[thesteve]

I dropped this over at DIYStompboxes...figured I'd drop it here for good measure.

I've been working on a 1590A enclosed FET-based Minimal Blender working off of the perf layout found here: perf layout for a blender?

and the schematic here: http://seanm.ca/stomp/minblend.html

A friend of mine wants to be able to blend a fuzz signal with a dry guitar signal. I am using a switchless design so the signal is always going through the entire circuit. I've been working on this off and on for awhile and have reached a point where I feel like I need to start over. Here's a description of what I've done and the results:

As of right now the circuit is put together as described in the perf layout, noting that the jacks in the layout are wired wrong, I have corrected for this and also connected all sleeves to the input ground. The only variation from the circuit I've made is putting a 0.1uf cap on the input instead of a 0.01uf. On the seanm page, it doesn't seem like this should be an issue. The JFET is the 2N5457. The pedal is powered by 9V adapter (Godlyke Power-All).

Right now when I plug into the circuit and have no pedal in the loop, the circuit passes signal just fine. As soon as I put a pedal into the loop, things get sketchy. My understanding is that this blender should pass the dry signal at 100% regardless of the setting of the knob. Instead what happens is that when I have a pedal in the loop with the pedal volume at 0 and the blender at 0 and the pedal on, I get a very weak signal through the output. With the pedal off, things go back to normal. I've tried this blender with a hand-built pedal a friend of mine made, and thinking that it could be a weird interaction with the pedal, I also tried it with a DS-1 and got basically the same result.

Has anyone else built this and had similar issues? I think at this point I'm ready to scrap the perf board in there right now and start all over, but I want to make sure that what I think the blender should do is actually what it will do. Any help I could get working through this would be really great. Thanks.

[thesteve]

Turns out my understanding of the functions of this box were a bit off. I was thinking that it passed 100% dry signal all of the time. How it is actually set up is to pass 100% dry in one position, 100% wet in another position and 50/50 (theoretical) in the center position, with variations within the sweep.

Here's some pictures I took...

[musicgoround]

Hey there Steve, just taking a quick look at the blender setup -- the "volume" knob is not a volume at all, but rather a blend or fader. Turn it all the way to one side and you will get the clean, straight tone, and cranked the other way you should get the sound from the pedal hooked up to send/return. It may not cut off the sound of either completely, but should be substantially diminished.

[S.B.Nichols]

On these types of blender circuits I always end up doing away with the 'blend' pot and using a dual concentric pot. Wire it up as a volume control on the dry circuit, and a reverse volume on the wet circuit. Connect the two outputs, and there you go.

[thesteve]

Hmm...that's an interesting idea SBN. Have you ever run into phase inversion issues with them? If so, what did you do about it? This one actually hit the problem the first time it got used by the person I made it for. The Guyatone TZ-2 apparently has some phase inversion so that when you have the dial set to be roughly 50/50 and the fuzz is in bypass mode, the clean signal is really weak.

[S.B.Nichols]

I've not run into that problem, but I can see that it could be an issue...I wonder if it would be as simple as adding a buffer after the return jack and before the pot.

I've not built this particular circuit....the one I've made for a few guys here is called the buff n blend (here). After making the modification of the dual concentric pot I have had no reported problems. I think tenwatt came up with a layout a few months ago.