Help: Stereo to Mono Summing Box with 4PDT Switch

[jb1]

Hi everyone!

My name is Juan and I'm giving my first steps into DIY. I'm a guitarist and pedal enthusiast.
I just downloaded the almighty "DIYLC" software and did this layout for a "Stereo to Mono Summing Box with 4PDT Switch". The values and wiring are based on a RANE article I found online ("WHY NOT WYE").

The general idea is to make a box for the end chain of a pedalboard that would have a stereo pedal plugged in all the time (i.e. a TC Electronic HOF Reverb) and with the flick of a toggle switch be able to make it Mono (both outputs the same sumer signal) if I'm going to only one amp or keep it Stereo (true bypass) if I'm going to two amps or a mixing desk.

I read that with higher values resistors you get better stereo separation but you can't drive long cables and with lower values resistors the other way around. I've seen the same schematic with 470omhs, 1k, 10, 100k... I'm a little confused there. My idea is to drive a buffered signal (from the reverb and the rest of the pedals) to a guitar amp, so cables would be like 5/6 meters (16/19 feet) long at maximum. Of course the ideal would be a great channel separation with any sound loss for the length of cables/setup.

Can somebody check it for me and tell me if it's ok? Share your thoughts on the values if you think they could be better ones.

Thanks to all in advance and since is my first post, if I'm in the wrong forum or thread just let me know and Ill change it/move it.

Best regards to all.
Juan

[ashcat_lt]

When you're summing the signals, you don't want stereo separation.  When you're not summing, the resistors should be completely out of the picture.  Use the smaller ones so you can drive anything, including line and even some mic inputs.

[PRR]

> how to attach a pic to be visible

A PDF file is not "a pic". This forum does not support PDF viewing inside a post (which is probably a bad idea anyway).

Link is fine.

Or extract/convert the part of the PDF to a GIF, PNG, or (worst) JPEG, post that to a public server, and use the IMG tags.

FOUR POLES??

Either of these will work fine:

[jb1]

When you're summing the signals, you don't want stereo separation.  When you're not summing, the resistors should be completely out of the picture.  Use the smaller ones so you can drive anything, including line and even some mic inputs.

Hi there. You're absolutely right! I don't know why I was worried with stereo separation when the resistors are out of the circuit on the "stereo" side of the switch . I got confused with a really simple thing jaj.
Do you think 470Ω resistors RANE suggests are fine?.
Do you think the wiring it's correct?

Thanks a lot for your help.
Cheers
J

[jb1]

> how to attach a pic to be visible

A PDF file is not "a pic". This forum does not support PDF viewing inside a post (which is probably a bad idea anyway).

Link is fine.

Or extract/convert the part of the PDF to a GIF, PNG, or (worst) JPEG, post that to a public server, and use the IMG tags.

FOUR POLES??

Either of these will work fine:

Pics: Got It! I couldn't make it work in the aronnelson site but I followed your pic address and did it with tinypic. Simple and easy. Thanks!

Circuits: So on your SPST circuit you basically use the switch to short the two channel together and you put the resistors before the switch right? Pretty clever. As you stated, the signal coming from the stereo jacks are from pedals (ON) yes.
But what about the sound? is there any changes with the resistors on the path (because I understand that this circuit is not true bypass).

I don't understand the second drawing with DTDP sorry.

Thanks a lot for your help.
Cheers
J

[Fender3D]

The 2nd drawing, switches resistors off when in stereo mode
and, of course, "inserts" them when in mono mode.

But what about the sound? is there any changes with the resistors on the path (because I understand that this circuit is not true bypass).

2nd drawing will get rid of this...

Anyway, you may get very heavy change in sound if your stereo pedal plays with phase inversion to achieve the stereo effect

[jb1]

The 2nd drawing, switches resistors off when in stereo mode
and, of course, "inserts" them when in mono mode.

But what about the sound? is there any changes with the resistors on the path (because I understand that this circuit is not true bypass).

2nd drawing will get rid of this...

