Modifying DOD Ice Box Chorus for Stronger Chorusing

[DaveM]

I'm looking to make my recently purchased DOD FX64 Ice Box Chorus less subtle.

Right now, when you slow down the LFO speed less than 10-o-clock, the chorus isn't very noticeable, even with the Level and Depth cranked.

Here is a schematic. (pdf) http://www.schematics.ca/modules/PDdownloads/display_download.php?img=http://www.schematics.ca/uploads/PDdownloads/dod_fx64_ice_box_stereo_chorus_pedal_schematic.pdf&title=DOD%20FX64%20Ice%20Box%20Stereo%20Chorus%20Pedal%20Schematic 

It appears there is always a clean blend going on in the pedal, and when bypassed, the wet signal is just disconnected by a J201.  So reducing the level of the clean signal (coupled to the output buffers [stereo] by C11) would affect the bypassed signal as well. So I'd need to increase the level of the wet signal.  I could do this by increasing the gain of U2A or U2B, which are a 4558 opamp. 

So the questions are, are all my assumptions correct here, and if so, which opamp should have its gain increased, and by changing which resistor values?

Thanks,
Dave

[Quackzed]

off hand it looks like u2a + u2b are indeed part of the effected signal, to make it stronger you could
1. jumper r21(22k), or use a lower ? 10k resistor at r21 for more gain for that stage at u1b
2. increase the gain going into u1b at u2b by making r27  20k-47k for more gain at u2b... some things to try

[DaveM]

Alright, so I so tried using test leads and a potentiometer to lower the value of R21.  That resulted in louder chorus, but not stronger chorus.  Likewise with reducing R35.  It seems I don't need louder chorus, but deeper chorus.  Time to mess with the LFO! I could mess around with the value of the depth pot, but it is a reverse log taper. Hurrah.  I'll have to play with the resistor values around the depth pot, and see what happens.  But I'll save that for tomorrow.

[Mark Hammer]

Um, that's how they work, basically.  When sweep rate is slowed down, the chorussing "effect" virtually disappears.    There is not really much you can do to intensify it at slow sweep rates, other than change the delay range so that you get audible pitch wobble.  But even that becomes less noticeable when the sweep rate is slow.

The most useful thing you can get from a chorus at slow sweep rates is if you have stereo outs, or rather wet/dry outputs, and can route the two signals to separate amps.  You can get some nice spatial swirl that way.  But forget about doubling.

The limitation is not in the circuit; it's in the human brain.

[zombiwoof]

Are you using a battery or an adaptor to power the pedal?.  I have an earlier Made In USA DOD Chorus, and it really needs to be on an adaptor to work the best IMO.  And I agree with Mark, when the rate is slow you have to raise the depth and res (or what ever it has for the feedback) to get a deep chorus.  On faster rates you generally lower those controls.  If that pedal is used, maybe someone messed with trimpots inside it, if it really isn't working right.  My DOD Chorus is great, and gets a nice deep chorus (it's a four-knob like yours), so I know the DOD chorus pedals are capable of that.

Al

[Quackzed]

and if you do want to try more wobble by increasing the delay range, c28 (50p) i believe is the delay cap. if you made it 150p it should make the wobble deeper, but as mark said, at very slow speed settings it may not be enough, and at high speed settings its likely to get 'seasick' wobble that you may or may not like... the depth setting cap is usually butted right up against the 3101, situated very close to the chip. thats where you should find c28, try making it bigger say 150p for starters and see if that gets you a bit more wobble at slower speed...

[DaveM]

Already checked for trimpots inside, nothing to adjust.  I also played around with C28., the delay cap, and by increasing it to around 250p, I've gotten the sound I was after.  It actually chrouses at lower speeds, and gets that "seasick" tone at high speeds and high depth.  Lower the depth a bit, and it tames back down. 

Thanks to everyone who lent a hand here!
Dave

[paulyy]

Im looking to mod my dod icebox but I noticed the traces on the board are really thin. Not sure if i want to attemt to mod this pedal. Now I know why theres not awhole lot on how to mod this pedal. I want to see if I can get a tremolo effect out of it or deeper fuller chorus.

[Quackzed]

i got a good choppy on/off type tremolo out of a rocktek chorus, which is pretty similar circuit, by hooking up the lfo to the flip flop, turned the pedal on/off/on/off fast or slow depending on the rate pot . you could search "rocktek chorus mods". and compare the schematics..