Rotary switch for NFB?

[funkgang49]

I am looking to install a 3-way switch to select between 3 different values of NFB, something like 22K/56K/75K on the front control panel of a SE amp I've been fideling with. I would prefer the 3 different choices as opposed to a variable control pot. What would I need to look for to implement this? Rotary switch?

[martin manning]

You could do a DPDT on-off-on toggle switch with a 72k across the poles and a 33k and a 120k that get paralleled with the 72k in the on positions.

[randalp3000]

http://www.tubesandmore.com/products/P-H395

[Phil_S]

If you aren't in a hurry, this is a decent price for just one Alpha switch, particularly because shipping is included, but it comes from China and you need to be patient.
/290968151201?pt=LH_DefaultDomain_0&hash=item43bf0da4a1
http://www.ebay.com/itm/1-3-pole-4-posi ... 2c6d071f71

Or if you like, I just ordered a 5 pack that should be here in a few days:
http://www.ebay.com/itm/251392659512?ss ... 1497.l2649
We can figure out how to share ;-} It looks like you will need to supply the washer(s) and nut.

These are 4 position switches (what I need). Just jumper the 4th position to the 3rd position so you don't end up with no contact or you can go for 4 values. I just tried for 3 pos switches on eBait and didn't see anything I liked.

[rfgordon]

You could also use a pot, as long as it's in series with a resistor that sets your minimum value. I do this a lot on amps because it gives great control over the headroom of the PI.

[Smokebreak]

Here's an Alpha from Mammoth that has a little locking mechanism washer thingy that allows you to select between 2-12 positions. http://www.mammothelectronics.com/ALPHA ... p2-12t.htm

[tubeswell]

What Martin said is the way to go about it. Keep a resistor permanently wired in and have other resistors switching in parallel

[Smokebreak]

You could do a DPDT on-off-on toggle switch with a 72k across the poles and a 33k and a 120k that get paralleled with the 72k in the on positions.

Oh wow that is a great way to do it. That would take up less space too, though I still like a pot
I had to draw it to make sense of it :

[iknowjohnny]

A rotary makes no sense when a pot can give you any degree of NFB from the maximum (set by a say 22k in series w/pot) to a minimum right where it barely even apparent. I'm using a no load so at minimum NFB setting with the pot all the way clockwise theres zero NFB. You have infinite control over how much or little NFB u want.

[teemuk]

But the effect is usually rather subtle and therefore doesn't require extreme fine tuning. Most people find a switch and few different feedback settings ample enough for the task.

[roberto]

I think it depends on the kind of customers will put their hands on.

I'd prefer a pot, but I've seen many people just ask for something simpler when I propose some pots, expecially for the NFB.

I'd go for the pot or the on-off-on switch.

[Ang3lus]

you should wire a pot first and test it, listen to the positions which have the most effect, check the resistance with a multimeter and put it on a switch, I have a /250k) pot now, and it's only really useful in one position, I had a 1M pot before and it was only useful in like 2 positions, no big change to no audible change at all in the rest of the positions, I want to make it switchable for 3 positions, which will be stock/mid-nfb range/no-nfb

[Roe]

best solution is resistor in series with pot IMHO

[Structo]

I use a switched pot on the presence in my 100w ODS.

When off the tone is very raw and louder.

[Phil_S]

Recommended reading: the sticky on Presonance control.