Mark Hammer Idea

[Kipper4]

I just tried it with a tremolo and phaser and it works as intended. It can be a little tricky setting the envelope gain so It functions as you want but it's still early days.
I can see this being useful for any 2 effects of your choice with provisos.

[Kipper4]

I've added a few bells and whistles.
Envelope sensitivity pot. Must be a BAP
also a pot to adjust the gain of the effect that kicks in.
Some adaptation to envelope gain.
Corrected the vactrol led in the drawing. Changed the vactrol to a ready made model.
Today is a good breadboarding day.
#CheersDino.

#Get me being all modern......

[StephenGiles]

Had my wife not been admitted to hospital for emergency treatment on dangerously infected leg ulcers I would have been able to speak from the breadboard, but unlikely for the time being as current regime of hospital/work/hospital seems open ended at the discression of Axa PPP's willingness to pay!

[Kipper4]

I'm sorry to hear that Stephen.
I hope she recovers soon.
I dislike hospitals. I also hope you get AXA to cough up.
Take care of yourself my friend.
Wishing Mrs Giles to get well soon.

I wish my breadboard spoke to me.
It would have said "Your wasting you're time tonight boyo, might as well pack it in."
I would have gone to bed a lot earlier last night.

Rich

[StephenGiles]

Thanks for your good wishes.

[EBK]

I'm sorry to hear that Stephen.
I hope she recovers soon.
I dislike hospitals. I also hope you get AXA to cough up.
Take care of yourself my friend.
Wishing Mrs Giles to get well soon.

+1

[KarenColumbo]

+1!! Hope she'll get well soon!!

[duck_arse]

me too on the get wells.

[StephenGiles]

Thank you all.

[Kipper4]

Because of the uneven number of op amps. I changed the input buffer to an N channel fet type.
Which meant adjusting the envelope gain again and the sensitivity pot more in line with the impedence. Or at least thats how I imagined it. So I changed it to much smaller and It's better.

I may well change the envelope to a darlington envelope.
I also lowered the bias point of the envelope to around 2v. Which should give me more swing.

I'm not sure if the led driver is going to work off the breadboard it too may need a biasing resistor to the +input pin.

Also on the cards is to try using the darlington envelope detector with an Expandora led driver.
Thanks for that one Dino.

More later.
Rich

[Kipper4]

Following something RG said.
http://www.diystompboxes.com/smfforum/index.php?topic=117220.0


I've hatched a new cunning plan.
I'm fishing for opinions.
Might this work with Toms OTA crossfader (Seen here
http://electricdruid.net/wp-content/uploads/2015/06/VCBigMuffTonecontrol.jpg
)

[EBK]

Following something RG said.
http://www.diystompboxes.com/smfforum/index.php?topic=117220.0

Some great discussion of OTAs and current mirrors in that thread, but it could have used some of Mark Hammer's award-winning analogies to jazz it up a bit more.   

I've hatched a new cunning plan.
I'm fishing for opinions.

I can't help but think that if you push that op amp buffer over so that it replaces the left hand transistor in that mirror that it is essentially where you started.  In other words, I think you're using more parts than you need to (something I do in every single circuit I design, by the way  )....  But, I haven't had my coffee yet.

[Kipper4]

Never mind the thread Eric. What dya think of what i've come up with? You think it will work?

[EBK]

Maybe you could give my tired brain a quick boost and tell me the max voltage you expect across C67.

My hunch is that this will not work, but again, coffee.
I'll expose my thinking a bit here, but no judging me if I'm flat out wrong right now.
When your voltage is at 0 (C67 fully discharged), your current will be (9 - 0.7 - 0)/47 = 0.177A, enough to destroy the OTA utterly.

[duck_arse]

I'm going to be of no help whatsoever and say - kipper, the ET env diodes are pointing 'backwards', and Merlin has used non-polar caps there. you might need to check the voltage generated and its polarity there, or just use poly caps and don't think about it. arse-about always confusels me.

[ElectricDruid]

I agree with Eric. I think the 47R in that current mirror isn't big enough. When that transistor starts conducting, the OTA is toast.

I've been wrong before though. But it never saved an OTA.

Tom

[Kipper4]

I had to go look at a milliamperes to amps converter. Ain't google marvellous.
From what I can gather the current would be in the 100x too large.
0.002=2ma.
Theoretically I therefore surmise I'm gonna need a resistor at least 5k resistor right?

Should I swap the 47R to 5k or use a series 10k to be sure on the current mirror output.
Thanks for any guidance you can offer.
I appreciate it.
Rich

[EBK]

No time for a thorough answer, at the moment, but a few quick things:
1. This one would be good to fully test without the OTA, so you can take some actual current measurements, to be safe. 
2.  It may be a good idea to throw some overvoltage protection on your rail here (that current is based on a voltage that is essentially referenced to your positive supply -- I'm not using enough words here to explain this properly)
3.  There will be some temperature dependence here, but I don't know if it would matter (this one just randomly jumped to the front of my engineering mind while I was writing the others)


Hopefully, I'll have time to take a better look later.

[Kipper4]

Well thanks Eric.
I already have my envelope detector on the breadboard and a box of breadboard transistors. Random bunch of raggle taggle things though they are.
Puts me in mind of going to see Bob and the wailers back around 1979.
I'll stick the DMM on the current mirror output and have a gander.
Cheers.
Rich

[Kipper4]

I use a regulated 9v power supply so most of the time. Don't encounter issues but I guess it might be wise to use a Zener over the power supply cause you never know who's gonna plug what into it.

I know zilch about temperature dependance. In fact I have two left feet I can't dance.