Members tape Posted February 10, 2009 Members Share Posted February 10, 2009 I only see a total of an 8-pin opamp there the ground and + is probably just his CAD program that powers both halves of the opamp. my guess. besides, from what I'm seeing here, a special opamp isn't even needed. so yeah a common dual should work Link to comment Share on other sites More sharing options...
Members Kayzer Posted February 10, 2009 Members Share Posted February 10, 2009 Request for a Schumann PLL Clone Link to comment Share on other sites More sharing options...
Members MrChrisos Posted February 10, 2009 Members Share Posted February 10, 2009 This is back on? Fantastic! I don't want to hear new suggestions, clones, and there are enough fuzzes in the world (there, I said it). This has come so far already, and will be a real one off. Well done guys, I wish I could help, but my pedal building skills have only recently hit BYOC. Godspeed gents. Link to comment Share on other sites More sharing options...
Members ambient Posted February 10, 2009 Members Share Posted February 10, 2009 This is back on? Fantastic!I don't want to hear new suggestions, clones, and there are enough fuzzes in the world (there, I said it). This has come so far already, and will be a real one off.Well done guys, I wish I could help, but my pedal building skills have only recently hit BYOC. Godspeed gents. This. Also your avatar? Awesome, I think it's from a national geographic I have. Link to comment Share on other sites More sharing options...
Members MrChrisos Posted February 10, 2009 Members Share Posted February 10, 2009 This.Also your avatar? Awesome, I think it's from a national geographic I have. Hey thanks, I got obsessed with those little things when I was learning to scuba dive. I keep thinking about changing it though, a lot of people think it's a psychedelic mushroom. Link to comment Share on other sites More sharing options...
Members ambient Posted February 10, 2009 Members Share Posted February 10, 2009 Hey thanks, I got obsessed with those little things when I was learning to scuba dive. I keep thinking about changing it though, a lot of people think it's a psychedelic mushroom. amazing stuff at the bottom of the sea. Link to comment Share on other sites More sharing options...
Members amp_surgeon Posted February 10, 2009 Members Share Posted February 10, 2009 Someone PM me an address and I'll send the prototype we built to you. I'm sure the problem is related to having to float the +4.5V centerline for the op-amp, since the bleed is coming through the ground line. You can hear the timer even when the pedal is in bypass, and the only part of the pedal circuit still connected to the signal circuit in bypass is the ground. My schematic drawing program is an old version of OrCAD. When I created the schematic symbol for the op-amp I told it that there were two parts in the package, and to show the power pins. The program ends up showing the power pins on both parts. So, yes - there is only one op-amp chip. I suspect the problem is a combination of two things. First, the fact that a phantom power rail had to be created at +4.5V in order to provide a centerline for the inherently bipolar op-amp. Any disproportionate current draw between R1 and R2 is going to make that +4.5V rail float around. It might be worth trying a 5V regulator instead of the R1/R2 voltage ladder. The rail doesn't have to be +4.5V - it just needs to keep the signal somewhere around the middle between 0V and +9V so that it isn't clipped by the op-amp. Second, the output of the timer is going to be a square wave between a little more than 0V and a little less than +9V. The FET is only supposed to turn on for a very short time every cycle of the clock - just long enough to flash charge C4. The FET is then supposed to turn off, and C4 will hold the charge (or discharge very slowly into the input of the next op-amp) until the next clock pulse. The first thing to do is to convert the square wave into a series of very short pulses, which is what C8 and R9 are doing. The rising edge of the square wave causes a brief positive pulse out of C8, while the falling edge causes a brief negative pulse. We don't want the negative pulse going to the gate of the FET, so it's blocked by CR1. R10 and R11 form a voltage ladder like R1 and R2, which set the baseline for the pulse that turns on the FET. Still, the pulses going to the gate of the FET should be controlled so that the gate isn't driven negative with respect to the +4.5V rail on the channel of the FET. If you can think of a better way to "shape" the clock signal going to the gate of the FET then you might reduce the clock noise quite a bit. Anyway, I think the key is controlling the interaction between the artificial +4.5V power rail and the pulses from the clock circuit. The noise is difficult to see on my digital o-scope because the noise is travelling on the ground line, and my digital scope is ground referenced, meaning the noise is present on both the reference and the probe, so it cancels out. Link to comment Share on other sites More sharing options...
Members melx Posted February 10, 2009 Members Share Posted February 10, 2009 yes, lets do it!! Link to comment Share on other sites More sharing options...
