Cassette tape speed adjustment
in [Repair]
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From: Bob Larter on 12 Dec 2009 00:18 On 10/12/2009 2:42 AM, N_Cook wrote: > Ron<ron(a)lunevalleyaudio.com> wrote in message > news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... >> N_Cook wrote: >>> Ron<ron(a)lunevalleyaudio.com> wrote in message >>> news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... >>>> N_Cook wrote: >>>>> Arfa Daily<arfa.daily(a)ntlworld.com> wrote in message >>>>> news:vbKTm.64350$Dl4.48926(a)newsfe08.ams2... >>>>>> "N_Cook"<diverse(a)tcp.co.uk> wrote in message >>>>>> news:hflv4c$p04$1(a)news.eternal-september.org... > >> >> Set up a sig genny and test him out > > > Much easier to say the test tape is stretched. > Perhaps perfect pitch testing would only work by playing the likes of JSB > Tocatta and Fugue in D major, not pure tones > > How come I cannot google the rpm of an audio cassette capstan? A calibrated > strobe and tipex mark on the capstan periphery should give a definite answer > (assuming the spindle is clean and not worn). > It should be determinable from tape speed of 1 7/8 in per sec and spindle > diameter, that is about 1.9mm, but what should it be to 0.1 percent > accuracy? You should be able to get a very accurate reading of the diameter of the capstan with one of those cheap digital verniers. -- W . | ,. w , "Some people are alive only because \|/ \|/ it is illegal to kill them." Perna condita delenda est ---^----^---------------------------------------------------------------
From: Bob Larter on 12 Dec 2009 00:27 On 12/12/2009 3:31 AM, bz wrote: > "N_Cook"<diverse(a)tcp.co.uk> wrote in > news:hft7vv$nsr$1(a)news.eternal-september.org: > >> 3 of them made on the same batch of tape and on the same machine but >> more than 15 years ago. As they are all stored in the same environment >> they could theoretically all have chemically degraded/stretched to the >> same degree. I'm trying to find some process that gives an independent >> verification that does not require a know good machine. >> eg quartz controlled (so low tens ppm) f-meter coupled strobe fed to >> rotating capstan if diameter/s of the spindles are manufactured to >> specific dimensions of precisely known tolerances. Perhaps 1.9 +/- 0.002 >> mm and 2.4 +/- 0.002mm say, no such data found googling. I can only >> measure to +/-0.02 mm and no slip gauges for absolute calibration. >> +/-2 in 200 or so, is not accurate enough >> > > Suggestion: > > Google for > guitar tuning meter > > There are meters available for ~20 bux and even some 'on line' meters. > > Record a known good 'string note' frequency and use it for your standard. > Should get you close enough for any audiophile's ears <nods> 440Hz is the usual reference tone. -- W . | ,. w , "Some people are alive only because \|/ \|/ it is illegal to kill them." Perna condita delenda est ---^----^---------------------------------------------------------------
From: N_Cook on 12 Dec 2009 04:01 Bob Larter <bobbylarter(a)gmail.com> wrote in message news:hfv8rv$i4r$1(a)blackhelicopter.databasix.com... > On 10/12/2009 2:42 AM, N_Cook wrote: > > Ron<ron(a)lunevalleyaudio.com> wrote in message > > news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... > >> N_Cook wrote: > >>> Ron<ron(a)lunevalleyaudio.com> wrote in message > >>> news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... > >>>> N_Cook wrote: > >>>>> Arfa Daily<arfa.daily(a)ntlworld.com> wrote in message > >>>>> news:vbKTm.64350$Dl4.48926(a)newsfe08.ams2... > >>>>>> "N_Cook"<diverse(a)tcp.co.uk> wrote in message > >>>>>> news:hflv4c$p04$1(a)news.eternal-september.org... > > > >> > >> Set up a sig genny and test him out > > > > > > Much easier to say the test tape is stretched. > > Perhaps perfect pitch testing would only work by playing the likes of JSB > > Tocatta and Fugue in D major, not pure tones > > > > How come I cannot google the rpm of an audio cassette capstan? A calibrated > > strobe and tipex mark on the capstan periphery should give a definite answer > > (assuming the spindle is clean and not worn). > > It should be determinable from tape speed of 1 7/8 in per sec and spindle > > diameter, that is about 1.9mm, but what should it be to 0.1 percent > > accuracy? > > You should be able to get a very accurate reading of the diameter of the > capstan with one of those cheap digital verniers. > > -- > W > . | ,. w , "Some people are alive only because > \|/ \|/ it is illegal to kill them." Perna condita delenda est > ---^----^--------------------------------------------------------------- The mechanical structure of a digital is the same as a vernier or DTI one . With the same susceptibility for the plate-form arms to deflect from unrelieved manufacturing stresses , let alone abuse. Compared to micrometers which have a more rigid , less internally stressed, rod like basic structure. Just because you can read to greater accuracy does not necessarily mean better measurement in absolute terms
From: Bob Larter on 15 Dec 2009 00:01
On 12/12/2009 8:01 PM, N_Cook wrote: > Bob Larter<bobbylarter(a)gmail.com> wrote in message > news:hfv8rv$i4r$1(a)blackhelicopter.databasix.com... >> On 10/12/2009 2:42 AM, N_Cook wrote: >>> Ron<ron(a)lunevalleyaudio.com> wrote in message >>> news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... >>>> N_Cook wrote: >>>>> Ron<ron(a)lunevalleyaudio.com> wrote in message >>>>> news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... >>>>>> N_Cook wrote: >>>>>>> Arfa Daily<arfa.daily(a)ntlworld.com> wrote in message >>>>>>> news:vbKTm.64350$Dl4.48926(a)newsfe08.ams2... >>>>>>>> "N_Cook"<diverse(a)tcp.co.uk> wrote in message >>>>>>>> news:hflv4c$p04$1(a)news.eternal-september.org... >>> >>>> >>>> Set up a sig genny and test him out >>> >>> >>> Much easier to say the test tape is stretched. >>> Perhaps perfect pitch testing would only work by playing the likes of > JSB >>> Tocatta and Fugue in D major, not pure tones >>> >>> How come I cannot google the rpm of an audio cassette capstan? A > calibrated >>> strobe and tipex mark on the capstan periphery should give a definite > answer >>> (assuming the spindle is clean and not worn). >>> It should be determinable from tape speed of 1 7/8 in per sec and > spindle >>> diameter, that is about 1.9mm, but what should it be to 0.1 percent >>> accuracy? >> >> You should be able to get a very accurate reading of the diameter of the >> capstan with one of those cheap digital verniers. > > The mechanical structure of a digital is the same as a vernier or DTI one . > With the same susceptibility for the plate-form arms to deflect from > unrelieved manufacturing stresses , let alone abuse. Compared to micrometers > which have a more rigid , less internally stressed, rod like basic > structure. Just because you can read to greater accuracy does not > necessarily mean better measurement in absolute terms Sure, but you can zero out a digital vernier each time you use it, which helps. And for your purpose one should be plenty accurate enough. -- W . | ,. w , "Some people are alive only because \|/ \|/ it is illegal to kill them." Perna condita delenda est ---^----^--------------------------------------------------------------- |