I did a search on this topic, and quite frankly I was left a little more confused than enlightened. I'm working on a Ge Fuzz Face (with transistors from small bear). Here's what I think I've figured out so far:
1. DC jack is bad? I read someone saying they wouldn't use a DC jack because it can fry the transistors if the voltage is incorrect/inconsistent.
Here's what I'm confused about:
1. If you know your power supply is a reliable, steady 9 volts, and you want to use one, the circuit has to be positive ground for it to work? Is this right? It seems to be the opposite of what I'd expect.
2. How do you ground the jacks in a positive ground circuit?
No help here, but I'm wondering if you could use a tip positive adapter.
That, or reverse the wires coming from the jack using a tip negative adapter, maybe? As long as positive voltage goes where it's supposed to, in this case to ground, shouldn't it work?
Nothing like answering a question with more questions. :D
Here are the issues:
Most pedals follow the Boss standard, Ground negative and the tip of the jack negative. This means the jack body/barrel must be isolated from the enclosure. It also means that if you have a pedal with a positive ground you cannot run it from the same supply as your other pedals.
You can use a seperate supply for your positive ground pedal and all will be well.
There are debates about the sonic quality of running a classic fuzz from a supply, but that's another can of worms I'll ignore here.
Ron
Quote from: Ronsonic on November 03, 2006, 12:38:46 PM
Here are the issues:
Most pedals follow the Boss standard, Ground negative and the tip of the jack negative. This means the jack body/barrel must be isolated from the enclosure. It also means that if you have a pedal with a positive ground you cannot run it from the same supply as your other pedals.
You can use a seperate supply for your positive ground pedal and all will be well.
There are debates about the sonic quality of running a classic fuzz from a supply, but that's another can of worms I'll ignore here.
Ron
I'm sorry, but when we say jack (in terms of isolating it), we're talking about a DC jack, not the in and out jacks, right?
I think I'm going to go the purist route and just go with the positive ground and use battery power. For a positive ground circuit do the in and out jacks still get grounded to the batt(-) terminal? You definately wouldn't want to connect them to the ground on the circuit board because that would send 9V to the ground on your in and out jacks.
Quote from: MikeH on November 03, 2006, 12:48:45 PM
Quote from: Ronsonic on November 03, 2006, 12:38:46 PM
Here are the issues:
Most pedals follow the Boss standard, Ground negative and the tip of the jack negative. This means the jack body/barrel must be isolated from the enclosure. It also means that if you have a pedal with a positive ground you cannot run it from the same supply as your other pedals.
You can use a seperate supply for your positive ground pedal and all will be well.
There are debates about the sonic quality of running a classic fuzz from a supply, but that's another can of worms I'll ignore here.
Ron
I'm sorry, but when we say jack (in terms of isolating it), we're talking about a DC jack, not the in and out jacks, right?
I think I'm going to go the purist route and just go with the positive ground and use battery power. For a positive ground circuit do the in and out jacks still get grounded to the batt(-) terminal? You definately wouldn't want to connect them to the ground on the circuit board because that would send 9V to the ground on your in and out jacks.
Yes, I meant the DC power jack. The usual arrangement is to connect the ring terminal on the signal input jack to the Positive terminal of the battery. Then when the guitar is plugged in the positive is connected to ground. All grounds are then positive and connected. GGG has some very clear drawings of just about every variation of PNP positive or negative ground and NPN negative ground. Those three pictures are better than all my words.
Ron
In simple terms, and as I understand it, the choice to go negative ground with a circuit designed for postive gound circuit such as the FF carries a couple of risks.
The main one is: IF there isn't a low-resistance path for any signal on the circuit's power supply line to flow to ground, that signal might show up where you don't want it. Like back into the input. Because low frequencies have the highest resistance to earth through capacitors, the resulting oscialltions will probably be at low frequency, and will be a form of "motorboating".
