Theoretically very simple splitter box. Why won't it work?

[butter side down]

Hello good people,

I'm having a real head-scratching time with a design that should be fairly simple, and I need some help understanding why it's not working, and, hopefully, finding out if there's any way I can make it work.

First, a little explanation...

I have a Maxon AD999 analog delay pedal that has two outputs (one for the dry signal, and one for the delayed signal). If you just plug into the delay out, it mixes the signals, but if you plug into both outputs, it keeps the signals separated. I wanted to take advantage of this so that I could run the delayed signal through, say a phaser or chorus, and leave the dry signal unaffected. I realize that I could do this by using two amps, but I really don't want to have to lug two amps to every show every time I play. Plus that would mean that I wouldn't be able to run the two signals together to the same amp. So, I thought, hey, I'll build a little box that will act as a switchable splitter, that way I can enjoy the best of both worlds.

Here's a rough drawing of the unit I built...



Basically, when the switch is in position 1, the signals are split and the dry signal goes straight out, while the delay signal goes through any following effects before going to the output. When the switch is in position 2, the signals are mixed and go through the following effects together before hitting the output to the amp.

When I test it with a jumper cable between the effect out and the effect in (see below), it works like a charm.



BUT, once I hook up an actual pedal into the effects loop (see image below), it gets wonky. When the signals are mixed before going to the effect loop (switch in position 2), everything works just fine; however, when I split the signals (switch in position 1), the delay signal returns from the effect loop at regular strength, but the dry signal is very, very, very faint in the background.



I have checked each joint and I've got connectivity all the way round.  It's only when the signals are split and then rejoined at the main output of the splitter box that the problem occurs.  When I run into two separate amps (as below), both signals arrive at their respective amps full strength.



I'm fairly new to electronics, so I'm sure there's something obvious that I'm missing (impedance mismatch maybe?) but I have to admit that I'm not advanced enough to figure out what it is, or, more importantly how to correct it. Anyone here feeling patient or generous enough to explain the obvious folly to a newbie?

Any help appreciated.

[Morocotopo]

In drawing three, if your pedal inverts the phase of the signal, when you mix the delay dry out with the pedal´s out you might be getting cancellation because the signals are 180 degrees out of phase. Something to consider. Also, your drawing doesn´t show grounds, something else to keep in mind.
I´m not an expert, just suggestions. Hope it helps.

Morocotopo

[grapefruit]

Yes, Check the ground connections.

The problem is you don't need a splitter, you need a mixer. My guess is the output impedance of the effect unit is pulling down the dry signal of the delay pedal. A mixer on the output should do the job. Search here for mixer or splittter mixer for a schematic. One of the summing resistors will go from main out to effect in, the other from switch common to dry in. If the're 100k it should handle most phaser, flanger peadals.

Ideally you'd have a mixer for the dry/delay signal as well but because they probably have the same output impedance it's ok.

Stew.

[butter side down]

Morocotopo, you're right, for simplicity's sake I did not include the gounds.  They are there, though.  As for inverting the phase, that is a possiblility.  However, it hapens no matter what pedal I place in the loop (phaser, distortion, chorus).  Although true bypass pedals do not cause the problem when they're bypassed.  Still, I suppose it's possible that they all invert the phase when engaged.  I'll check and see if that could be the case.

Grapefruit, thanks for the tip!  I'l search for mixers and see what comes up.

[butter side down]

Ok.  Here's version 2.  Everything seem in order?

For the mixer section, I'm planning to try the MiniMixer (http://www.generalguitargadgets.com/diagrams/mixer_sc.gif) from the general guitar gadgets site.  I'm sure there's probably a better way to wire the switch also.