Mini Diamond Theremin Speaker

Hi all! Ever since I started playing, I've been using this little diamond speaker with what's left of the original amplifier to drive the speaker. Even sawed off, that amp head was still to bulky and heavy to transport on away missions, so I've been searching for a better way to drive that mini diamond with a smaller amplifier without giving up quality of tone.

Found it! http://www.amazon.com/gp/product/B003P534SW/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1

The Lepai amp is only a few inches in size, and draws very little power. it's a perfect match for the Jensen 20 W, 8 Ohm speaker I'm using. The little amp even has the ability to alter the tone, or bypass the treble / bass controls.

I mounted the Lepai amp to a bit of wood, and attached a couple of 2 hole pipe straps to the other side of the board. Now the amp can be slipped straight on to my mini diamond's stand, and connected with speaker wire that easily connects to the back of the amp via spring clip inserts.

The amp has two ways to get audio into it. Either via a mini plug for mp3 players, or RCA jacks. The amp is stereo, and has two speaker connectors, as well as stereo RCA jacks. That might come in handy if one builds a larger diamond speaker with two 20 watt speakers in it.

If one is building a larger theremin cabinet, such as an RCA style cabinet, this little amp certainly won't take up much space inside it.

Now I've got a lot more room inside the gig bag with this little amp to drive my diamond speakers with. It also opens the way for mass producing diamond speakers. For larger diamond speakers, one could slip this little guy right inside the diamond speaker to hide it, or build it into the speaker's floor base. Lot's of new possibilities here.

I wanted to get, and still will, once available again, the aluminum version, because the case of the Lepai looks a quite like the LV-3 theremin's case. What a nice match that would be. I suppose one could opt to mount the Lepai on the mic stand where the theremin is to make for even easier access to the controls, but at the trade off of a longer speaker cable run. Either way, you gotta run something to that speaker stand. LOL :)

Cost? The lepai is less than 20 bucks. I'm sure there are amps like this which can be driven with batteries. That would make for great busking possibilities. Not being able to run the Lepai on batteries was the only drawback, but it uses so little power, one could still power it with a portable power supply as I've seen done at HO2011 by several thereminists. :) Pics coming soon.

You can see pics of the little Lepai amp in use over in my photo album at:

http://thereminworld.com/photoalbums/view/14543

I hope this helps inspire some creative theremin constructs on the practical level as well as provide ideas for more airline friendly transporting of theremins. :)

You got that speaker so gussied up with all them flashin' lights, whirligigs and extension arms that it's startin' to look like SHARKTOPUS goes to Vegas!

Sure seems like ya scared the hell outta that cute lil pooch!

Thomas, do you find that amplifier interfering with your Theremin at all?  This is a Tripath T-mode switching mode amplifier so it likely generates RF on the speaker leads.

For those just looking for a module, I've used this:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-385

The output RC filter resistors burned up when I was looking at the high-end roll-off point, I replaced them with conventional leaded resistors.  Output has quite a bit of HF hash.

@Coalport.  You're confusing this one with the big grand speaker. :) Reset assured, production models of larger diamond speakers will be more like this little one, less detailed, and portable.

@Dewster: No interference at all. It is digital, so, not quite like the analogue gear, but it's purpose is to be a monitor, and not serve the audience in a medium sized venue setting. However, it sounds way better than I thought it was going to sounds.

Thanks for the modular amp link. That actually could be installed into an Etherwave over on the volume side, it's so small.

"No interference at all. It is digital, so, not quite like the analogue gear, but it's purpose is to be a monitor, and not serve the audience in a medium sized venue setting. However, it sounds way better than I thought it was going to sounds." - Thomas

I think you might just have bee lucky, Thomas! - Not so sure one could rely on that luck if one was to put this kind of amplifier inside a cabinet containing theremin RF circuitry, or even rely on this type of amp if driven from a theremin with sloppy output filtering (ie - the majority! ;-)

These amps do give astounding value for money - About a year ago I used the same IC's for a client's prototype Ipad dock - but needed to add extra filtering on the power supply input (a crappy SMPSU was provided - the whole kit is being mass produced now in China - they removed my filter because it added about 20p to the cost - and IMO it now sounds metalic at the top end).