However, even really low frequencies can be beaten. Big or many caps on the power supply help (try 4 x 1000uF or 2 x 4700uF). Also, a smaller cap on the input will help (0.47uF instead of 2.2uF for a Fuzzface).
Batteries are a poor choice environmentally, though NiMH rechargeables are better that throw-away types.
cheers
Here's another can of worms- I built the ggg neg ground pnp fuzz face, and for some reason have no complaints...
ditto
neg ground PNP FF working fine for 1 year with me. (with big cap power supply)
Quote from: Meanderthal on November 04, 2006, 10:48:04 AM
Here's another can of worms- I built the ggg neg ground pnp fuzz face, and for some reason have no complaints...
That's what you get for using a proven design in a good layout and decent construction practices. I hope you've learned your lesson.
Ron
just wondering, can someone explain to me the point of positive ground circuits? it just messes with everything i have learned so far. what are the differences with the circuits that need it? they can easily be converted to negative ground, right?
i guess what i'm asking is: why does positive ground exist?
PNP...
pnp as opposed to npn: i guess, why would they make pnp in the first place? or, they make equivalents in both styles, right? then why would someone design a circuit with pnp?
i know it's obvious i don't know much about it...
a large amount of old germanium transistors are PNP, its harder to find NPN ones
All my PNP positive ground FF's work great, tried a neg ground and had all the detailed problems !
I've made a few NPN Ge neg grounds and that's all good too, got a handfull of AC127's that are useable
but the OC140's (CV7112) that aron/steve stock are just fantastic !
Battery powering a FF should last a VERY long time, so long as you remember to unplug it !
MM.
Quote from: Seljer on November 05, 2006, 06:24:49 AM
a large amount of old germanium transistors are PNP, its harder to find NPN ones
so the main reason for positive ground (in our area) is germanium transistors which are mostly PNP. and fuzz faces like these. am i understanding this correctly?
what about the original purpose of these germaniums? why would they be made to operate like that? it had to be abnormal, even back then, right?
Someone with more "tech spec" needs to chip in, but from what I remember
making PNP Germanium devices is easier and more reliable than NPN Germanium.
Has to do with the substrate / Layers and how they are formed in manufacture.
... so there's more "good" PNP Germaniums around in general.
MM
MartyMart is correct about germanium and PNP.
Germanium has the quirk that it's more suited to a PNP type bipolar transistor than NPN. So most germaniums were PNP, and the best germaniums were PNP. It was only late in the germanium life cycle that NPN germanium was made and sold as commercial products.
As a sidelight, the inherent PNP-ness of germanium was one thing responsible for the loss of a generation of EEs who never made the leap over from tubes to transistors. The difficulties in making PNP devices work properly with a negative ground like tubes always used, and the idea that power supplies even could be positive ground, as well as just the idea of how they worked literally put many EEs out of a job back in the time.
Silicon is more inherently NPN. That's why the first commercial bipolars in silicon were NPN, and why PNP silicon was rare, expensive, and poor performance for many years. It was not until silicon devices got about 15 years of experience on them that really complementary power devices were feasible for audio power output devices. That's the reason that the quasi-complementary output stage even existed - it was the solution to the lack of good, reasonably priced PNP silicon outputs.
:icon_mrgreen: :icon_mrgreen:
.... Torchy told me about this some time ago BTW !
MM.
There are two kinds of people in this world.
(a) people who have had circuits not work properly because of reversed-ground wiring
and
(b) people who have not yet run into this situation.
I tell you three times - there are situations where you can get uncontrollable oscillation from reversed-ground wiring that cannot be cured by anything except putting the wiring back to the correct ground. Enjoy playing with this if you like, but be aware that if it works you got away with something.
Quote from: choklitlove on November 05, 2006, 06:49:47 AM
Quote from: Seljer on November 05, 2006, 06:24:49 AM
a large amount of old germanium transistors are PNP, its harder to find NPN ones
so the main reason for positive ground (in our area) is germanium transistors which are mostly PNP. and fuzz faces like these. am i understanding this correctly?
what about the original purpose of these germaniums? why would they be made to operate like that? it had to be abnormal, even back then, right?
