my snow white auto wah seems to lack sensitivity

[chemosis]

it dosent seem sensitive enough to fully open up the filter and seems a little dark and dull.the sensitivity knob does work though. I used the fuzzdog pcb with the r18 and c8 mods and also tried mpsa 18 ,bc550b,and now bc550c. maybe try increasing sense pot?

[chemosis]

i used a cheap cermaic cap for c12 100nf and 8.2k for 7.9 k but those are the only changes i made

[Kipper4]

A link to the schematic might encourage posters to reply more.

[Elijah-Baley]

i used a cheap cermaic cap for c12 100nf and 8.2k for 7.9 k but those are the only changes i made

I had just built this circuit. I used a 100nf ceramic, too, and two resistors in series replaced the 7.9k, getting 8k. Works fine.

Need your schematic. Try to make a check around the components close the the sensitivity pot.

[chemosis]

its the fuzzdog schematic. {7 of dwarves} i built another since i bought 2 pcbs and it works fine. the only difference between this one and the last is the 1n34a for diode 3 instead of 1n4148 and i used a box instead of cermic for 100nf. my new one works great but i would still like to get my old one working but i could be wrong about the sensitivity. maybe its to sensitive im not sure.

[Elijah-Baley]

http://pedalparts.co.uk/docs/7ofDwarves.pdf

I'd say 100nf ceramic or box cap doesn't matter (someone tells ceramic is better with a 78L05). I did the replacement of thatdiod with a 1N34A. (I made even that other two improvement on the pdf).
Check all components looking the two boards, if you have both. As usually, maybe a wrong value or orientation, check the wires and contacts. Check the pot sensitivity with your multimeter, values and contacts. Take a look to the solder side.

If you want post a picture of your boards. It will be like a game: find the differences.

It is you first PCB or first debug?

[Kipper4]

The mods are R17 C10 right? Not R17 C8

Changing R17 from 20k to 47k will reduce the gain of the op amp feeding the rectifier from a gain of 5 to a gain of 2.
Which may account for some of what your experiencing, maybe not.
Changing the charging cap C10 from 2u2 to 1uf will mean the charging cap will charge up and discharge quicker so you will probably experience less rise and decay time of filter action too.

C9 the 100nf is not in the audio path and is used as a power smoothing cap for the Vbias supply.
Ceramic or box should do. I wouldn't worry about it.

Without reading the datasheet said for the differant bjt you tried it's difficult to say what gain difference they made to the rectifier output.
Since they are arranged as a Darlington.

I built two of these and was never really satisfied with the overall effect. It works but it just wasn't what I thought it would be compared to the demo videos I heard on the tube.
Just my two cents.
It's hard to know what you want from an envelope filter, everyone's taste is different.
I hope you get it sorted.

[Quackzed]

yeah, r17  from 20k to 47k will lower gain/sensitivity, try the original value 20k or lower . 10k even... then dial the sens pot up/down and find a r17 value that gives you the range you want...

[Elijah-Baley]

I have to say I find this effect pretty fun.
Those mods should do what you write, we can find some information about it on tagboard and somewhere else.
Back to the originale schematic could be a solution to compare better the two boads, but one of those mod should do the sensitivity more useful and usable, just it.
Anyway, there is a video on youtube where the two versions is compared, and I can't hear much differences.
So, maybe there's just something wrong on the board.

[chemosis]

ok well i built another and it works fine so everythings good except for the fact that i love this filter and really wish it had more options. like how can i make the sweep stronger. how can i change the sweep. how can i add attack parameter. im not a fan of the mutron or its clones. there just not synthy enough for me but i love all the options that the meatball or riddle q balls has and i wish i could incorprate them into my snow white or add a couple more paremeters to the maestro fsh-1. i already know about the common mods for the snow white like the side chain mod and the couple others but what about other mods like i mentioned above. im using guitarpcb pcb. called super snow white. looks like i need mark hammer again lol.

[anotherjim]

Do check the voltage at the source of the input J-FET. It needs to be somewhere between 3 and 6 volts. This is the voltage across R4 (10k) in this scheme.

There seems to be something marginal in this design with the input J-FET - Q1, a 2N5457 in the scheme referred to above. The bias voltage on the gate can be too high for some examples of 2N5457 resulting in little headroom for any signal as the output on the source is fixed close to the + supply.

If Q1 is clipping at all, the envelope sweep will be less than it should be.

I for one have always had good results supplying the gate bias resistor (R3 here) from 0v with this J-FET instead of a higher reference voltage (Vr) as per this example...

True, it's usually best if the bias supply voltage can be whatever is needed to set the source voltage to +V/2 for maximum headroom, but how much higher? J-FET parameters vary so much from part to part, that you cannot exactly fix the bias and expect it to suit every part.

So if the J-FET source voltage is too high, either select a different J-FET (same or different N-channel such as J-201) or try connecting the gate bias resistor R3 (1M) to ground instead of Vr.

[chemosis]

the quackspike demo modded fx25 clone is awsome. im mentioning this because i heard theres alot of similarites between the dod fx25 and swaw and i love the sounds of the fx25. i never bought one because they dont have the controls a envlope filter should have. very limited control but the sounds even bigger and thicker than the swaw. IS there A WAy to make the swaw sound more like the fx25 b??? the swaw seems to have a weak sweep. just dosent go that deep.

[Kipper4]

Take both schematics side by side and compare the caps in the filter.

[chemosis]

thanks kipper. but im not sure what id accomplish by doing that??? sorry im good at soldering but im still learning basic electronics so i dont have the understanding you do. what do those filter sec caps do exactly???

[chemosis]

i know this is really old thread but ive finished another snow white and have the same old issue that ive had with other swaw. so many have had this issue and will prob have it again. thanks alot kipper. i get a weak auto wah sound with all the sense way down but thats it. all knobs work but most of my signal is way too clean. im using a swaw pcb from fuzzdog called the 7 dwarves.i changed q1 thinking it could be the issue. changed the mods back to the original including the diode mod. i will swap q2 and q3 soon the lm13700 check some voltages and tie the 1 m input resistor to ground instead of  +v. thanks again kipper