> discrete resistors with rotary switch instead of pots. .... I can get better responce with the use of this kind of pots, gain control, volume , filters ?
The big advantage of a pot is that it is cheap and usually works OK.
But it is a resistor that is not sealed and has a metal finger dragging on it. The finger has to drag lightly so it won't wear-out the resistor. The resistor stuff has to be picked for toughness against friction and resistance to air, not for stability or "sound".
Amazingly enough, pots really do work great in most audio. If they didn't, we'd be paying a LOT more for everything. While many people say they hear "sound" in resistors, after we lost the worst carbon composition (pencil shavings in a wax cylinder) resistors, all modern resistors sound the same to me: pots, carbon film, metal.
Affordable pots don't allow you to hit the EXACT same setting every time. (There are 10-turn pots with vernier dials for big $$$, but even they aren't as precisely repeatable as you could wish.)
And the thin resistor stuff used in pots isn't very good for very low-ohm settings. As Alan says, a mike amp gain-set resistance normally needs to be lower than 100 ohms for all mike-level gains, which means 10 ohms or less at maximum gain. Many cheap pots won't even give less than 100 ohms, or they jump suddenly from many-dozen ohms to under 1 ohm.
And because the dragging metal finger in a pot has to drag lightly to avoid wear, it tends to lose contact on dirt or bumps. "Scratchy". This is worst on the high-gain circuits like mike amps.
Now consider a switch and resistors. The switch contacts are just contacts and can be made very rugged with high contact pressure to bite through dirt. The resistors are separate and can be picked from any golden-ear type you like. The switch contact resistance is typically 0.001 ohms, maybe 0.1 ohms when old and weak, so a 10 12 15 18 22 ohm sequence of gain resistors gives you exactly the resistance you expect, not whatever sloppy value the pot lands on.
But a GOOD switch is expensive, especially in the many-position configuration you normally want for a mike-amp gain control. $20 each for the switch (and $5-$20 for the resistors) isn't expensive. DACT charges well over $100 for gold-plated precision switched resistor networks (and doesn't stock one in mike-amp values). Multiply that times your 16-in board, it's expensive.
If you can find a GOOD reverse-audio 5K pot, it is usually perfectly acceptable. It will get scratchy after months or years of use, but you can buy another pot.
If you need precise gain repeatability, then you want a switch. If you are sure you can hear the "sound" of the resistor-stuff inside a pot, then you want a very-good switch to go with your very-good resistors.
If you have to ask: go with the pot. Some mighty fine machines use pots.
If you are using an SSM chip- don't try to turn a hound-dog's ear into a Gucci hand-bag. The SSM is a fine beast, but kinda defines your project as something that doesn't squander lots of dollars in exotic parts. If you were building around the Jensen 990 or one of the SSL preamps, a cheap pot would be a sin and a very-very-good pot might be harder to find than a good gold switch.