It's all they freeking had. There were no silicon transistors, or they were rare and expensive and NPN germanium were also more expensive and frequency limited. It seems hard to believe but back in the sixties even the full audio range was difficult with transistors.
The funny thing is the sound of that clanky old technology for amplifying and distorting a guitar sorta stuck and it's considered part of the instrument now.
Ron
I could be off base here but, many older U.S. and European automobiles used Positive ground electrical systems strange as it may seem.
I just built a neg ground tonebender with pnp trannies and have built several others including a FF and have only had problems with batteries which were failing slightly. No problems whatsoever with the power supply which is a regulated multi-point. When the batteries have fallen below arounf 8.5v the circuits tend to get noisy and oscillate. I need the neg ground as I use them alongside other pedals.
Col
Quote from: col on November 06, 2006, 03:54:30 AMI need the neg ground as I use them alongside other pedals.
You can still use a positive ground effect in line with other traditional negative ground effects can't you?
QuoteI need the neg ground as I use them alongside other pedals.
QuoteYou can still use a positive ground effect in line with other traditional negative ground effects can't you?
Negative and positive ground pedals can be used together in any combination.
What you can't do is use one single-polarity power supply for positive and negative ground pedals. The positive ground pedals connect the positive side of any power supply that gets connected to them to signal ground internally. The negative ground pedals internally connect the negative side of any power supply that gets connected to them to signal ground. If you have a positive ground pedal and a negative ground pedal with a signal cable between them on a single power supply, then both the negative and positive sides of the power supply are connected to signal ground, and the power supply is shorted.
The answer is to use two different power supplies. One power supply can run as many negative ground pedals as you like, the other power supply can run all of the positive ground pedals. You just can't have the ground on a single power supply connected to both positive and negative sides.
This is a slippery concept to beginners - did everybody get that OK?
i might be mistaken, but i thought the 1 spot can run both. it has those connectors.
here's what it says on the page:
"Reverse Polarity Converter for Yamaha (CYR):
* Allows the 1 SPOT and MC5 cable to power Yamaha keyboards, samplers, and drum machines, as well as certain reverse polarity effects pedals"
here:http://www.visualsound.net/1spot.htm (http://www.visualsound.net/1spot.htm)
Just to add to RG's, some power supplies have multiple isolated outputs so the same box can provide power to a mix of pedal.
You just need to be very sure that's what you have.
Ron
Quotei might be mistaken, but i thought the 1 spot can run both. it has those connectors.
I do happen to know about the 1Spot.
It's a single power supply output with low noise and high output. So it can run any reasonable number of the same polarity effects at the same time. The reverse polarity converter does just that - it inverts the polarity on the plug. It doesn't (and can't!) make a new, isolated output.
So if you are running things from 1Spots, you will need one unit for all of your normal negative ground pedals, and one for all of your positive ground pedals. Fortunately, they cost little enough that two of them to do this is very reasonable.
Despite many warnings about building a Neg ground circuit with PNP tranny's I decided to try it out anyway. When I had it on the breadboard, it didn't oscillate at all, just gave me a nice fat fuzz. Actually pretty damn quiet as well. Sounded awesome. Well, I made my PCB using Tonepads layout and soldered it up. When I hooked it up to my test rig, it started oscillating like friggin crazy; making all kinds of noise. I messed with the controls and it stopped. Didn't oscillate anymore, at any setting, no matter how hard I tried to get it to. Wierd. Before, I must have played with it for hours on the breadboard and it never oscillated once. Wierd again. The Fuzz face is a mysterious thing. I'm going to try and put a gigantic Electrolytic cap across the + and - to try and make sure it doesn't oscillate, if that doesn't work, I guess it's pos ground time.
Congratulations! You got away with it... probably.
Quote from: R.G. on November 06, 2006, 10:10:48 AM
QuoteI need the neg ground as I use them alongside other pedals.
