(stock image, the one shown is one channel, mine was two, unbalanced)
Make / Model: Shallco Attenuator
Purchased: Shallco, 2003
Price: $300? $400?
When I setup my mastering room, I needed a super decent way to adjust the volume of the speakers.
The problem is, most stereo potentiometers are NOT accurate between the left and the right channels. Even the best ones track a little off. And as they get used, it varies.
The LAST thing you want to do in a mastering room, is mistakenly correct the left/right balance of a recording with a bunch of hours behind it, simply because your $20 volume knob, is being just that.
So you use a rotary switch instead. And each position of the switch, uses precision resistors so that left/right tracks evenly. Also, if balanced, all of the signal tracks evenly.
Building these things is painstaking, so I ordered one, from the company who made them for everyone, back when people gave a shit about that kind of thing. Shallco, down in North Carolina.
You call up Shallco, and tell them what you want them to build. As they build switches for all kinds of stuff, you specify for audio use, what the impedance should be, how many steps at what rate of attenuation, how many decks (IE one channel, two-channel unbalanced / one channel balanced, / two channel balanced, etc).
And it was awesome.
They key to using one of these is making sure it works well between your source, in this case, a Benchmark DAC1, and the amp, in this case, a 3B-ST. So I got in touch with the folks at Benchmark, and they had their engineers figure out what the best setup would be: IE which jumper setting to use on the DAC1, and what Impedance attenuator to order.
And it turned out great!
When I closed my studio down, I sold it to an audiophile in Japan.