Cassette tape speed adjustment
in [Repair]
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From: Ian Jackson on 9 Dec 2009 12:33 In message <slrnhhvj3n.kj1.aznomad.3(a)ip70-176-155-130.ph.ph.cox.net>, AZ Nomad <aznomad.3(a)PremoveOBthisOX.COM> writes >On Wed, 9 Dec 2009 15:42:00 -0000, N_Cook <diverse(a)tcp.co.uk> 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 > >Has anyone ever heard of a tape stretching enough to be detectable? >I find that very hard to believe. Far more likely that the motor's >speed control is off. > >Do you have another deck you can use? Record 5 minutes on the reference >deck and then compare the time to play the same on the test deck. >I've used a CD recording and then played the CD at the same time as >playing the tape on the test deck. If they fall out of sync then the >test deck is running at a rate different than the reference deck. That's exactly the way I have (occasionally) adjusted the speed of a tape deck. Record a CD track on a known (or hopefully) good deck, and play it back on the suspect deck, while simultaneously re-playing the CD. A bit of skilful nudging of the tape deck 'pause' and 'fast-forward' buttons will be needed to get the audio adequately synchronised. As you tweak the tape speed control, you will may get the two tracks in almost perfect synchronism (producing a pleasant echo effect!). However, this condition will probably hold for maybe only 10 or 20 seconds, after which the tape audio will start to creep either 'early' or 'late', and may even wander between the two. At the end of a typical 3 minute track, the audio may be a a few seconds out, and no matter hard you try, you are never going to do better. But not even the most ardent audiophile with perfect pitch could ever detect that the speed was incorrect. -- Ian
From: Ron on 9 Dec 2009 13:15 Ian Jackson wrote: > In message <slrnhhvj3n.kj1.aznomad.3(a)ip70-176-155-130.ph.ph.cox.net>, AZ > Nomad <aznomad.3(a)PremoveOBthisOX.COM> writes >> On Wed, 9 Dec 2009 15:42:00 -0000, N_Cook <diverse(a)tcp.co.uk> 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 >> >> Has anyone ever heard of a tape stretching enough to be detectable? >> I find that very hard to believe. Far more likely that the motor's >> speed control is off. >> >> Do you have another deck you can use? Record 5 minutes on the reference >> deck and then compare the time to play the same on the test deck. >> I've used a CD recording and then played the CD at the same time as >> playing the tape on the test deck. If they fall out of sync then the >> test deck is running at a rate different than the reference deck. > > That's exactly the way I have (occasionally) adjusted the speed of a > tape deck. > > Record a CD track on a known (or hopefully) good deck, and play it back > on the suspect deck, while simultaneously re-playing the CD. A bit of > skilful nudging of the tape deck 'pause' and 'fast-forward' buttons will > be needed to get the audio adequately synchronised. > > As you tweak the tape speed control, you will may get the two tracks in > almost perfect synchronism (producing a pleasant echo effect!). However, > this condition will probably hold for maybe only 10 or 20 seconds, after > which the tape audio will start to creep either 'early' or 'late', and > may even wander between the two. > > At the end of a typical 3 minute track, the audio may be a a few seconds > out, and no matter hard you try, you are never going to do better. But > not even the most ardent audiophile with perfect pitch could ever detect > that the speed was incorrect. You underestimate audiophiles sir! ;)
From: bg on 9 Dec 2009 14:04 N_Cook wrote in message ... >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$1(a)news.eternal-september.org... > >> >> Set up a sig genny and test him out > > >Much easier to say the test tape is stretched. >Perhaps perfect pitch testing would only work by playing the likes of JSB >Tocatta and Fugue in D major, not pure tones > >How come I cannot google the rpm of an audio cassette capstan? A calibrated >strobe and tipex mark on the capstan periphery should give a definite answer >(assuming the spindle is clean and not worn). >It should be determinable from tape speed of 1 7/8 in per sec and spindle >diameter, that is about 1.9mm, but what should it be to 0.1 percent >accuracy? > > > pi times diameter gives the circumference of the capstan. 1 7/8 ips divided by circumference gives the required revolutions per second. You can measure the RPS of the flywheel, but that does not guarantee that the tape is traveling at 1 and 7/8. The bottom line is that you need a calibration tape and a frequency counter. You can measure the frequency at several spots on the tape to see if the tape pack and such, has any effect on speed. BASF used to make an excellent calibration tape. I do not know if they are still available, and they are not cheap.
From: Arfa Daily on 9 Dec 2009 21:15 "N_Cook" <diverse(a)tcp.co.uk> wrote in message news:hfoghs$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$1(a)news.eternal-september.org... > >> >> Set up a sig genny and test him out > > > Much easier to say the test tape is stretched. > Perhaps perfect pitch testing would only work by playing the likes of JSB > Tocatta and Fugue in D major, not pure tones > > How come I cannot google the rpm of an audio cassette capstan? A > calibrated > strobe and tipex mark on the capstan periphery should give a definite > answer > (assuming the spindle is clean and not worn). > It should be determinable from tape speed of 1 7/8 in per sec and spindle > diameter, that is about 1.9mm, but what should it be to 0.1 percent > accuracy? > > The rotational speed of a cassette capstan is not a fixed given. The diameter of capstans vary from machine to machine, and the correct speed of tape transport is then a function of how fast you drive the capstan round. The reference in my strobe tape, is indeed the mains. I have been using this tape for many many years, and I have //never// had anyone complain that the speed of their machine is off, after I have used it to set one up. Konig must think that the mains is a good enough reference, otherwise, there would be no point in them marketing the tape for the purpose of setting up speed. Exception to this. As Ron said, very occasionally, when an owner has recorded tapes when the machine was running at the 'wrong' speed ... Arfa Arfa
From: N_Cook on 10 Dec 2009 03:33
Arfa Daily <arfa.daily(a)ntlworld.com> wrote in message news:wRYTm.105473$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 -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |