Cassette tape speed adjustment
in [Repair]
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From: Ron on 10 Dec 2009 04:21 N_Cook wrote: > Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message > news:wRYTm.105473$iT5.66666(a)newsfe12.ams2... >> "N_Cook" <diverse(a)tcp.co.uk> wrote in message >> news:hfoghs$f07$1(a)news.eternal-september.org... >>> Ron <ron(a)lunevalleyaudio.com> wrote in message >>> news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... >>>> N_Cook wrote: >>>>> Ron <ron(a)lunevalleyaudio.com> wrote in message >>>>> news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... >>>>>> N_Cook wrote: >>>>>>> Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message >>>>>>> news:vbKTm.64350$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? >>> >>> >> The rotational speed of a cassette capstan is not a fixed given. The >> diameter of capstans vary from machine to machine, and the correct speed > of >> tape transport is then a function of how fast you drive the capstan round. >> The reference in my strobe tape, is indeed the mains. I have been using > this >> tape for many many years, and I have file://never// had anyone complain > that the >> speed of their machine is off, after I have used it to set one up. Konig >> must think that the mains is a good enough reference, otherwise, there > would >> be no point in them marketing the tape for the purpose of setting up > speed. >> Exception to this. As Ron said, very occasionally, when an owner has >> recorded tapes when the machine was running at the 'wrong' speed ... >> >> Arfa >> >> Arfa >> >> > > > http://www.dynamicdemand.co.uk/grid.htm > Wokingham, Surrey, UK monitored mains frequency, > is instructive, try it in the middle of a national televised football match > or similar > > > spindle consistency > Not from my random sample of 8 audio cassette capstan spindles, all were > 1.9mm or a bit lower say 1.89, with no cleaning etc, just as found. > If 1.9mm then rotational speed of 478.72 rpm and if the specified diameter > (cannot even find that) is 0.075 inches (bit less than 1.9mm) then speed is > 477.46 rpm for 15/7 ips. > Googling including "478" or "477" throws up nothing, googling on rev/sec not > possible in like manner > But compact cassette was never intended to be a precise method of recording, almost everything about the system is inexact - the recording medium itself is hardly a precision piece of engineering. The whole system was designed for convenience over performance. Admittedly, there are/were some very very good machines available which I`m sure way outstripped the original design specs. Cassette machines intended for 'homestudio' quality recording generally run the tape at a faster speed and have a facility for varying that speed. they still tend to use a crappy brushed dc motor and rubber belt drives though. Ron
From: N_Cook on 11 Dec 2009 03:22 Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message news:wRYTm.105473$iT5.66666(a)newsfe12.ams2... > > "N_Cook" <diverse(a)tcp.co.uk> wrote in message > news:hfoghs$f07$1(a)news.eternal-september.org... > > Ron <ron(a)lunevalleyaudio.com> wrote in message > > news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... > >> N_Cook wrote: > >> > Ron <ron(a)lunevalleyaudio.com> wrote in message > >> > news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... > >> >> N_Cook wrote: > >> >>> Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message > >> >>> news:vbKTm.64350$Dl4.48926(a)newsfe08.ams2... > >> >>>> "N_Cook" <diverse(a)tcp.co.uk> wrote in message > >> >>>> news:hflv4c$p04$1(a)news.eternal-september.org... > > > >> > >> Set up a sig genny and test him out > > > > > > Much easier to say the test tape is stretched. > > Perhaps perfect pitch testing would only work by playing the likes of JSB > > Tocatta and Fugue in D major, not pure tones > > > > How come I cannot google the rpm of an audio cassette capstan? A > > calibrated > > strobe and tipex mark on the capstan periphery should give a definite > > answer > > (assuming the spindle is clean and not worn). > > It should be determinable from tape speed of 1 7/8 in per sec and spindle > > diameter, that is about 1.9mm, but what should it be to 0.1 percent > > accuracy? > > > > > > The rotational speed of a cassette capstan is not a fixed given. The > diameter of capstans vary from machine to machine, and the correct speed of > tape transport is then a function of how fast you drive the capstan round. > The reference in my strobe tape, is indeed the mains. I have been using this > tape for many many years, and I have file://never// had anyone complain that the > speed of their machine is off, after I have used it to set one up. Konig > must think that the mains is a good enough reference, otherwise, there would > be no point in them marketing the tape for the purpose of setting up speed. > Exception to this. As Ron said, very occasionally, when an owner has > recorded tapes when the machine was running at the 'wrong' speed ... > > Arfa > > Arfa > > I've since found 2 capstan spindles of 2.4mm diameterm so no fixed specification for cassette tape dynamics. Another possibility as a test tape - record some constant tone, any f, on a few minutes of tape, pull out a long length and pass a magnet over two parts a measured distance apart. retract, and then time the interval between dips in play mode
