Noobie questions...+ve ground in pedal chain and biasing - Rangemaster pedal

[glesconz]

Hi, Id like to make a Rangemaster booster, I have a few really old OC44's and OC71's so it would be nice to build the original PNP circuit...but Im wondering will this play merry hell with my other pedals, all -ve earth. I know I cant daisy chain them all up with a power supply, I was thinking maybe just have the Rangemaster battery powered.  But will having one pedal with a +ve earth being connected to one with a -ve earth produce unwanted weirdness??

I have some old germanium NPN trannies too, so if it is a problem then I will go that route with the NPN circuit..

Also, I have read about transistors being "biased". What is this  and how and why is it done? What effect does this have on the sound of guitar pedals? If all this can be explained in uber-noob speak it'd be much appreciated...just pretend you're trying to explain it to a drummer and I should be able to understand...

Thanks,
Glenn

[ryanuk]

But will having one pedal with a +ve earth being connected to one with a -ve earth produce unwanted weirdness??

I believe it will - regardless of whether running on batteries or PSU, the screen of the input jack on a Rangemaster clone will be +9V, whereas on most pedals this is ground. I would think this woudl cause issues.

I've never really understood the negative/positive ground thing, and why there is such a big issue.

Look at the schems on the GGG site for the PNP Rangemaster. What I dont understand is that why +9v is switched at the input jack. Why not build the circuit so that Q1 emiiter, 3k9 res, 68k res and QTy 2 47u are still connect to +9V. But then still swith the -ve side of the battery in the conventional pedal-fx-battery-switch way. Surely, in electronic terms, the circuit will function the same, and will be friendly with other pedals??

EDIT: I just found this link which confirms my point http://www.muzique.com/lab/fuzzface.htm
I suppose I've answered my own question!! Chuffed!! 

Also, I have read about transistors being "biased". What is this  and how and why is it done? What effect does this have on the sound of guitar pedals? If all this can be explained in uber-noob speak it'd be much appreciated...just pretend you're trying to explain it to a drummer and I should be able to understand...

My understanding is that when using a transistor as an amplifier, it needs to biased at an appropriate operating point (usually somwhere near the middle of its operating range).

Think of the guitar signal as an alternating wave signal which bounces around 0v. Some of the "signal" is +V, some is -V. Very simplistically, a non-biased transistor can amplify the +V signal, but not the -V signal.

The solution is to bias the transistor by inistroducing an idle voltage at the base. This way the transistor kinda always "sees" a +V which can be amplified.

Hope this makes sense.

RyUK

[R.G.]

But will having one pedal with a +ve earth being connected to one with a -ve earth produce unwanted weirdness??

I believe it will - regardless of whether running on batteries or PSU, the screen of the input jack on a Rangemaster clone will be +9V, whereas on most pedals this is ground. I would think this woudl cause issues.

This is kind of correct, but the terminology is a bit off.

The screen of the input jack on a Rangemaster clone will be at signal ground, just like the screen of the input and output jacks on any other pedal. What's important is that the power supply side of the battery (or power supply) will be negative side on a Rangemaster, but on a more normal pedal, the power supply side of the battery or power supply will be the positive side. As long as each pedal has its own power supply, or battery, there are no issues, and everything works fine.

The problem happens when you try to use ONE power supply to run both a normal pedal with the negative side of the power supply attached to ground on a daisy-chain connection with a pedal like the Rangemaster which has the positive side of its power supply connected to ground. When you plug in the signal cable between them, the cable shield connects the screen of the output jack of one to the screen of the input jack of the other. Now you have wires connecting the battery/power supply positive side to the screen of a jack on the Rangemaster clone, through the audio cable shield to the screen of the jack on the other pedal, which has a wire connecting it to the negative side of the battery power supply in that pedal. There is a string of wires connecting the positive side of the battery/power supply to the negative side, and this constitutes a short across the power supply. Smoke ensues. 

This cannot happen if the two pedals have separate power supplies which are isolated.

I've never really understood the negative/positive ground thing, and why there is such a big issue.

It's a big issue because, like you, most other people do not understand it.

Look at the schems on the GGG site for the PNP Rangemaster. What I dont understand is that why +9v is switched at the input jack. Why not build the circuit so that Q1 emiiter, 3k9 res, 68k res and QTy 2 47u are still connect to +9V. But then still swith the -ve side of the battery in the conventional pedal-fx-battery-switch way. Surely, in electronic terms, the circuit will function the same, and will be friendly with other pedals??

