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Recycled Hard Drive Based "Synth"
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peritus
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Joined: 28 Feb 2007
Posts: 14

PostPosted: Wed Feb 28, 2007 9:57 am    Post subject: Recycled Hard Drive Based "Synth" Reply with quote

New here.. cool site...

So I've had this idea developing in my head for about a year or more...

Similar devices:

Mellotron
http://en.wikipedia.org/wiki/Mellotron

Chamberlin
http://en.wikipedia.org/wiki/Chamberlin

Optigan
http://en.wikipedia.org/wiki/Optigan

Melloman
http://www.mysterycircuits.com/melloman/melloman.html

Minimoog
http://en.wikipedia.org/wiki/Minimoog

Mostly like the Melloman... EXCEPT..

Instead of really long loops, there would be short waveforms (saw-wave ESPECIALLY) at adjusted pitch..

Each key would be assigned a hard drive that had been reconfigured to read/write in analog INSTEAD OF DIGITAL.. The platter would contain the loop(s) in concentric circles (MUCH LIKE THE OPTIGAN's optical storage)...

All hard drives would run at the same speed?...

Main controls would be

1 octave of keys (to start with)
Speed control (controls the speed of all hard drives, simultaneously)...
Volume

===========

All in all, there are an infinite number of configurations for the idea...

For instance...

A monosynth could be created by using a single hard drive with a single waveform loop calibrated to "middle C"...

When any key is pressed, a controller would then adjust the current speed of the hard drive to match the targeted pitch.. Therefore producing something similar to lovable moog monosynth sound... The trick would be getting the change to be really quick, but not instant (for effect)..


I really lack the tech skill to build it.. But I know it can be done.. Please help my idea and I grow!

Thanks,
Joshua
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peritus
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Joined: 28 Feb 2007
Posts: 14

PostPosted: Wed Feb 28, 2007 11:39 am    Post subject: Reply with quote

Maybe I could put drawbars on it..

http://www.soundonsound.com/sos/nov03/articles/synthsecrets.htm
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peritus
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Joined: 28 Feb 2007
Posts: 14

PostPosted: Wed Feb 28, 2007 12:03 pm    Post subject: Reply with quote


image from:
http://www.almaden.ibm.com/st/magnetism/ms/gmr/
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peritus
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Joined: 28 Feb 2007
Posts: 14

PostPosted: Wed Feb 28, 2007 12:41 pm    Post subject: Reply with quote

Another thought:


Hard drive platter based tape delay.....

Similar to the following... but platter based...
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peritus
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Joined: 28 Feb 2007
Posts: 14

PostPosted: Wed Feb 28, 2007 1:20 pm    Post subject: Reply with quote

Another use...

And since people really dig tape compression...

Output ONLY the delayed (and therefore processed) signal and then place an erase head between the record and playback heads to blank out the "tape"...

This would produce the beloved tape compression that audio engineers adore...

Please keep in mind that devices that SIMULATE tape compression are selling for huge amounts these days...

Example ($1649.00): http://vintageking.com/s.nl/it.A/id.6624/.f?sc=18&category=921&fromsla=T
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peritus
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PostPosted: Thu Mar 01, 2007 12:48 pm    Post subject: Reply with quote

Here's a composite image I made of what the delay might look like...
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peritus
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Joined: 28 Feb 2007
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PostPosted: Thu Mar 01, 2007 1:10 pm    Post subject: Reply with quote

http://www.physics.ucla.edu/demoweb/demomanual/acoustics/effects_of_sound/science_of_sound_tape.html


"7. Delay Distortion

Speech and music with some frequencies delayed in transmission: This demonstration was simulated by using a delay system with multiple recording heads located around a rotating magnetic disc. the sound is split into two bands by high-pass and low-pass electronic filters that have a cross-over frequency of 3000 cps. (The music is a trumpet fanfare by Semmier.) "
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peritus
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Joined: 28 Feb 2007
Posts: 14

PostPosted: Thu Mar 01, 2007 1:14 pm    Post subject: Reply with quote

http://www.cedmagic.com/history/instant-replay-hs-100-deck.html

"Disk recording of broadcast video was first tested in a CBS football broadcast on July 8th, 1965. Because of the extreme storage requirements this was only used for brief bursts to demonstrate slow motion, stop motion, and instant replay. Ampex introduced the commercial HS-100 instant replay deck in 1967. This unit was essentially a hard disk used to record analog video rather than digital computer data. The disc rotated at 1800 RPM and had a 30 second record capacity. Each concentric track stored one frame of video, so freeze frame was achieved by holding the head stationary, and slow motion by moving the head across the surface at less than 30 frames per second."
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peritus
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Joined: 28 Feb 2007
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PostPosted: Thu Mar 01, 2007 1:27 pm    Post subject: Reply with quote

http://www.vidipax.com/museum/msm33.html

"Built by MVR to CBS specifications, the VDR-210CF could continuously record black-and-white video, play back the most recent 20 seconds and freeze the action at any moment. The information was stored on the top surface of a 12" aluminum disc coated with nickel cobalt. In 1967, the VDR-250 added slow-motion playback capability."
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peritus
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Posts: 14

PostPosted: Thu Mar 01, 2007 2:21 pm    Post subject: Reply with quote

http://vintagehofner.mysite.wanadoo-members.co.uk/factfiles/amplifiers/hofamp.html

"Hofner KV-50 Combo Amplifier
A three channel amplifier, fitted with two 12" speakers. Tremolo, reverb, and analogue delay effects are built in.

