Mockman Schematic ... a better Rockman
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From: billdurham on 27 Sep 2009 23:46 Steve, just to explain a little how it works.. you have two identical stages of amplification.. the input side has the signal from the guitar and it gets amplified by the first stage. The gain of the circuit is the ratio of the input resistor, which is 10k or 10,000 ohms to the feedback resistor which is the 1M or 1 megohm resistor that is across pins 1 and 2. That ratio represents a gain of 100. which I think translates to 40dB of gain.. its been a while since I have messed with that stuff. The 2nd stage takes the output of the first and does the same thing again.. In theory.. thats a gain of 80dB from the input source. Without out getting too technical, the gain of opamps is limited by the DC voltage that supply power to the opamp. This circuit uses a voltage divider circuit to provide a psuedo plus and minus power supply to the opamps. The vref voltage is created by the two resistors that are connected in series across the battery. One of the properties of a circuit like this is as long as the value of the two resistors are the same, the voltage in the middle is half of the voltage going into the first resistor. For audio purposes.. this 4.5v point represents the point where the sine wave of an audio signal goes from positive to negative. So.. if you picture in your mind a sine wave that starts at the 4.5v point, goes positive up to 9v point, then goes negative to the 0v or ground point.. then back up to the 4.5v point.. thats what happens in the opamp. If you want the signal to be totally clean, you adjust the gain of the circuit so that the sine wave will never go beyond the 9v and 0v "peak" levels. If you setup the gain of the circuit to exceed that voltage swing of the sine wave, the signal gets clipped into a square wave. The higher the gain of the circuit, the more distorted the sine wave will become. This is a very simple explanation of how it works, and there are lots of reasons for the choice of the values used in the circuit.. but that is a pretty generic opamp circuit called an inverter. If you look, you will see that the audio signal goes into the - or negative input of the opamp. This causes the output of the first stage to be inverted phase wise relative to the input.. so the second stage flips the phase back and gives you an in phase output relative to the input signal. The biggest reason to use the inverter type circuit is it takes fewer external components to accomplish the gain you need, but the phase thing makes it require an extra stage of opamp. Sometimes, that extra stage is needed anyway, other times its not. One other thing.. in the case of mic pre's and other circuits that are supposed to be clean no matter what, you will find that the power supply voltages will be plus and minus 15v minimum as opposed to the psuedo plus and minus 4.5v used in this circuit. Most of the current opamps have a max voltage around +- 24v, so you have a total of 48vdc of swing before the opamp will clip. At that voltage level, they will run pretty warm though.. so most companies will back off to around +- 18vdc as the operating voltage of the chips. AT 36v of AC swing.. thats how mic pre's can claim an output of +28dBu without clipping. I used to mess around with this stuff back when I worked in the electronics parts business. I spent 10 years selling the stuff, so it was a pretty natural thing to want to play with it some.. BD Steve_Karl wrote: > Mockman ... a better Rockman guitar amp. > > http://www.runoffgroove.com/mm2.html > > I can solder with the best of them but I can't read a schematic like this. > If someone can translate this into a parts list ( or point me to a place to learn the language so I can order / buy the parts ) > I'd build it. > > Steve Karl > > >
From: Tom B on 29 Sep 2009 14:54 I know enough to pick up the correct end of an operating soldering iron. It took a while, but now I know. I have learned by trial and error so to speak. Some theory reading. Some web reading. Built a few tube amp kits ,effects, and such. I know voltage dividers, and if I read just a bit more I think I can handle basic high/low pass filter stuff. What you mentioned below is not really in my knowledge base so to speak. Maybe it is now, but figuring out gain and such I'm pretty lost on. I see the double inversion to get the signal back to match input but I would not be able to tell you what sort of gain was going on. I can go part way through a circuit but when parts start wrapping back into the circuit, I get confused as to how it's actually working on the input signal. I was looking at a circuit representation of a guitar pickup recently. Inductor in series with resistor and capacitor in parallel with those. But when they show the circuit with ac applied I have a hard time still seeing the cap a parallel and want to see it a series. First two graphics on this page. http://buildyourguitar.com/resources/lemme/ It's kind of funny, when you hear it explained, it just seems to make sense but yet you can look at things forever and never see it. So I pick up pieces here and there but nothing formal. I wish I knew a lot more than I do. -- Tom