From: Ron on 11 Dec 2009 04:20 N_Cook wrote: > Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message > news:wRYTm.105473$iT5.66666(a)newsfe12.ams2... >> "N_Cook" <diverse(a)tcp.co.uk> wrote in message >> news:hfoghs$f07$1(a)news.eternal-september.org... >>> Ron <ron(a)lunevalleyaudio.com> wrote in message >>> news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... >>>> N_Cook wrote: >>>>> Ron <ron(a)lunevalleyaudio.com> wrote in message >>>>> news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... >>>>>> N_Cook wrote: >>>>>>> Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message >>>>>>> news:vbKTm.64350$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? >>> >>> >> The rotational speed of a cassette capstan is not a fixed given. The >> diameter of capstans vary from machine to machine, and the correct speed > of >> tape transport is then a function of how fast you drive the capstan round. >> The reference in my strobe tape, is indeed the mains. I have been using > this >> tape for many many years, and I have file://never// had anyone complain > that the >> speed of their machine is off, after I have used it to set one up. Konig >> must think that the mains is a good enough reference, otherwise, there > would >> be no point in them marketing the tape for the purpose of setting up > speed. >> Exception to this. As Ron said, very occasionally, when an owner has >> recorded tapes when the machine was running at the 'wrong' speed ... >> >> Arfa >> >> Arfa >> >> > > I've since found 2 capstan spindles of 2.4mm diameterm so no fixed > specification for cassette tape dynamics. > > Another possibility as a test tape - record some constant tone, any f, on a > few minutes of tape, pull out a long length and pass a magnet over two parts > a measured distance apart. retract, and then time the interval between dips > in play mode > > Far simpler, find a known good machine - your chum with perfect pitch will help here - record a known frequency on a tape which you know to be good. Play said tape back on customers machine with freq counter hooked up to the headphone socket and adjust for same frequency - sorted. My test tape is 100hz, I spose the higher the frequency, the better accuracy you can get. Don't expect miracles.
From: N_Cook on 11 Dec 2009 04:34 Ron <ron(a)lunevalleyaudio.com> wrote in message news:79mdnU8QxrtKk7_WnZ2dnUVZ8u-dnZ2d(a)bt.com... > N_Cook wrote: > > Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message > > news:wRYTm.105473$iT5.66666(a)newsfe12.ams2... > >> "N_Cook" <diverse(a)tcp.co.uk> wrote in message > >> news:hfoghs$f07$1(a)news.eternal-september.org... > >>> Ron <ron(a)lunevalleyaudio.com> wrote in message > >>> news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... > >>>> N_Cook wrote: > >>>>> Ron <ron(a)lunevalleyaudio.com> wrote in message > >>>>> news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... > >>>>>> N_Cook wrote: > >>>>>>> Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message > >>>>>>> news:vbKTm.64350$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? > >>> > >>> > >> The rotational speed of a cassette capstan is not a fixed given. The > >> diameter of capstans vary from machine to machine, and the correct speed > > of > >> tape transport is then a function of how fast you drive the capstan round. > >> The reference in my strobe tape, is indeed the mains. I have been using > > this > >> tape for many many years, and I have file://never// had anyone complain > > that the > >> speed of their machine is off, after I have used it to set one up. Konig > >> must think that the mains is a good enough reference, otherwise, there > > would > >> be no point in them marketing the tape for the purpose of setting up > > speed. > >> Exception to this. As Ron said, very occasionally, when an owner has > >> recorded tapes when the machine was running at the 'wrong' speed ... > >> > >> Arfa > >> > >> Arfa > >> > >> > > > > I've since found 2 capstan spindles of 2.4mm diameterm so no fixed > > specification for cassette tape dynamics. > > > > Another possibility as a test tape - record some constant tone, any f, on a > > few minutes of tape, pull out a long length and pass a magnet over two parts > > a measured distance apart. retract, and then time the interval between dips > > in play mode > > > > > Far simpler, find a known good machine - your chum with perfect pitch > will help here - record a known frequency on a tape which you know to be > good. Play said tape back on customers machine with freq counter hooked > up to the headphone socket and adjust for same frequency - sorted. > > > My test tape is 100hz, I spose the higher the frequency, the better > accuracy you can get. Don't expect miracles. Things counldn't be easier with a "known good machine " . My 3 test tapes were created on what was supposed to be such a machine in a pro AV studio. One tape got knackered at one point but rest of tape agrees with the second one. The third remains unused while first 2 agree with one another, using any old speed consistent machine for cross-comparison, in relative rather than absolute terms.