QuoteYou can still use a positive ground effect in line with other traditional negative ground effects can't you?
Negative and positive ground pedals can be used together in any combination.
What you can't do is use one single-polarity power supply for positive and negative ground pedals.
Sorry for bumping this old thread.
It's very clear for me why you can't use a single-polarity power supply for positive and negative ground pedals.
But what's still strange to me, is the fact that you can put two effects after each other, one neg and the other pos ground.
Because like this, you are connecting pos ground and neg ground to each other with the patch cable, no?
So I don't get this.
Can anyone explain?
Thanks...
"Positive Ground" is kind of a slang term. Ground is always 0 volts. A 'positive ground' pedal runs off -9v, the battery + is connected to ground, but it's still 0v.
GROUND IS RELATIVE...
Quote from: carrejans on December 11, 2010, 02:03:34 PM
But what's still strange to me, is the fact that you can put two effects after each other, one neg and the other pos ground.
Because like this, you are connecting pos ground and neg ground to each other with the patch cable, no?
So I don't get this.
Join the club my friend. I cant wrap my head around it either. By jacking a Positive ground pedal to a Negative one (i.e. a PNP Fuzz Face to a NPN Booster) you are essentially connecting the V+ from the PNP to the V- of the NPN. I have had people tell me that using 2 seperate power supplies (one for each effect) solves this problem but you are STILL shorting the two together via the Output jack of the PNP and the Input jack of the NPN or vice versa.
It baffles me even after the multiple explanations ??? ??? ??? :icon_redface:
Quote from: Govmnt_Lacky on December 11, 2010, 04:55:36 PM
Join the club my friend. I cant wrap my head around it either. By jacking a Positive ground pedal to a Negative one (i.e. a PNP Fuzz Face to a NPN Booster) you are essentially connecting the V+ from the PNP to the V- of the NPN. I have had people tell me that using 2 seperate power supplies (one for each effect) solves this problem but you are STILL shorting the two together via the Output jack of the PNP and the Input jack of the NPN or vice versa.
It baffles me even after the multiple explanations ??? ??? ??? :icon_redface:
Draw the schematic, using just a box for the effect circuit, but coloring in the jacks, signal, ground, and battery wiring for two effects.
The issue is not where the grounds go, as was noted. It's where the power supply leads must go to get the two kinds of ground.
Draw the picture.
Quote from: R.G. on December 11, 2010, 10:46:52 PM
Draw the schematic, using just a box for the effect circuit, but coloring in the jacks, signal, ground, and battery wiring for two effects.
The issue is not where the grounds go, as was noted. It's where the power supply leads must go to get the two kinds of ground.
Draw the picture.
Ok... Lets go about this a different way.
Take 2 wall warts and cut the plugs off the end of the wire on each unit.
Now, wire the V+ from one of the wall warts to the V- of the second wall wart.
Now..... PLUG THEM BOTH INTO A WALL SOCKET!
WHAT HAPPENS? :o
This is essentially what you are doing when you use two seperate wall warts. One to power the PNP and the other to power the NPN. The only difference is that you are doing this via a pedal to pedal jumper cable.
Am I wrong in thinking you will have a MAJOR problem with blown fuses by doing this?
> WHAT HAPPENS?
Draw the darn schemetic, the CIRCUIT.
Show the LOOP that your electrons run around.
Wall-warts introduce black-box mystery. Take two 9V batteries. Connect JUST the + of one to the - of the other (leaving two other terminals unconnected). What happens? Where are the electrons flowing?
> Except when skydiving
Conversely, if you are a fish, surface level is an UPPER limit not the lower limit as when air-breathers sky-dive.
Quote from: Govmnt_Lacky on December 11, 2010, 11:09:43 PM
Ok... Lets go about this a different way.
Take 2 wall warts and cut the plugs off the end of the wire on each unit.
Now, wire the V+ from one of the wall warts to the V- of the second wall wart.
Now..... PLUG THEM BOTH INTO A WALL SOCKET!
