Adding High/Low Pass/cut to the Splitter Blend

[jammybstard]

I'm going to make a Splitter/Blend pedal to parallel some effects on my board.

The circuit seems good but I'd like to add the ability to cut frequency ranges from the send side of the circuit so I could for instance send Full frequency through distortion effects in parallel with high frequencies going through modulation efects and then re-combining (just an example)

I could either build it into the SplitterBlend or add an EQ pedal into each chain.

Are there any suggestions out there for an active EQ I could build into the Send circuit pref around a MPF102 (I have a few)

Any help appreciated

[Jeff B.]

Have a look here for some EQ ideas.
http://www.geofex.com/article_folders/eqs/paramet.htm

[jammybstard]

Cheers Jeff

From your link:


This sounds like an interesting alternative to a traditional EQ!

A notch filter with variable freq and width; that could work sweet.

I could use three TL072 to build the two channels, or possible swap out the first buffer for a MPF102 Tillman preamp type circuit!

Thoughts? Has anyone tried this type of circuit in anger?

[tjk3052]

Here's a schem of an eq pedal I designed. There is one knob to adjust the bass/treble balance similar to a big muff tone control, and one knob that actively boosts/cuts the center frequency. The center freq is set with a switch at 400hz (Fenderish), 650hz (Marshallish) or 1000hz (Voxish). If I remember right, I set the mid boost/cut at about +8db/-16db, and it gives a very usable range of tones. The last op-amp is a gain stage that also mixes an auxiliary input to connect an mp3 player or something.

It makes for really simple controls but also very effective. I made a layout for it on vero, if you're interested.

[jammybstard]

Thanks tjk; that looks interesting.

I think What I'll do next is build the Original SplitterBlend as shown at the top and get that working on Vero; Then I could quite easily jump off the Vero just after the buffer at the splitter stage and try some EQ ideas out on breadboard. I think that would work quite well on this build.

RE the original Circuit at the top: are the 10u Electrolytics used to decouple the output stage overkill?
Assuming an output z of 1M from the splitterBlend and an Imput Z of 1M for the next device. total Z would be about 500K.
F = 1/(2*Pi*R*C) = 1/(2*Pi*500k*10u) = 1/31 = 0.03 HZ

I'd rather use some of the polyprop caps I have;
I have 4u2, 2u2, 560n, 470n, 330n and on

How low do you think I could safely go?