loss of longer delay time when adding lfo to rebote2

[jmasciswannabe]

Hi!!
I am adding this aux lfo:
http://commonsound.org/tremulus/auxlfo_modulate.pdf

to this delay circuit (except for a 100k:
http://www.tonepad.com/getFile.asp?id=50

after reading this thread:
http://www.diystompboxes.com/smfforum/index.php?topic=28599.0

I didn't wire up the predelay and range pots and maybe thid would solve the problem, so I will do that next. My problem is that I can not get the longer delay times with the lfo added. All the way up on the pot on the delay pot gets me about a quartere ofthe delay i used to get.

Any ideas?

Thanks
ian

[DuncanM]

Have you wired up the LDR to go across the 1k resistor or across the 1k resistor AND the 50k pot?

I think it should just go across the 1k resistor - if it goes across the pot as well then the LDR will be in parallel with the WHOLE resistance that determines the delay time and can/will reduce the maximum delay time as you describe. It depends on the resistance of the LDR...

It may just be that one of the wires is going to the wrong side of the 50k pot and that swapping it to the other side will cure the problem.

I'll be interested to see how this works as I want to do this mod to my rebote2.5 to get that tape type modulation thing going.

[soggybag]

I tried this with a PT80 delay and it worked well. I put the LDR across the delay pot and switched the delay pot to 250K. The LDR at max resistance is very high. So the delay pot ends up being something a little less than 250K. I left the 1K resistor there since the PT2399 has a minimum delay time.

I used a VTL5C2 which has an off resistance of 1M. At max resistance it should be about 200K.

[jmasciswannabe]

soggy - thanks for the advice, I wired the ldr up in parallel with the 1k resistor and it worked. I am using the vcl5c2 for the led/ldr combo. Working out a few preferences with the rate and depth.....I will let you know how itturns out!

Thanks again!

[soggybag]

I left the 1K resistor as is and put the LDR in parallel with the 100K pot. I may be off in my thinking but, I think the 1K resistor sets the minimum delay time, so it should not change. The LDR in parallel with the pot varies the delay time set with the pot.

[stobiepole]

I did the same thing as soggybag. I made the LFO switchable, so that turned off it had no effect on the delay. I also added another 250K pot parallel to the delay pot which I labelled 'lo-fi', just for getting those extra long (but low fidelity) delays.

Chris

[soggybag]

With a second pot in series with the first you can set a minimum delay time.

Using the common sound LFO, which has a depth control, you can set the amount the LFO would effect delay time. It seems like this should set the range of resistance of the LDR. Turning the depth pot all the way down should leave you with a 1M resistance in parallel with delay pot.

I'm not sure if turning the depth all the way down completely removes the LFO though.

I'm trying to box mine up right now. I have the box done I still need to stuff everything inside and connect all of the wires.

[jmasciswannabe]

Frustration....the LFO has died. I am now getting no modulation at all. The light still flashes and I have replaced the vactrol and ic, checked all the traces and parts for continuity. It happened after I powered it down and powered it back up, so maybe the eletro blew. Haven't got to replacing it yet. While it was working I reallyl iiked the modualtion on short times a lot but couldn't get the delayed signal to go up in pitch (or down) on longer delay times. I had an old ibanez ad202 rack unit that did this.

Anyway, I put an fx loop in this sucker and I am pretty stoked. I placed it right after the 1uf and before 12k mixing resistor in the wet path. I have only begun messing with effects in the delay path but I love overdriing it so that you get a clean attack and then overdriven repeats.....killer.

[stobiepole]

You can try sticking an LED in to temporarily replace the Vactrol, just to see if it's doing anything.

I had to migrate my Rebote to a bigger box after pimping it out with too many options...you should try adding an expression pedal socket to the delay pot as well. That can be fun.

[soggybag]

I noticed on my Rebotes that they would not work if I had the repeats turned up to the feedback point when I turned it on. I'd hae to turn down the repeats and then plug it back in again. Maybe if the PT2399 gets over whelmed at start up it refuses to work?

[stobiepole]

You could use a momentary foot switch to temporarily bypass the feedback resistor. That way you get the nice dub reggae effects without any other fiddling.

[jmasciswannabe]

Allright....I finally got the LFO up and running again. I'm still trying to get more depth and speed out of it though. I am going to mess with some different pots and see what happens....but all in all this is turning out to be one hell of a stomp box. Stobie.....your last post reminded me of something I had read a while back where Mark mentioned a "tail echo mod"

http://www.diystompboxes.com/smfforum/index.php?topic=34587.0

Also I have got an itch to try to make a blend pot like on the memory man or at leat a dry level attenuator. If I have done my research right, then I think replacing the 22k mixing resistor with a 20k in series with a 50k pot should do the trick, for the dry level attenuator that is. If anyone has a better idea please do share! Having a blend pot would be great especially with the fx loop!