WHAT HAPPENS? :o
This is essentially what you are doing when you use two seperate wall warts. One to power the PNP and the other to power the NPN. The only difference is that you are doing this via a pedal to pedal jumper cable.
Am I wrong in thinking you will have a MAJOR problem with blown fuses by doing this?
Is this what you had in mind? (some details left out)
(http://i832.photobucket.com/albums/zz249/Perrow_MLP/Random/twosupplies.png)
I say, count the loops. I see none. You can even omit the diodes.
Quote from: PRR on December 12, 2010, 02:18:49 AM
Conversely, if you are a fish, surface level is an UPPER limit not the lower limit as when air-breathers sky-dive.
Sky is still up though ;) But I see your analogy and amaze at how you incorporated my OT humorous remark to point at something relevant to this thread. *applause*
Quote from: MikeH on December 11, 2010, 02:36:36 PM
"Positive Ground" is kind of a slang term. Ground is always 0 volts. A 'positive ground' pedal runs off -9v, the battery + is connected to ground, but it's still 0v.
That was always my take too....it'd be much less consuing to simply say negative supply (pos ground) or positive supply needed for a circuit!
Quote from: Gurner on December 12, 2010, 08:29:53 AM
Quote from: MikeH on December 11, 2010, 02:36:36 PM
"Positive Ground" is kind of a slang term. Ground is always 0 volts. A 'positive ground' pedal runs off -9v, the battery + is connected to ground, but it's still 0v.
That was always my take too....it'd be much less consuing to simply say negative supply (pos ground) or positive supply needed for a circuit!
Remember Reinhold Niebuhr's serenity prayer?
QuoteGod, grant me the serenity
To accept the things I cannot change;
Courage to change the things I can;
And wisdom to know the difference.
It would indeed be less confusing to say positive supply or negative supply.
It would also be less confusing if Benjamin Franklin had guessed correctly about what came eventually to be known as the polarity of charge carriers. Electricity is carried in metals and resistors as moving electrons, which are negatively charged. So we have the curious situation where electrical current is viewed as moving from more positive to more negative places while the current is carried by negatively charged electrons flowing from more negative places to more positive places. But we're stuck with it. It would be much simpler if he'd guessed the other way round. The math works both ways, but we have to keep two pictures in our heads at the same time.
Fortunately, we are capable of doing this if we try.
Quote from: R.G. on December 12, 2010, 12:00:44 PM
The math works both ways, but we have to keep two pictures in our heads at the same time.
Fortunately, we are capable of doing this if we try.
To paraphrase Friends; "R.G is a girl!" :icon_wink:
Quote from: R.G. on December 12, 2010, 12:00:44 PM
Remember Reinhold Niebuhr's serenity prayer?
QuoteGod, grant me the serenity
To accept the things I cannot change;
Courage to change the things I can;
And wisdom to know the difference.
Whilst it's always a pleasure & joy to see one of my posts flush out some prose, fear not, this actual issue causes me about three femtoseconds of pondering once every 5 years or so.
carrejans/govmt lacky:
Allow me to jump in here. Someone please correct me if I am wrong in my explanation. The PNP circuit adds a negative bias to the AC component from your guitar and operates below 0 V ground, hence the "positive-ground" reference point of operation. This signal then has that DC bias removed by the output coupling cap and the AC component is just a "normal" AC waveform cycling around a 0 V center reference point again as it travels to the NPN device via the signal cable. The NPN circuit then adds a positive DC bias to the AC component and operates above 0 V ground. At the NPN device's output, the DC bias is again filtered out, leaving just the AC component again. It is the isolation of the DC operating points of each circuit which makes this work. You aren't really shorting anything out when you use the separate, isolated power supplies, or two different batteries to power each circuit. They just enable you to operate at different points in reference to the 0 V ground reference point. This works by making the 0 V ground reference point either "more positive" or "more negative" than the operating point of your circuit, whichever it may be, but ground is still ground and "0 Volts" for both circuits.
