Mark Hammer Idea

[Kipper4]

So Mark suggested something like this. At least that's how I read it.
If it's incorrect Mark please say.

The idea being that when played with a less dynamic style the effects sound normal amplitude but when played harder it triggers the envelope detectors variable resistance and creates deeper notches in the effects.   

By deeper notches I guess you mean more amplitude.
Shout up If you guys think it's something you guys think you'd want to build too.

Rich

[Mark Hammer]

Think of it this way, Rich: the LFO is always working, but the pick attack determines what the LFO is doing.  If you're playing hard, you get to hear the LFO sweeping phase-shift stages, and if you back off a bit, it settles into tremolo.

So, it's very much like your notion of morphing from one effect into another via envelope control, but the two morphed effects share a common LFO.

In many respects, it would be a less jarring transition.  And in other respects it could also be something that appears to play a trick on the ear, because the modulation rate would remain constant, but the listener would mistake the constant rate for a constant effect, potentially resulting in a "Wait, did I just hear what I think I heard?" reaction.

But yes, your diagram captures the signal flow perfectly.  Consider it the aural equivalent of what gets called "trompe-l'oeil" in the visual arts. https://en.wikipedia.org/wiki/Trompe-l%27%C5%93il

PSYCHOLOGY!

[Kipper4]

Thanks for the clarification Mark.
I got it now.
I can be done in a similar fashion to the EnvoBlender I'm sure. However I fear it won't be as clear cut as one might think since you always get some bleed/blend of the two signals.
Once I'm done with the EnvoBlender I'll put my thinking cap on and research some likely candidate circuits to work with.
It might be an idea to use an op amp lfo. Some I've seen have dual wave options, triangle,square.
I also plan to look at AnotherJims soft delay and preamps over the coming weeks. Those little cd4007ub circuits sound mint.
Thanks again and all opinions and ideas greatfully received.
Dig in

Rich

Ps Mark did you listen to some of the other demos on the tube?

[ElectricDruid]

Nice idea. It feels to me like there must be a way to use one combined circuit rather than a separate phase-shifter and tremolo in parallel. I mean, aren't they pretty similar, fundamentally (ok, not *that* similar). But with a bit of tweaking?

The phase-shift stage is basically a differential amp. If the cap in the standard op-amp phase-shift were a resistor, the stage would be a tremolo, wouldn't it? (since the resistor to ground is variable).

That would change the problem into cross-fading between something that acts like a capacitor and something that acts like a resistor.

Dunno. I'm not there yet, I realise, but I'm sure there's a way to do it just out of reach.

T.

[Kipper4]

Maybe a flux capacitor Tom?

[StephenGiles]

Aha, ETI tech tips had a similar idea I put on paper back in the 1980s if anyone can find it!

[ElectricDruid]

Maybe a flux capacitor Tom?

I've got one here in the workshop somewhere. I think I left it behind the box of dilithium crystals.

T.

[StephenGiles]

Aha, ETI tech tips had a similar idea I put on paper back in the 1980s if anyone can find it!

It was CMOS Fuzz/Tremelo in ETI September 1982 Tech Tips, I can't find my copy though.

[Kipper4]

Thanks Stephen.
I'll look for it.

[samhay]

>It feels to me like there must be a way to use one combined circuit rather than a separate phase-shifter and tremolo in parallel.

If you take an op-amp phase shift stage (Phase 45, 90, etc, etc.) and short the feedback resistor between output and (-) input, the dry signal is removed and you get a variable low pass filter. This can sound quite nice and might be suitably tremolo-y.

[StephenGiles]

Thanks Stephen.
I'll look for it.

It's here! http://www.americanradiohistory.com/ETI_Magazine.htm

[Kipper4]

Excellent thanks guys.

[Kipper4]

As Baldock says
"I have a cunning plan."

[ElectricDruid]

>It feels to me like there must be a way to use one combined circuit rather than a separate phase-shifter and tremolo in parallel.

If you take an op-amp phase shift stage (Phase 45, 90, etc, etc.) and short the feedback resistor between output and (-) input, the dry signal is removed and you get a variable low pass filter. This can sound quite nice and might be suitably tremolo-y.

That's exactly the sort of thing I had in mind. Thanks.

That Fuzz/Tremolo actually does a hard switch from one to the other, if I'm reading it right. It'd be nice if you could get a softer fade between the two effects based on average level. So if you were to replace the feedback resistor in the op-amp phase shift stage with an OTA-acting-as-a-resistor, you'd be able to cross fade from phase shifter to lowpass.
I know the OTA-as-resistor thing works best if one end of the resistor you're replacing is grounded. Does it also work if that's a virtual earth not a real ground point?

Still, at this point, the circuit is perhaps getting complicated enough that there isn't much to be gained over a two-circuits-in-parallel approach.

Tom

[Kipper4]

For Instance.
What about if I used something like this to effectively make R15 very small (negligable)
Would that do the trick of nearly a short or just lower the gain.
Or do I need to completely remove R15 for the effect?
I still havent looked at the article. Just supposing......

[samhay]

That could work.

If it's easier to light an LED rather than make it dimmer (with the signal envelope) you could move the LDR so that it is in series with R14.

[Kipper4]

That could work.

If it's easier to light an LED rather than make it dimmer (with the signal envelope) you could move the LDR so that it is in series with R14.

Either is easier light or dark. It all depends on led orientation and to which rail, with the envelope I have in mind.
Good idea Sam.
Appreciate the input. I'll bare this in mind when I come to the breadboard stage.
Rich

[StephenGiles]

Don't forget that in 1982, ETI were paying £20 for any old drivel to put in Tech Tips. I took as much advantage of that as I could. However, I did have the Cmos Fuzz/Tremelo working..........but I was so much older then, I'm younger than that now!!!!!

[Kipper4]

Thanks Stephen.
I'll look for it.

It's here! http://www.americanradiohistory.com/ETI_Magazine.htm

Noted and printed off Stephen Thanks.
Inverters hmm intresting. I've only used them in one distortion.
Looking like a whole new world of possibilitys.
Cheers Rich

[Kipper4]

I've been diving into some research for this. Part of that turned up this.


Credit to Tom

This is going to feature in the early breadboard stages because of the low parts count and lack of crosstalk.
Next will be putting it on the breadboard with an envelope detector controlling the crossfade voltage divider (pot in the above).
Sounds so simple right.......