b3 theremin

Dear all, 

I bought a b3 theremin sometime ago, but i mistakenly bought a stage monitor amp for it and found out its full of inference if i put them together. 

I then realized b3 is designed to work with guitar amp afterward, is there anything i can do to make it work with the monitor amp? I tried the b3 with a guitar amp , and the same setting with etherwave all are working fine, therefore i ruled out other inference and grounding problem.

I just dont understand whats the difference between guitar amp and stage. monitor amp. Grateful if anybody can give me some advice.

Thanks, 

Ally

Hello Ally,

The B3 most likely must work with an amplifier that has a 3-Prong power plug. For a theremin to work at its best it must have an earth ground which is the third pin on the plug.

My guess is the monitor amp has two pins on the plug.

Christopher

Christopher is (almost) right.

The stage or guitar amplifier question is secondary and a question of frequency response and volume level. The B3 can we'll be played through a studio monitor, I for example play it through a Yamaha MSP-5.

Interference is a complex topic when it comes to Theremins. Since these are highly sensitive radio frequency devices, they can, depending on the environment, act as a radio receiver or capture radiation from switched mode power supplies as you find them in computers, laptops, cell phones, energy saving light bulbs, dimmers, and sometimes in amplifiers, too. One way to reduce these problems is to set up the theremin in a most radiation free environment. That, in combination with a well grounded circuit, solves 95% of problems. Well grounded means that exactly one device in the chain is grounded via the third pin of a three pin wall plug. Since the small B3 power supply has no ground pin, it is very important that the amplifier (be it for guitars, keyboards or whatever) has one. This ground contact is then "routed" to the theremin via the shielding of the audio cable between the instrument and the amplifier. Seen the relatively high sensitivity of a theremin, it is very important to use a well shielded cable, the cheaper ones don't do that job.

Although I own many different Theremins, I make always sure that there is only one running at a time and that all other not needed electrical devices are switched off, too. Furthermore, I use only "classic" light bulbs in my 180sqft music room and I make sure that I have always a radius of 6ft which means a diameter of 12ft of free space around the theremin which I play. The result is that I have no interference problems, neither with the B3, nor with other Theremins.

Thanks for your reply. I did tried to tackle the grounding problem. 

All the monitor amp and transformer of b3 have three prongs so i thought the top one are the ground. 

Since i live in hk so i used an adaptor for b3 to convert 220v to 110v, as there's no ground between the adaptor , so i wired the gnd prong of b3 to the ground plate of monitor amp. Seems it didnt help, am i doing the gounding correctly?

I have been using 110v etherwave with monitor amp at same location which is a pretty large room and it works prefectly.. Both settings was tried in different locations and still having interference for B3,  and I use planet wave cable.  

The more interesting thing is that b3 works with a guitar amp without interference at same place. 

I am so puzzle now..:(

Hi, I purchased a B3 Deluxe a while ago, and we lost the power adaptor cord. Can anyone tell me what what the requirements are (please read your power adaptor and let me know the following:

Input: example -120 Vac 6Hz 6w;  Output: example - 12VAC 0.33A

thanks

The input depends on the region of this world where you live, either 110, 115, 120, 220, 230, or 240V and 50Hz or 60Hz.

The output parameters are more important: 12V DC regulated, 200 or 300mA. But caution: it must be a power supply with LINEAR regulation, no (energy saving) switched mode power supply (SMPS, sometimes also called chopper circuits). The latter produce so much stray RF which tends to interfere with the Theremin's RF oscillators, so that the instrument would become unplayable.

The input depends on the region of this world where you live, either 110, 115, 120, 220, 230, or 240V and 50Hz or 60Hz.

The output parameters are more important: 12V DC regulated, 200 or 300mA. But caution: it must be a power supply with LINEAR regulation, no (energy saving) switched mode power supply (SMPS, sometimes also called chopper circuits). The latter produce so much stray RF which tends to interfere with the Theremin's RF oscillators, so that the instrument would become unplayable.

Thank you Thierry, for your quick response..... but I am still at a loss of what power adaptor cord to purchase. I live in Canada, so I guess 120V is correct, but as for the rest I am not sure. I have looked at other power units for other gadgets and they vary widely so I did not know which one would work. 

When I look at the labels of the power adaptors it states Input: xxVac xxHz xxW and Output xxVAC xxA

so I was wondering if someone would please look at their (if in North America)  Theremin power adaptor and list what it says so that I can match it up.

Many thanks!!!

Hello Barks,

Sounds like my wife back in the day.

Here is Dan Burns website and email address. Drop him a note, he responds quickly.

Christopher

OK, for Canada it has to be Input 120VAC 60Hz whatever W and Output 12VDC (not VAC!) 200mA.

This one on eBay.ca is perfectly suited in terms of voltage, current, and plug polarity :

http://www.ebay.ca/itm/PPI-1220-UL-AC-DC-OEM-Power-Supply-Adapter-Charger-DC-12V-200mA-/231441745551?pt=LH_DefaultDomain_0&hash=item35e300c68f

Yeah, thanks so much Thierry.... I found one that may do the job. I went to Value Village and bought 10 Adapters yesterday... 2 of them are soooo close. If not I will order the EBay charger you linked me to. Hey, our weather dropped 26 degrees Celsius from Friday, it was +13 now -13.... burrr.. Hope weather in France is nicer. I lived in France for 6 years back in my early days and was back to visit 5 years ago. What a great City.

PS  Hey oldtemecula I can relate to your wife (ha ha). I was down around San Diego last year, working a puppy mill bust and brought 6 dogs to Canada. Sure loved loved your area!!!