EDIT: I just found this link which confirms my point http://www.muzique.com/lab/fuzzface.htm
I suppose I've answered my own question!! Chuffed!! 

This comes up every time someone new re-discovers the positive/negative ground problem, and cleverly reinvents or discovers the "reversed-ground" idea at another web site. It is a baby-steps electrical engineering idea that any circuit can have either side of the power supply grounded if you do a number of steps correctly. It works in the theoretical world, and even works with some but not all real-world situations.

However, there are complications in the electrical engineering sense that make it somewhat problematic. These have to do with the impedance the circuit "sees" to ground and its power supply, the amount of decoupling, the amount of gain available to make any imperfections obvious, and other subtler issues. The result is that the simpler and lower gain the circuit, the more likely the "reversed-ground" setup is to work. The higher gain and other issues in the circuit, the more likely this is to cause excessive noise and oscillation. The problem areas are very, very hard to predict, and sometimes very hard to cure.

What generally happens is that a beginners find the problem, read the "just do this!" web sites, get a lowish-gain pedal to work - like perhaps a Rangemaster if the wiring layout isn't too bad - and think "cool! This works!". Then they try it with a higher gain or more complex pedal and it starts not working. Some of these issues can be cured, some can't. If you read more about the "positive ground" or "reversed ground" issues here, you'll find multiple instances of people having problems with the reversed ground setup that was cured instantly by putting the grounds back to where they should have been in the first place.

I guess I'm going to have to write up an article for Geofex on why the reversed-ground setup won't always work. Apparently people find the web sites first and never read my explanations here. This issue has become an illustration of why the internet is wide - but not very deep.

[DougH]

There was another "positive ground" thread on here a week or two ago. Try searching for it too. My advice, after many years of dealing with this stuff is if you don't have an "undaisychained" power supply (like a voodoo labs pedal power plus, for example, or something else with isolated dc power sources for each plug), just use a battery. It's much easier and less hassle in the long run. Alkaline batteries can last a long time in a Rangemaster circuit. They can be stored for a long time without leaking too. I built a positive ground booster last summer and the battery I installed still reads over 9v. When you get that kind of life and lack of hassle with a battery, it's kind of a no-brainer AFAIC to just go that route instead of trying to adapt a pos-gnd effect to work with a standard PS arrangement.

[ryanuk]

RG

Thanks for correcting me.

I woudl really like understand this. Googling "postive ground" gives a lot sites relating to car grounding. I;ve read some of this to see if relevant but the results simply suggest that in a +ve ground car, the chassis is grounded. No other differences? Not sure if this helps or confuses the issue.

One clarification - does a Rangemaster effectively operate on -9V?? I.e. with the positive side of the supply to signal ground, the reference potential at the negative side is -9V?? Apologies if this is a completely inane question.

RyUK

[R.G.]

There was another "positive ground" thread on here a week or two ago. Try searching for it too. My advice, after many years of dealing with this stuff is if you don't have an "undaisychained" power supply (like a voodoo labs pedal power plus, for example, or something else with isolated dc power sources for each plug), just use a battery. It's much easier and less hassle in the long run. Alkaline batteries can last a long time in a Rangemaster circuit. They can be stored for a long time without leaking too. I built a positive ground booster last summer and the battery I installed still reads over 9v. When you get that kind of life and lack of hassle with a battery, it's kind of a no-brainer AFAIC to just go that route instead of trying to adapt a pos-gnd effect to work with a standard PS arrangement.

That's a good way. There is another that works well too.

There are only two ways a single 9V power supply can be grounded - positive ground and negative ground. Using a daisy chain works in many, many cases for all of the pedals on one type of grounding. So if you have only one positive-ground pedal, using a daisy chain for all of the normal pedals and a battery for the single positive ground is a good solution. The other solution if you have more than one positive ground pedal or just don't want to buy batteries is to buy a second power adapter and run all of your positive ground pedals from that second adapter. I know that it is possible to get a quality second power adapter for between $20 and $30, which is quickly made up for in the price of batteries at $2.50-$3.00 at a time. People don't like to think beyond one power adapter, but sometimes and in some circumstances, it's a reasonably priced and reasonable complexity solution.

[R.G.]

Thanks for correcting me.

