Following up on R.G.'s excellent post, I'd like to start this thread so we can help the beginners on what matters/doesn't matter in regards to our low voltage effects.
Please post to this thread and it will be incorporated into the FAQ.
Of course these are all generalizations.
We use 1/4 watt resistors, but in reality, you can use any type of resistor even if it's larger (i.e. 1/2 watt)) and the measurement doesn't fall totally out of range. (+- 5%). Provided you can fit them on the board.
You can use film caps instead of electrolytics provided you can fit them on the board and they are the same value.
If you don't have a specific value resistor or capacitor, you can string two or more of them together to get the desired value. If you can't find the exact resistor, one that is within 5% is OK unless the circuit calls for extreme tolerance.
If a schematic calls for a polarized capacitor (electrolytic, tantalum), you can substitute a non-polarized capacitor and it will work.
If a circuit calls for a 16 volt 22uF capacitor, you can use any 22uF capacitor that has a voltage rating that is higher. For example a 24 volt 22uF capacitor. The same goes for film. You can use a 630V film capacitor in a 9 volt pedal.
If a schematic has been built by many and is pretty much verified correct, and your build "doesn't work". Despite what you may think, you have made a mistake in your circuit or a component is bad. It's hard to accept, but it's true.
Usually the components that may be "bad" are transistors and ICs and rarely resistors and capacitors.
You can use a 10M [instead of 22M] before the input cap of a Micro Amp...does it make a difference?..I doubt you'd be able to tell, I used the 10M because it was there, could have built a 20M as there were two, opted for the 10M...
I used 22k's [instead of 10k's] for the voltage divider, because they were there, would I find it different?...I wouuld have to buy more resistors to find out.
I've been using 386's though for voltage dividers, I don't notice any difference when using them.
Pulldown resistors...do you need them? I use them when an effect pops during switching...there's the reason for these.
Power protection diodes, there is a reason for them, I often forego the pleasure, because I don't reverse battery polarity [knock on wood]...
Some things you can 'fudge' with no problems and no percieved difference...others have to be .. say within' the standard 10% tolerance for a circuit to work, or to work 'right'.
Good thing about reading here is that 'we' try everything at least once...or have read about someone trying 'it', or we're about to find out by experimentation...
Most of the circuits around here have been gone over with a fairly fine tooth comb as far as what's possible and what's not possible, what mods do what, a simple question almost invariably gets a concise answer...just type about it and get feedback, or try it yourself to see...if you really need or want that...input buffer for instance.
Using Carbon Composition resistors in Fuzz Faces and other low voltage circuits for "vintage sound" or "brown sound" is pure marketing hype. They add nothing to the sound other than NOISE...usually something like a "hiss." For better results, use 5% Carbon Film resistors, and for best results, use 1% Metal Film resistors.
Phillip
Always use sockets for IC's. It prevents heat damage (some are expensive), and allows for easy swapping.
All grounds do not have to connect to the same point, but all grounds need to be connected together.
Old germanium transistors cannot be tested properly with just the hfe range on your multimeter. You will need to test them according to the "How to select transistors....." documet over at Geofex (insert link here), or with a 1950:s transistor checker that is equipped for leakage testing.
Always use a cooling device (flat pliers) when soldering a leg of a transistor - or use a transistor socket.
Use sockets for capacitors and clipping diodes in circuits where changing them is how you dial in the amount of distortion or bass/treble response.
Never assume the pinout of a specific transistor is the same from one manufacturer to the next.
Tubescreamer fans: A twenty year old JRC4558D chip sounds no better than a new JRC4558D chip. Save your money, forget the mojo and hype, and buy the new chip. Truth is, there are better IC's out there for the TS-9/808: RC4558, RC4559, NE5532, TLO72, to name a few.
Always double check the polarity of components BEFORE you solder them in. Electrolytic caps, tantalum caps, diodes, and LED's.
(Almost?) all dual opamps use the same pinout.
Makes for easy swapping and experimenting if you use a socket!!
Single opamps and dual opamps DO NOT have the same pinouts.
Use a DMM to double check your resistor's value's just before you solder them in.
A digital multimeter is a required tool.
If you are hand-wiring with perfboard, never cut a lead off a component until you are sure you don't need the lead anymore.
pulls are your friends - they can save you lots of money, and can help you experiment. Boards with solder on one side are _much_ easier to pull from than double solder boards.
And yes, as mentioned in the first post, the tiny 1/8 watt resistors are good for effects.
Yes you can use left over leads from components to create jumpers, lengthen leads etc....
tin every twisted copper wire before soldering it.
Any brand jack will work fine, but for 1/4" jacks, Switchcraft seems to be the best. In general, the Radio Shack jacks will work, but are probably not worth the cost and aggravation.
Pre-tinning a wire/lead can help you solder a bit easier. Solder flux is very useful when soldering onto hard-to-solder surfaces.
If possible, test your board before putting it in the enclosure. This way you know the board worked before securing the board to the enclosure etc...
You can exchange "audio", "log" etc... tapered pots with linear. It will work and you can always replace the pot with the correct type later on. Don't let this stop you from building the effect.
The same circuit can sound different from another "identical" circuit and usually does. :?
