DOD 440 (reworked-with mods)

[MAO]

I have modified johnk's original layout to include 3 mods: Resonance, Attack and Decay. (Mods suggested by Mark Hammer on DIY and noted at GGG)  

The nice thing about these mods is not only are they all effective, they are easily bypassed.  

Resonance: It was suggested to add a 100k pot in series with the 430k feedback resistor. I found 100k was to much and caused a distorted oscillation just after mid point (with the Range turned past 2 o'clock). I went with a 50k so the entire range of the pot would be useful regardless of the position on the Range control. Turning the pot fully counterclockwise bypasses this mod.

Attack: Add a 1K pot between D2 and positive side of C4. Slows the attack just the right amount.  Turning the pot fully counterclockwise bypasses this mod.

Decay: Switch in additional capacitor(s) parallel to C4. 4u7 and 10u were suggested values. I originally was going to use a DPDT on/off/on to choose between either additional cap, with the center position bypassing the mod. But I found the additional 10u was a bit to long of a decay for my taste. I went with just the 4u7 mounted on a DPDT on/on switch to either add in the extra cap or bypass it.

I also socketed the 2M2 resistor and the 100n at the Range pot, lug 2.

2M2 resistor: This value suggested by GGG increases the usefulness of the Range pot. I tried the original schematic's 470k and the Range pot was only useful the last 1/4 turn or so. With the 2M2, the entire range of the pot is useful and the effect seems more lively. However, the 2M2 resistor adds a bit of noise with the Range pot fully clockwise, which was the same result with a 1M8 and a 1M5 resistor. I stuck with the 2M2 as the additional tones from the Range pot are worth it (just can't go past 9 on the pot)

100n cap:  It was suggested increasing this value would help track lower notes better without adding additional lows to the output. I tried 220n and couldn't hear the difference, all notes tracked well with my Les Paul & Tone Zones, so I stuck with the 100n. Maybe it's useful for bass players, I don't know.

End result, added versatility to this excellent envelope filter. This pedal is a lot of fun and sounds great. Definitely a keeper.

Verified by me








   
         

[Silver Blues]

Very cool. This is a comparatively simple circuit for an envelope filter, I like it.

[MAO]

I was surprised on how well it sounds, literally played it for over an hour after I fired it up.

IMO, all three mods are worth adding.

[Silver Blues]

How'd you say it sounds compared to a Snow White? I really like the Snow but damn it it's a big bitch. So far it's my favorite of all the envelope filters I've researched, but if I can avoid the big board I will. (I like simple circuits with lots of functionality.) I'm asking as a bassist if it makes any difference, idk if you have any opinion in that sense.

[MAO]

Sorry, I haven't tried the Snow White, maybe John K will chime in. I seem
to recall he has modified quite a few effects for bass. And he originally
posted the 440 layout.

[Silver Blues]

No worries man. It certainly does look interesting.

[Muadzin]

Question: Is there any kind of LDR/LED combo that I could use instead of the VTL5C4/2. Those optocouplers can be pricy and I would probably have to order from a different supplier.

[clockman]

just bought these ldr.

https://www.ebay.co.uk/itm/Silonex-NSL-Dual-CdS-Light-Dependent-Resistors-Photo-Cell-NOS-Unbranded-Qty-10/133019686420?_trkparms=ao%3D1%26asc%3D20140728113935%26meid%3Da11c82d0f7d84be3b4503cb3a82ada43%26pid%3D100148%26%26itm%3D133019686420&_trksid=p2059210.c100148.m2813
I built  John K's layout and it works.
Very happy there's an alternative to the VTL5C4/2.

also while working with this I found that the very inexpensive and readily available GL5506 ldr also works in this circuit. solder two ldrs together in series and use a 3mm red led. space is tight but worth a try for the price.

good luck!
 quick revision, just posted the right Ebay link for product I bought. sorry if any confusion.

[kragg]

Hello,
Thank you for the layout.
I am about to build this circuit, and i would have one question : is the TL022 mandatory, or is there any alternative, giving similar results ?

[MAO]

Madbean used a 4558 in his SAWSE project and said it worked well.

The bigger issue is the obsolete dual LDR, others may work, but may not give the same DOD440 response.

[kragg]

Thank you, MAO.