Spectra 1100, AC adapters

Read more on the Acoustat Spectra 1100 in our home audio section

Ben Henry2004-02-23 22:21

Dear Andy, I am writing today because I was wondering if you know where I could go to get the ac adapters which convert the voltage to power the electrostat on the 1100 speakers. In reading through the information you have provided, they seem to require a 15v supply at 150 Mamps. I can not find that kind of ac/ac adapter locally or on the web. Do you have any information as to who might make this? The speakers are in great shape, and everything else looks good on them, but they did not come with the original transformers to plug into the wall. If you have any information, I would be very thankful. Kindest regards, Benjamin Henry


Andy Szabo2004-02-23 22:21

I\'m sorry to hear that you are still having problems with your speakers. I double-checked the Mouser part number, and it should work (assuming that you get one that works!).

When you measured the output of the wall transformers, did you use a meter set for AC volts? If the meter is set for DC volts, then little or no output will be measured. Make sure the meter is set to AC volts. For a 15 VAC wall transformer, you will measure a higher voltage when it is not loaded (i.e. not plugged into the speaker). You may see as high as 20 VAC. The 15 VAC rating is the voltage produced when the transformer is delivering full rated current.

Acoustat may have used a three-conductor (or ”stereo”) jack for the AC power input. However, only two conductors are used: the ”tip”, and ”ground”. The ”ring” conductor is left unconnected or also connected to ground. A two-conductor plug inserted into a three-conductor jack will, depending upon its design, either make no connection to the ”ring”, or short it to ground. This is a compatible combination for this situation, and no ”mono-to-stereo” adapter is required.

The correct size plug for the speaker is 3.5 mm, sometimes called 1/8”. A two-conductor or three-conductor plug can be used. Radio Shack part number 274-858 (gold-plated/three-conductor) is a good choice, although any electronics store should carry a suitable part. Solder the output wires of the wall transformer to this plug: don\'t be concerned about polarity because this is AC current. If you use a three-conductor plug, leave the ”ring” terminal unconnected or connect it to the same wire as the ”ground” terminal.

Andy Szabo2004-02-23 22:21

The Spectra Series requires a wall transformer rated at 15 volts AC, with a minimum current output of 150 milliamps (mA). Therefore, any wall transformer that puts out 14 to 16 volts AC, at 150 mA or more, will work just fine. Checl the Available parts page for more information.

Ben Henry2004-02-23 22:21

I wrote to you in February asking where I might find AC adapters for the Acoustat Spectra 1100s that I bought earlier this year. I have had quite a bit of trouble trying to get the speakers up and running, and I think it may be the adapters, but I\'m not positive. This is what I\'ve done so far.

I took your advice and ordered a set of the adapters you recommended from Mouser Electronics. I got the exact adapters you mentioned, but had several issues come up. First of all, my grandfather (who is an electrical engineer) and I found that the adapters were non working. (He tested them with a voltmeter after removing their backs and plugging them in and they were not hot.)

In working to get the speakers operational several questions were raised. Do you know if the plug on the original adapters was a stereo plug or not? My grandfather pulled the plate which houses the AC plug port off of the back of the woofer enclosure and thought that for some reason Acoustat used an AC plug port that has two leads soldered to it, meaning you have to have an AC plug which has two points of connection on it like an 1/8 stereo plug. Also, the plug which these Mouser AC adapters used was a 3/32” plug, so we had to use adapters to get them to fit. Not having any experience in these matters, I can offer no opinion one way or the other. To continue, I had Mouser send another set of AC adapters out which again did not work to power the electrostats. Again, I had to use the 1/8” adapters on these, which may have affected the equation somehow. I might mention I was not able to test the 2nd set from Mouser as I did not have a voltmeter on me at the time.

I have now ordered the AC adapters from Digi-Key. They are interesting in that they do not come with any connectors. You have to buy the connector and connect it to the screw terminals on the AC adapter. If you could tell me exactly what kind of adapter plug I need to attatch to the adapter I might finally get to fire these speakers up. Thanks in advance for any help you can offer. Sincerely, Ben Henry

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