Not mandatory, but a capacitance meter can be extremely helpful for building, debugging, and tracing . Here's an inexpensive ($29.95) one that covers the entire range of useful values.
http://www.electronickits.com/gold/capacitancemeter.htm
when testing outside a box, you might experiance some noise that sheilding will take care of. Don't worry about that.
It usually matters that copper traces and solder lugs are clean before you try to solder to them (especially if you don't have any flux) - you can use an ink eraser to clean them up.
Sound clips from effect's sites are only a general guide as to the pedal's character. They can and will sound different than your pedal, due to the guitar/pickup/amp differences between you, and the rig they were recorded on.
I think Aron just made this thread to get his post count up :twisted: :twisted: :twisted:
jk :D
"The same circuit can sound different from another "identical" circuit and usually does."
That's because of the differences in the tolerances of the parts. Kind of like no two guitars of the "exact same make and model number" don't sound the same - no two pieces of wood are going to have the same density, mass, pickups can be slightly different from one to another, etc., etc. Sometimes all this works out for a great sounding guitar and sometimes you get a dud. That's why I would never buy a guitar without playing it first. The classic stompbox example is the original Ge Fuzz Faces.
Brush after every meal!
RDV
Always test the voltage of your battery before you start debugging a problem with your circuit.
If you are using a DC jack, make sure it is isolated from your enclosure. Most commercial guitar effects are center negative.
Don't forget to use a current limiting resistor with your LEDs. They will get fried on 9V.
alwais use a paper template tapered on the enclosure to drill it. it's fast
and accurate!
If you are a beginner start with verified schematics that are known to work correctly.
Beginner's read the FAQ :roll:
Search the archives before asking basic questions that have been asked thousand times before :twisted:
if you cant find what your looking for, dont be afraid to ask. Everyone was a newbie once(some continue to be :wink: ), and we all asked/ask dumb questions every now and again...
Just look in the archives before hand... :wink:
This is a great thread. I figured many of these things out the hard way. :oops:
Is it hit or miss?
Try a few FF's and see...
Dist+'s too
Tubescreamers
BMP [well I don't know if that would count even as sounding 'right', I only tried one].
Having built these in small batches [FF's would consittute a large batch], some just work 'better' than others.
These same boxes and switches have seen circuits come and go through them, I've got them 90% filled now [lol...I'm always tweekin'] with effects I like to use regularly, which wasn't the case say 5 or 10 circuit swaps ago. Seems the more circuits I try, the better the boxes work overall.
For me it's still a bit like shooting in the dark, for example, I don't compare and check bais voltages [other than to see that they're close enough to work] and diode clip thresholds, I suppose that's what pedal makers would do to get more perfect consistancy from one pedal to the next [?].
I like running random experiments with them, every so often [1 in 3? or so] I get a magic one that turns out to pass the "Keeper Test' over a long enough period of time to be secure in it's home [the box].
Consistancy experiments might be cool too though...having never run them, and in the absence of a scope, I got by ear, and the board trim or surface mount pot, and therefore can only speculate blindly as to what resultant difference such fine tuning would make. ...lol I sure have gone through alot of diode swaps...
It is purported that using some 1% tolerance resistors, in certain places or entire build, and close tolerance caps makes a difference, I tried some 'fancy' caps, don't know that I really heard a difference, or whether it 'made' a difference...I've been kind of meaning [ :roll: ] to build something with all the most expensive components available to see if there really is a functional difference warranting the higher price considerations, and parts roundup tribulations.
1. Keep It Simple, Stupid
2. Many, many NPN transistors are 'general-purpose'. RARELY do you need a specific type.
3. Doubling or halving the value of a pot may give strange results, but the circuit should still work.
4. Boxes, switches, batteries are expensive. Resistors, capacitors, diodes and transistors are cheap. If you damage a cheap component, or think it is damaged, throw it away.
5. A quick lash-up, no matter how cool, will let you down on stage.
6. Captain Scarlet is indestructible. You are not. Remember this and do not try to emulate him.
7. If it's your first build, get it from ROG.
Don't sit on your soldering iron! :shock:
For mad scientists who keep brains in jars, here's a tip: why not add a slice of lemon to each jar, for freshness?
OK, a real one:
AC128 transistors will not sound good in a fuzzface circuit 9 times out of ten. Show me an original 1960s fuzzface with AC128 transistors and original solder joints and I'll show you hen's teeth.
Small Bear is a much better solution than buying trannies on ebay that I and people like me have already picked through for the good ones.
Yes, you can use stereo jacks in place of mono jacks, and yes, you can used switch jacks in place of non-switched jacks.
Don't use metal DC jacks when dealing with center negative DC plugs.
Always chassis ground (if you are using metal shafted jacks, that's no problem, but if they're plastic, go out of your way to make sure that there is a chassis ground).
When you can here the effect or a tone when the effect is bypassed, use a grounded input bypass scheme.
Hammond boxes are always better than RACO boxes.
Yes, you can use the taiwanese jacks, and yes, they will break faster.
