Circuitbenders Forum
Circuitbenders Forum => Circuitbending discussion => DIY Synths => Topic started by: untune on November 23, 2010, 08:50:37 PM
-
No doubt everyone is familiar with the Melloman
http://www.mysterycircuits.com/melloman/melloman.html (http://www.mysterycircuits.com/melloman/melloman.html)
I also found this little beast
http://blog.makezine.com/archive/2007/09/make_a_mellotron_out_of_w.html (http://blog.makezine.com/archive/2007/09/make_a_mellotron_out_of_w.html)
I'm a big fan of tape and I think it's make a great lo-fi sampler... now it's gotten me thinking. Would there be a way to take a cheap walkman and have JUST ONE with whatever you wanted on the tape, which could then be fed via some kind of simple analogue keyboard (resistors/trimmers for each note?) to create a monophonic lo-fi keyboard/sampler?
In my head I see a constantly playing/looping walkman, the output of the circuit is fed into a keyboard where each key acts as a switch, bridging the circuit as it went. Anybody got any idea how it might work? I've got a keyboard which would be pretty much perfect for the job, now the fun part is working out the feasibility of such a task :P
-
You could have a loop with a single sustained note, and use the keyboard and resistors to drive the motor speed controller. I don't think it would stay in tune very well, and you'd have a fairly long portamento as the motor sped up and down.
I've got no idea how you could do percussive sounds; maybe use a stop foil and sensor so that when you triggered it, it would play the entire "sample". If you were really ingenious you could make a similar kind of wire spring arrangement to a real Mellotron and use a solenoid to drive the pinch roller against the tape, after picking the right motor speed.
It's all getting a bit complicated...
-
Wow. It's a cool idea... I see potential there. Not really sure how you'd make anything useful with just one walkman unless you could adjust the playback speed but 36 walkmen all loaded with different string samples could be interesting. Certainly cheaper than buying a mellotron.
-
Haha yeah, the idea is to shoot for simplicity. One walkman, with one tape (lets say a loop of approximately six seconds, I forget what the actual length of a tape loops is) outputting it's audio via the headphone out (could be modded for a better output I'm sure) and modded to loop constantly when the power to the circuit is on.
The tape would be a recording of a single sustained note. The controls on some walkmans (volume, bass/treble boost) could even be utilised here. The audio output would then have to be regulated (ie pitched to the correct note, let's say the middle C, assuming whatever is on the tape is always recorded at the correct pitch) via an analogue keyboard/switch setup. Polyphony would need multiple tape players (well 13, enough to accomodate 25 seperate notes) but I'm not really fussed about that. This can be the lo-fi mono synth version :P
The keyboard I'm thinking of is a 2 octave, I was inspired when I saw what this guy had done with the shell of his Memoplay:
http://haamu.com/soundlab.html (http://haamu.com/soundlab.html)
which is the shell I now have since the board is corroded. I might yet be able to fix it but I like the idea of building something in the case as it's in great condition. Make no mistake, I'd love to have a Soundlab to put in there but the cost/complexity of that project makes it a bit out of my league :P
His 6th and 7th photos down are of the original memoplay analogue keyboard. Wires that are pushed into contact with bars. Then from that he has made his own PCB to do the same. I assume that his uses a gate/trigger/CV on the synth. This would simply need a way to adjust the pitch of the sound output based on the key that is pressed. Failing that, it would have to be 13 microcassette dictaphones and a lot of effort :P
Anybody got any ideas? :)
-
Been thinking this over... I was thinking about this all wrong. Just having different resistors for each key would do nothing... I forgot it needs to adjust the pitch of an audio signal, not an oscillator :S
Anyways... the tape motor idea. It's technically do-able - it has been done using MIDI (with very poor range) and theres also a thing called Motorkeys (google it) whereby a guy has built a simple 1 octave keyboard that controls a motor using a very complex programmed circuit.