B. "billdurham" <billdurham(a)comcast.net> wrote in message news:h9pbih$g2a$1(a)news.eternal-september.org... > Steve, > just to explain a little how it works.. you have two identical stages of > amplification.. the input side has the signal from the guitar and it gets > amplified by the first stage. The gain of the circuit is the ratio of the > input resistor, which is 10k or 10,000 ohms to the feedback resistor which > is the 1M or 1 megohm resistor that is across pins 1 and 2. That ratio > represents a gain of 100. which I think translates to 40dB of gain.. its > been a while since I have messed with that stuff. The 2nd stage takes the > output of the first and does the same thing again.. In theory.. thats a > gain of 80dB from the input source. Without out getting too technical, > the gain of opamps is limited by the DC voltage that supply power to the > opamp. This circuit uses a voltage divider circuit to provide a psuedo > plus and minus power supply to the opamps. The vref voltage is created by > the two resistors that are connected in series across the battery. One of > the properties of a circuit like this is as long as the value of the two > resistors are the same, the voltage in the middle is half of the voltage > going into the first resistor. For audio purposes.. this 4.5v point > represents the point where the sine wave of an audio signal goes from > positive to negative. So.. if you picture in your mind a sine wave that > starts at the 4.5v point, goes positive up to 9v point, then goes negative > to the 0v or ground point.. then back up to the 4.5v point.. thats what > happens in the opamp. If you want the signal to be totally clean, you > adjust the gain of the circuit so that the sine wave will never go beyond > the 9v and 0v "peak" levels. If you setup the gain of the circuit to > exceed that voltage swing of the sine wave, the signal gets clipped into a > square wave. The higher the gain of the circuit, the more distorted the > sine wave will become. This is a very simple explanation of how it works, > and there are lots of reasons for the choice of the values used in the > circuit.. but that is a pretty generic opamp circuit called an inverter. > If you look, you will see that the audio signal goes into the - or > negative input of the opamp. This causes the output of the first stage to > be inverted phase wise relative to the input.. so the second stage flips > the phase back and gives you an in phase output relative to the input > signal. The biggest reason to use the inverter type circuit is it takes > fewer external components to accomplish the gain you need, but the phase > thing makes it require an extra stage of opamp. Sometimes, that extra > stage is needed anyway, other times its not. One other thing.. in the case > of mic pre's and other circuits that are supposed to be clean no matter > what, you will find that the power supply voltages will be plus and minus > 15v minimum as opposed to the psuedo plus and minus 4.5v used in this > circuit. Most of the current opamps have a max voltage around +- 24v, so > you have a total of 48vdc of swing before the opamp will clip. At that > voltage level, they will run pretty warm though.. so most companies will > back off to around +- 18vdc as the operating voltage of the chips. AT 36v > of AC swing.. thats how mic pre's can claim an output of +28dBu without > clipping. I used to mess around with this stuff back when I worked in the > electronics parts business. I spent 10 years selling the stuff, so it was > a pretty natural thing to want to play with it some.. > BD > > Steve_Karl wrote: >> Mockman ... a better Rockman guitar amp. >> >> http://www.runoffgroove.com/mm2.html >> >> I can solder with the best of them but I can't read a schematic like >> this. >> If someone can translate this into a parts list ( or point me to a place >> to learn the language so I can order / buy the parts ) >> I'd build it. >> >> Steve Karl >> >> >>
From: billdurham on 2 Oct 2009 23:40 Tom, Yeah.. I'm with you on the theory stuff.. AC circuits get really complicated.. and my explanation of that pedal was really simplfied.. but opamps are pretty easy to work with. Working with low impedance sources is a little easier than guitar pickups.. you really have to be careful with high impedance stuff. Tom B wrote: > I know enough to pick up the correct end of an operating soldering > iron. It took a while, but now I know. > > I have learned by trial and error so to speak. Some theory reading. > Some web reading. Built a few tube amp kits ,effects, and such. I > know voltage dividers, and if I read just a bit more I think I can > handle basic high/low pass filter stuff. What you mentioned below is > not really in my knowledge base so to speak. Maybe it is now, but > figuring out gain and such I'm pretty lost on. I see the double > inversion to get the signal back to match input but I would not be > able to tell you what sort of gain was going on. > > I can go part way through a circuit but when parts start wrapping back > into the circuit, I get confused as to how it's actually working on > the input signal. I was looking at a circuit representation of a > guitar pickup recently. Inductor in series with resistor and capacitor > in parallel with those. But when they show the circuit with ac applied > I have a hard time still seeing the cap a parallel and want to see it > a series. First two graphics on this page. > http://buildyourguitar.com/resources/lemme/ > > It's kind of funny, when you hear it explained, it just seems to make > sense but yet you can look at things forever and never see it. So I > pick up pieces here and there but nothing formal. I wish I knew a lot > more than I do. >