-Colin
Always start out with a bigger box than you need if you are just starting out. There is no substitute for having ROOM in a box. Many beginners try to start out with too small a box and have problems when they have to cram everything in a small space resulting in shorts or broken wires etc.....
Following up on RACO vs. Hammond 1590 series. Aluminum is much easier to drill than the steel RACO boxes. That is the primary reason why a 1590 series box is so easy to use. The RACO is functional, but tough to drill. USE A VISE to hold the box.
When you drill a box, use goggles. It looks and feels stupid, but it works and protects you.
If you don't have a UniBit/VariBit, run and buy one now!!! These are great for drilling holes in enclosures. I have been using mine for years now, and it has been one of the best investments that I have ever made.
Never run your finger along the side of a brand new EH box that has corners. :cry:
There is no known tool for making oversized holes slightly smaller. The opposite is not true.
Blunt classroom scissors are safer than sharp ones. The opposite is true for drill bits.
When screws are put down on a bench, they run away when no-one is looking.
When handling small, rare, expensive objects, gravity and eyesight are your enemies.
A misused screwdriver is a vein-opener, not a box-opener.
The thought, "I shouldn't be doing it this way" comes only seconds before painful injury. If you're lucky.
An undersized Allen key is a drill for making hexagonal holes round.
Quote from: Ge_Whiz
An undersized Allen key is a drill for making hexagonal holes round.
An Allen key, that would be PERFECT.... :D
Quote from: anonymousexperimentalistDon't use metal DC jacks when dealing with center negative DC plugs.
Unless circuit is positive ground, then it doesn't matter...
Edit: but don't use the same adapter to run negative ground pedals too!
Darn little screws with legs!!! :evil:
And I guess I could add, that if something falls off of your work bench, it will invariably fall into the absolute worst possible spot for liberation...
Never Never Never drill a metal box while your pots are still in it! :oops: The metal fragments are very hard to wash out.
63/37 solder MATTERS! if you use 60/40, you're being masochistic.
I _finally_ bought some, and i'm loving it already!
Power supply regulation and filtering can make a difference.
If you're experiencing noise problems and are using a 'regular' Wall Wart, try a battery and see if that helps.
Don't read voltages associated with multi-megohm impedances with a cheap 1M multimeter. :oops:
Don't look for corroboration - ask for advice.
And of course - if it works, DON'T FIX IT.
My all time favorite Murphy's law:
"If you think everything is going well, it's because you don't have the slightest idea of what's going on!"
When running pos and neg ground effects, can two opposite ground boxes, when touched together cause a spark?
The reason I ask is that some time ago I was running a PNP FF. and some other +Gnd. boxes and had sparks fly...
Seems like the DC Blockers would Block - on the Pos ground, and + on the Neg ground though...{?]
If you're planning on building only one or two circuits, and not doing much tweeking...
It probably isn't worth the 15 minutes to make a test jig for your baords, so you can place them in a non conductive tray, and clip them right up and test, having the whole affair connected with cables 'n jacks.
I wouldn't advise anyone to plan on building only a couple circuits and box them without tweeking them.
parts:
One Large RACO [or other 5 sided box]
one cardboard tray use the RACO mount screws to mount the tray.
2 x: 1/4'' mono jacks
3 alligator clips
3 wires
run the hot wires [input and output] and the ground wire so they reach at least the middle of the tray [through the cardboard increases stability of the wire to hot jack connection, slide the clips insulators sleeves on the wire and solder on the clips]
Poke holes and screw the cardboard tray to the RACO.
A little about transistors...
In a bipolar transistor (BJT) amplifier stage, the base voltage needs to be at least 0.6V above the emitter voltage; and the current through the collector is controlled by the current through the base.
In a JFET amplifier stage, the gate voltage needs to be below the source voltage and the current through the drain is controlled by the voltage difference between the gate and the source.
In a MOSFET amplifier stage, the gate voltage needs to be above the source voltage and the current through the drain is controlled by the voltage difference between the gate and the source.
1/2V+ is a great point to set the output bias of a transistor gain stage to first test your circuit, but once you are sure everything works as it should, be sure to go back and find the sweet spot. It may be 1/2V+, but it just as well may not. (Does not normally apply to opamps)
Chances are 1/2V+, for a transistor stage, will NOT be the point of greatest head room, that is halfway between V+ and the voltage on the emitter/source.
What doesnt matter:
1. little words on a computer screen
2. what your parents wanted you to be
3. yesterday
4. failed attempts
5. disappointment
6. what's on t.v.
If you are struggling to fix a pedal, or get something to work correctly, the best way is to simply walk away for a bit, and go do something unrelated to pedals. Let your head clear and when you come back you will most likely see the problem staring you in the face! :)
Take care,
Brian
http://www.indyguitarist.com/
Quote from: caseyWhat doesnt matter:
1. little words on a computer screen
2. what your parents wanted you to be
3. yesterday
4. failed attempts
5. disappointment
6. what's on t.v.
Nice. :D And I agree...
(Yeah I know its a year old but I don't remember it. :D )
Doug
Nice bump, Doug.
Thanks
~ Charlie
After you build something on stripboard, use a meter to check whether any trace is connected to the next trace, and whether every cut in the track is in fact a cut, BEFORE powering up.