Not really a correction, as what you had and read was correct as far as it went. Really, it was just more information for you.

I woudl really like understand this. Googling "postive ground" gives a lot sites relating to car grounding. I;ve read some of this to see if relevant but the results simply suggest that in a +ve ground car, the chassis is grounded. No other differences? Not sure if this helps or confuses the issue.

The whole positive ground versus negative ground thing is a place where the language and terms helps prevent understanding.

If you have a battery that you're going to power an isolated circuit with - like maybe a flashlight - then which side you consider "ground" is almost immaterial. You can choose either side of the battery as "ground" reference for voltage measurements, or any other point, as long as you are consistent.

However if there is more than one circuit involved, the two circuits need to agree on what voltage is the reference, the fundamental place of zero volts from which all other measurements are taken. In the case of an auto, the chassis is used as a ground reference and also as a power return cable, because they're all metal and to take power to one place (headlights, for instance) or another (tailights), you only need to run one wire to the place where power is to be used, and the return path can be the metal car body. It's convenient and economical to use the car body as an all-pervasive "ground" from which every electrical bit can run. I'm not sure where or when the practice of using either the positive or negative side of the battery attached to the auto body originated, but it's important. Starter motors are DC motors, and they spin backwards if you reverse the power leads. One lead of the starter motor comes from the battery, and the other is its connection to the auto body. So the battery connection has to be the right way round, at least for that car and its particular starter motor. You can do it either way - positive side of battery attached to auto-body-ground or negative side-grounded, but you have to do it consistently for the things inside that auto and how they perceive how their incoming power is to be.

That consistency is not needed in pedals powered by independent batteries or power supplies. Each one is its own power-domain, and as long as the circuits inside the one pedal are happy with what "ground" and "power" are, it's fine. But connecting other pedals necessarily ties the signal grounds together because they have to have a ground reference they can agree on or hum and noise result. And with a connected ground comes the need for the power supplies to either agree on polarity and voltage or otherwise to not interact at all.

One clarification - does a Rangemaster effectively operate on -9V?? I.e. with the positive side of the supply to signal ground, the reference potential at the negative side is -9V?? Apologies if this is a completely inane question.

Nope, it's a pertinent question, and you are accurate. A Rangemaster, and the original PNP germanium Fuzz Faces, and a few others, have the positive side of their battery tied to signal ground, and the negative side tied to what the circuits consider "power". So yes, the Rangemaster power supply is -9V.

[DougH]

That's a good way. There is another that works well too.

Okay, I get it. Just buy more One-Spots...Lots of more One-Spots, right R.G.?

(You sly dog...)  J/K 

[R.G.]

Sly indeed. 

Actually, I was quite careful not to mention the "1" word  because a Boss adapter or any other suitable power adapter would work there. We make what I think is a good one, but I'm very aware it's not the only one.

[DougH]

Actually it's a great idea. If you have more than one pos-gnd, use another daisy chain, otherwise just use a boss adapter for a single pedal. If you do use another daisy chain I would strongly suggest marking the dc-plug ends with tape or something so you don't get the two chains mixed up.

[R.G.]

You're very correct about marking the daisy chain ends.

One good way to do this is with the plastic tool-handle dip from a hardware store. Comes in many colors, and dries to a tough, flexible plastic. Get some yellow, or red, or pink, or whatever other than black and paint the color on one daisy chain to indicate it's different.

In today's world of increasingly better protected pedals, reverse polarity tends not to be a disaster, only an annoyance. However, if you have even one 9Vac adapter in your setup, it makes sense to paint that one bright red, or even red-black-yellow (like a coral snake's bands) because 9Vac - or 12Vac, or 18Vac - will kill normally protected pedals dead. That one is a pedal killer.

[PRR]

Everybody else, skip this. It is just to fill a small bit of R.G.'s universal knowledge-bank.

> Starter motors are DC motors, and they spin backwards if you reverse the power leads.

Contrary to common sense: they don't (or didn't).

Starter motors have a wound rotor and a wound field. As long as both carry current the same direction, the rotation is as designed. Swap the battery lugs, it still rotates as designed.

Same applied to car Generators, with a small glitch. If started on a flat-dead battery, the initial field is residual in the iron. Preferably, when you get a good charged battery, you would "flash the field" before starting. Short the field relay to dump battery voltage (and polarity) into the field iron. Then the generator would come up in correct polarity, even if it had been used the other polarity before.

