What does this jumper between clipping paths do?

[DDad]

In the Mojito Deluxe there is a connection (in yellow below) between clipping paths on an op-amp gain stage. What does that do? Any clipping I have seen that has multiple diodes does not have that. Mojito Deluxe schematic I will eventually breadboard it to find out, but holding off on ordering parts right now.

 

[micmac]

I'd like to know, too!

 

[kd9998]

Theoretically not much. If one set of diodes is forward biased, the other is reverse biased with or without the bridge. There is a little junction capacitance added, but it's on the order of 4pF for 1n4148 and 15pF for 1N4004.

Paul Cochran, creator of the original Timmy pedal claims there is a subtly audible difference. Did you end up breadboarding to see if you heard a difference? I don't hear one if I add/remove a jumper, but I'm in my 60s and my ears are kind of shot anyway.
The first place saw this was in a Timmy/Timmy clone schematic where it allowed use of a SPDT with open center position to provide 2 options:
1) open - 2 diodes in each direction
2) short out a diode pair for 1 diode in each direction
3) switch in a single diode in one direction for asymmetrical clipping.

Search "Timmy clone Super-Freq schematic" for a drawing. There is also a bit of discussion in the various DIY forums and PaulC participated at times.

 

[drew.spriggs]

Basically nothing, unless your name rhymes with Saul Lochran

 

[HamishR]

Saul Lochran?? I went to school with him! Damn... I wonder how he's doing?

 

[HamishR]

If you see how the original Timmys were made you'll see that it was easy to solder one end of each diode to the board and just twist all the other ends together and solder 'em together. Maybe it was a time-saving thing that sounded "subtly better"?

 

[micmac]

Thanks everybody!

 

[Fama]

If you see how the original Timmys were made you'll see that it was easy to solder one end of each diode to the board and just twist all the other ends together and solder 'em together. Maybe it was a time-saving thing that sounded "subtly better"?

"I get more pedals done in less time? That does sound better!"

 

[paulc]

Basically nothing, unless your name rhymes with Saul Lochran

That jumper was used to short out 2 diodes - nothing more. Fsb was kind of brutal towards me back in the day. When they started talking about that link I played along with the stupidity and played it up. Lollar and other builders included it which had me thinking they really didn’t have a clue

 

[DDad]

That jumper was used to short out 2 diodes - nothing more. Fsb was kind of brutal towards me back in the day. When they started talking about that link I played along with the stupidity and played it up. Lollar and other builders included it which had me thinking they really didn’t have a clue

I am not sure this is correct (the diode clippers still work) - 'That jumper was used to short out 2 diodes'. Robert or Chuck or others who have that level of knowledge, care to contribute?

 

[VanWhy]

I am not sure this is correct (the diode clippers still work) - 'That jumper was used to short out 2 diodes'. Robert or Chuck or others who have that level of knowledge, care to contribute?

I mean, he is the guy that designed the pedal so I would think he's a pretty good source.

 

[DDad]

But it's not doing anything the clipping. Both clipping paths still function.

 

[jimilee]

so they guy that designed it is wrong? How’s that work?

 

[Aentons]

That jumper was used to short out 2 diodes

By "short out 2 diodes", do you mean something like this?

 

[paulc]

By "short out 2 diodes", do you mean something like this?
View attachment 114539

This is how I did it. For the Tim leave off the single diode and use a spst for 4/2 diode combinations. For the Timmy use a spdt on-off-on for 4/3/2 combinations.

 

[HamishR]

Paul, I really appreciate you taking the time to post. I'm sure we all do. (well, except for the weirdos) A lot of my player friends are huge fans of the Tim and Timmy. You have quite the fan club in Western Australia.

 

[drew.spriggs]

That jumper was used to short out 2 diodes - nothing more. Fsb was kind of brutal towards me back in the day. When they started talking about that link I played along with the stupidity and played it up. Lollar and other builders included it which had me thinking they really didn’t have a clue

Well that makes a lot more sense - I've never seen anybody include the switch to short out the diodes!

I've seen years of people stating including it (sans switch) lead to tonal differences that only they could hear, and used you as their evidence for it

 

[DDad]

In the original diagram in the first post, the jumper doesn't really short anything out - both clipping paths still function, correct?