Because, you can see the meter easier without smoke in the way :wink:
A nice second (or first) build is a power supply. Your going to need one and it has tons of uses aside from powering effects.
Use spare parts to build jigs and other useful bits, I built a continuity tester so i dont have to use my meter for this purpose. Check out www.diyguitarist.com for other cool ideas
take your time
Use a battery for your first power up.
Before putting IC's (opamps and other) it their sockets put the project on power and verify the supply voltage is correct and not accidently reversed.
(SME testing is annoying and expensive ) (SME??? ....Smoke Means Error)
Unless it's a very, very simple project, don't sit down today and try to build something you want for tonight's rehearsal or gig. You'll be in a hurry and that will only add more mistakes to the number of mistakes you inevitably make when you're not in a hurry. You lived without that Super Murder-Face Fuzz this long; you can wait another day or week until you have plenty of time to enjoy building it right.
Quote from: aronWhen you drill a box, use goggles. It looks and feels stupid, but it works and protects you.
protective cups are very nice too. i learned this the hard way when i first drilled a raco box on teh back porch table without a clamp :oops:
Still just a n00b, but...
Make sure you have transistors and IC's in your sockets before you start desoldering 8)
If you think there's something flakey about your build, there probably is.
Some cheap multimeters come with a simple transistor tester useful for determining NPN and PNP pinouts.
There's a lot of value in enjoying the effect you just built before rushing onto the next one.
It's nice to make the enclosure before you start soldering to make sure everything will fit.
Most wires don't have to be nearly as long as it seems they would.
A continuity tester can be extremely helpful when debugging.
Sometimes taking a break is a necessary step in problem solving.
Solid core wire seems great until it breaks.
What sounds great at home rarely sounds the same at band practice.
P-90's sound great as long as you're not playing near flourescent lights or a computer monitor.
The true masochist solders dressed in a bathing suit.
Quote from: RickThe true masochist solders dressed in a bathing suit.
*or* a birthday suit...
:lol:
The white dot on a schematic denotes a gap wheras a black one denotes a solder junction.
MIND THE GAP !!
Using a toothpick to open up a filled solder pad is one of the best tips I ever used.
Heat up the solder blob and then stick the toothpick in where you want the hole to be.
Great thread, I should really spend some time reading over some of the older posts on this forum.
The support of your family while you're in the garage/lab not spending time with them. Remember that....MarkM can back me up on that one.
A great time to test for non-continuity between PS +/_ is just before applying voltage for the first time.
Build an Audio Probe ('Debugging' thread).
It's the smartest 5 minutes I ever spent with a soldering iron.
Measure twice, cut once.
If you're a beginner, build using stock values first THEN apply mods. If you are certain you will want to try mods, socket the relevant components then get the circuit working with stock values installed. It's a good idea to research mods before you order your parts for the build.
Buy some lead-based solder while you still can.
Measure twice, cut once.
Yupp...the other side is: Measure long, cut twice !
I use this second method on 'inside fit' wood pieces, and perfboard projects.
On perf I also, sometimes, measure long, cut once, then add that 'other little circuit' instead of cutting the second time.
Buy a Dremel. You will not find more uses out of a single tool in anything else you will ever buy. Period. And buy a corded one. You will be glad you did once you've been working on a something with it on for a long time without the worry of a dying battery. Plus, corded power tools are usually more powerful than cordless ones. So the benefits far exceed the drawback of not going cordless.
Jeff
If you don't have a desoldering bulb or desolder braid, you can just strip some thick stranded wire (like speaker wire) twist it together and it will suck up solder.
What matters? every part in a design.
Therefore Beginner's guide to tinkering with other people's designs:
1. If you swap around parts, and you don't notice a difference, it probably has to do with noise filtering or power supply regulation. Everything else, you must mess with, or you're not a real man. (disregard this statement for your first few builds)
2. Words are your friends. There is a lot of great info on sites like here, GeoFX, Beavis Audio, AMZ, (freestompboxes.org) etc. There are also some decent books out there by folks like Wampler, Orman, and Anderton. The more you understand what you are doing, the more smoothly things will go.
3. On a related note, the more schematics you look at, the more you will eventually understand. The do, eventually, become interesting. :icon_surprised:
4. Solderless Breadboards are great tools, but they are far from perfect tools.
Quote from: Fret Wire on July 14, 2004, 04:54:44 PM
Use a DMM to double check your resistor's value's just before you solder them in.
In a Triangle Big Muff the 120 ohms resistor and one of the 10K resitors are a source of big troubles!!!
people - little pieces of metal that, when arranged in certain ways, vary something about a small alternating current.
oh, but get some double sided tape. I put a little on the edge of my bench because that's where most of my caps, transistors and resistors wind up when I'm changing out components. It's also where my forearms wind up. Before this, the other stuff would,ultimately, wind up on the floor. Now, not as big of a problem.
An oscilloscope is not strictly necessary for debugging, but it sure makes things a lot easier. Esp. when building complex stuff (read: flangers).
