The Quackmire: A simpler vactrol LP envelope filter for 1590A

[rankot]

Never mind, I will try it, once I get PCB.

[rankot]

Built it, works like a charm! Unfortunately, didn't see v1.1 schematics in time, so this is without the switch (although I don't know where'd I put it anyway)





No gut shots, I forgot to do it when it was naked, now I'm too lazy to pull everything out.

[rankot]

Just to mention, I've rolled my own vactrol (for the first time), used 3mm orange LED with GL5516 photoresistor (bought at Aliexpress). Works fine.

And for those willing to build this baby, here's the PCB:



I even found some place to put a switch (see faint rectangle below RANGE pot), in that case don't put 10u tantalum on PCB, use 1u there and solder positive leads of 4u7 and 22u to switch poles, connect switch middle to point A and negative leads of those two caps to point B.

Unmarked part above BAT85 is 100mA PTC; above that is 3W 11V Zener diode serving as both overvoltage and reverse voltage protection, if you don't need overvoltage, just put 1n4007 there, or you can omit it completely if you don't need protection (and you can simply short PTC if you don't need that, too).

I suggest you to drill a hole for adjusting volume trim, so you can do it later w/o need to remove PCB from enclosure. In that case, use Piher or similar 5mm trim with top/bottom adjustment screw.

[rankot]

OK, here are the guts 

[sevrien]

Hello,

I've got an LM358 IC in stock, would it be a good replacement for the NE5533?
Pin layout seems to be the same.
I'm a complete noob in electronics so, I just ask.

[rankot]

Better use TL072.

https://www.electronicspoint.com/forums/threads/lm358-not-for-audio.243233/

[pinkjimiphoton]

hey ranko,
if ya get any boards burned for this, please let me know, i'd love to try one bro.
thanks!!

[Fancy Lime]

@rankot
This is officially awesome! I'll try and back-trace the new schematic as soon as I can. Great that you even found a place for the switch! Gotta get me some new etching solution and make me one myself. My own stripboard build has a bad contact somewhere, which I have not been able to locate yet. So I might as well just do it right.

@sevrien

I'm a complete noob in electronics so, I just ask.

Wlecone to the game! The LM358 should work (probably). Just build the thing with a socket for the opamp (which is always a good idea) and stick the LM358 in and see if it works. It can't do any harm. Worst case: it does not sound good and you'll have to spent 30 cents on a different opamp. I used the NE5532 in the design because it is a very popular opamp that many diyers keep around. It is cheap, low noise and is good at delivering a decent current into relatively low resistance at its output. If you want to intensify your diying, I would suggest to order some NE5532 next time you order something else anyway. The NE5532A variant has a certified maximum noise, the NE5532 (without the A) does not, but in my experience the difference is negligible in most guitar effects (there may be another letter following, like NE5532P or NE5532AP, where the P denotes the packaging. You normally want P for through hole Dual Inline Package). The TL072 suggested by Ranko is "the other" very popular opamp. It has a JFET input stage and therefore a higher input impedance, which is sometimes important (though not for the Quackmire). So get you some of those as well, they are also cheap. I would advice against the TL072 in the Quackmire, however, because in some settings the opamp may go into clipping and the clipping of the TL072 sounds quite awful (to me) compared to the NE5532. The (now discontinued) JRC4558 would probably also work and is also widely used in diy projects. But really almost any dual opamp can be used in the Quackmire and most should work just fine (there are hundreds of opamps on the market). The ones that I keep around besides the NE5532 and TL072 are NJM2068 (very low noise and relatively modest current draw but less output drive capability than the others), NJM4556 (or JRC4556, same thing different name, bit more noisy, very high output drive capability, good for headphone amps and line drivers and such) and TLC2262 (more expensive, rail-to-rail mosfet opamp that sounds very good when pushed into overdrive).


Cheers,
Andy

[rankot]

To be honest, I used OP275 for Quackmire. Also tried NE5532, but there was no audible difference (not for me).

It would be much easier to find a place for a switch if I had that in mind before drilling pot holes, now it is a real challenge! Wish me luck

[Marcos - Munky]

I'll try and back-trace the new schematic as soon as I can.

Is this one?

[pinkjimiphoton]

weird, can see the graphic here, but it won't actually load so i can snag it!!

[sevrien]

For who might be interested

[Fancy Lime]

I'll try and back-trace the new schematic as soon as I can.

Is this one?

Yes, that's the current version and should be the one corresponding to Rankos laste PCB layout, if I understood him correctly.

@Jimi
Maybe it works as a link:
https://postimg.cc/34FTvT52

@sevrien
Ooh, nice, a proto-board layout! I'll try and verify that one as well by back-tracing. Sorry if it may take a while, since I am extremely busy at the moment and hardly have the time to even glance at the forum once or twice a day.


Cheers,
Andy

[rankot]

I actually left one 1N4148 going from IC1a output to ground. Is it needed or not?

[pinkjimiphoton]

i can see the thumbnail here, it links to a page, but the image won't load, if i try to reload it or anything i just get a 404

[pinkjimiphoton]

changing ".org" to ".cc" doesn't work, comes up with an invalid certificate warning.
if you advance, tries to run an executable in the browser window.

be careful with that link. if anyone else has it, and wants to reattach it, i'd be grateful. thanks!

[Fancy Lime]

I actually left one 1N4148 going from IC1a output to ground. Is it needed or not?

Nope, that one is not needed, it has no effect. Was a design error in the first version.

@Jimi
Freshly uploaded, see if this works:



Andy

[pinkjimiphoton]

thanks andy and everyone else,
i'm stumped. i can get the thumbnail, but the page won't display the pic

check that... its freekin firefox or something.
got it fine with IE just now.
thanks much!!!
looks like its gonna be fun

andy, you rule dude!!

[sevrien]

Update,

found a fault in the power supply, corrected in this version

[rankot]

Finally managed to find a place for capacitor switch - used tantalum 1u, 4u7, 10 and 22u. Sounds cool.

Now I have a little problem with contact at input jack, when I push it to the end it loose contact, but I'm sure I'll fix it.