50 k-ohm, more likely.
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| Anybody ever try using something like this? |
Making the pot function is easy. Rigging up some kind of remote control to activate the motor is the tricky bit. I'd bet that most DIYers use some commercial part for this. There are kits out there complete with the remote for this purpose.
No, I don't remember where I saw one last.
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| Also has anybody ever used a digital pot? |
The only DIYer I know of who has is forum member fixup, who does the Supermini and related compact headphone amps. He uses the DS1802 in push-button mode.
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| What kinds are out there? |
There are two main types for the resistive element, as I see it. By far the most common for audio use is a resistor string with an electronic switch from the input to each node along the string. A control circuit selects which switch connects the input to the resistor string. This is basically the solid-state version of a stepped attenuator. Examples of this are the DS1802, LM1972, and CS3310.
The other major type uses some kind of general-purpose DAC chip. Either you'd use a linear DAC with thousands of steps to approximate a log curve, or you'd use a log DAC of some sort. Analog Devices makes several such ICs. This is more of a hack than a thing people typically use for audio. The resistor-string-and-switches type is simpler and is likely to have less distortion than the general-purpose DAC approach.
The other major differentiator is outside control. There are three main kinds.
First, there's simple pushbutton control. If you've got a modern portable CD player or MP3 player, you've probably seen this in action. Simple up/down buttons. I dislike this for DIY because the panel-mount pushbuttons DIYers are likely to use are ugly or bulky. (In the fixup amps, he's not using panel-mount switches, so he can avoid this problem. It requires more care in enclosure design to pull it off than DIYers typically employ, however.)
The next common control method is some kind of simple serial digital protocol. By "simple" I mean that the protocol's only purpose is to communicate a number (the pot setting) to the chip. Despite the simplicity, you do need a microcontroller on-board to speak this protocol. I'm not aware of any pre-made chips that speak these protocols, probably because each chip speaks a different one. For instance, all three of the DS1800 series chips speak a different protocol; nevermind compatibility between chips from different manufacturers.
The final method is a complicated serial protocol. This can be one of the standardized protocols (I2C or SPI, typically) or a nonstandard protocol specific to the chip. These complicated protocols allow for addressing multiple chips on a single bus, reading data back from the pot, controlling special modes, etc. This gets you deep in to microcontroller land.
Now you see why these are not popular for DIY.
