Hello, I am Talking Newspaper volunteer, serving local community of sight and other disability.
Our problem is the transition from Philips 1 hour tape cassette , high speed duplicated and posted out to our listeners, to CD. Possibly thumb drives will follow in due course .
Our problem will remain in our customers who mainly cannot cope with technical change. So, we will have to carry on recording on tape cassette and run digital CD production in parallel.
The high speed tape copier copies at 20X speed. The pogramme output is newspaper extracts read by our volunteers.
If Audacity could produce a high speed analogue SHRIEK signal this could be head to head coupled into our Copiers master cassette slot, or wired into its replay circuitry. In fact, to increase Audacitys 3X speed facility to 20X. This would make our service run much more smoothly and restore valuable family and pub time.
Does anybody out there have experience or advice to offer on this piece of retro but socially valuable technology?
If the consumer had to use a computer to hear the recording on the thumb drive you might as well deliver the audio via podcast.
For consumers who do not have a computer at home perhaps you could send them a loaded mp3 player through the post.
They could return the MP3 player (for reuse) through the post when they have finished with it .
Audacity can play files a number of times faster than “real time”, but the downside is that high speed copying will always lower the sound quality. The faster you copy, the more muffled the sound becomes.
The easiest way to increase the playback speed is to change the track sample rate.
To do this in Audacity 1.3
Click on the name of the track
In the drop down menu select “Set Rate”
Click on “Other”
Type in the desired sample rate.
The amount of speed-up depends on both the original sample rate and the new sample rate. For example, if the track was originally 44100Hz (shown below the track name) and you want it to play twice as fast, then you need to set the new sample rate to double the original (44100 x 2 = 88200). If you want it to play 10 times faster, then you need to set the new sample rate to ten times the original (44100 x 10 = 441000).
In Audacity 1.3.9, the maximum sample rate is 1000000Hz (1MHz), so yes, you can get Audacity to play the sound 20x faster (20 x 44100 = 882000) but the cassette recordings will sound terrible (you would hear little more than a rumble). The maximum speed increase that allows sufficient sound quality for speech would be about 4x, but even that would sound pretty poor.
These are professional high-speed cassette copiers that are designed to run at 20X. They won’t do music, but they’re fine for speech. Back in the dark ages I used Wollensack machines that ran at 16X (would do a C-60 - both sides at once - in 2 minutes). Properly set up (heads aligned, bias set) they made remarkably good copies.
The main drawback is getting the required frequencies out of the computer sound card. Even if you could put up with telephone quality (3000 Hz) you’d need a sound card that could output 60,000 Hz. Doesn’t seem likely.
The upper frequency output on most sound cards is limited to around 20kHz. Copying sounds from the sound card at 4x would give your tapes a frequency response of up to 5kHz when played at normal speed, which should sound OK for speech but rather too dull for music.
(There’s got to be some awesome frequency response from the record heads in tape copiers that can run at 20x - I wouldn’t like to be the one responsible for footing the bill when it’s time to replace them)
Its very heartening to see so many seriously considered responses to my cassette copying dilemma. in fact some guys in our region have been sending out thumb drives... but they dont get them back, presumably pinched by extended family et al… Talk about the Law of Unintended Consequences.
I have come to agree about impossibility of grinding an Audio card at 16 or 20X output speed. I think it is time to look laterally at PWM which is cheap and cheerfully obtainable from ARDUINO micro boards, or maybe some of you senior experts remember Clive Sinclair`s early audio PWM
chip which had huge AF bandwidth as well as interesting MF interference ability.
Another avenue could be using Video rated DAC stage , fed from CCD audio RAM itself clocked out at high speed?
I may have to get out my blowlamp and do some soldering. Incidentally I still use lead based solder and it never did me any harm.
ha ha.
Anyhow, if anyone has the knowledge of such matters please blow some oxygen this way.
Inevitably, passage of time will solve all our problems, but I would like to get to grips with this while there is still a market so to speak.