From: Ron on 11 Dec 2009 04:36
N_Cook wrote: > Ron <ron(a)lunevalleyaudio.com> wrote in message > news:79mdnU8QxrtKk7_WnZ2dnUVZ8u-dnZ2d(a)bt.com... >> N_Cook wrote: >>> Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message >>> news:wRYTm.105473$iT5.66666(a)newsfe12.ams2... >>>> "N_Cook" <diverse(a)tcp.co.uk> wrote in message >>>> news:hfoghs$f07$1(a)news.eternal-september.org... >>>>> Ron <ron(a)lunevalleyaudio.com> wrote in message >>>>> news:vZCdnX7J1q8uL4LWnZ2dnUVZ7rVi4p2d(a)bt.com... >>>>>> N_Cook wrote: >>>>>>> Ron <ron(a)lunevalleyaudio.com> wrote in message >>>>>>> news:0dednd3AmaG0B4LWnZ2dnUVZ7tqdnZ2d(a)bt.com... >>>>>>>> N_Cook wrote: >>>>>>>>> Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message >>>>>>>>> news:vbKTm.64350$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? >>>>> >>>>> >>>> The rotational speed of a cassette capstan is not a fixed given. The >>>> diameter of capstans vary from machine to machine, and the correct > speed >>> of >>>> tape transport is then a function of how fast you drive the capstan > round. >>>> The reference in my strobe tape, is indeed the mains. I have been using >>> this >>>> tape for many many years, and I have file://never// had anyone complain >>> that the >>>> speed of their machine is off, after I have used it to set one up. > Konig >>>> must think that the mains is a good enough reference, otherwise, there >>> would >>>> be no point in them marketing the tape for the purpose of setting up >>> speed. >>>> Exception to this. As Ron said, very occasionally, when an owner has >>>> recorded tapes when the machine was running at the 'wrong' speed ... >>>> >>>> Arfa >>>> >>>> Arfa >>>> >>>> >>> I've since found 2 capstan spindles of 2.4mm diameterm so no fixed >>> specification for cassette tape dynamics. >>> >>> Another possibility as a test tape - record some constant tone, any f, > on a >>> few minutes of tape, pull out a long length and pass a magnet over two > parts >>> a measured distance apart. retract, and then time the interval between > dips >>> in play mode >>> >>> >> Far simpler, find a known good machine - your chum with perfect pitch >> will help here - record a known frequency on a tape which you know to be >> good. Play said tape back on customers machine with freq counter hooked >> up to the headphone socket and adjust for same frequency - sorted. >> >> >> My test tape is 100hz, I spose the higher the frequency, the better >> accuracy you can get. Don't expect miracles. > > > Things counldn't be easier with a "known good machine " . > My 3 test tapes were created on what was supposed to be such a machine in a > pro AV studio. > One tape got knackered at one point but rest of tape agrees with the second > one. The third remains unused while first 2 agree with one another, using > any old speed consistent machine for cross-comparison, in relative rather > than absolute terms. > > So you are saying that you already have a test cassette? |