Quote from: Fret Wire on July 14, 2004, 04:40:59 PM
Tubescreamer fans: A twenty year old JRC4558D chip sounds no better than a new JRC4558D chip. Save your money, forget the mojo and hype, and buy the new chip. Truth is, there are better IC's out there for the TS-9/808: RC4558, RC4559, NE5532, TLO72, to name a few.
Better is subjective. In my
specific case testing proved the stock TA75558P best and the vintage RC4558P 2nd.
Quote from: Paul Marossy on July 14, 2004, 04:30:24 PM
All grounds do not have to connect to the same point, but all grounds need to be connected together.
Except when you use something like a 555 in your project... then it's a whole different story. Found that out the hard way :icon_mrgreen:
Well, it took five years but I need to correct myself:
Quote from: Jay Doyle on July 21, 2004, 09:50:18 AMIn a bipolar transistor (BJT) amplifier stage, the base voltage needs to be at least 0.6V above the emitter voltage; and the current through the collector is controlled by the current through the base.
The above is wrong.
The current through the collector/emitter is controlled by the base-emitter
voltage.
The base current is an error current due to the construction/action of a bipolar transistor.
The reason that beta is so variable is because the base current/collector current ratio (
i.e. beta)is based upon an error current and is also why transconductance is a better, and infinitely more stable/predictable, parameter to use in designing BJT circuits.
Regards,
Jay Doyle
Quote from the textbook "Introductory Electronic Devices and Circuits" by Robert T Paynter, currently in its 7th edition:
Chapter 5 Bipolar Junction Transistors
QuoteThe transistor is a current controlled device. The base current (IB) can be varied to control the amount of emitter current (IE) and collector current (IC).
FETs are voltage controlled.
Favourite tool when building? Swiss Army Knife.
It's like your wire strippers, cutters and trace cutter all in the same place.
If you're stuck for bench space, it's a great piece of kit. Still pretty good even if you have acres of room.
Also...
Print off a second copy of any diagram you're working from. Use this copy to tick each component as you solder it in place - or even draw a trace for it if you're etching. Finding you've missed a component off your super-neat PCB you were so pleased with can be a bit of a downer. <speaks from experience>
Quote from: newfish on June 03, 2009, 05:44:25 AM
Print off a second copy of any diagram you're working from. Use this copy to tick each component as you solder it in place - or even draw a trace for it if you're etching. Finding you've missed a component off your super-neat PCB you were so pleased with can be a bit of a downer. <speaks from experience>
Good point :icon_cool: - I use a highlighter pen.
Try to keep a journal of everything you do that day at the workbench. It might pay off later.
still newbie at pedals but lots of soldering experience, steel wool is great stuff, rub a little over your circuitboard or perfboard and the solder will stick to it much better. its also great on the back of pots when grounding them in guitar wiring or any jacks or whatever that look a little dull.
Quote from: ClinchFX on June 02, 2009, 07:47:38 PMQuote from the textbook "Introductory Electronic Devices and Circuits" by Robert T Paynter, currently in its 7th edition:
Chapter 5 Bipolar Junction Transistors
QuoteThe transistor is a current controlled device. The base current (IB) can be varied to control the amount of emitter current (IE) and collector current (IC).
FETs are voltage controlled.
Somehow, I knew this would happen. I can't even say that
I am wrong without someone disagreeing! ;)
- First, just because something is repeated
ad nauseam as 'the truth' doesn't make it so.
- Second, I am sure Mr. Paynter is a very capable engineer/educator/author, but your quote from his work just proves that you can't believe everything you read.
- Third, take a BJT, emitter tied to ground, collector to some V+ and then attach to the base a current source which originates from some V- (below ground, so that the voltage required for the CS to operate doesn't also effect the base-emitter voltage). No matter how stiff, perfect, or large that current source is, unless you are able to find some way to bring the
voltage at the base up to the cut-in
voltage of the base-emitter junction (around 0.5V for Si, 0.1V for Ge), you will
not be able to get the transistor to conduct at all.
- Fourth, taking a gander at the Ebers-Moll model for emitter current:
IE = IES (eVBE/VT - 1)Where:
IE is the emitter current.
IES is the reverse saturation current of the base-emitter diode (
i.e. the leakage current,
NOT the injected base current); normally on the order of 10
-15 to 10
-12 amperes.
e is the exponential function or 'Euler's Number', an irrational number and mathematical constant with a value of 2.71828..., and the inverse of the natural logarithm.
VBE is the base-emitter voltage.
VT is the thermal voltage; approx. 26mV at room temp.
(There is also a 'correction' factor constant,
n, which sometimes precedes the
VT term, ranges in value from 1 to 2, and is material and somewhat device dependant.)
Therefore, the only
NON-constant in the equation is
VBE. (While the reverse saturation current and the thermal voltage 'vary', once determined for the device and situation, respectively, they are, for all intents and purposes, constants.)
Nowhere in the equation for emitter current is the term
IB, the base current.
