mini mixer tone sucker

[Neutral]

I built the mini mixer off GGG and it works fine exept for two issues.

1, I had to elimintate the 100k input resistors to get any volume out of it.

2, It sucks all the bass out of my tone.

Dose this mixer always change the tone?

I just want to blend two signals together evenly, without amplification, like a Y lead but with the inputs isolated, is there and eaiser way?

[Nasse]

Dont know if we have enough info to solve your problem, but smells like bad impedance mismatch or too weak signal at what is feeding your mixer.

Or it could (?) be something like cold joint or broken component in input circuitry. Are you sure that your caps are the right value??? Try with another 1 uf or something for input dc blocking cap. Sometimes mistakes or faults are very very difficult to find...

:mrgreen: I just had a six hour DJ gig few days ago with my very much similar self made mixer, and for that experience I know that such circuit should work well if you can fix it with correct components and connections. But dont use gaffa tape for construction like me.

[gez]

1, I had to elimintate the 100k input resistors to get any volume out of it.

2, It sucks all the bass out of my tone.

Replace the 100k input resistors, they're there for a purpose and this is the main reason you have no bass!  Increase the single 100k in the feedback loop (R9) for more volume.  If bass response is still poor increase the input caps to each 100k (they're a bit on the small side).  

Don't really understand why a buffer has been added after the mixer, it's a bit superfluous...

The input impedance isn't too high which doesn't helping matters, if you use a FET input amp you could increase all the resistor/pot values to improve this.

[gez]

I just want to blend two signals together evenly, without amplification, like a Y lead but with the inputs isolated, is there and eaiser way?

Inverting op-amp mixer is the simplest trouble free way to do this.  Seeing as you only need two inputs you can do away with J3 & J4 (plus all their connected circuitry)

[smoguzbenjamin]

I breadboarded the mini mixer from GGG, worked fine except for a little volume loss... I solved the problem by adding a small amplification stage at the end

[Neutral]

Increase the single 100k in the feedback loop (R9) for more volume

Ahh, under a decent light all is revealed. My R9 was a brown, black, black BROWN, (1k) not brown, black, black, ORANGE. (100k)

So with the input resistors back in place and my R9 at 100k all is working perfect.

I breadboarded the mini mixer from GGG, worked fine except for a little volume loss... I solved the problem by adding a small amplification stage at the end

You can also lower R13 for more gain. I halved mine to a 50k and it gives a moderate amount of extra boost.

Thanks guys again for all the support

[smoguzbenjamin]

Hmmm... once again my knowledge about op-amps in increased. Hell there might be a day that I can seriously design my own pedals without having to ask a dozen people, haha!  

Congrats on your successful build!