Author Topic: Brown Box ?  (Read 67 times)

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Offline ducatidoc

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Brown Box ?
« on: August 06, 2018, 06:17:10 am »
Anyone else have one to control their input voltage ? I've been told that the older Sunns were built to work optimally at 110V AC, although my '69 2000S says 117V on the rear.  The outlet Ive been using reads about 121V so the box brings it down to 117V.

Offline Isaac

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Re: Brown Box ?
« Reply #1 on: August 06, 2018, 08:44:47 am »
I've never heard of a Brown Box. For years, I've read of people using autotransformers such as Variacs to adjust the input voltage, but that's usually to use it as a kind of master volume.
Isaac

Offline ducatidoc

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Re: Brown Box ?
« Reply #2 on: August 06, 2018, 01:06:48 pm »
Here's a link to the one I got:

https://www.amazon.com/gp/product/B07D842D53/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

If you scroll down to the description it says "Be sure to Check the Manufactures info plate on the rear of the Chassis for input watt requirements or simply call us, we love to help", which sounds mighty friendly of them. My '69 with tube rectifiers says 117V, so that's what I adjusted the box to. 

Offline Ryan Phelps

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Re: Brown Box ?
« Reply #3 on: August 07, 2018, 07:32:53 am »
Variacs have been used for ages......either to adjust the AC voltage to the amp's original specs, or just to "brown" the sound......more distortion. Eddie Van Halen was noted for doing this back in the day.

The Brown Box manufacturer is referring to AC wattage consumption (amps x volts = watts) of the amp. In the case of this device, it is limited to 5 amps of current.....which will handle most amplifiers.

A more rudimentary version of the Brown Box is a bucking transformer.....basically reduces the AC wall voltage down to something closer to the old voltage in years past. These have been used for years by tube hi-fi guys. A major benefit of using one of these devices is to lower the secondary voltages coming from the power transformer so that the voltage rating of the filter capacitors are not exceeded.....and the filtered DC voltages fed to the plates of the tubes, are closer to the original design. Lots of schematics for these on the interweb, but not for amateurs!

For tube rectified amps, one can substitute for a less efficient rectifier that has more voltage drop....thus reducing the secondary voltage fed to the power supply and tubes. But need to be sure the rectifier tube does not exceed the current capacity of the amp's power transformer.