Simple Tails mod for delays.

[LaceSensor]

I am not sure I understand.  If you get a minute can you make a diagram/snippet of schematic?  Thanks.

Foot switch:

1 4
2 5
3 6

4 = LED
5 = Ground
3 = VB

The VB connection is necessary because the Multiplex doesn't have a coupling cap at the PT2399 input and there's significant DC offset (~2v)

1 = IC1 pin 1
2 = Rotary A

6 is either not used, or you could use a 2-color LED to flip between bypass and delay

Cut the trace between IC1 pin 1 and rotary A. I'm pretty sure the trace is under the PCB.

In designs where there is a coupling cap before the PT2399s, you can use the simple shunt bypass I used in the Hamlet if you don't want to use Merlin's bypass scheme. That's what I did in my ZPSDX.

sweet, thanks

[LaceSensor]

can confirm this works. Cut the track on the bottom of the PCB coming off IC1pin 1 connecting to Central pin A of the Rotary
a nice VB connection is the positive side of C3. Tack a bit of wire onto that, its got some space next to it on the underside of the PCB too.

[timbo_93631]

With this you'd just wire the board in/outs direct to the jacks because you'd be switching between the sending the signal through the delay line or a path from the input direct to the output?  Could you use an optotron with this?

[LaceSensor]

Opto tron unrequired, just a dpdt switch as suggested.

[timbo_93631]

Thanks guys, brilliant mod.  My build is now in the 1776 build report sub-forum.

[Cortexturizer]

Hey guys, I was looking at adding tails to the cave dweller, but it looks different than the examples out there that this tails circuit has been used with. Any advice?

[kothoma]

Bad news. Here's what happens in the Cave Dweller:
Input goes into the first op amp (pin 16) whose output (pin 15) is internally connected to the delay line.
This output is also used to mix it (via R3) with the delayed signal (via R7) at another opamp at pin 13.
So with this design you can't simply switch off the input of the delay line without losing the dry signal in the mix.

[Cortexturizer]

Yeah, I was afraid of something like that. Well it's no biggie, I will just use it in a regular way then, it's not a dealbreaker for me.

[diablochris6]

There is a simple circuit that I saw a while back where you could route the signal clean or through an effect. It has very few parts (an IC and a few resistors and caps) and might be able to be designed to fit around a footswitch. I will try and find what I am talking about when I get home. If you are trying to fit the thing in a 1590a, it probably wouldn't work though...

[diablochris6]

Cortexturizer, here is the schematic I was thinking of. I saw it somewhere on the web and copied it down by hand. Unfortunately, I can't give whoever created this any credit since I can't remember where I saw it. I just drew it up in Eagle for more clarity. In theory, it looks like it could work for your predicament.

[mafew129]

Which cap would you replace in this layout?
http://2.bp.blogspot.com/-oPSs9IbXTPM/U_uPy7SeJAI/AAAAAAAAIg8/iUMKUKzsfrA/s1600/CultureJam%2BNeptune%2BDelay.png

Would it be the 1uf coming off of IC2 in the top left? Is that correct?

[madbean]

Not to derail, but there is another method for tails I've tried which works great. You can use this with a DPDT and make the other set of contacts switch an LED on and off. It doesn't pop. All you need to do is replace the coupling cap from the input stage to the delay stage with the little circuit shown. This will work on most PT2399 delays. If, however, you have another op-amp stage between the input and PT2399 (like a sallen-key filter) then you make the two resistors 1M and attach them to Vb instead of ground. In that case the circuit replaces the coupling cap and the biasing resistor of the second op-amp.

[mafew129]

How would you go about making a toggle switch to choose between trails bypaths
Bypass and true bypass?
I see there's something similar on page 2 of this thread, but will rhatbwork with the updated trails mod you just posted above ?

[Cortexturizer]

this is what puzzles me, why would anybody prefer having that switch anyway? what is there to gain with cutting your delays off and "preserving" the tone. I am not trying to initiate a debate or something, it's just, if you put that switch do you really think you will turn off the tails occasionally, really?

[Neur0]

Hi all,

As a novice, before I start to wrap my brains around this, is this mod also applicable in the Rebote3? (which I have already built, but not boxed)
Thanks