The other idea I had would be to use some kind of pitch shifting circuit. I've looked into using a voice changer (if there was a pitch resistor, I guess that could be connected to the keyboard) but it would mean using a digital IC, and that would no doubt introduce some pretty nasty artifacts (low sample/bit rate and cheap ADC/DAC). Very lo fi though, so perhaps not all bad.
The rest of my ideas are fairly mental, to be honest. Seperate tape heads linked to individual keys, micro loops of tape glued around supply/takeup reels from inside cassettes arranged on a big motor-drive rotating bar. It gets crazier :P The original idea was to make it easy to have lo-fi samples stored on seperate tapes. Rather than having to change 13 tapes, just change one :P
Is there any simple/efficient way to pitch shift in the analogue domain?
-
Have you seen the Chamberlain, the forerunner to the mellotron?
It had about 60 very long tape loops with a head for every key. Theres a section about it in the Mellodrama documentory but there also used to be some video here http://www.sonicstate.com/articles/article.cfm?id=101# (http://www.sonicstate.com/articles/article.cfm?id=101#) but i can't get it to work.
-
I think over the last few nights I've read about every single possible tape-based sampler, manufactured or DIY, ever made haha.
The Chamberlain looks ace, though I think I read there was some serious shock hazard on the inside? :D
Shame I can't seem to get that video to work either, but it certainly does look interesting! It's a shame there's seemingly no way to compress this down to something portable, that uses a single tape... cheers for that link thoguh :)
I've been pondering the idea of motor control some more. With some kind of direct drive walkman (well a DD walkman?) would it be possible to do 2 whole octaves? An octave down is 1/2 and an octave up is 2x, if I'm not mistaken. So technically having a constant C3 recorded on tape, being able to play the motor 2x the speed or 1/2 the speed would be sufficient?
How about hacking a walkman to be driven directly by a motor? Any idea if any of these are feasible?
-
sounds like a major headache for probably little end result, though i do appreciate your creative enthusiasm! ;D
-
hats off to anyone who takes on this ambitious project. i am totally impressed! too many moving parts for me. i would, however assume that this "mellotron" would work best with auto-reverse walkmans...
-
sounds like a major headache for probably little end result, though i do appreciate your creative enthusiasm! ;D
I think that sentence sums up pretty much everything I've ever done :P
In truth I've just dropped nearly 20 quid on a broken early 80s analogue keyboard and don't want to see such a cool and retro looking case going to waste! :P I'm gonna get a refund though, just let them keep a bit for me keeping the keyboard.
My problem is that I can picture how ace it would look with a cassette tape revolving through a window in the top of it, and how cool the warbled old analogue sounds would be... it's just getting from A to B where the trouble starts :P
I've just managed to land a pair of identical micro reel to reel recorders for a tenner. So a full on analogue tape delay will be in the works shortly :P
-
How hard would it be to "remake" an Optigan?
You'd need to work out a way of rotating an acetate disc at a fixed speed, and then work out a way to draw circular "film soundtrack" strips. Print them off onto laser printer OHP acetate, then arrange an LED behind each track. Would you need a photocell for each track? I just don't know...
-
hack a discman and burn a cd of samples? is that possible?
it seems like i read something, when cd players first came out, someone covered a cd with some kind of mack, and poked holes in it...play the cd and you hear weird randomness!
-
@Gordon
I don't think remaking one would be incredibly difficult, however - the process of making some kiind of acetate disk might be. I'm going to do some more research into the Optigan over the weekend. A quick look on the site though reveals a service schematic for the optigan... that might even be handy for designing a keyboard aswell :P
http://www.optigan.com/content/tech/service-faq/ (http://www.optigan.com/content/tech/service-faq/)
-
That's interesting, I hadn't read the service manual.
For the disc, I was thinking of some unholy mishmash of gnuplot and sox ;-)
-
Gordon, if you're still reading this... I gather you've got some Arduino experience from doing some searching on the forum. I've only come across it recently. How difficult would it be to use an Arduino to either:
1) take the input from a keyboard and use it to change the speed of a motor, effectively pitching the sound up/down
2) run constant analogue audio output into it and somehow use keyboard-triggered DSP to pitch shift it in real time?