Nothing in a car cared much for polarity until alternators and transistor radios. Oh, sparks work 10% better on a certain polarity, but that's minor, and may be corrected at the spark coil primary.

Synchronous vibrators for radio do care about polarity; it is notable that vacuum rectifiers were far more common. Swap-battery will ZAP a sync vibe, the vacuum rect radio works fine.

PNP power transistors require a polarity and alternator rectifiers have polarity built in.

Common sense in motors is based on a mere 60+ years of Permanent Magnet motors. The stator field is "fixed polarity" when they put the magnet in. The rotor field is according to how you connect the battery. In a PM motor, reversing the battery does reverse the rotation.

Many minor car motors are now PM: heater, wipers, seat-tilts. The window and seat-lift motors rely on specific polarity for 2-way action with consistent switching.

PM starter motors exist for cars. But my 2002 Honda has a plain old field-coil motor. At this power and duty-cycle, a coil can be overloaded for 2-30 seconds, a permanent magnet does not overload at all, so the coil is cheaper in this application.

[R.G.]

ACK! Yep, you're right. Wound field motors are polarity insensitive. It's permanent magnet motors that are polarity sensitive. I hereby sentence myself to go replace a starter motor on the pickup!

[ryanuk]

One clarification - does a Rangemaster effectively operate on -9V?? I.e. with the positive side of the supply to signal ground, the reference potential at the negative side is -9V?? Apologies if this is a completely inane question.

Nope, it's a pertinent question, and you are accurate. A Rangemaster, and the original PNP germanium Fuzz Faces, and a few others, have the positive side of their battery tied to signal ground, and the negative side tied to what the circuits consider "power". So yes, the Rangemaster power supply is -9V.

R.G. - thanks for taking the time to explain this. I think Im finally beginning to understand the fundamentals - although clearly there is still a LOT to learn. 

Now that I've established that I'm kinda confsed as to how the circuit could operate if wired negative ground, as suggested by the link I posted below. I suppose its an equal potential (9v), but different polarity. Do the conventional/electro current arguments come into play here??

As I said previously, I have searched for info on postive ground. Nowhere could I find assurance that positve ground reference means the circuit operates on a -ve voltage. This really helps me get my head round it! Thanks RG. I second that article for your site!!   

I guess my next question is - why does this circuit operate best on a -ve voltage? One source I read simpy states that Ger PNP trannys were the cheapest common part in 1970s, and they were designed to operate on a postive ground. Was that a delibrate design characteristic or simply inherent? Can anyone elaborate on that? Most Sil PNP or NPN can operate on either system, no?

[R.G.]

R.G. - thanks for taking the time to explain this. I think Im finally beginning to understand the fundamentals - although clearly there is still a LOT to learn. 

We all have a lot to learn, forever. Remember that I once knew far less about electronics than you do now. It's a journey, not a destination.

I suppose its an equal potential (9v), but different polarity. Do the conventional/electro current arguments come into play here??

No. The electron flow/current flow issue is a distraction. Electron flow does have a place in understanding electronics, but it applies only at the level where you have to understand the internal working of an amplifying device or diode, and principally in understanding vacuum tubes or other devices that rely on current flow in a vacuum. Outside a vacuum tube, the current flow view of electronics is equal to the electron flow version. It's only inside the tube itself, where the impossibility of getting anything but electrons to move across the vacuum forces us to face up to the fact that it's electrons do the current flow, and that being backwards to how we normally think of it. For a beginner, I strongly encourage you to IGNORE the electron-flow explanations of current flow until you get enough background that you need to start thinking about charge carriers inside the devices. You have some time yet before you need that. 

why does this circuit operate best on a -ve voltage? One source I read simpy states that Ger PNP trannys were the cheapest common part in 1970s, and they were designed to operate on a postive ground. Was that a delibrate design characteristic or simply inherent? Can anyone elaborate on that? Most Sil PNP or NPN can operate on either system, no?

This is a complex subject. Let me start by saying that I don't know all of the story, and especially the pivotal issue you're looking for. I can only speculate based on some historical facts I've read.