It would be both ironic as well as funny to me if Mr. Paynter's book happened to include a discussion of the Ebers-Moll model, while stating that a BJT is current controlled, because in order to determine the current through the emitter -
the only variable available is the voltage between the base and emitter. In other words:
a bipolar junction transistor is a voltage controlled device.- Last, though by no means the least, I will supply my own quote:
"The BJT is a voltage operated device, and the base current that flows is merely an inconvenient side-effect of the collector current induced by said base voltage. This is why beta varies more than most BJT parameters; the base current is an unavoidable error rather than the basis of transistor operation." - Douglas Self,
Audio Power Amplifier Design Handbook, 4th Edition, Newnes, 2006, page 337
(Note that this book is in it's fourth edition because of actual updates to the content, not just simply reformatting the old content to change the page numbering, and/or other trivial changes, which is common in textbook publishing to force students to buy the newest edition, rather than allowing them the choice of reusing/buying old editions - as the latter results in zero profit for the publisher.)
Regards,
Jay Doyle
[
edited to correct typo]
You don't HAVE to etch your own PCBs. Perfboard or Vero are perfectly acceptable.
Provide strain relief for parts, using the enclosure itself as that relief when possible.
Imagine seeing through every step of the build process. Now mulitply that time times 10 and spread it over a few days or nights. That's called patience.
A cheap Dunlop inductor is perfectly acceptable in a wah. *Wah questions or myth-busters here: http://www.diystompboxes.com/smfforum/index.php?topic=74969.0 *
Quote from: JDoyle on June 03, 2009, 02:54:41 PM
take a BJT, emitter tied to ground, collector to some V+ and then attach to the base a current source which originates from some V- (below ground, so that the voltage required for the CS to operate doesn't also effect the base-emitter voltage). No matter how stiff, perfect, or large that current source is, unless you are able to find some way to bring the voltage at the base up to the cut-in voltage of the base-emitter junction (around 0.5V for Si, 0.1V for Ge), you will not be able to get the transistor to conduct at all.
And conversely, if you attach a pure voltage source - incapable of sourcing or sinking current - to the base of a BJT, you will
not be able to get the transistor to conduct at all. Accepting the quote from Douglas Self,
Quotethe base current that flows is merely an inconvenient side-effect of the collector current induced by said base voltage
the transistor will still not function unless that base current can flow.
Quote
- Fourth, taking a gander at the Ebers-Moll model for emitter current:
IE = IES (eVBE/VT - 1)
Where:
IE is the emitter current.
IES is the reverse saturation current of the base-emitter diode (i.e. the leakage current, NOT the injected base current); normally on the order of 10-15 to 10-12 amperes.
e is the exponential function or 'Euler's Number', an irrational number and mathematical constant with a value of 2.71828..., and the inverse of the natural logarithm.
VBE is the base-emitter voltage.
VT is the thermal voltage; approx. 26mV at room temp.
(There is also a 'correction' factor constant, n, which sometimes precedes the VT term, ranges in value from 1 to 2, and is material and somewhat device dependant.)
Therefore, the only NON-constant in the equation is VBE. (While the reverse saturation current and the thermal voltage 'vary', once determined for the device and situation, respectively, they are, for all intents and purposes, constants.)
Nowhere in the equation for emitter current is the term IB, the base current.
I've also seen the Ebers-Moll model used to prove that I
C=ßI
BI'm not about to get into a quoting contest. These are effectively two different theoretical ways of explaining how a BJT works, and the Ebers-Moll model can be used to explain both.
I apologise if I caused you any distress. I'll turn away from this thread now.
Peter.
Quote from: ClinchFX on June 03, 2009, 08:20:58 PMI've also seen the Ebers-Moll model used to prove that IC=ßIB
You don't need to use ANYTHING to prove that ß = I
C/I
B as that is the definition it was given when it was created - by humans NOT by Mother Nature. There are simply no laws of physics that relate to beta - which is why it is so variable.
Beta is entirely a human construction, whereas the V
BE to I
E relationship is related to actual device physics.
One varies widely from device to device even within the exact same type of transistor.
The other is a universal formula for all bipolar transistors.
Which sounds more accurate?
Why is it so hard to believe that the conventional wisdom is wrong? ESPECIALLY in the field of physics.
QuoteThese are effectively two different theoretical ways of explaining how a BJT works, and the Ebers-Moll model can be used to explain both.
Except that the voltage controlled version is correct and universal, whereas the current controlled version is misleading, at best, because it relies upon a relationship CREATED OUT OF THIN AIR by man, and varies wildly from part to part, instead of one that had to be DISCOVERED yet is relatable to every situation. There is a reason Beta has no unit of measure, in no way does it relate to nature.
AND - what you said in the quote above, is NOT what you said in response to my previous post - you flat out called my post incorrect, or rather, used someone else to do so, in a condescending manner that implied ignorance on my part. Am I not allowed to defend myself?
None of this 'distressed' me in the least, I enjoy a good debate even though my writing style apparently comes across as acrimonious. I completely realize we are not curing cancer here, but that doesn't mean we shouldn't want to be correct in how we approach these things.
It seems to me that the one who is distressed is the one who is heading off into the sunset once the debate became not so clear cut as they thought. It's a lot easier to build them than it is to know what really makes them tick, isn't it?
Regards,
Jay Doyle
I noticed that the posts have slowly slid from what matters to general advice so in that vain...
