Anyone tried the Ramp up/down Mod for EASYVIBE?

[orangetones]

Anyone tried R. G. Keen's ramp up and down mod for the easyvibe?

[RickL]

I tried it a number of years ago on something (can't remember exactly what) and it didn't work as well as I had hoped it would.  I seem to remember that I couldn't get the range of up/down speeds that I wanted.  I didn't fiddle too much with values so it's quite possible I could have got it working better if I'd spent a little more time.

You might be able to find my report by searching with my name as the criteria (I don't post as much as some of the regulars) but there may be a fair amount to wade through.

[orangetones]

Thanks,

Was it this ramp up/down mod here?  or the LERA mod that he has on his site?

http://www.geofex.com/FX_images/ramp-lfo.pdf

[R.G.]

I'm guessing Rick was using LERA. His comments are correct - in some situations, the LDR change is either too big or not "biased" to the right middle of swing, or both; and both can be corrected by tinkering.

[orangetones]

R. G., are you referring to the LERA?  or also to the Easyvibe ramping modification your suggest on your site?

As well, I have a couple of questions if you don't mind now that you have responded to this thread.

1. I believe I can, but... can I use TL064's (or 74's) for this modification?  They seem to have the same pinout as the LM324 that you suggest.
2. The 470k variable resistor on the schematic... I would assume that you would just use a 500k linear pot or trim pot there. (how would I connect the lugs? 1 and then 2 and 3 tied together?, or just connect one and 2?)
3. The 2 speed pots, are they linear 10k? or log?
4. Are both transistors 2N3904?

Lastly I have heard that a reverse log pot is best for the depth control.  Any thoughts on this?

Thanks again for the help.  This is a fantastic forum for discussion.

[R.G.]

R. G., are you referring to the LERA?  or also to the Easyvibe ramping modification your suggest on your site?

My comments were about LERA.

As well, I have a couple of questions if you don't mind now that you have responded to this thread

.
Trust me to open my mouth and get into trouble... 

1. I believe I can, but... can I use TL064's (or 74's) for this modification?  They seem to have the same pinout as the LM324 that you suggest.

Sorry, you can't. The pinout is the same, but the circuit needs the opamps to have inputs which work correctly at the same voltage as the negative supply, ground in this case. The noted opamps do, but the TL0xx series cannot do this. They will not work correctly in this circuit. The magic words on the datasheet are "Input common mode range includes ground" or some other that says the inputs work when they're at V-.

2. The 470k variable resistor on the schematic... I would assume that you would just use a 500k linear pot or trim pot there.

Yes, a 500K would work fine.

(how would I connect the lugs? 1 and then 2 and 3 tied together?, or just connect one and 2?)

I disagree with numbering schemes for pots, as I've seen multiple different ones. I use CW, Wiper, and CCW. But either way you state works equally well.

3. The 2 speed pots, are they linear 10k? or log?

Good question, and one that I don't remember anyone ever asking before. I would use log. The reason is that the speed is linear with voltage, and we'd like the speed to change faster on a per-cycle basis as it gets faster. Log does that in this application.

4. Are both transistors 2N3904?

Actually, almost any modern high gain, low noise NPN bipolar will work if you get the pinout correct. Just make sure the specified DC current gain is 200 or more.

Lastly I have heard that a reverse log pot is best for the depth control.  Any thoughts on this?

Hard to say. I nearly always use linear first, and only go to a tapered pot if I can't get what I want out of a linear. I would handwave this issue, except it really will depend on the light/ma curve of the LEDs in the pedal and the ohms/photon flux in the LDRs. Both are semi- linear and variable depending on device.

The only good advice is - try it. I would use linear, change if needed.

[orangetones]

Thanks so much R. G.  You are truely helpful.  Your points are well taken.  I am looking forward to testing this out.  I will have to change my parts list (opamps) for the layout I posted here.  Have you seen the layout?  It is in a nother post further down:

http://www.diystompboxes.com/smfforum/index.php?topic=72068.0

I have not verified this layout yet, but am pretty sure I have connected everything up correctly.  Have to see if it jives when I solder one up.

Cheers

[RickL]

Sorry about the confusion, I was indeed refering to the LERA. I wasn't aware that there was an Easyvibe specific mod. I'll have to give it a try.

[orangetones]

Another simple (hopefully) question for R. G. or anyone about this mod. 

The two speed controls, it appears to me that they would have the same speed range.   Is this true?

If so, how would one go about having a limited range for separate slow speed and a fast speed pots?  Would you just need to sub in a smaller pot for one and then a fixed resistor and a smaller pot to get the other range?

Thanks again for all the help!

BTW I ordered the parts form smallbear that I needed, should be a fun build when I get them!

[orangetones]

R.G.?  Anyone?