This goes to the very definition of what "ground" is. Originally, ground meant just that - a metal rod driven into the dirt. The entire planet is a good reference voltage for us, and the early experimenters used it. Eventually, experimenters with electricity (and I'm talking the 1500s through 1800s here!) realized that in many cases you could simply measure the difference in voltage between any two points you chose, and get an accurate answer between those two points. But to determine the voltages between three or more points, you really needed as a mental abstraction to define one of your points as the reference against which all the others were measured. And that's the standard we use today. "Ground" means "a reference point against which all the other voltages in the circuit are measured." Confusingly, in AC power situations, it's still used for defining the wire attached to a metal pole driven into the dirt, but let's ignore that one for now.

The very notion of positive and negative are arbitrary. An early experimenter named them, and happened to choose the terms in a way that's confusing. All of the math involving electronics and charge carriers, charge on particles, physics, everything, works the same if we had chosen the charge on the electron to be one unit positive and the proton one unit negative. But they didn't, and so we're left with the complexity that current runs from positive to negative, and that current is electrons flowing from negative to positive, which are both true at the same time. UGH.

All of this positive/negative/"which is ground" was pretty academic stuff until electron/vacuum tubes were invented. The polarity of batteries was long determined by the time of DeForest and Tesla. And then they found that electron tubes only worked one way. No electron tube could be made to function with the cathode positve with respect to the plate, and in fact "anode" and "cathode" come from the terms for "positive terminal" and "negative terminal". But it was found that tubes only operated with the plates/anodes positive, and the cathode more negative, and that furythermore, the signal provided worked best feeding the grid near the cathode voltage. So (I'm starting to guess here) the idea that an AC signal compared to the reference voltage "ground" would be nearer the negative terminal/cathode of the tube and the output signal was nearer the plate, and you had to have a battery with its negative terminal tied to the signal ground to make this work without a lot of capacitors. Capacitors were VERY  expensive in those days, so they tried to minimize them. A lot. I'm guessing that this is the origin of the "negative is ground" school of thought.

Along comes transistors. FETs were actually thought of if not made work before bipolars, but it was Shockley's team's work on transistors that gave use the bipolar. They used a slab of germanium with indium pellets sitting on it and heat-diffused into the base-slab of germanium. This is where the term "base" comes from, by the way; also where "emitter" which is where the charge carriers were injected into the "base"/slab by the positive terminal of their batteries/power supplies, and the "collector" which collected up the charge injected into the "emitter". It took a while to realize that what was really happening was that the difference between the base and emitter was what was making things go. Here's where my biggest gap in understanding the history happens. I *think* they decided by analogy to the vacuum tube to make "ground" be on the emitter side rather than the collector side because that's the closest analogy for signal grounding. But I'm not sure. I guess I need to go read all the history more clearly. Paul may have more info about this that I do, or others.

Only PNP transistors worked initially, and PNP always worked better than NPN in germanium, for reasons to do with the physics of the materials and the crudeness of the  processing available. In germanium transistors, we had a device that worked fundamentally backwards to the vacuum tube, and was best understood in terms of currents, not voltages. In fact, there was a whole generation of EEs who never could make the transition to transistors from tubes, and were marginalized after about 1960.

On a theoretical level, it really doesn't matter whether we call the most-positive power supply "ground" or the most negative-side "ground". The equations and physics work the same way. However, the equations we can actually write are an approximation to reality. For example, we think of copper wires as "short circuits" between two points. They are not. They are really resistors, with an easily calculable value. They are also inductors, with an inductance determined by their physical shape. They are also capacitors, with a capacitance to every conductor in the rest of the physical universe, and the capacitive value determined by the shape of the conductor and the shape and spacing of that "everything else in the physical universe".  And that's just for a copper wire. All components are actually all POSSIBLE kinds of components if you measure them with fine enough resolution.

What we do is to approximate. A 1K resistor is *principally* a 1K resistor, within some tolerance, with both a capacitance from wire lead to wire lead, an inductance of the leads, and both distributed capacitance and inductance inside the resistance and its leads. There are semiconductor effects inside the resistive material. We'd never get there if we had to write out exactly what it is, and each resistor would be different. So we approximate, and we do this for all components to be able to understand the main effect of the components. Where this really matters is where we try to understand power supplies. A power supply is supposed to be a pure difference in DC voltage. In fact, it's not pure, it's a voltage with some resistance, capacitance, inductance, and many other effects. It's not pure.

All of that build-up is background to this: in theory, you can call either the + side or the - side of the power supply to a single-power-supply circuit "ground", but only to the extent that the power supply is a pure DC offset, with zero AC impedance. Real power supplies never are "pure".

