Buffered Blend question

[mhoss32]

Wondering if any electrical Gurus have any insight on a couple of questions

I came across this schematic of a buffered blend pot deisgned to take inputs of different Impedances and/or outputs

 

I have 2 questions
1: would it be possible with this schematic to replace the 10k pot with a 3 position switch? like a normal pickup selector switch but with the advantage of working with very different pickups?
2: if you had 2 individual pickup volumes upstream, would there be a big/noticeable drop in output volume if the switch was set to both pickups, but 1 pickup was at 0 volume?

 

i know these are kind of odd questions haha, its for a pretty unique application

 

thanks in advance if anyone can help!!

[Bigguy2017]

1. Yes.

Both op-amps are shown unity gain so one might need an input resistor (Rin) on pin5 and a resistor (Rf) in the neg feedback loop (pin 2) to match the levels with differing pickups.

Gain = Rf / Rin

2. If vol pots were before the op-amps then no, as U1 is acting as a buffer.

[mhoss32]

Ah awesome, thanks for the response!

the application is quite a bit different to the intended purpose, im wondering about having individual 2 band preamps for each pickup, and then feeding them through the buffered blend to ensure there weren't substantial differences in volume.

in theory would this work? and how would it sound if one pickup was run passive and the other through an active preamp before the blend control?

 

 

[itu]

If you have a preamps already before the blend, you can use a simple blend pot (Bourns 250k, or 500k MN), as the outputs after the eqs are lo-Z (low impedance).

If you want a lo-Z ("active") blend, you can buy a Noll Mixpot. This works with hi-Z and lo-Z signals. There are individual level settings for both inputs in the PCBA.

It can not be said that the two entities push similar levels, as the eqs can push lots of extra. (Volume could be understood as a full freq band eq, and individual eqs as partial freq band volumes. Confused, no?) You do can match the levels at certain settings (eq pots @ center detents).

[mhoss32]

I Think i Understand, forgive my slowness

the practical question is, if i had 2 pickups, each with their own 2 band EQ and an active/passive switch, would this be a reasonable way of ensuring that if 1 pickup was in active and the other was in passive, there would still be a reasonable blend of both?

and if not is there a solution?

here is an outline of the setup im thinking about:

this is based on using 2 identical, passive pickups

[itu]

Looks functional. You might benefit from Mixpot, because it includes level adjustments for both channels. Not overly expensive, but you have to be careful with soldering. The PCBA is a bit crowded.