1. Don't leave the soldering iron on the floor and walk around in bear feet.
2. When you first plug in a new effect expect that it won't work
3. Before you shell out $$ for odd parts search for work arounds. The Reverse log pot work around (RGs secret life of pots) is an example
4. Test pedal and then drill holes for in your box. I made a nice univbe box and then didn't get the thing to work.
5. Just because you're feeling confident with 9v don't move up to 240v (mains electricity) I have no idea how many times I've received a 9v shock because I can't feel it. You don't want to risk that with 240v
6. Check to see if adjoining solders joins are touching each other - if you're soldering is as messy and bad as mine was in the beginning this will be likely.
7. Check everything. I almost threw out a pedal I had checked over and over again when I realised the output from the board was not connected to the jack - very dumb but it's so sobvious you forget.
For fear of making myself look silly I'll stop there
Quote from: Chris S on June 04, 2009, 10:21:40 PM
1. Don't leave the soldering iron on the floor and walk around in bear feet.
Maybe you meant "bare" feet? Although, how sweet would it be to have "bear" feet. Gimme a lion's head too while you're at it. :icon_lol:
Quote from: Chris S on June 04, 2009, 10:21:40 PM
6. Check to see if adjoining solders joins are touching each other - if you're soldering is as messy and bad as mine was in the beginning this will be likely.
7. Check everything. I almost threw out a pedal I had checked over and over again when I realised the output from the board was not connected to the jack - very dumb but it's so sobvious you forget.
These are both so very true. I've been doing this kinda stuff for several years now and feel like I've gotten pretty good with soldering and I still find mistakes on a regular basis.
Always put the 0.1 uF cap as close as possible to BOTH the positive and negative pins on microcontrollers.
Magnetic Parts Tray + Harbor Freight Tools = :)
You can't use Texas Instruments 4069 and 4066 ICs in the MXR Envelope Filters!!! Use Fairchild for best results.... grrrrrrr
Build a compressor... I was amazed at how much that *improved* my guitar sound... Even the drummer's wife commented on it :icon_eek:
Quote from: FlyingZ on May 30, 2009, 01:27:41 PM
Quote from: Fret Wire on July 14, 2004, 04:40:59 PM
Tubescreamer fans: A twenty year old JRC4558D chip sounds no better than a new JRC4558D chip. Save your money, forget the mojo and hype, and buy the new chip. Truth is, there are better IC's out there for the TS-9/808: RC4558, RC4559, NE5532, TLO72, to name a few.
Better is subjective. In my specific case testing proved the stock TA75558P best and the vintage RC4558P 2nd.
Since you did this test for yourself, and you're the only one using the result (I assume, anyway) I have no problem with this. BUT, I have read a number of reviews of totally ridiculous audio tweaks where the listener "proves" to themself that the tweak works, even when it can be shown through measurable scientific observations that it does not.
Quantum dots improve CD player "imaging" - but only for 10 CDs, then the quantum dots are all used up. (http://www.positive-feedback.com/Issue18/intelligentchip.htm)
Genesis - the $13,400 power cable - nevermind the 20 cent wire it plugs into. (http://www.virtualdynamics.ca/content.php?id=201&secondary_id=43)
Put this wood thing in your listening room. "I really like the flexibility of tuning you can get by moving them around the room. Most importantly, they made the sound more natural - smoother, with more harmonic decay. Everything was less etched, less hifi." (http://www.6moons.com/audioreviews/shakti/hallograph.html)
Put this ultrathin mat on top of your CD when it's in the player, and it will sound better! (http://www.hometheaterhifi.com/volume_12_3/marigo-labs-signature-3d-mat-7-2005.html)
And on and on.
The point isn't that you are one of these crazy people - I'm sure you're not. I'm sure you really do hear the difference. I'm just saying that it's quite common for people to really hear something which isn't there. It's an interesting psychological phenomenon. What I take from it is that it's useless to try take someone else's word about how things sound - especially when all involved agree it's a minor difference at best.
Quote from: bobp1339 on June 12, 2009, 12:58:50 AM
You can't use Texas Instruments 4069 and 4066 ICs in the MXR Envelope Filters!!! Use Fairchild for best results.... grrrrrrr
Actually, you can! You just have to play with the resistor on the ground side of the voltage divider for the clock. The schematic calls for a 100k. I used a 100k trimpot in it's place, adjusted down until the sound stopped. Then I slowly turned it up until the sound came back. Works great! The final value was about 37k.
peace
Quote from: Taylor on June 12, 2009, 01:53:24 AM
Quote from: FlyingZ on May 30, 2009, 01:27:41 PM
Quote from: Fret Wire on July 14, 2004, 04:40:59 PM
Tubescreamer fans: A twenty year old JRC4558D chip sounds no better than a new JRC4558D chip. Save your money, forget the mojo and hype, and buy the new chip. Truth is, there are better IC's out there for the TS-9/808: RC4558, RC4559, NE5532, TLO72, to name a few.
Better is subjective. In my specific case testing proved the stock TA75558P best and the vintage RC4558P 2nd.
Since you did this test for yourself, and you're the only one using the result (I assume, anyway) I have no problem with this. BUT, I have read a number of reviews of totally ridiculous audio tweaks where the listener "proves" to themself that the tweak works, even when it can be shown through measurable scientific observations that it does not.
