Test of the new blog!

Posted: May 25, 2016 in Uncategorized

test may 2016

Spectral Piano, live at SFU!

Posted: January 14, 2013 in Uncategorized

A new venture into social media…I just made myself a facebook event to promote the debut of the Spectral Piano, Tuesday Jan 29 at Simon Fraser University’ downtown campus in the old Woodwards complex. The performance is on the second floor in the “World Arts Center”.

I made the event, and right away things started happening!  Most interesting.  I am totally newb at facebook.

The event is posted at:    http://www.facebook.com/events/157647561049142/

I think that should work, if not it is called “The Three Faces of Midnight”.

Music upload coming soon!

Posted: December 10, 2012 in Uncategorized

So the spectral piano sounds great. I am thrilled!   I have recorded some music, and will post shortly.  Seems I was too busy building and composing to think of the domain name &^%$#^&*

Doug

So I belatedly thought to look at the domain name. spectral piano.com…. and on Sept fourth 2012, someone registered it!  Tragedy!!!!   The person with the domain is taking an old piano apart to look for new ways to play it, with mallets, striking it, and so on, in the style of “prepared piano”. That’s all fine… but now what do I do?  I either need a new name… or something like a .ca domain. I am not sure what to do… any ideas anybody?

disaster… and recovery

Posted: October 28, 2012 in Uncategorized

So,,,, all done! All ready!!!           Small issue…about 10 dead amplifiers 😦

This became a tragic story of friendship and perseverance.  I had no idea how to make the rest of the amps work. Everything looked fine to me!  I consulted Andrew, who designed the PCB’s, and he had no real suggestions, and as he’s comfortably ensconced in his place in London, England.  I  phoned up the professional audio techs I have worked with, and no one was interested in looking at custom stuff. I took it to my friend Shea, who really wanted to help, but he was just overwhelmed with other work, and after a week it became apparent that he just had no time.

So…

It became obvious that I’d have to fix them myself. I confess i was pretty sure that the culprit was sloppy solder joints.  That I figured I could handle, if I was prepared to deal with admitting to myself that I must be blind 😦  

Having gone through the required self-evaluation, I thought I’d resort to the high tech of a huge magnifying glass, and sure enough, once I could actually *see* those tiny little spots I had soldered, it was fairly painless to search through the hundreds of solder joints, locate the bad ones, resolder, reassemble, and …amnd…successs!!!!    well… success if I only powered one amp up at a time…as soon as I had two amps up, the whole system shut down.  Boo.

So, here is the 24 channel amp and power supply, all ready to go!  I sure look happy…little did I know the future….

The Asymmetrical Force!

Posted: October 8, 2012 in Uncategorized

Lovely to have that splendid looking amplifier…but not much use without the power supply. A note about the amplifiers I used here is perhaps in order. Those not interested in Geek may skip this.

The amplifiers will drive electromagnets, which will vibrate the strings.  Piano strings are made of tempered steel, which is attracted by magnetic force, so the magnets should be able to exert a force on the strings in the piano.

Now, an amplifier normally has what is called a positive and a negative swing.  Basically, they output an alternating series of push/pull/push/pull, and so forth. You can feel or see this by looking at a speaker in motion: they push out and suck back in again at a rapid rate in response to the push and pull force they get from the amplifiers. That’s fine to drive a speaker, but driving a string is a bit of a different thing, as the magnetic force of the electromagnet is in fact going to create a pulse of attracting magnetism on both the push and the pull part of the cycle, as the string is attracted to a magnet regardless of polarity (the push/pull, North-South fields emitted from a magnet). So, if you send a signal that is supposed to vibrate 440 times a second, it in fact has 440 pushes, and 440 pulls, both of which will attract the string!  That means the string is vibrated at 880 times per second, which is a doubling of the input signal’s frequency that the same signal would produce in a speaker. Andrew McPherson’s custom amplifier bypasses this issue by “level shifting” the signal so that the entire signal is a “push”, so the input frequency remains as the frequency that the string is agitated with and also outputs.  That means that it’s a reasonable  supposition that the power supply for such a device to have lots of power on the positive “push” side, with less required on the “pull”.
I have to thank Andrew McPherson for the custom amp PCB’s.  It’s possible to bias the strings with permanent magnets, and use conventional amplifiers, or I would think use conventional amplifiers entirely, provided one was prepared to send a signal at one octave below the desired string resonance.  Andrew’s piano is a different beast than my spectral piano, able to drive all the strings of the piano at once, unlike mine, but restricted to generating a single timbre at any given time. Both piano augmentations however share the common need for many amplifiers, ideally well suited to driving the electromagnets required to excite the strings.
Ok…  this is the innards of the power rack. A 240watt fanless 24volt dc supply for the “Push” (the positive “rail” [interesting term]), and a 150watt supply for the “pull”.

