flutter Testing

Have you tried testing the wow and flutter of another machine? I'm wondering whether this could be an artefact of the tape rather than the machine. As I understand it, commercial test cassettes were actually duplicated on specially modified reel to reel machines rather than on a cassette machine.
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Old 1st Oct 2022, 9:12 am   #27
Ted Kendall
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Default Re: Wow and Flutter Testing

Record and playback wobbles move in and out of phase as the tape is played, and this can cause peaks in the reading.
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Old 1st Oct 2022, 10:42 am   #28
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Default Re: Wow and Flutter Testing

I would echo what James has said. If you can check the tape on another machine, make sure that you're not seeing a foible on the tape. As I wrote on page 1, test cassettes should be made on specially adapted reel machines, with full-track heads.

£5 for that meter is bargain of the year!

edit - Ampex reel tape from the 90s is well known for shedding. The cassette used to make the test tape is likely very old. A shed issue could potentially create serious wow. Another reason to check the tape on another machine. I doubt test tape is the issue here (although, it has to be said, the 0.05 book value for the RS-B747 is high for a reference machine) and the cyclical behaviour is down to the TFK machine, but it's worth getting a 2nd opinion on the reference tape.

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Old 1st Oct 2022, 3:17 pm   #29
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Default Re: Wow and Flutter Testing

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Originally Posted by Uncle Bulgaria View Post
4-5 seconds could be long enough for a belt or drive error to come round again. Could it be mechanical in some such way? I guess you need to check another machine as you say, in case it's a bizarre quirk of the measurement rather than the source.
You could well be right, I was thinking it is more likely to be mechanical related.

Some tests on other decks should help to understand if deck, tape or measuring meter related.

David
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Old 1st Oct 2022, 3:24 pm   #30
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Default Re: Wow and Flutter Testing

Quote:
Originally Posted by knobtwiddler View Post

edit - Ampex reel tape from the 90s is well known for shedding. The cassette used to make the test tape is likely very old. A shed issue could potentially create serious wow. Another reason to check the tape on another machine. I doubt test tape is the issue here (although, it has to be said, the 0.05 book value for the RS-B747 is high for a reference machine) and the cyclical behaviour is down to the TFK machine, but it's worth getting a 2nd opinion on the reference tape.
You do not hear so much about cassette tapes suffering from SSS (Sticky Shed Syndrome) but I am sure some must do.

I am not familiar with the book value reference, where can one find this sort of information ?

David
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Old 1st Oct 2022, 5:34 pm   #31
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Default Re: Wow and Flutter Testing

The "book value" is referring to the wow and flutter spec given in the user manual for the RS-B747. The figure quoted on a cassette deck site is 0.05%.

You could check the wow and flutter of your test tape by playing back on the RS-B747 to check if that shows any large excursions. It might be better to record another test tape on some newer tape and see if the problem has gone away.

Paula
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Old 1st Oct 2022, 7:33 pm   #32
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Default Re: Wow and Flutter Testing

Thank you Paula, book value now all clear.

Yes am planning to do some testing recordings for test tapes to see if same problem.

David
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Old 1st Oct 2022, 8:05 pm   #33
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Default Re: Wow and Flutter Testing

Did W & F test on my Technics RS-BX601 Stereo Cassette Deck (another good Forum purchase), got similar but slightly better results.

The tape signal on the scope was a little more stable (less jitter) and measured around -0.5% drift on the Philips meter. The Wow & Flutter was slightly better at around +/- 0.1 to 0.15% but once again every 4 to 5 seconds the Wow & Flutter pulses up to over double (RS-BX601 W & F book value is +/- 0.2% (DIN), 0.07% (WRMS).

So from 2 different decks showing the pulsing high Wow & Flutter reading probably points to the issue being related to the test cassette (cassette itself or the recording) or the Philips meter. Will test a couple of other cassette decks to be sure and try some home made W & F test cassettes.

David
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Old 1st Oct 2022, 8:45 pm   #34
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Default Re: Wow and Flutter Testing

Quote:
Originally Posted by wd40addict View Post

Some time ago I wrote an audacity plugin which allows you to visualise the wow and flutter components, see:

https://www.vintage-radio.net/forum/...d.php?t=127882

Note input file must be mono.
Following the instructions in the linked Thread I successfully got 'Wow and Flutter Visualiser' to appear under the 'Analyze' menu but cannot see the Wow & Flutter plugin when going to "Plugin Manager" to enable it ?

This is for latest Audacity version 3.2.0

David
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Old 1st Oct 2022, 9:42 pm   #35
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Default Re: Wow and Flutter Testing

After restarting/rebooting laptop for an unconnected issue, the Wow & Flutter plugin is now showing under the Plugin Manager and showing as "enabled".

David
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Old 2nd Oct 2022, 1:28 pm   #36
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Default Re: Wow and Flutter Testing

Next deck (third) up on test (still using the Ampex 3kHz test cassette) is Technics RS-B465, I have not used this for well over 3 years so happy to see it still works well, the damped cassette door is very sluggish to open so another little job to look at some time.

Of the three tested so far it is the slowest at around -1.5% drift, although sounds fine on music cassette playback. I must look at the schematic to see if any speed adjustment.

Of the three the W & F was just about the best at around +/- 0.15% and as before the pulsing W & F every 4 to 5 seconds was present. I tried to measure the periodicity using stop watch on mobile phone, but could not get a consistent reading, I think the time period is actually varying (approximately between 4 and 5 seconds) and finger reaction time on the mobile phone is not helping to get a more accurate reading. There was less frequency jitter seen on the scope.

For a 4th test used my Tandberg Educational Audio Tutor A771 mono portable recorder, this is a nice looking recorder that I got from car boot sale.

Speed wise this was the slowest of the 4 so far tested at -2% drift (frequency on counter as low as 2,930Hz) and maybe surprisingly the best W & F at < 0.15%, the pulsing W & F every 4-5 seconds is still present (as before pulsing up to around twice the average value).

On the scope the signal waveform was the best frequency stability/jitter wise but the worst looking sinewave shape plus maybe the worst amplitude jitter/variation.

Playback of music cassettes on the Tandberg sounds excellent, a really good sound.

David
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Old 2nd Oct 2022, 2:43 pm   #37
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Default Re: Wow and Flutter Testing

Now it's enabled how does the visualiser output look?
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Old 2nd Oct 2022, 6:49 pm   #38
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Default Re: Wow and Flutter Testing

I have yet to run it with a signal input, hopefully soon will.

David
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Old 2nd Oct 2022, 8:41 pm   #39
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Default Re: Wow and Flutter Testing

Not sure if it's been mentioned. Speed stability can change at the beginning and end of tapes partly due to the different take up and back tensions on the tape. Even dual capstan designs may not fully isolate the tape from the influence of tape tensions outside of the closed loop.
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Old 2nd Oct 2022, 11:52 pm   #40
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Default Re: Wow and Flutter Testing

Quote:
Originally Posted by frsimen View Post
The "book value" is referring to the wow and flutter spec given in the user manual for the RS-B747. The figure quoted on a cassette deck site is 0.05%.

Paula
The manual spec for Wow & Flutter for the RS-BX747 (not sure if there actually is an RS-747 or RS-B747) is 0.05% (WRMS) , +/- 0.14% (DIN).

Not really familiar with the WRMS measurement, I have been using the Philips PM6307 meter with the internal filter switched in, which according to the manual is the weighted frequency response according to DIN standard 45 507, I assume this DIN standard is the same as the "DIN" reference quoted in the cassette deck manual specifications.

David
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