The Theremin Temple

Hi Chris,

At this moment I cannot give you info for any off-the-shelf product.. This does not mean that one doesnt exist - it just means that I cannot reccomend anything in particular.. But I will browse and see what I can find.

My main audio interface is a Hercules 16/12fw which is a multi-channel 96kHz firewire unit - it is excellent - but I use this mostly in my "studio" section connected to my big dual Xeon PC.

Lab conditions tend to be a lot harsher - all sorts of HF signal sources, particularly if one has breadboards and wires radiating HF all over the place.. the typical conditions that occur in my tiny lab even when I am trying to be tidy..

When I worked in my lab, I had a box as described in my last - it has RCA sockets for connection of audio inputs and outputs which go to HF filters before going to leads with plugs, and a USB lead going through a filter.. I simply drop my USB sound module (the box accepts my Roland UA-100 or any of my other small / cheap USB units) into the box, plug in the connectors, close the box up, and am ready to use it in the "battlefield" LOL ;-)..

This arrangement is useful as it allows me to select the best "module" for any particular requirement.. For example, if there is a danger of any destructive signals I can insert either my cheapest or my most robust module..... I dont only work with audio..... So I can also drop one of my USB 'scope modules into this box..... I did a lot of research on so-called "free energy" devices for example, and these sometimes produced huge transients - electrostatic discharge 'sparks' sometimes jumping to the closest ground... Having my sensitive monitoring electronics in a grounded steel box with discharge tubes and filters on the inputs was essential - Alas, I only realized the hazards after I blew up a £250 Pico 'scope.. But it was ok - I was being paid a lot of money at the time for the research I was doing.

IMO, most PC kit one can buy is not really designed for a theremin lab environment - it will be specified for operation with other 'compliant' equipment - an open breadboard with oscillators running above 250kHz could well be radiating more than 'complient' equipment is supposed to.. and from my expierience, the time spent constructing a simple enclosure with filters has huge payoff. Just think of the hours you have spent chasing ghosts, the number of times you have been dissapointed because people hear things in your samples which you dont.. What if these things they hear are ALL the result of the environment and equipment you are using to record these sounds? ... You may be wasting tons of effort chasing ghosts which dont exist. A couple of hours with a drill and soldering iron could save you months.

Fred.

This is a typical low cost good quality USB interface http://www.behringer.com/EN/Products/UCA202.aspx

about £24 in the UK

or FCA202 http://www.behringer.com/EN/Products/FCA202.aspx which requires firewire, and is 96kHz sampling at 24 bit resolution for about £60 in the UK

Drop this into a box with filters as I described, and I think your problems will dissapear..

But who knows - you may even find you dont need the box..

I don't own one, but I second Fred's UCA202 suggestion(?).  The UCA222 is I believe identical, but comes with a different software bundle.  I have an ECHO MIA sound card in my PC that is quite nice, but which might not make it past the next OS upgrade (grrr).  Not sure what I'll turn to when that happens.  Why, oh why can they land a man on the moon, but mountains perfectly decent hardware gathers dust and moulders for lack of some kind of universal driver?

Aliasing is most apparent to me when a highish fundamental frequency is sweeping - it's highest overtones will go in the opposite direction.  Many (most?) sound cards will act up, even when playing back, in this scenario.  Aliasing is non-linear, and therefore impossible to remove once introduced.  The non-harmonic harmonic intervals can add harshness to the tone.  Visually, Moire patterns (men's thin striped suits and ties strobing on TV, poorly scanned images in books that show false patterns) are two dimensional aliasing.

You might also want to experiment with less aggressive MP3 compression.

"Why, oh why can they land a man on the moon, but mountains perfectly decent hardware gathers dust and moulders for lack of some kind of universal driver?" - Dewster.

Quite a simple answer to that, I think...

A universal driver would remove the need to buy new hardware - therefore less product would be sold - therefore less profit would be made - therefore there would be less "growth" (angry LOL).

Bottom line.. The consumer is being screwed again, deliberately, mercilessly - all this "redundant" hardware which works perfectly will eventually be dumped - some will end up in the 3rd world and stuff from it "salvaged" by poor labourers (including children and other slaves) who will be poisoned by the toxic substances released in the process.

And a tiny few slave masters will get rich from the salvaging operations - and employment will be provided in making replacement components for the (mostly needlessly) dumped components, and a tiny few will get rich from the sale of these replacement parts.

It all works perfectly! (if you are in the 1% of the population who benefit from the sufferring caused to the victims, and the destruction you cause to our planet).

