Spectra 11, Interfaces, resistors

Read more on the Acoustat Spectra 11 in our home audio section

Don Layman2004-02-23 22:21

Dear Andy my name is Don Layman I have written you recently and apologize for bothering you again. Im rebuilding my Spectra 11s and my tech asked me if I could locate 4 of each 330kiloOhm and 620 kiloOhm resistors to replace ones that arced and blew a hole in interface. He is going to cut out with a dremmel the circuit board and paint with epoxy where arcing occured between the two resistors. On the schematic it says these two resitors that are side by side are 330 kiloOhm he wants to replace with 620kiloOhm but it does not specify voltage of the resistors. Would you know this off hand and does this sound like a viable fix.Are there any other upgrades I can do to my beloved speakers. Thanks for the awesome website.

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Andy Szabo2004-02-23 22:21

The resistors in question (330-kohm) control the Spectra sectoring, and I do not recommend changing these from the original value. Much listening and experimentation was done to determine the optimum value. Note that these resistors have nothing to do with the crossover point between ESL and woofer.

I do remember that some speakers were built with two 680-kohm resistors in parallel, yielding an effective resistance of 340-kohm, which is close enough. This was done only because the 330-kohm resistors were not available at the time.

Under ”Refurbishing - Available Parts”, Lee Sulka found a good source for high voltage resistors at Newark Electronics. I recommend the CGH-5 series, which is rated at 5 watts and 20 kV. The voltage rating does not need to be that high (5-kV is enough), but they should be rated for at least 5 watts.

My Newark catalog lists the closest value at 300-kohm, which may be too much of a deviation from the desired value. However, the catalog does state that other values are available, so you\'ll need to contact them on that subject. You may need to parallel two resistors to obtain the proper value. But by all means, stick with something close to 330-kohm!

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