-
@Gordon
I don't think remaking one would be incredibly difficult, however - the process of making some kiind of acetate disk might be.
Mmm no.. Pull out yor scissors ! Here you go, acetate for the masses.
(http://www.frontierpc.com/ProductImages/Large/10007424.jpg)
or
(http://t1.gstatic.com/images?q=tbn:vlKp9mKvI-dX7M:http://www.textually.org/ringtonia/archives/images/set3/CD-Blank.gif&t=1)
Maybe some karma huh ? ;D
-
You could use an arduino to control the motor speed. I don't think it's got enough grunt to do the DSP part successfully, and it doesn't have enough RAM. By the time you go down that route, you may as well build a microcontroller-based sampler ;-)
Using a variable resistor to control the speed won't be terribly effective - low starting torque will be your enemy, and it will probably wow a bit as the load changes when the splice goes through the rollers. What you need is a PWM controller, which will apply the full voltage to the motor, but only in short bursts. The inertia of the motor and flywheel will keep the speed constant but give you that portamento, so there's a tradeoff. Ideally what you need is to have some sort of speed sensor, maybe by drilling some equally-spaced holes in the capstan flywheel rim where it won't affect the belt, and using a light or Hall-effect sensor to pick up the speed of rotation.
You used to get old computer tape decks that had three motors, one for the capstan and one for each reel drive. I was never successful at getting it to run slow enough to play back "ordinary" tapes, but iyou could record a nice long loop at high speed and haul the tape through faster.
If you want to go down the multi-track route, try contacting recording studios and pro audio repair places to see if you can scrounge an old 16- or 24-track head stack ;-)
-
Ahhhh thats a shame, I only just found the Arduino and it looked pretty exciting with all the possibilities! I think that would be the best way of implememnting keyboard control too, though all the tutorials I read were based on inplementing a keyboard matrix for a keypad or QWERTY keyboard rather than anything musical.
I had an idea of meeting halfway with the optigan and the mellotron, and instead of using cassette, use the tape, but wrapped round the circumference of a disc, say 3 inches in diameter. Drive this directly with a motor, no gears, wheels, belts etc. The tape head could be mounted next to the disc and then the speed of the 'tape disc' is adjusted with PWM. I've been pondering the possibility of (somehow) getting my hands on an old DD walkman which used disc drive as opposed to belts.
A few people have had success controlling motors with Arduino and PWM, as per Youtube, but my only concern is whether that will stretch over 2 octaves. The whole transport needs to do nothing but play back, therefore the pause, stop, RW/FF functions are all irrelevant, so I reckon the system could be simplified. I've even thought about using one tape per octave, but that would complicate things where I'm striving to simplify :P
I do actually have a dead Tascam 4 track that needs repairing. I'm not sure exactly what went wrong with that, I think the motor is dead so I can't test if the head is functioning. With a 4 track head, using a single cassette, you could then (somehow - this is where I get lost) configure the 2 octave keyboard to have a track per 6 semitones. Each track of the cassette could be a long sustained note at every half an octave. So it'd have to be something like Trk1=C2, Trk2=F#2, Trk3=C3, Trk4=F#3. Then the motor needs only know how to swap between 7 speeds (to cater for that elusive 25th key, which would be C4 in this case.)
I know that the actual melloman idea works great using 13 walkmans, but everytime I come back to that idea I think 'OK, where does one purchase 13 identical, high quality walkmans for next to nothing?'. If I answer that question, I might have a starting point :P
-
can you imagine some machine with 13 walkmans attached to it! surely there must be an easier way to make music :o
-
electoyd, i think that is the same thing they said about the mellotron! lol
-
I just think it would look/sound cool to have a really unusual keyboard with its own character and an analogue sound source
-
Well go for it Untune, dont let my negative waves put you off. Have you seen the machine built by nervous squirrel, Its like 8 furby encased (and bent) in a big box, he turns a big handle on the side which activates the furbys in turn almost like a manual sequencer, flipping through the crazed furby sounds. Cool bit of work called the furby gurdy or something like that, but its always good to hear about someone thinking outside the box, even if the results could probably be achieved easier using other means.