Fred.

"A universal driver would remove the need to buy new hardware - therefore less product would be sold - therefore less profit would be made - therefore there would be less "growth" (angry LOL)." Fred.

Isn't that a rule of acquisition?

Rule of aquisition # 224 if I remember correctly, should cover that.(kind of)

In His Service ---- Dana

I like the sound of your theremin RS Theremin

http://chirb.it/BkDDEz

in the recording above I was trying to get it to sound like a voice.It's my diode enhanced EW standard with a bit of fiddling with graphic equalizer on the amp and tone shaping controls on the theremin.I used a cheap microphone in front of the speaker.It still manages to sound a bit voice like.

Fred what's the difference between a nerd, a geek and a dweeb..they are all nerds but a dweeb is a nerd who has never had a date with a member of the opposite sex...a geek has a partner and a job and is a successful nerd..and a nerd per say is between a dweeb and a geek.So when you announce something is for nerds and geeks don't forget the dweebs...they always get left out.

"don't forget the dweebs...they always get left out." - IJ

LOL ;-) .. Funny the different interpretations one can find..

My understanding was that a Geek was a wanna-be Nerd.. That a Nerd was usually focussed, often incomprehensible to most except other Nerds - bright "lab coat" types usually...

Wheras a "Geek" was unfocussed, sloppy, and usually not-too-bright.. Someone who wants to be, or sees themself as a "nerd" but actually are easily spotted by (and mostly disliked by) true nerds. Geeks tend to often be misidentified by "normals" as "nerds" and give Nerds a bad rep for this reason.

Fred. (a wanna-be normal)  ;-)

Fred. (a wanna-be normal)  ;-)

I know I am normal because I am on Lithium and Clonazepam . It is kind of like a controlled madness. Fred I have my eye on you. LOL

I bought something today less than $100, could have got the UCA202 but I want to try something original first. I have wasted so much money on all this. Over $10,000 is not unrealistic and have no equipment to show. You designers know what I am talking about. Then a kid shows up saying he does not want to spend a lot of money.!#$%

Edit: This aliasing issue is driving me nuts, is this something you hear or view in software. What does it sound like or look like. When I feedback my audio to the RF oscillators I think it adds something positive but then this would bring forward RF to confuse a sound card. I think the answer is to go to amp - speaker then mic to sound card for the best results.

Christopher

I've used this circuit and it works almost exactly as simulated.

It's called a Linkwitz - Riley filter.

Here's the response for the values shown...

" This aliasing issue is driving me nuts, is this something you hear or view in software. What does it sound like or look like. When I feedback my audio to the RF oscillators I think it adds something positive but then this would bring forward RF to confuse a sound card. " - Christopher

You can hear it?

That probably depends on your hearing.. Clonazipam might alter your audio peception though - it has a powerful dampening effect on some synapses related to audio perception, but exactly how, why or where are unknown last I heard.. Looked into it years ago when my mother suffered Tinitus.

Chris, lets be honest - the cocktail you are on is going to be a severe handicap.. Your only hope I think is to follow good design practice when designing and building, and then letting others judge if there are any ghosts in the machine..

Yeah, its a bummer - But we all need feedback from others, because, even without a hearing or other problem, we are all subject to self-delusion.

 You can see it?

If you know what you are looking for, and have a simple waveform, possibly -(An analogue 'scope is best to see it), but easiest is to measure it. If you have a fixed audio frequency (replace antenna with fixed capacitor, tune the audio manually by trimming var or ref oscillators) and measure the distortion with a distortion or spectrum analyser.

What does it sound like or look like ?

Mostly enharmonic "ghosting" tones if one has simple monophonic waveform - the more complex the waveform, the more horrible it generally sounds.

When I feedback my audio to the RF oscillators I think it adds something positive but then this would bring forward RF to confuse a sound card -

No, it shouldnt - if you are FM modulating the RF with the audio, it shouldnt produce "more RF" on the audio..

ALL the RF should be eliminated at the filter following the detector - w0ttm has shown a pair of standard low pass filters in series - I think that having at least one active LPF following the detector is a good idea.. only I would probably increase the resistor values to 10k and reduce the capacitor values to 220pF if putting this filter following the detector, as the 1k impedence is probably a bit low for this section. Reducing the capacitors moves the rolloff frequency higher, increasing them moves the rolloff lower - 470pF (with 10k) will make a noticable cut in the higher audio harmonics, and is probably as big as you should go - and no less than about 220p

Fred.