Blend vs Stereo Potentiometer

[garfo]

What is the difference between a Blend pot and a stereo pot?I'll have to use a pot to blend two active signals(two low-pass filters, exactly the same circuits) with 1k of output impedance each.
I've always been told that a blend pot should be used here, but I can't seem to find a 10 or 20k blend pot.Would a stereo pot work?

[jkokura]

I'm not sure what you mean by 'blend pot.' Are you suggesting there's specific product out there calling itself a 'blend' pot?

Usually, a Blend pot is a linear pot with the outside lugs attached to two sources and the wiper providing the output. I personally feel this is a deficient system because inevitably the signal still leaks through from the side that should be blended out.

There are some solutions to blending that ground the signal that's blended out. Some of them, like the Panner/Paralyzer circuit I've released, do this with a single gang pot. There are some solutions that use a dual gang pots as well, simply using them as a pair of shunts to ground wired opposite from each other. I can't seem to find a link for more reading right now, but you can work it out if you already have an idea how this stuff works.

Jacob

[garfo]

Yeah,those pots existe, they are labbeled blend pots, usually for guitar.I will study you solution.thanks

I'm not sure what you mean by 'blend pot.' Are you suggesting there's specific product out there calling itself a 'blend' pot?

Usually, a Blend pot is a linear pot with the outside lugs attached to two sources and the wiper providing the output. I personally feel this is a deficient system because inevitably the signal still leaks through from the side that should be blended out.

There are some solutions to blending that ground the signal that's blended out. Some of them, like the Panner/Paralyzer circuit I've released, do this with a single gang pot. There are some solutions that use a dual gang pots as well, simply using them as a pair of shunts to ground wired opposite from each other. I can't seem to find a link for more reading right now, but you can work it out if you already have an idea how this stuff works.

Jacob

[garfo]

Have you got the link for that project?at first, my idea was to use ggg minimixer.it mixes two low impedance signals and combines them in a opamp.it uses two 10k volta pots for each channel.my idea is to use Only one pot, inatead of those two because this is going to be an onboard bass preamp.

[RobA]

Bourns makes the blend pots for guitar. As far as I know, they only come in 250k and 500k variety. I've got one in one of my guitars. Here's the data sheet, http://www.bourns.com/data/global/pdfs/PDB182-GTRB.pdf. The thing that differentiates them from a normal dual gang is the MN taper.

[garfo]

I was thinking, isn't using two volume pots, one for each preamp and than connecting them in parallel to a single master better than using a dual gang pot?
My main doubt is If is it really necessary to build another board.do you  know what I mean!?

[RobA]

The blend pots (also called balance pots sometimes, it might help to search with that term) that work well for this type of thing have a special taper on the two sections. When the pot is in the middle, both are at full volume. Moving the pot CCW leaves one side at max and lowers the other side to ground so that at full CCW you only have the max side. Going CW does the same thing except with the sides reversed. So, if you want to have complete control of the final volume, you still need a master volume to follow.  You can do the same thing with two independent volumes on the two sides. That would give you the same level of control as a blend followed by a master, just with the controls looking different. To me, in that situation, having the two independent volumes feels more natural.

If you don't want the master level control, the blend pot is a pretty slick control. On the guitar I have it on, I prefer having either one or both pickups at full volume all the time. So, a single blend works perfectly. On other guitars, where I want to be able to have both pickups on at say 3/4's volume, it makes more sense to just have two independent volumes.

[garfo]

Rob, that's what I thought the difference was.Wasn't sure though.At the moment I do have a true Blend pot in my bass and it wired passively, at the end I use a master pot.
Now I will built these two identical circuits and perhaps use a single true blend knob to combine both circuits.I'm not sure if the design deserves a post buffering between the blend pot and the master volume.