-
Well go for it Untune, dont let my negative waves put you off. Have you seen the machine built by nervous squirrel, Its like 8 furby encased (and bent) in a big box, he turns a big handle on the side which activates the furbys in turn almost like a manual sequencer, flipping through the crazed furby sounds. Cool bit of work called the furby gurdy or something like that, but its always good to hear about someone thinking outside the box, even if the results could probably be achieved easier using other means.
I've not seen that actually but it does sound cool! I'll have a look for it :D
Yeah, I understand what you mean. It does seem to be a bit of a long way round, but the 'easiest means' aren't always the most enjoyable :D
My mini reel to reel recorders arrived today anyways, so I reckon a little bit of restoration and the contruction of a tape delay should suffice til I've had time to think this one over :P
-
I have an old copicat reel to reel delay box that i got given there is something quite cool about the old tape echo boxes, good luck with your project dude!
-
I'm not sure this is relevant in any respect but a couple of years ago i got hold of a thing called a Recordon which is some kind of very early dictaphone made in the 1940's. It uses a circular magnetic disk and a read/write head on an arm which is mounted in a spiral groove so it moves towards the centre of the disk as the platter rotates. Imagine a writable vinyl deck, only nothing like what you're thinking of ;)
Unfortunately its full of valves and the guy i bought it from obviously had something against packaging as he just stuck it in a box that was way to big and posted it. After rattling around through the post for a few days it wasn't really working 100% afterwards and i don't have replacement valves.
(http://home.kpn.nl/kalma99/Recordon/R_Pics/voice1.jpg)
Theres a bit more information here http://home.kpn.nl/kalma99/Recordon/Recordon.htm (http://home.kpn.nl/kalma99/Recordon/Recordon.htm)
-
Create a topic, and post a pic of the insides and a list of valves. I'll see what I've got, although 1940s valves may be hard to track down.
(Edit)
This may be somewhat related:
http://ftldesign.com/Timex/index.htm (http://ftldesign.com/Timex/index.htm)
The square boxes are "Triode Couplates":
http://glowbugs.net/CentralabPEC.pdf (http://glowbugs.net/CentralabPEC.pdf)
(Further edit)
From http://www.vintage-radio.net/forum/showthread.php?t=47365 (http://www.vintage-radio.net/forum/showthread.php?t=47365) ->
"""The scrolled plate ensured compatability with other Timex, and I suppose Mail-a Voice/Recordon, machines.
I understand that the "plane" spiral groove could be made "wavy" for security and when used in matched pairs the message could only be read by a machine with the corresponding scrolled plate. Many different pairs could be made by varying the position of the locating peg on the same scroll. John. """
So, by using a different wobbly spiral you could disrupt the recording, presumably playing back garbled fragments out-of-sequence if you used the wrong wobble. Can anyone else see the possibility of this sounding rather dope when applied to drum loops?
-
great name for a band WALKMAN MELLOTRON yeah 8) ;D
-
That's a very cool piece of gear :D
I think the best way to think about this thread now is 'how can I play back a magnetic recording with a keyboard?' :D
-
Can anyone else see the possibility of this sounding rather dope when applied to drum loops?
Instant break core FTW !
circuitbenders what do you want for your Recordon ? :D
-
I'll start another thread on the recordon when i've had a chance to look inside, otherwise this is going to go wildly off topic.
Cheers for the links Gordon, and the valve related stuff you sent me via PM Untune
-
I decided to email Mike Walters last night to see if he had any ideas on how to do something similar. He said funnily enough last night he was talking with friends about making a microcassette version of the melloman :)
He said he seems to remember something controlling a motor called a Monotron (not the Korg one!) about a decade back that he's not really heard of since! Using the same principle as discussed - a motor controlled cassette playback keyboard. It's sounding like that's the most viable option.
So far I like the idea of using a 4-track tape head to group 4 half-octaves, meaning that the motor has a much smaller range of speeds to cover. The keyboard matrix is the part that has me stumped.
