[Help] Phase 90 Ramp Up/Down

[Slade]

Hi,
I'm thinking on add the R.G.'s Ramp mod to a Phase90 I want to build, I want to make a PCB and post it here because I can't find one anywhere, but I have a doubt with the buffer.
Originally, in the Tonepad Pez 90's PCB, this circuit uses a TL072 at IC1 for the buffer, but in the mod's schematic the second opamp of this IC is changed for the second opamp of the LM358. I know the LM358 is vital for the ramp LFO, but I'm wondering now what could I do with the buffer

Am I missing something here?

Thanks!

[R.G.]

Am I missing something here?

Yes. Count opamp symbols and divide by two. On the Pez90 you get 3, and on the up/down Phase 90 you get 3.5.

There is one more half-opamp used in the ramp up/down circuit because the original P90 used the quick-and-dirty version of the integrator/Schmitt trigger oscillator by using a lone cap as an integrator. The ramp up/down version uses the full two-opamp version, with half of the 358 as an integrator and the other half as a Schmitt. That means that there is one half opamp that is unused in my ramp up/down version.

I personally would use that extra half to replace the PNP mixer. I deliberately left that detail out to make the changes less formidable seeming to beginners.

...I have a doubt with the buffer. Originally, in the Tonepad Pez 90's PCB, this circuit uses a TL072 at IC1 for the buffer

The buffer is still a TL072 in the up/down version. It's just that the original used half of the input-buffer opamp for the LFO. In the up/down version, a whole 358 is used for the LFO, leaving half of a TL072 unused.

[Slade]

Thanks, R.G., much clearer now, I'll make another PCB for this circuit then, if this works right I would like to post it here, hope you don't have problems with this.
Greetings.

[R.G.]

No trouble at all! I encourage anyone who wants to give it a go to do some layouts and share. Good for us all! 

I only get incensed about people sharing my work as their own. Your layout is *yours*.

[Slade]

Well, I have the layout almost complete, but I have a doubt now. I want to make this LFO switcheable with the sine LFO, but I'm not really sure what I NEED to switch.
I think I just have to switch the 10K r from Pin 7 of the LFO to "Open and Close"  and the 3M3 r to 15uF cap and to "ramp integrator". For this I'd need only a DPDT, but I'm not sure if this two poles are really needed to switch and don't know if there could be another thing to switch.
Any help is much appreciated!
Thanks.

[shadowmaster]

Instead of making the LFO's switchable being either of them is ON, why not make an option that makes both of them ON.

You might love the sound that would come out of you phaser if the two LFO's are fired-up together (I'm lovin' the sound in mine).

Just make the connection of the 150K resistor going to the FET's open or close. This should suffice I believe.

[R.G.]

I want to make this LFO switcheable with the sine LFO,

What sine LFO?

[Slade]

Instead of making the LFO's switchable being either of them is ON, why not make an option that makes both of them ON.

You might love the sound that would come out of you phaser if the two LFO's are fired-up together (I'm lovin' the sound in mine).

Just make the connection of the 150K resistor going to the FET's open or close. This should suffice I believe.

That's the other part of my build! I want to select between them and make them work together too. I think I'll try this by just joinning the two LFO outs together.
For now I'm wondering just how could I select between the two LFO's.
Thanks!

I want to make this LFO switcheable with the sine LFO,

What sine LFO?

I mean the stock LFO , I just want to switch between them.

[Slade]

Any more suggestions about this? 

[shadowmaster]

I used 2 two-position DPDT. One switching the stock LFO on/off and the other switching the ramp up/down LFO on/off. So basically I had an option where both LFO's are off which I think you really don't want. I used DPDT because I totally isolated the oscillator connections (3.3M going to gate of FETs and 150K going to source of FETs) to the phase shift stages which was not really necessary but can be beneficial for debugging purposes or so I thought. So I'll mention again that switching only the connection of the 150K going to source of the FETs is OK.

In your case, I would suggest using 1 three-position SPDT on-on-on or a three-position DPDT on-on-on (just use one pole) such that one side of the switch turns only one of the oscillators, the other side turns only the other oscillator and the center-position turns both oscillators.

[Slade]

Thanks for answering,

I think that switching the 150k that you mentioned would "turn off" any LFO I'm using, is it so?
Also I believe that the way to switch between the LFO's would be cuting the trace between the 3M3 resistor and the 15uF cap, and cuting the trace from PIN7 of the LFO Opamp to the 10K resistor, installing a DPDT (on-on) there that in one position [join the 3M3 to the 15uF cap]/[cut the trace between pin7 and 10k Resistor] and in the other position [join the 3M3 resistor to the ramp part, leaving the 15uF cap out]/join the pin 7 to the 10k resistor]. This two changes are the ones that make all the difference between the modes, am I wrong?

To make the "LFO mix" I would just mix the connections, sending the 3M3 resistor to the 15uF cap and to the ramp part also and leaving the 10K resistor connected.. Is it right?

Greetings.

[shadowmaster]

I get your idea. I built mine on the safe side. I used an LM741 for the buffer, TL074 for the phase-shift stages and a TL071 for the stock oscillator. I completely created the ramp-up/down LFO using LM358 thus the switching suggestion I gave you. So I have two completely separate LFO's and did not employ the "reuse" of opamp or switching out the integrator cap for the intergrator circuit.

Your idea should work if utilizing stock LFO alone or the LFO ramp-up/down alone but for the LFO mix option, I'm not too sure about it.

Let's wait for others to chime-in.

[Slade]

Yeah, that's exactly what i'm saying 
Would be nice if it could work this way, if not, I'll do it your way.
Thank you!

[Slade]

Anyone else have tried this? 

[Slade]

I'm wondering if there could be a way to make this LFO mix controlled by a potentiometer. Pot at minumum you have stock LFO and at maximum you have the ramp, at the center you have the LFO mix. Would it be possible to make? How?!.

[Labaris]

Hi my friend. Good to find you here!

I've been trying to solve this problem since we talked about the idea.
Here's what I've i got so far (simulated in Livewire):


Triangular


Sint

[Slade]

That's awesome! Thanks, I have to try it, when I do I'll let you know, my friend.

Greetings!