This model was an early hybrid design with a solid state preamp and a tube power amp ( 2x EL34 providing 50 watts). Two Goodman 12" speakers apparently were fitted. The power amp section was located at the bottom of the cabinet and connected with an octal plug to the preamp section in the upper cabinet. (Just like the old Selmer-Truvoice amps.) The delay unit contained a magnetic disc, similar to the old Baby Binson echo units, and three delay heads."

Edit: Scratch this post. Baby Binson was magnetic drum based.. not disc...
http://www.penumbra.co.nz/allthegear.html#drums
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peritus
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PostPosted: Thu Mar 01, 2007 2:38 pm    Post subject: Reply with quote

http://museum.nist.gov/panels/notched/notched.htm

" The use of magnetic discs for the recording and reproduction of music was well known before 1948 when a representative of the U.S. Army Aberdeen Proving Grounds asked NIST engineers to suggest and develop a magnetic memory device of very large capacity and of very short access time.

The use of magnetic discs was obvious but the problem of large storage was difficult. The discs would have to be separated by appreciable distances so the writing and reading heads could move between them. It was important to mount the discs very close to each other and still have room to reach their surfaces without separating or moving them off their normal bearing supports. This was achieved by cutting a notch in each disc that extended from the periphery to a point about half the radial distance from the center. By using only the area of the disc on each side of the notch, three quarters of the area of each disc could now be accessed with the disc firmly mounted on its bearings and without the disc being separated by any appreciable spacing from discs on both sides. "
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Thu Mar 01, 2007 3:57 pm    Post subject: Reply with quote

Hey Peritus,

Sounds like a very cool project. I have never seen those machines before. In my opinion if you use hard drives to make this you would have to spin them quite slowly. I would use a standard audio read/write head to record and pickup the audio from the hard drive.

Using the mechanism from an existing inexpensive tape deck would be the way to go since you wouldn't have to re-invent the wheel. Actually the motor from a tape deck that usually spins the tape could be rigged to slowly turn the hard drive platter. The outer area of the disk would allow you more room to work and a longer sample.
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peritus
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Joined: 28 Feb 2007
Posts: 14

PostPosted: Fri Mar 02, 2007 7:37 am    Post subject: Reply with quote

Alan wrote:
Hey Peritus,

Sounds like a very cool project. I have never seen those machines before. In my opinion if you use hard drives to make this you would have to spin them quite slowly. I would use a standard audio read/write head to record and pickup the audio from the hard drive.

Using the mechanism from an existing inexpensive tape deck would be the way to go since you wouldn't have to re-invent the wheel. Actually the motor from a tape deck that usually spins the tape could be rigged to slowly turn the hard drive platter. The outer area of the disk would allow you more room to work and a longer sample.


Thanks for the reply....

Yeah, speed is definitely going to be an issue.. My plan is to try to match the standard reel to reel speeds (inches per second):

http://en.wikipedia.org/wiki/Inches_per_second

"30 ips: The highest professional speed.

15 ips: The most common professional and studio speed for reel to reel including multitrack.

71⁄2 ips: The lowest professional speed, used on some single-speed studio recorders including multitrack."

And you're right... The outside edge is where I'm thinking too... Not only would it allow a longer sample and more room, but "linear" dimensions lend itself to using a larger head.. Also, working on the outside of the platter will lower the requirements of the spindle motor... I've yet to get the math down, but I'm sure it doesn't need to spin as fast as normal hard drives....

On the subject of regular cassette tape heads... I'm worried about problems with them...

Concerns with cassette tape heads:

quality... Besides the IPS of a magnetic audio recording, the track width is also a major factor... 1/2" 2 track sounds better than 1/2" 4 track.... Cassette tracks are extremely narrow.... R2R quality > cassette quality..... Therefore, I think it would be great if I could get my hands on a 1/2" 1-track headset (1 for each record, playback, erase)...

contact with medium.... I'm worried that floating any headsets over the platter would fail to record... One of the most important factors in a hard drive is the fact that the aerodynamics of the head to platter contact allow for the head to float just shy of touching the platter.. The main reason being two things, boundary effect and the lightweight of the head....

Overall, I'm hoping to farm some expertise from someone who can lend a technical word or two.... I would like to use the 1/2" mono headset, but I'm not sure if it would be feasible...

Thanks again...
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peritus
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Joined: 28 Feb 2007
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PostPosted: Fri Mar 02, 2007 8:23 am    Post subject: Reply with quote

This document leads me to believe that contact is necessary... Still searching though

http://www.sprague-magnetics.com/library/tapehds.pdf
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Fri Mar 02, 2007 8:33 am    Post subject: Reply with quote

If you want the recording medium to travel 30 ips you will need around 120 rpm giving you only about a 1/2 second sample. Is that a long enough sample?

Before you go too far down this road I would do a quick test to see if the hard disk platter medium will record the fidelity you are looking for. This idea is possible but i am not sure it would a high end solution where track widths etc. would be a concern.
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