As I say, for the money, these cant be beaten - But I personally dont like their sound much.. perhaps its too clean, perhaps I just like something chunky that wastes a few watts in heat and gives just a tad more noise and distortion! LOL ;-)

"Res*t assured, production models of larger diamond speakers will be more like this little one, less detailed, and portable." - Thomas

"Production" ?  - Seriously, Thomas - If you plan on putting these into production, I strongly advise you to avoid this type of amplifier - The theremin environment is simply the worst possible environment for an amplifier of this topology! - There are plenty of low cost analogue amplifiers far better suited to this application! ... At some point, and IMO probably sooner than later, deciding to go with a digital / switch mode amplifier WILL give you a headache!

You can get amplifiers based on an IC like the Panasonic AN17830 for only a little more expensive than the class D boards

Fred.

@FredM: Well, I do have more research to do, but without the Digiverb pedal between the theremin, and Lepai, I heard what you described too. I do still need to see what affect that amp would have in close proximity to all of my theremins, as in inches away, but so far, it does a nice job. Lucky? perhaps. I'll have to try with another of the same model. I will also look into analogue amps at the low cost end that can drive this type of speaker, but they've got to be small, and cheap.

Thanks for the heads-up.

" but they've got to be small, and cheap." - Thomas

yeah - It always comes down to this sort of balance.. How many potential customers would you lose for an extra $10 on the selling price, versus how many would you lose because they dont like the sound..

Personally, there is absolutely no way I would risk class D for the application you are exploring - The risk is too great IMO... Even if people like the sound, I suspect that the cost of servicing returns / complaints due to RF interactions will far outweigh any additional cost you add due to opting for analogue.

And I am fairly sure you will lose potential customers by selecting class D - even if there are no obvious "problems". There are those (like me) who would never buy an amplifier / powered speaker which sounds the way class D sounds (and this includes "class T" - Class "T" is not actually a true "class" - its a proprietery brand identifier, and is actually "class D").

I have been down this path with my client - He had ambitions to produce a real "Hi Fi" enclosure for the Ipad - real wood, good speakers, and good amplifier... He liked the sound from the class-D amplifier, I didnt... He had a batch of prototype units built, and 20% of those who sampled it didnt like the sound - He came to me, I added the filter (he wouldnt go the analogue route I suggested) - About 5% of those who heard the modified prototypes didnt like it... This got sent to his client in China - they deemed costs too high, removed my filter, cut back on other expensive bits, and the unit sold about £10 cheaper than it would have been (about 6% off the price it would have been) ... It was too expensive for the average purchaser, and not good enough for those who would be willing to pay for quality... So price was reduced just to clear the stock, and manufacture was discontinued. 

I would quite like a diamond speaker - I am sure many people would be interested in buying one.. I would however have no interest in buying something with a metalic quality to the high tones, or with the potential risk of problems if I changed to a different theremin or was playing where a possibly incompatible theremin was playing - My first priority would be that the speaker woudnt do anything "active" to the field - That apart from the obvious ground influence, I could know that it would not radiate or influence my theremin (or anyone elses) or setup in any way.. The second priority would be the sound from this speaker.. Price comes after these priorities IMO...

IMO, whatever the additional cost, Class-D is not the way to go for theremins! --- But I may be wrong ;-) .. I am so damn cautious that I never end up putting anything into production, LOL .... And I can see that if everyone was like me, there probably wouldnt be any of the technology we have - all the technology would be in the labs of self-doubting inventors who never braved the risks of exposure, or were too worried about supplying imperfect product to the public.

Fred.

@FredM: Fair point. Quality rules here. I will indeed reconsider analogue amps, or at least transistorized ones when considering production speakers. Thanks for your thoughts. They'll not be wasted.