Anyway, you may get very heavy change in sound if your stereo pedal plays with phase inversion to achieve the stereo effect

Hi there! the second drawing makes more sense then, but i can't understand the wiring. Can somebody please quick draw it on top of the switch as i did?. Sorry for my lack of knowledge on this...
By the way, I don't think it would be problems with the phase inversion you mentioned because the stereos pedals are a Strymon Timeline Delay and a TC Hall of Fame Stereo Reverb. As far as i know any of those have the phase inverting thing.

Thanks a lot for your help.
Cheers
J

[PRR]

> Strymon Timeline Delay and a TC Hall of Fame Stereo Reverb. As far as i know any of those have the phase inverting thing.

Simple audio toys (without time-effects) may pass signal straight or inverted.

Mixing straight and inverted will cancel.

TIME-based toys, the whole concept of "phase" or "polarity" is totally messed-up. For many-tone speech/music, there is no simple analysis and in practice this is not a problem.

The output of a rich reverb comes through at all possible phases and wide range of time delays. When mixed with itself (or another reverb set slightly different), the sum adds and subtracts all different ways. The average energy is unchanged by the mixing. Specific frequencies at specific instants may come out louder or softer, but overall mixing does not harm (or really change) the signal.

Delays can be simpler. For an extreme case, a 3-Minute delay comes back so late it can't possibly interfere with the straight sound. Short (20mSec) delays will add/cancel, the same as playing against a hard wall 10 feet away. The sound is different but not wrong.

Anyway the switch-box is so simple, you should just hay-wire one and try it.

[ashcat_lt]

The 2nd drawing, switches resistors off when in stereo mode
and, of course, "inserts" them when in mono mode.

Hi there! the second drawing makes more sense then, but i can't understand the wiring. Can somebody please quick draw it on top of the switch as i did?. Sorry for my lack of knowledge on this...

Why don't you give it a shot and post it for somebody to review?  Best way to learn sometimes is to work it out yourself, and this kind of simple thing is a good place to start.

[jb1]

The 2nd drawing, switches resistors off when in stereo mode
and, of course, "inserts" them when in mono mode.

Hi there! the second drawing makes more sense then, but i can't understand the wiring. Can somebody please quick draw it on top of the switch as i did?. Sorry for my lack of knowledge on this...

Why don't you give it a shot and post it for somebody to review?  Best way to learn sometimes is to work it out yourself, and this kind of simple thing is a good place to start.

I will!!! I have my parts coming in the mail next week. I'll try the SPST and the 4PDT I draw and compare the difference in sound between them. The one I don't quite get is the wiring on 3PDT, I understand the concept but can't figure out how to wire it...
I'll post the results when I'm done for sure.

cheers!
J

[jb1]

FOUR POLES??

Either of these will work fine:

Hi there. i've been trying to translate your last drawing (summing stereo to mono with dpdt switch) to a clear wiring (for me ). Is this ok? Would let pass the signal true bypass when up and mix it with the resistors when down?
Thanks a lot for your input.
Regards, J

[ashcat_lt]

That's not gonna work.  In the pencil sketch, the four dots furthest left are the four outside (top and bottom) lugs of the switch, and the two that are indented with arrow coming from them are the center lugs.  The top "triangle" made by those dots is one side of the switch, and the bottom is the other.

[jb1]

That's not gonna work.  In the pencil sketch, the four dots furthest left are the four outside (top and bottom) lugs of the switch, and the two that are indented with arrow coming from them are the center lugs.  The top "triangle" made by those dots is one side of the switch, and the bottom is the other.

I see. Something like this then?



Regards,
J

[ashcat_lt]

Nope.  Both resistors go from their top lugs to their middle lugs.  There's a jumper from the bottom left to the center right.  The bottom right is not connected.  Leave your in and out wires where they are.

[jb1]

Nope.  Both resistors go from their top lugs to their middle lugs.  There's a jumper from the bottom left to the center right.  The bottom right is not connected.  Leave your in and out wires where they are.

AaaH! How about this one?



Regards,
J

[PRR]

> How about this one?

Yes.

Here's what I was gonna post before a friend showed up. You posted while I was image-whacking (arg).



The two are equivalent.

[jb1]

Hi guys!

Thanks a lot for the confirmation and the general help. It's amazing how this little switches can have so many combinations (at least in my head ).

Thanks again to all.
Hugs,
J