I hope that explains it better. It can be pretty confusing. Especially when you try to envision what the actual electrons are doing during the entire AC cycle at each stage and within each bias situation.
http://www.muzique.com/lab/fuzzface.htm
Ok. Like Im a 6 year old... ::)
Lets say I have a PNP Positive ground Fuzz Face and I have a TS-808.
I have NO plugs in the Input or Output jacks.
I plug BOTH pedals into the same DC power supply.
Will I short out my PS even though the pedals are not connected by an audio cable?
Probably not.
If your FuzzFace is TRUE positive ground (the sleeve connection of your guitar cable is connected to +9V) then the guitar cable will be shorting + to - plain and simple.
Without the cable, the two circuits are happily living in their own little worlds.
The solution would be to do like the AMZ article says, so all sleeves are connected to the negative pole.
Quote from: edvard on December 14, 2010, 12:07:47 PM
Probably not.
If your FuzzFace is TRUE positive ground (the sleeve connection of your guitar cable is connected to +9V) then the guitar cable will be shorting + to - plain and simple.
Without the cable, the two circuits are happily living in their own little worlds.
The solution would be to do like the AMZ article says, so all sleeves are connected to the negative pole.
I proposed that earlier in this post I believe.
On the Fuzz Face, run your +V from the DC jack ONLY (no battery)... to the ground rail of the board and to the 3PDT (for the LED). Then connect your -V to your Input ring, Output ring, LED (via resistor), DC jack -V, and the -V input to the board.
This way, the +V is still getting to the ground rail as it does in the "normal" positive ground circuit BUT..... you now have your input/output jack rings connected to -V.
Quote
I proposed that earlier in this post I believe.
On the Fuzz Face, run your +V from the DC jack ONLY (no battery)... to the ground rail of the board and to the 3PDT (for the LED). Then connect your -V to your Input ring, Output ring, LED (via resistor), DC jack -V, and the -V input to the board.
This way, the +V is still getting to the ground rail as it does in the "normal" positive ground circuit BUT..... you now have your input/output jack rings connected to -V.
And you were correct (IMHO), you could even include the battery so long as it was switched out by the DC jack, but that's a given.
I think we've all muddled the whole thought process.
We've all been conditioned to associate "negative" with "ground" from staring at "normal" schematics for days/weeks/years on end.
Then we get this crazy idea to build a "proper" Fuzz Face with it's quirky PNP circuit, and we have to somehow flip our thinking.
So we call things "positive ground" and "negative supply" in an attempt to get our head around it and end up more confused.
I propose we think of two different worlds: Circuit World and Outside World, and propose a few rules for how to interact between them:
The boundary of Circuit world starts at the first semiconductor entry point and ends at the last semiconductor exit point.
Outside world consists of all the various jacks, cables and switches (hardware and semiconductor) that direct Signals into or around Circuit World.
In Circuit World, there is no such thing as "Ground", only Negative and Positive.
When working with Op-amps, there is "Ground", but it is simply a point halfway between Negative and Positive.
In Outside World, "Ground" does exist and by necessity it is always connected to Circuit World's Negative lead.
Signals traveling between Circuit and Outside Worlds must pass through a capacitor upon entering and leaving.
The last problem being Oscillation, which R.G. and others have described, which in most cases can be cured by proper application of a power supply decoupling capacitor.
But barring that, whaddya think?
Quote from: edvard on December 14, 2010, 02:43:26 PM
But barring that, whaddya think?
I think that this is the exact same thing that I have been getting beaten up about for a few threads now! :icon_rolleyes:
I like your Circuit World/Outside World terminology! :icon_lol:
That was actually the FIRST post that made 100% sense to me regarding the whole Negative ground/Positive ground debate!
According to your terminology... and my idea about wiring... A Fuzz Face would still get the same inputs to "Circuit World" however, the inputs to "Outside World" would change so that a common power supply would NOT short out when this "Positive Ground" Fuzz Face is connected to another "Negative Ground" pedal.