-
Another quick question, as it's something I can't find an answer to and someone with more electronics knowledge might know.
I know how a keyboard matrix works (at least roughly, I do) with the groupings of 5 or 6 keys to minimize scans... but in the case of a monophonic one, I don't understand how it knows to stop the last note you played when you press a new key?
-
Still thinking about this idea....
I've bought a few microcassette recorders lately and have been pondering how I could do it with those instead. I'm thinking 5 microcassettes, each one handles 5 keys.
Each has a base note and 2 notes on either side, which would be very subtle changes in motor speed (about 5% per note.) That way 5x5 = 25 keys/2 octaves. An Arduino could be set up for a 5x5 scanning matrix and coded so that it uses a PWM to control the motors. Could be done with walkman style cassette players too I reckon. I need an arduino to play with methinks!
Would have to be mono as a stereo microcassette would be nigh on impossible to find alone, let alone a bunch of them.
Plus if the quality is a bit poor it'll just add a bit of charm... could ewven experiment with wiring up a microcassette head to some better circuitry! Ideas ideas...
-
Arduino eh? Y'know, I wonder how well an Arduino would do polyphonic wavetable playback...
If you replace the sine table in the Arduino synth code I posted with a single-cycle sample of a bowed string, you'd maybe get a good effect.
-
Arduino eh? Y'know, I wonder how well an Arduino would do polyphonic wavetable playback...
If you replace the sine table in the Arduino synth code I posted with a single-cycle sample of a bowed string, you'd maybe get a good effect.
So it'd technically be a lo-fi digital sampler in that case?
Sounds very intriguing :P I've been working on uni stuff solid for the last 3 weeks and I've got a bit of a break at the minute so I've been looking back over all these old ideas.
You know the Arduino well Gordon - is it possible to drive 5 simple cassette player motors from a single Arduino Uno? I've been looking at the motor shields but they only support 4 motors, but I'm curious whether they're not suited to something more complicated than what I'm thinking of.
-
I guess you could. There are six PWM channels, and you could easily roll your own motor controller board. Since all you're doing is switching a motor that runs in one direction then just using a MOSFET as a switch to pulse the motor supply would work. I *think* you'd need a higher supply voltage than normal for the motor, because you want it to go faster and my gut feeling is that you probably want it to be running at about 50% PWM at "normal" speed so you've got a lot of headroom. This will let you speed it up quickly - bang the throttle open until it gets up to speed.
Oh, that's the other thing - you could be excessively clever and detect the motor speed by various means (photosensor and a timing mark on the shaft maybe) so that it's a closed-loop system. That way you can control the motor speed precisely regardless of the load the tape presents.
-
Yeah, using PWM at 50% gives it plenty of scope - I worked out the notes are roughly 5% apart but not exactly - sometimes it's 6%, it all varies depending on the note frequency you need to get. But it only needs to go about 12% faster or slower at maximum, so that shouldn't pose a problem.
I'm thinking it might be best to do this with MIDI input to the Arduino - can be controlled by any 2 octave keyboard then, or even a sequencer.
I'm not quite sure where I'd start with a motor controller, I was hoping to use something pre-built to save making things more complex :P
Same for detecting motor speed - might be a bit beyond my scope of ability (well perhaps the whole thing is really but it's a learning project :P)
-
I thought my prayers had been answered before when I found this
http://www.solarbotics.com/products/mcm/ (http://www.solarbotics.com/products/mcm/)
and this
http://www.solarbotics.com/products/mcm2/ (http://www.solarbotics.com/products/mcm2/)
which would allow a real polyphonic Mellotron to be constructed much like the Melloman - except for a few problems. First being that 25 would be required and also that it would require an amplifier circuit (could you have just one with all those heads attached to it, or would it need one per cassette?)
Either way, even with a bulk discount, 25 of them plus international shipping from Canada works out VEEERY expensive and renders it a pointless exercise. Looking at over £100!
Still, it would be easier to construct since the Melloman proves it can be done. Plus if you could source a load of those 1 minute endless loop answering machine tapes...