When a circuit amplifies the difference between what it thinks is "ground" and the signal wire, it necessarily amplifies any wiggling around on "ground". Since real power supplies are not pure, neither are real grounds, and especially neither are real "grounds" that are reversed from what the circuit expected. And that's the bottom line: if you flip whether you consider the positive side or negative side of the power supply to be "ground", it means you connect the outside world signal to a different place, and that different place has different parasitics and different impedances. So what you amplify is different.

That matters almost not at all for low frequencies and low gains. The higher the gain, the higher the frequency, the more it matters. For Rangemaster clones, you generally get away with it, because the gain and frequencies are low. For Fuzz Face clones, you get away with it most of the time unless you do a bad job on the power supply, but sometimes only flipping the power supply back to the normal way the circuit expected fixes noise and oscillation issues. For higher gains and more complex circuits, the getting-away-with-it ratio goes down. Unfortunately, the internet multiplies the "just use the other side of the power supply as ground" advice which is given by people who have not yet run into a situation where it doesn't work.

I rambled a lot. Did that help or hurt?

[glesconz]

Thanks for all your help, guys, altho the thread did start to get hijacked there! (Im gonna refrain from putting a  motor in my Rangemaster, no matter how much that effect name sounds like a car!) Its been bought to my attention there is biasing and biasing to taste and perhaps that is my mistake....perhaps an article could be posted on tweaking transistor resistor values, what to do, not to do etc in very simple terms would be good to get the best out of our builds..

Once again, thanks,
Glenn

[PRR]

> Ger PNP trannys were the cheapest common part in 1970s

Say "1960s". Though many designs lingered into the 1970s, good NPNs were reasonably cheap by the late 1960s.

The pivotal part may be CK722 and similar. Late 1950s, GE was making tons of high-spec parts (mostly PNP because the process was simpler) and still making a lot of rejects. "20V" parts that broke-down at 17V, etc. What to do? Package them for retail sale with thin or no specs, and publish a lot of 3V and 6V Experimenter Projects. Projects that didn't always work too good, but ANY transistor toy was a thrill in those days. The early fuzz experimenters learned their craft with such old/cheap reject parts, could think in PNP and negative-hot easily.

> a slab of germanium with indium pellets

There were variations; but yes. Transistor fabs grew very suddenly using uncommon materials, mostly not available in high purity form. The benefits of Si and other metallurgy could be predicted, but not produced easily or reliably. By happenstance, the materials that worked best with the least new-tech worked better in PNP form.

I bet the deal was: most of the impure Ge tended to be N-like. And not TOO expensive. We need two PN junctions. The P-type materials were more costly. So small dots of P were alloyed into a slab of N-type, P-N-P.

By stewing quasi-pure pellets together and selling them, the industry raised money to develop better materials and processes, with the option to make NPN 95%-105% better/cheaper than PNP.

> inside the tube itself, where the impossibility of getting anything but electrons to move across the vacuum forces us to face up to the fact

The stunning fact is that electrons will leave a hot surface.

Taking a loose definition of "vacuum", positive ions DO move through empty space.

Now we fact the fact that ions are at least 1800 times heavier than electrons, move much slower, so that even in a gas tube the electrons fly and the ions drift. And gas tubes are still typically slow. While the early '01 "vacuum tube" is really a thin-gas tube, most of the story of radio is high vacuum tubes and electrons.

Nevertheless, nearly every tube-circuit geek I knew drew current flowing from plate to cathode (opposite of electron flow). For the math-minded, this reduces the minus-signs we have to keep track of.

Ground.

Leaving aside power-safety and audio-interference issues: as R.G. says, when you have more than a few parts, it gets confusing. Even one part with three legs (tube or transistor) is confusing.

Every simple circuit must form a complete loop. A transistor has an input loop, an output loop, and a power loop. We could imagine a part where these three loops would be separate, like the beer or olympic interwoven rings. That would need 6 leads, two per loop. But we only have three leads. The loops must intersect. Generally we intersect them at the emitter. Input flows base to emitter and back. Power flows collector to emitter and back. Output flows collector to emitter and back. Since all three loops are "common" at the emitter, we call it common-emitter.

Now build two transistors as one complex amplifier. We could have a separate battery for each transistor. It is convenient to "common" the common points together, so the same battery may be used for both.