Members Dolf Posted February 10, 2009 Members Share Posted February 10, 2009 doooooooooooooooooooo iiiiiiiiiiiiiiitttttttttttttttttttttttttt Link to comment Share on other sites More sharing options...
Members BoredGuitarist7 Posted February 10, 2009 Members Share Posted February 10, 2009 Link to comment Share on other sites More sharing options...
Members tape Posted February 10, 2009 Members Share Posted February 10, 2009 thanks for the additional info amp surgeon! getting extremelly narrow pulses from the 555 isnt too hard, though personally I prefer using a 40106 or something. so I guess some of us will take the existing schematic and tweak it in our own corners. it would be good to post the tweaks to see if advantages can be combined. I havent looked at it yet. I only had 10 hours sleep between last friday, saturday and sunday so I pretty much just crashed last night. realistically, I'll probably only breadboard it next week, so dont count on me too much if you want something fast. Link to comment Share on other sites More sharing options...
Members RoboPimp Posted February 10, 2009 Members Share Posted February 10, 2009 DO IT NOW! Link to comment Share on other sites More sharing options...
Members Ponda Boba Posted February 10, 2009 Members Share Posted February 10, 2009 id really like to do a limited paint run of pedals if production persists and its ok with the folks putting this together. like 5 enclosures. no dipped in a vat of mixed paint donnerbox-esque stuff either...all detail, all killer, no filler. Link to comment Share on other sites More sharing options...
Members Gunner Recall Posted February 10, 2009 Members Share Posted February 10, 2009 I have no idea what some of these posts are about...but I want it Thanks for putting (what appears to be) so much work into this guys. Link to comment Share on other sites More sharing options...
Members ambient Posted February 11, 2009 Members Share Posted February 11, 2009 much want. Link to comment Share on other sites More sharing options...
Members amp_surgeon Posted February 11, 2009 Members Share Posted February 11, 2009 thanks for the additional info amp surgeon!getting extremelly narrow pulses from the 555 isnt too hard, though personally I prefer using a 40106 or something. It's easy if you want a fixed frequency with a fixed duty cycle. It's pretty hard when you want a broad adjustable frequency range. The duty cycle changes with the frequency, and that's not what you want. The objective is to get the FET to conduct just long enough for C4 to charge up to the instantaneous voltage coming out of U1A, but NOT long enough for the signal coming out of U1A to change by any significant amount. As long as the FET is conducting then the input on U1B is going to be whatever is coming out of U1A, and you don't want entire cycles or even portions of a cycle of the input signal getting through. You want "samples" of the input signal voltage at specific instants of time. This means the pulse on the gate has to be very short, regardless of the clock frequency. The conventional way to do this is to use a couple of 555's - the first in astable mode, and the second in monostable mode. That seemed like overkill for this circuit, since a short time constant RC would do the trick. The pulses coming out of the RC circuit aren't square, but they don't need to be for this application. Anyway, that's only half the problem, and probably not what's causing the clock noise. The 555 output goes close to 0V, which is way too low to be driving the gate on the FET. If the voltage on the gate goes even a little below +4.5V then the FET will glitch like crazy. Link to comment Share on other sites More sharing options...
Members thisISjoel Posted March 4, 2009 Members Share Posted March 4, 2009 oh hai... remember this??? Link to comment Share on other sites More sharing options...
Members MathiasWilliam Posted March 4, 2009 Members Share Posted March 4, 2009 Link to comment Share on other sites More sharing options...
Members Bill Cosby Posted March 5, 2009 Author Members Share Posted March 5, 2009 1 knob fuzz it is. Link to comment Share on other sites More sharing options...
Members turnitto11 Posted March 5, 2009 Members Share Posted March 5, 2009 1 knob fuzz it is. That would be killer. Would the knob be for volume? Link to comment Share on other sites More sharing options...
Members Bill Cosby Posted March 5, 2009 Author Members Share Posted March 5, 2009 that or gain, then trim pots for whatever is missing. Link to comment Share on other sites More sharing options...
Members SharkMinusBear Posted March 5, 2009 Members Share Posted March 5, 2009 Single knob delay! Link to comment Share on other sites More sharing options...
Members onyxrhino Posted March 5, 2009 Members Share Posted March 5, 2009 1 knob fuzz it is. yeah, that would be special Link to comment Share on other sites More sharing options...
Members Bill Cosby Posted March 5, 2009 Author Members Share Posted March 5, 2009 yehza Link to comment Share on other sites More sharing options...
Members RoboPimp Posted March 5, 2009 Members Share Posted March 5, 2009 the results of this thread pretty much sum up what this forum is all about these days Link to comment Share on other sites More sharing options...
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