mojoDodo

I've got this multi-effects pedal, the zoom G1 for anyone who knows it, and it's got this control input for use with the wah-wah effect and many more. Basically i want to make an expressions pedal for this and from what i found out this is just a pot mounted in a pedal like those used for wah-wahs. I've got this 100K wah wah pot but seems like it doesn't work. Anyone have any ideas why this is please help out. Thanks. MojoDodo

Well unfortunately the biasing cannot be avoided in any way. The biasing is what allows for the transistor to amplify with no distortion. It could be made much better by using more sophisticated biasing circuits, but this means more transistors hence more space, not to mention the actual designing which is a real pain. One way to make a better amp is to use multiple stages, but again there's more components and a somewhat complicated design.

Hey pete, thanks for the reply. I sort of realised that might be the problem, and i plugged in my guitar just like you said. Unfortunately the problem is still there only slightly better than before. As for the transistor, i have biased it at 4.5V as required but i'll play around with that see if it helps. mojoDodo PS: the POT's i'm using in the circuit i have connected to the board using solid core wire that i've only rapped around the contacts. maybe there's not enough conductivity and maybe that explains the noise. I'll try soldering them and see what that does.

just a note of something i just realised. maybe the noise is due to the clutter i've created or maybe i have a defective breadboard, or maybe just bad connectivity of my components. oh and when i increase the volume i get this squealing sound which gradually becomes a buzzing kind of noise.

Hey guys, i'm having problems with the f/r amp. i've assembled the circuit on a breadboard seen as it's fast and easy. i tested the circuit with an 8 ohm mid-range speaker i have, with my laptop as input. the output is very very noisy unlike the clip i heard of a recording someone made. i set the gain to basically zero otherwise the output was even worse. if anyone has any ideas of why this could be i'd greatly appreciate it. i would include an image of what i have but it is way too messy and my mobile doesn't have macro mode for good quality pics.

Actually i always use a breadboard before i solder a circuit together. It's easy to use and everything comes off right away in case something starts overheating. As for the FET there's no way it could overheat as long as the bias current isn't too high, and in this case it's ok. The 100K POT will protect it. My only problem is that apparently using a BJT rather than an FET will not work. I recall reading a post about this, although it did seem somewhat unusual. I assume whoever wrote that doesn't know much about amp design. BJT's will work just as well as FET's only difference being that the biasing circuit must be altered. In the case of the f/r the 1M ohm gate resistor will have to be removed if a BJT is to be used instead. This is only used for FET's where a voltage rather than a current at the gate/base must be provided. In the post the person was replying to someone who was having trouble with the circuit. Turns out he was using a BJT than the FET's listed. That person replied that the BJT won't work, so i just want to make that clear: BJT's are equally capable for a pre-amp stage. Keep Rockin'!!! mojoDodo

Hey, so i've been looking around for components i need to make the fetzer/ruby amp for the sustainer, thing is though that i cannot find the required FET transistors in any electronics shop i know of. They're all n-channel FET's, and they're all general audio transistors, so i was thinking maybe i could just use any low voltage/current FET i can find. I searched and i found a low voltage/current MOSFET ( code: 2n7000) and is an n-channel enhancement mode FET. I am quite familiar with transistors, and i'm pretty sure this will work, i just need someone to basically confirm my choice. If anyone knows please let me know asap.

this definitely helps, i simply failed to realise the function of the circuit. i do know a thing or two about fourier theory, but it's good that you explained all this for the greater good. i agree 100% percent with you on the 'test before you install' mentality, i've had problems in the past too. i do have an idea, though, about creating harmonics. i don't know if you are familiar with PLL's (phase locked loops), but one way of creating a tunable output is using one such circuit. a good thing with this type of circuit is that it has a feedback loop and allows for the incoming signal to be locked and therefore sustain that specific frequency. the only downside with this is that a proper good quality design costs a bit. a cheaper design can be made but i cannot guarantee the results will be respectable. now if someone simply wants harmonics of higher order, then a simple frequency divider can be used to emulate this. i know it's nowhere near what it really is, or what it should be for that matter, but i'm sure i could get something interesting out of this. i'll give it a try this summer and post with any respectable results. as for the PLL, this needs alot more work and design so, unless someone's already done this, i'll be trying out some designs see where it takes me. give me some feedback on what you think of this, i'd greatly appreciate it. the lead reversal/phase switch method is not bad, yet it only gives a mixed output. with a PLL this can be fixed, giving true harmonic output, and in conjunction with the phase switch method you get a full sustainer kit. be prepared, though, coz PLL's aren't easy to build. cheers, mojoDodo

Hey pete, thanks for the reply it's alot of help. As for the harmonics, i do know a little about filters so i could probably get something on filtering to give more than just harmonic/mixed output, maybe some sort of tunable harmonic output. As for the phase switch i don't quite see how this gives harmonic output. I assume that the lead reversal you said is basically phase switching. Some help here would be great. mojoDodo

one other thing i forgot to mention, i'm interested in driving the sustainer with an amp that can give a harmonic output. if anyone has any designs please let me know, i'd love to have them.

hey all, i'm new to this forum. i'm glad i found it though, it's got so many things i can do with my guitar. being an electronic engineering student and all this stuff is just cool. anyway back to my question. i've read some of the pages on this huge thread, but i'm not quite sure about one thing: does the driver need a blade iron core or can it be made using the little bobbins found in a pickup? And also, could i just use one of those magnets found on a guitar pickup with or without a core? Also, i'm interested in making a circuit that will give me harmonics as well, if anyone has something i'd appreciate it. One last thing which isn't directly related, i'm thinking of making my own pickup but i'm not sure what thickness wire to use. anyone knows just reply.

Hey all, i'm new to this forum. i know my way around electronics but i'm having a little trouble with the sustainer. Firstly, from what i understand the driver must be relatively thin (height wise), but this means if i were to use a magnet and an iron core it would come out at least 1.5cm in height unlike what i've seen around. Secondly, what thickness wire should i use for this. And last, i'm thinking of making my own pickup, what thickness wire should i use in that case?