Quantum dots improve CD player "imaging" - but only for 10 CDs, then the quantum dots are all used up. (http://www.positive-feedback.com/Issue18/intelligentchip.htm)
Genesis - the $13,400 power cable - nevermind the 20 cent wire it plugs into. (http://www.virtualdynamics.ca/content.php?id=201&secondary_id=43)
Put this wood thing in your listening room. "I really like the flexibility of tuning you can get by moving them around the room. Most importantly, they made the sound more natural - smoother, with more harmonic decay. Everything was less etched, less hifi." (http://www.6moons.com/audioreviews/shakti/hallograph.html)
Put this ultrathin mat on top of your CD when it's in the player, and it will sound better! (http://www.hometheaterhifi.com/volume_12_3/marigo-labs-signature-3d-mat-7-2005.html)
And on and on.
The point isn't that you are one of these crazy people - I'm sure you're not. I'm sure you really do hear the difference. I'm just saying that it's quite common for people to really hear something which isn't there. It's an interesting psychological phenomenon. What I take from it is that it's useless to try take someone else's word about how things sound - especially when all involved agree it's a minor difference at best.
If the did not upgrade the manufacturing process in 20 years would they still be in business? The point is that the chips ARE different, better or worse is up to you to decide.
As far as general internet claims and mods I consider them all varying depths of bull.
Yeah, but in general the sort of improvements they make have to do with decreased noise, better thermal handling, etc, where either it's only better (unless you like noise) or it doesn't matter for what we do (unless you play your TS inside volcanoes). There are a lot of parameters in ICs that are more or less meaningless for stompboxes.
I don't really have any feelings one way or another regarding Tubescreamers. I don't have one and never really wanted one (I play bass, FWIW). I just think the importance of stuff like this is somewhat overblown, as compared to, for example, the difference between two caps with the same nominal value but 30% tolerance. People don't seem to consider socketing all their caps and trying 20 of the same nominal value, even though this can often have a much more noticeable difference than ICs.
Quote from: Taylor on July 03, 2009, 10:13:49 PM
Yeah, but in general the sort of improvements they make have to do with decreased noise, better thermal handling, etc
Exactly and that affects "tone"
I used a vintage 4558D chip because I had one and it sounded a little better. Would I pay extra to buy one? No
Would I pay extra for vintage 4558P's for Orange Squeezers?.... Yes, lucky I still have six left :icon_biggrin:
Quote from: Taylor on July 03, 2009, 10:13:49 PM
People don't seem to consider socketing all their caps and trying 20 of the same nominal value
From experience if you have a "special sounding" pedal measure the exact values. I lost out on a great design because I could not reproduce the exact same tone and the prototype was dissembled :'(
Do you really think less noise and higher temperature handling change tone? Maybe for Merzbow, noise=tone, but for most musicians, I don't think so. I think maybe you're saying that whatever they have to do to change those parameters effects sound, and maybe that's the case. I don't think it matters enough to worry about. For me.
SS amps are better in every way then tube amps. I'll keep my tubes thanks.
Hmm... what? Is that part of this discussion we've been having, or are you starting a new topic? Not sure where you're going with that.
I was trying to say changes to make something cheaper and/or better can have a big impact on sound without altering the specifications.
It's really not a big difference between the 4558 chips. Use them if you have them. I agree with you that 99.99% of all internet mojo claims are false.
Quote from: FlyingZ on July 03, 2009, 10:49:24 PM
SS amps are better in every way then tube amps. I'll keep my tubes thanks.
I recently went in and asked one of our professors thus: "Are there any tubes left around here I could try to play around with to learn tube design?"
He said: "I don't think so... We haven't taught a class with tubes since 1970. Why do you want them anyhow? Nobody uses tubes anymore. 'Cept some diehard holdout guitar players, and if they think they can hear a difference they're just kidding themselves."
:P
i'm kidding myself.
I will continue to kid myself then... ::)
This thread should perhaps be sticky. :)
QuoteHe said: "I don't think so... We haven't taught a class with tubes since 1970. Why do you want them anyhow? Nobody uses tubes anymore. 'Cept some diehard holdout guitar players, and if they think they can hear a difference they're just kidding themselves."
When I was getting out of tech school (1994) I was reading up on tubes and mentioned that in a job interview. The interviewer was not impressed. I was lucky to get the job.
Oh, that was a good one Pete !
he he ha ha ho ho !
Quote from: aron on July 14, 2004, 03:30:24 PM
If you don't have a specific value resistor or capacitor, you can string two or more of them together to get the desired value. If you can't find the exact resistor, one that is within 5% is OK unless the circuit calls for extreme tolerance.
well, you actually wouldn't string the capacitors together, they behave opposite of resistors. you add caps in parallel to add the values, don't you?
For leads or other parts that need to be soldered but may be a bit corroded or dirty, you can use a simple pencil eraser to clean the leads.
Here is one that has both a pencil and pen eraser. You can use the pen side for more stubborn dirty leads.
(http://img.photobucket.com/albums/v494/CodeMonk/1012480965_zps6544dfa1.jpg)