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Old 3rd December 2001, 11:46 PM   #1
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Join Date: Apr 2001
Location: Brisbane Australia
What size (power handling) pot is required if putting the volume control on the output as opposed to the input. I can only locate 1/2 watt max in the dual gang variety required?

Alternately, is 12 steps enough for a stepped attenuator.

Cheers

Dan
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Old 4th December 2001, 12:12 AM   #2
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Location: Columbia, SC
Dan,
Assuming that you don't intend to drive your preamp from a power amp(!), 1/2W will be fine.
How many steps is enough?
Lots.
I don't think I could live with only 12 steps. Even if you accept the first step as being on the order of 20 or 30 dB, twelve steps isn't going to give you a lot of control. I wouldn't even consider a step larger than 1 dB; most manufactured units seem to be headed for .25 to .5 dB per step. Even the less expensive gear tend towards 20-24 steps, with the more elaborate setups going for 256 steps.

Grey
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Old 4th December 2001, 01:43 AM   #3
lohk is offline lohk  Europe
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I agree to Grey, in my experience even 24 steps can be not enough. You have to consider that you will have to deal with different input levels too.
And the most enoying thing can be when just the right level is right between two steps...

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Old 4th December 2001, 03:41 AM   #4
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Would this be of benefit to sound quality?
I will be using a rather poor quality carbon track dual gang for the volume control until I can afford (time and money) to get something better.

"Wire your pot as a shunt ...
Most people have their pot wired as a series element.

To rewire as a shunt, choose a fixed series resistance, say 10-20KOhm (get a relatively decent one). Hook up pot so that it "shunts" the output (after resistor) to ground. Thus you need 0 Ohms at zero volume setting, probably 50-100K (is this not what your pot is?) when turned up all the way."

Originally posted by Petter in another Pass linestage volume control thread.

Dan

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Old 4th December 2001, 03:44 PM   #5
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Dan,
If I follow your quote from Petter, it sounds like a recipe for turning a linear pot into a log pot. Yes, you'll need a log (audio) taper pot somehow.

Grey
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Old 5th December 2001, 01:11 AM   #6
bawang is offline bawang  Malaysia
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Default Volume control for BOZ

ding,

Try this pot from Farnell Components part number 3071145. It's a small PCB mount conductive plastic Spectrol 5k log pot. I used it for my BOZ preamp and have found no fault with it. And it costs 'only' approx US$2.50! Have fun!
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