Quote from: edvard on December 14, 2010, 02:43:26 PM
The last problem being Oscillation, which R.G. and others have described, which in most cases can be cured by proper application of a power supply decoupling capacitor.
The thing that ruined that "most cases... cured... proper application..." is that I found some instances where no amount of proper, well thought out, experienced, skilled power supply decoupling will fix the oscillation.
Just noting that one has never had a problem with elephants from trampling the roses does not mean that there are NO lawn which need regular doses of elephant repellent to keep the roses healthy. Just because you're paranoid doesn't mean that no one, anywhere is not out to get you. :icon_lol:
Quote from: R.G. on December 14, 2010, 08:11:46 PM
Just because you're paranoid doesn't mean that no one, anywhere is not out to get you. :icon_lol:
Thanks for the input RG. I think you may have the wrong idea. Please don't mistake paranoia for the need or desire for an explanation that actually makes sense to those of us that do not do this for a living. I merely wanted a laymans perspective regarding this idea that I had floating in my head. I meant no disrespect... it just so happens that edvard was able to do in one post, what many have not been able to do in multiple posts!
I now have a better understanding of the PNP positive ground vs. negative ground.
No biggie. I really was chuckling.
The positive/negative ground is infinitely confusing, and I've been typing much the same stuff for well over a decade now. I guess that ought to incent me to go write a "Technology of Positive Ground" . :icon_biggrin:
The negative side of a power supply is used for ground so often today that it's common to think of negative as ground. That's the first stop on confusing beginners. Second stop is that it's so very inconvenient to use two supplies (or was: AC power adapters are now so cheap that getting a second $20 supply is often the best idea) that people start looking for tech secrets to "fix" this, and they latch on the first layer of EE knowledge: Hey! Either side can be used for ground, just do the caps and pullups right and it all works. And mostly it does, until the times it doesn't. Many of those can be fixed. But some can't.
It's a confusing area, and each layer of new info has its own gotchas attached.
Quoteit just so happens that edvard was able to do in one post, what many have not been able to do in multiple posts!
I am humbled that you found my explanation so helpful; glad to be of service ;D
Though I do agree with R.G. there are some cases where oscillation simply happens and cannot be cured (Hell, that happens with some "normal" circuits I've cooked up... :icon_redface: ), I think it's just something in the nature of how Fuzz Faces work that makes them act so persnickety.
Quote from: edvard on December 15, 2010, 06:59:25 AM
Hell, that happens with some "normal" circuits I've cooked up... :icon_redface:
Call it a tone generator and stop debugging :icon_mrgreen:
Quote from: edvard on December 15, 2010, 06:59:25 AM
I think it's just something in the nature of how Fuzz Faces work that makes them act so persnickety.
My particular counterexamples were not fuzz faces, though.
> I found some instances where no amount of proper, well thought out, experienced, skilled power supply decoupling will fix the oscillation.
If you have built a good oscillator, better supply decoupling will improve the oscillation.
Amplifiers oscillate. Oscillators don't. Murphy never sleeps. Corgis keep elephants out of the roses, but won't keep Murphy out of the electronics.
Quote from: PRR on December 15, 2010, 09:59:25 PM
> I found some instances where no amount of proper, well thought out, experienced, skilled power supply decoupling will fix the oscillation.
If you have built a good oscillator, better supply decoupling will improve the oscillation.
Amplifiers oscillate. Oscillators don't. Murphy never sleeps. Corgis keep elephants out of the roses, but won't keep Murphy out of the electronics.
Yeah. Murphy and I are old friends.
What still bothers me about this issue is that undoing the conversion to negative ground stopped the oscillations. Period. Reconversion started it. No amount of cleaning - or dirtying - the power supply impedance cured it. Makes no theoretical sense. Been through the theoretical and practical issues in depth, including consulting some guys I think are much better at electronics, including RF design, than I am.
I eventually marked that down as "don't do that". It's still an open issue with me.