DAM Meathead mod - desirable but random side effect.

[Naefunk]

Hi everybody. Since you were all so helpful last time I thought I'd put it out there -

I switched the 2n3904 in my Meathead with a 2n5306. It sounds much nicer and "fuzzier".

Occasionally, when playing higher up on the fretboard, an octave kicks in for a moment and then drops back out.

I happens at random (seemingly) but it sounds great and I am wondering how I can exaggerate this or make it more prominent. Since it happens at random I am guessing it is to do with frequencies or build up and discharge somewhere in the circuit?

I feel like this would be a case of changing the values of components already in there but I don't know enough to know what to change or where.

Luckily it's quite a small circuit; exactly this :

but with the 2n3904 replaced, so it should be pretty easy to fiddle around with this without getting too lost.

Penny for your thoughts.

[roseblood11]

Have you tried to use a trimpot for biasing?

[blackieNYC]

I had an octave down that was doing that, and I couldn't get it to go away. So I discovered that if I hit it harder it would give me that octave more consistently. Try a big boost in front of it. A pedal for starters. I think I did the same with my octave up pedal too. Neither became very noisy. These worked out well - often this method can get you squishy and dull.

[mcknib]

From what I can see the 4K7 is what you'd want to change for biasing this being a fuzz face variant you could use sockets and try different values or as suggested use a trimmer which you can do off board as such, putting it on the board would require a wee bit of surgery - so get around a 20K (203 code) trimmer, join legs 1 and 2 together place 1 in the top hole of the 4K7 and 3 in the bottom giving you variable resistance and adjust till you get what you want.

Not that I'm saying changing the bias will give you a more pronounced 'octave' effect I'm far from an expert and it's a bit more complex than that I think - here's some great info from RG explaining how it's done rectifying the audio signal and distortion in general I'd advise having a good look around Geofex as a beginner

http://www.geofex.com/effxfaq/distn101.htm

You could also use a pot and if you're into going a wee bit mental with modding mark it for the 'normal' position on the enclosure and for where you hear the 'octave' effect the most, if indeed you do! then you can turn it on the fly if changing the biasing gives you more than one sound you like.

There are a few mods kicking about for this pedal changing the input and output caps using DPDT switches to get darker sounds and so on. Mod it and learn Nathan that's what I say! Go Mental.

http://tagboardeffects.blogspot.co.uk/2012/02/dam-meathead-with-switchable-caps.html



There are lots of people on here than know a lot more than me so hopefully some will come in with some more informed information. Strangely enough someone's just posted here re: octave pedals

http://www.diystompboxes.com/smfforum/index.php?topic=111787.0;topicseen

[duck_arse]

someone here recently was fiddling their input caps to increase the effects of blocking distortion, I think. you could thy going big on the 10nF at the input. maybe play with the 120k feedback resistor shown on that layout.