Now when trying to understand the several circuit loops, it is convenient to keep one meter lead on "common" and reference all other points to that.

The simplest way to route the signal also uses "common" as the reference for everything else. And if signals are leaking out or in, a metal box connected to common tends to reduce the leakage.

With N-type devices (tubes and NPN) the power common node tends to be the negative end of the battery.

With P-type (PNP) devices it is convenient to call the positive end of the battery "common".

In many audio/radio circuits, these conventions are convenient but NOT required. It is perfectly possible to wire a PNP stage negative-ground, with emitter to the positive battery lead. If the battery is perfect, it works just the same. With imperfect battery, it may be better to take power and emitter bypass capacitors to common rather than to the emitter end of the battery. I just saw a transitional radio with positive ground negative hot, all PNP in the audio stage, but the AM/FM RF stages were NPN with emitters run "up" to negative supply and emitter bypasses run down to common.

Appendix:

> where the term "base" comes from, by the way; also where "emitter" ... gap in understanding the history happens. I *think* they decided by analogy to the vacuum tube to make "ground" be on the emitter side....

What Bell announced is NOT the transistor we know.

They had Point Contact. Even today a mysterious device. You "know" that emitter current is equal to collector current, actually a shade high. In the specs, Alpha is a number between 0.9 and 0.999. But in a Point Contact transistor, it is possible to show an Alpha of 3 or 4: collector current is greater than emitter current. And then the highest power gain is gotten with a Common Base connection. In fact the over-unity Alpha means most other connections are unstable.

I've ordered a copy of a later RCA symposium, from the Alloy era. Now Alpha was 0.9 and it was convenient to speak of Beta with value of 5, 10, maybe 20. Alpha and Beta express the same ratio, but 10 or 100 is easier to read than 0.9 or 0.99. These are parts _you_ could design with, albeit frustrating because Beta is so low. With such parts, maximum power gain happens with common-emitter connection. And at such low gains, with such expensive parts, max power gain is the only way to go. Emitter followers (common collector) is usually a few bucks more expensive for a given result. (An exception: for very high frequency work reverse-feedback spoils the gain, common-base connection rules above Beta cut-off.)

Stir the pot next week. Brain-cells fade but for another project I have been buying the old GE and RCA manuals to trace the 1955-1967 period.

[stringsthings]

... However, the equations we can actually write are an approximation to reality. For example, we think of copper wires as "short circuits" between two points. They are not. They are really resistors, with an easily calculable value. They are also inductors, with an inductance determined by their physical shape. They are also capacitors, with a capacitance to every conductor in the rest of the physical universe, and the capacitive value determined by the shape of the conductor and the shape and spacing of that "everything else in the physical universe".  And that's just for a copper wire. All components are actually all POSSIBLE kinds of components if you measure them with fine enough resolution....

... and IMO, this is one of those cool parts of electronics ... an average, ordinary, guitar cord also functions as a filter .... i've proved this to myself too many times ... all factors being equal, a longer guitar cord ( 25' > 10' ) will cause a reduction of high frequencies .... this may be desireable for some consumers ( i.e. jazz guitarists who prefer reduced treble response ) ....

I strongly encourage you to IGNORE the electron-flow explanations of current flow until you get enough background that you need to start thinking about charge carriers inside the devices. You have some time yet before you need that.  

... Did that help or hurt?

it helped

[ryanuk]

Thanks for all your help, guys, altho the thread did start to get hijacked there! (Im gonna refrain from putting a  motor in my Rangemaster, no matter how much that effect name sounds like a car!) Its been bought to my attention there is biasing and biasing to taste and perhaps that is my mistake....perhaps an article could be posted on tweaking transistor resistor values, what to do, not to do etc in very simple terms would be good to get the best out of our builds..

Once again, thanks,
Glenn

Apologies if I hijacked the thread ( ) but the +ve ground senario has always confused me (and many others I would suggest). There are a lot threads/sources on the net, and whilst they all agree that the early circuits use +ve ground, its not detailled why they use it. The contributions on this thread will serve to help others.

The answer to your original question is, yes, the rangemaster can be used with other pedals provided it uses its own power supply (whether battery or dc adaptor).

With regard to biasing transistors, I think it very much depends on the transistor and what you are trying to achieve. I believe transistor which isnt properly biased to extremes can produce some undesirable results.