anderton ultra-fuzz blend output?

[shzmm]

hello
i recently built the craig anderton ultra fuzz from the epfm book.  i am using a 5532 opamp.  unfortunately i don't have a scanner to upload the image but i hope someone may have a copy here and could help out with this quuestion.
basically what i'd like to do is instead of using an output pot i would like to turn this into a blend control.  my inclination is just to connect one leg of the output pot with the dry original signal, the other with the wet signal output from the effect.  i am thinking that i will have to pad the effect output somewhat as the signal is very loud.
will this work ok?  or will i have problems with the disparity in volume between the two signals?  also is it better to use a log or lin pot for a blend.  i really like the sound of this fuzz but sometimes it is just too intense and i feel like adding a little of the original signal will help
thanks for any replies

[R.G.]

i am thinking that i will have to pad the effect output somewhat as the signal is very loud.

That's correct. You may also have to buffer the dry signal and worry about DC bias levels between them, or insert DC blocking caps on both sides of the blend pot.

will this work ok?  or will i have problems with the disparity in volume between the two signals?

You will have problems between the volumes if you don't make the two signals similar in size.

also is it better to use a log or lin pot for a blend.

Linear.

[Harry Palms]

At least you know you've built it correctly! That thing is loud.
I had the same thought as yours. Almost exactly.

I split the signal at input between the CA fuzz and a "clean" gain stage at OA1, fed this into OA2 set up as a buffer driving it's own volume control. This shared one side of the blend pot with the CA fuzz' volume on the other leg and the total output off the wiper. None of the parts values were critical as far as just getting it up and running. You can fine tune it later to what you want to hear. Not sure how you powered yours so it wouldn't help giving you a play by play setup. Mine runs on the bipolar supply and some people like to rework them on a single supply. Not sure what you did.

I never drew it out. You can do this a number of different ways. Mine's just a pretty basic setup but it works really well and it makes a huge difference on the versatility of this effect. You can better control the overall output of the fuzz side and the mixing in of the clean signal just takes this to new places. Go for it.

Just the fuzz here.



Sidechain add on here.

[shzmm]

thanks harry and r.g.
i think you have the same idea i had harry but of course you were able to implement it!  i was wondering if you could share a little more information about building the buffer stage, i.e. parts, layout.  i am also using a bipolar supply. 
i guess my second question relates to the seperate clean volume control-- do you think it's neccessary if i can adjust the fuzz and buffered output to be about the same? 
the problem for me is that i have built the effect already and can't really afford the space to put a new pot on the outside.  maybe a trimpot solution would work best?
thanks alot for your help

[Harry Palms]

Yeah, I'd recommend using the clean volume control. It's just a simple way of controlling the output of that stage otherwise you've got it running full on into the the blend section and it'll swamp the fuzz at some settings. Now you've got 2 overly loud signals crashing into one another. It depends on how much time you want to hunt and peck with that section's gain resistors. I'd use it anyway just to better control the mix at the output and it makes gain setting choices simple.

The buffer is a bog simple unity opamp follower. OA1 output into OA2 input via the RC network of your choice. 100k resistor to the OV line off the + input. - input tied to output. Output sent through RC network of your choice to lug 3 of the volume control. I only used it because I had the unused side of the IC sitting there. You can get away without it most likely. There's a lot of signal through a small chain with an already low output impedance. The IC was a TL072 I think. You'd have to experiment with it and listen to decide.

Very basic setup in all. Worked well. It should give you just what you're looking for.