From: Michael on 2 Oct 2009 23:54 billdurham wrote: > > Tom, > > Yeah.. I'm with you on the theory stuff.. AC circuits get really > complicated.. and my explanation of that pedal was really > simplfied.. but opamps are pretty easy to work with. Working with > low impedance sources is a little easier than guitar pickups.. you > really have to be careful with high impedance stuff. True, but there are laws to be followed, and if you can use Kirchoff's and Ohm's laws fluently, every parallel RLC circuit has an equivalent series circuit, and you can treat them both the same: An outline of this? http://intranet.bell.ac.uk/sites/courses/Electrical%20Powerpoint/05%20Parallel%20RC%20-%20presentation.ppt A calculator for using the ideas? http://www.daycounter.com/Calculators/Parallel-Series-Imedance-Conversion-Calculator.phtml > Tom B wrote: >> I know enough to pick up the correct end of an operating soldering >> iron. It took a while, but now I know. >> >> I have learned by trial and error so to speak. Some theory reading. >> Some web reading. Built a few tube amp kits ,effects, and such. I >> know voltage dividers, and if I read just a bit more I think I can >> handle basic high/low pass filter stuff. What you mentioned below >> is not really in my knowledge base so to speak. Maybe it is now, >> but figuring out gain and such I'm pretty lost on. I see the double >> inversion to get the signal back to match input but I would not be >> able to tell you what sort of gain was going on. >> >> I can go part way through a circuit but when parts start wrapping >> back into the circuit, I get confused as to how it's actually >> working on the input signal. I was looking at a circuit >> representation of a guitar pickup recently. Inductor in series >> with resistor and capacitor in parallel with those. But when they >> show the circuit with ac applied I have a hard time still seeing >> the cap a parallel and want to see it a series. First two graphics >> on this page. http://buildyourguitar.com/resources/lemme/ >> >> It's kind of funny, when you hear it explained, it just seems to >> make sense but yet you can look at things forever and never see >> it. So I pick up pieces here and there but nothing formal. I wish >> I knew a lot more than I do.
From: Tom B on 13 Oct 2009 08:37
Thanks! I check these things out. Sorry, I just now say these replies. -- Tom B. "Michael" <muirheadNOm(a)MOREshawSPAM.ca> wrote in message news:nWzxm.310254$vp.77246(a)newsfe12.iad... > > > billdurham wrote: >> >> Tom, >> >> Yeah.. I'm with you on the theory stuff.. AC circuits get really >> complicated.. and my explanation of that pedal was really >> simplfied.. but opamps are pretty easy to work with. Working with >> low impedance sources is a little easier than guitar pickups.. you >> really have to be careful with high impedance stuff. > > True, but there are laws to be followed, and if you can use Kirchoff's and > Ohm's laws fluently, every parallel RLC circuit has an equivalent series > circuit, and you can treat them both the same: > > An outline of this? > http://intranet.bell.ac.uk/sites/courses/Electrical%20Powerpoint/05%20Parallel%20RC%20-%20presentation.ppt > > A calculator for using the ideas? > http://www.daycounter.com/Calculators/Parallel-Series-Imedance-Conversion-Calculator.phtml > >> Tom B wrote: >>> I know enough to pick up the correct end of an operating soldering >>> iron. It took a while, but now I know. >>> >>> I have learned by trial and error so to speak. Some theory reading. >>> Some web reading. Built a few tube amp kits ,effects, and such. I >>> know voltage dividers, and if I read just a bit more I think I can >>> handle basic high/low pass filter stuff. What you mentioned below >>> is not really in my knowledge base so to speak. Maybe it is now, >>> but figuring out gain and such I'm pretty lost on. I see the double >>> inversion to get the signal back to match input but I would not be >>> able to tell you what sort of gain was going on. >>> >>> I can go part way through a circuit but when parts start wrapping >>> back into the circuit, I get confused as to how it's actually >>> working on the input signal. I was looking at a circuit >>> representation of a guitar pickup recently. Inductor in series >>> with resistor and capacitor in parallel with those. But when they >>> show the circuit with ac applied I have a hard time still seeing >>> the cap a parallel and want to see it a series. First two graphics >>> on this page. http://buildyourguitar.com/resources/lemme/ >>> >>> It's kind of funny, when you hear it explained, it just seems to >>> make sense but yet you can look at things forever and never see >>> it. So I pick up pieces here and there but nothing formal. I wish >>> I knew a lot more than I do. > > |