EF440 a little buzzy?

WorkBench · February 23, 2011, 10:57:47 PM

So I built the DOD EF 440 kit from GGG. It all seems great, but when I dig in on a note there is a buzzy sounds with the wah effect. It sounds like the effect is clipping! It seems that it is dependant on the sensitivity of my playing and input volume to the pedal. If the volume going into the EF440 is higher than I have a bit more headroom before the buzz occurs. Is there a way to change the sensitivity of this pedal? Thanks!

Chris

WorkBench · February 24, 2011, 10:44:13 AM

The volume pedal is after the EF 440, so it is not changing the input there. Would changing C1 adjust the input sensitivity?

thedefog · February 24, 2011, 11:42:09 AM

I've built about 4 of these and even had an original for a short period of time. They all had this issue. I never bothered to try and mod to fix it though. It generally happens when the sensitivity is turned up most the way (which is pretty much necessary to even get it to work right).

My solution to the problem was selling all of them and building a MXR Envelope filter. Similar character and sound, slightly more complicated built, but no harmonic distortion or crap, and it triggers much better than the 440.

WorkBench · February 24, 2011, 06:52:30 PM

There's got to be a fix here?!?

WorkBench · February 25, 2011, 08:24:54 AM

bump

SISKO · February 25, 2011, 09:39:30 PM

One way to increase the sensitivity of the effect without affecting the input signal is to increases the gain of the detector opamp, which is determined by R4, R5, C2 and R16.
I would start by changing R5 to 3.3M or 4.7M, just try deferents values until you get the results you are after

WorkBench · February 26, 2011, 12:54:36 PM

Thanks a ton Sisko! This got me on the right track, but I was after the opposite effect. I needed to decrease the sensitivity. I am trying lower values for R5. It seems to be helping but I need to set the pot right at the exact spot and play low notes alot harder than the high notes. I need more leeway for playing here? Also, is there a way to make the low notes more responsive, while not increasing the high note response?

Chris

WorkBench · February 26, 2011, 01:15:17 PM

OK, so R5 at 470K is working for me. It is still very senstitive. I find a sweet spot and if I turn my volume up just a touch on the guitar, it clips the pedal again. Then I have to compensate by turning the pot on the pedal down. The window of acceptable effect is way too small. Any thoughts?

Chris

SISKO · February 26, 2011, 01:32:46 PM

If you still need to increase the low notes sensitivity, then you should try increasing C2 to 1uf, or maybe 10uf With the negative lead pointing to the pot.

Its seems that you have a guitar with a lot of output signal and this seems to be the reason why the effect is clipping. To fix this you can try increasing R2 to 470k, try deferents values as before.

I apologize because I misunderstood the original problem. You can get around the problem by leaving the pedal with the stock values and making R1 larger.

So now, you can choose between leaving R5 = 470k and making larger R2, OR to leave the pedal stock and making larger R1
Sorry for any confusion, again!

WorkBench · February 26, 2011, 01:38:10 PM

No need to apologize Sisko! You have helped me out in a major way with this! Thanks! I will try the other options. I have 3 humbuckers in my guitar and a preamp in it, so it's active.

WorkBench · February 26, 2011, 08:15:52 PM

So, changing R1 to a larger value did not help the clipping, buzzy distorted issue. I ended up with R1 stock, R5 470k, and R2 180k. This seems to work best so far. Thanks again Sisko!

thedefog · February 28, 2011, 01:27:27 PM

When I first built this pedal, I thought I did something wrong because of the fizzing sound, so I got another kit and built another and had the same issue. I also tried minor fiddling around, but got frustrated quickly when I found it was still present. I'd love to see a working solution to this too. One thing I noticed this pedal does need though is something in front of it, like a compressor or an overdrive. Sometimes that negates the fizzy sound, as is the case with Jonny Greenwood.

WorkBench · February 28, 2011, 03:34:57 PM

The working solution seems to be to alter the values of R5 and R2. This is to balance with the level of output your guitar has. Worked well for me. Now I am trying the resonance mod that can be found here:

"The stock 440 envelope filter (you can see a project for it at generalguitargadgets) has controls for sweep width (envelope sensitivity, actually) and initial frequency. David notes that you can vary the resonance of the filter by altering the value of the 430k feedback resistor in the filter stage. He suggests adding a 100k trimpot in series with this resistor (which apparently is 470k in some units), although if you are building your own, a chassis-mount pot is a smarter option. See http://www.generalguitargadgets.com/v2/diagrams/ef440_sc.gif for the schematic."

but it seems to add a distorted sound when I put a 100k pot in series with the 430k resistor? Maybe too much gain here also. Maybe a lower value original resistor?

WorkBench · February 28, 2011, 08:04:46 PM

okay, I changed the feedback resistor to 330k, then put the 100k pot in series with that and now have a nice range of resonance to play with

WorkBench · February 28, 2011, 09:40:20 PM

Still looking for a way to get the sweet spot lower on the range knob when I have my guitar turned all the way up? Anyone?

Chris

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EF440 a little buzzy?