Simple Theremin Help needed

[col]

I would like to build the Simple Theremin from www.thereminworld.com/EPEArticle.asp and the transistors it mentions are BF195 which when I looked them up are RF transistors. I this important as the circuit relies on the frequency they produce or can i sub any npn transistor of similar Hfe in? The reason I am asking is that I have all the other components and I'm currently designing a stripboard layout and I need to know if the pins are CBE or BCE for the transistors. If I can just sub any trasistor I have some suitable ones but I don't want to proceed without checking first. The BD139 look similar and have a similar Hfe and are BCE pinout but I don't want to get stuck with this build.

I like theremins!

Col

[birt]

i have no idea. but for a simple theremin i built this one: http://home.att.net/~theremin1/101/101.html

sounds great, especially trough an uglyface

[funkbass187]

i have no idea. but for a simple theremin i built this one: http://home.att.net/~theremin1/101/101.html

sounds great, especially trough an uglyface

that one seems very interesting, i might try that as my first perfboard project. unless i can get a vero version, but when i see ic's in a schematic i get confused and can't ever figure out a decent way to set things up.

[col]

I have built two others, one which works and one which doesn't. The one that does work sounds great but is just missing something. I can get some strange sounds out of it though. I can't remember which one it was though. I'll search it out tonight.

[choklitlove]

i breadboarded this one the other day:

http://www.thereminworld.com/pics/schematics/simple.jpg

i couldn't get anything useful out of it.  i wasn't expecting much, but it only has a range of about a 1/2".  that's pretty pathetic.  i too am looking for a good theremin project.

[Paul Perry (Frostwave)]

Choklitlove, I seem to remember (somewhere.. years ago..) that the two oscillators would be better using different chips (possibly with some decoupling from the power rail as well) otherwise they will interact.
Notice that although the 4093 has plenty of spare sections, the pin numbering implies that TWO SEPARATE 4093 are used.

[choklitlove]

oh, i know.  i also looked at the datasheets for the chips and had to add/subtract a couple different pins from ground and +.  it took a while to get it to work the little that it does.

[birt]

the minimum theremins i built can have a range to up to half a meter and even a little more. but you must definatly use a multi turn pot for the calibration trimmer and don't tilt it to calibrate it. if the trimmer is at the bottom just hold the thing above your head, it looks silly but calibration is better when it's in the same position as when you play it.

the older version is a little more "singing" but it doesn't stay calibrated for a long time. the 2006 version (wich i built in a teddy bear for a friend who doesn't know anything about electronics) is still calibrated very well after a couple of months.

if you google you can also find PCB lay-outs.

[Ace]

Have you tried an "opto theremin" yet? http://forum.myspace.com/index.cfm?fuseaction=messageboard.viewThread&entryID=31790881&categoryID=0&IsSticky=0&groupID=100146210&Mytoken=3423EAD4-3272-409A-A5335438361DAC4067698753

[roofer1]

i'm fairly new to the game, but i perf'd this one after hearing the cool audio samples.  about 15 minutes after i had it done i had to go to band practice where my drummer (another home recording enthusiast) kidnapped the thing and i havnt seen it since.

http://www.oldtemecula.com/theremin/rs-opticaltheremin/rs-opticaltheremin.htm

check it out.

[col]

The best one I built was the 2chip_theremin but I can't remember where I got the schematic from. I think it was Caseyeffectpage and I can't get that up at the moment. I can check on Monday when I'm back at work. It uses a 4069 and a 4046. The sound is good but it's more of a growl/snarl/howl than a wooooo if you understand me. Technical terms.

[col]

I forgot to add. Does anyone know about the transistors?

[Paul Perry (Frostwave)]

Maybe this is the 4046 and 4069 theremin? http://www.imk.fraunhofer.de/ich-sehe-was-du-hoerst/theng_3bauelemente.html

[Ge_Whiz]

I would like to build the Simple Theremin from www.thereminworld.com/EPEArticle.asp and the transistors it mentions are BF195 which when I looked them up are RF transistors. I this important as the circuit relies on the frequency they produce or can i sub any npn transistor of similar Hfe in? The reason I am asking is that I have all the other components and I'm currently designing a stripboard layout and I need to know if the pins are CBE or BCE for the transistors. If I can just sub any trasistor I have some suitable ones but I don't want to proceed without checking first. The BD139 look similar and have a similar Hfe and are BCE pinout but I don't want to get stuck with this build.

I like theremins!

Col

Me too!

I've built this gadget and it's fine for woowee noises, but you'll find it hard to play a tune on it. However, that's true of all simple theremins. You really should use RF transistors for this design or you may have problems with the oscillators. They don't run at a particularly high frequency (hence the control range is short), but for reliable operation you'll find that RF types are best. Having said that, almost any NPN BF-series types will do. I don't think that BD139s will cut it.

You have to get the oscillators matched in frequency pretty closely to get an audio-range beat note. Long wires on inductors will mess this up a treat, and ideally you need a 'scope and/or a frequency meter to get them matched. Mine is fitted with a 50 pF variable capacitor from a scrapped radio to tune it. It took me a while to set it up, but, having said that, I built it from junk box parts, even winding the inductors on bits of broken ferrite rod myself.

Good luck!

[col]

I got some BF199s so I can do a layout for this as I have everything else. I doubt I'll get time this week though so it might be over the weekend. I'll put the details of the sound on here. The transistors are CEB pinout so i't a good job I checked!
I still can't find the source of the two chip theremin but it's very similar to that posted by Paul. If I can find the info for it the stripboard layout should be with it but my cupboard is in a real mess at the moment. I might sort that out over the weekend instead

[col]

The link for the 2 chip Theremin!

http://smg.photobucket.com/albums/v324/caseyseffectpage/Theremins/?action=view&current=2Chip_Theremin.gif