The Octopus Arrives

Posted: October 8, 2012 in Uncategorized

So, I managed to assemble the power amps.  The taps worked, and I bolted the parts to an old rack tray I had laying about. I added a little red felt to jazz it up, and a strain relief for the audio input cables.  The cables were and are a tragic story: imagine mail ordering like 25 cheap audio cables, expecting functional and flimsy, but instead getting cables thick enough to tie a boat to the dock with!  Normally, this would be a happy event, but in the case I had a real issue getting the cables all lined up together with strain reliefs build in such a way that the huge cables would not rip the flimsy 1/8th inch audio inputs right off the pcbs.  Once assembled, I was struck by the cephalopodic look of the device.

OK, wiki needs to explain that one…The octopus (play /ˈɒktəpʊs/; plural: octopusesoctopi, or octopodessee below) is a cephalopod mollusc of the orderOctopoda. Octopuses have two eyes and four pairs of arms and, like other cephalopods, they are bilaterally symmetric.

 

Next up was adding the wiring for the 24 outputs, and bolting the dsubs to the chassis.

Here it is!

24 channels and counting

Posted: October 8, 2012 in Uncategorized

After I finished all the soldering, wiring, and so forth on the basic amp pcb’s, it was time to actually build some sort of a complete amplifier out of all the parts. That involved yet another adventure, this one into the land of “Taps and Dies”. This area is all about how to bolt stuff into solid metal, something I needed to do to hook the heat sinks to the amplifiers. Wiki says this:

Taps and dies are cutting tools used to create screw threads, which is called threading. A tap is used to cut the female portion of the mating pair (e.g., a nut). A die is used to cut the male portion of the mating pair (e.g., a screw). The process of cutting threads using a tap is called tapping, whereas the process using a die is called threading. Both tools can be used to clean up a thread, which is called chasing.

Here is one of my heat sinks getting tapped….

I’d have never imagined this…but this is *fun stuff*!  Imagine being able to bolt stuff to solid metal…imagine the things I would have built when I was 13 years old if I only knew this secret!  I could have actually bolted the electric shock machine that I built to electrocute my brother to the inside of the small Mosler safe I was trying to protect, instead of basically just taping it in there, ready and waiting….

OK… what’s really scary is that I still have the safe!  I did remove the electroshock machine, however.

here it is:

So, i finished all 24 of the lovely arms pictured in the previous post. They were designed of course to attach to the suspension arm, which is placed inside the piano. I shot a few photos to illustrate the basic idea. Basically, the long suspension arm drops into a piano, and the arms for the electromagnets hang off of it.  The bar raises and lowers with the adjustments seen on the end closest to the camera; similar lifts appear on both ends of the arm. The arm can expand and contract in overall length, ideally continuously, but in the version I have to unscrew a section, then screw it together differently to match a given piano host.

The arms are held on the metal plates via magnetism: not the magnetism used to move the strings, but magnetism from little permanent magnets that are on the bottom side of the arms.  These magnets are attracted to  the metal plate which runs across the top of the suspension bar.  The goal for this was for me to easily be able to move the positions of the arms.  I orignally  considered screwing the arms down, but that would not allow easy adjustments. The next idea was to use velcro!  The issue with the velcro was two fold: first it was not strong enough, and second it was thick enough that the bars wiggled and rocked on top of it. The magnets I settled on are Neo-dynium type rare earth types, rated at ND-35 (not a top strength rating but locally available). It works great.