AndrewCE

Easiest fix around and it'll only cost you $0.50 or so:

http://www.bothner.co.za/articles/volumepot2.shtml

or

http://www.guitarnuts.com/wiring/volpass.php

I like the first one, but the second also shows a 150k resistor has nothing to do with fixing the muddyness. It just changes the curve of the pot so the volume change is less extreme at the end so I put it up in case you felt like adding it at the same time. edit: I just realized that the guitarnuts person simply got confused. He probably meant to talk about putting the 150k in series with the capacitor, which is a good tweek to this, and does just what the first link says. But he added a resistor in parallel, and that does something completely different. I'm not sure that 150k would be the right value to use in parallel, because it depends on if you have a 250 or 500k volume pot. I'd use a higher value, but a search will find you more detail.

If you already knew about these, sorry for being redundant.

Best,

Todd

i've already done that to my guitars ( I actually have a thread about it on this board somewhere). It works pretty well, but the volume taper is not quite the same. It only fights against the cable capacitance, but it would still be better if you could eliminate the capacitance.

It's never been a concern for me, I HATE that icepick in your forehead treble sound. I like a thicker, meatier sound.

I also think that most people probably couldn't tell the difference between a $100 3-foot long Monster cable and a 25-foot long $25 cable in a blindfolded test. This kind of stuff is psychoacoustics at work again. The same kind of snake oil hogwash as "oxygen-free copper".

I know, now you're going to tell me that you can hear the difference, blah, blah, blah. But can you really? Or are actually thinking that you can because you believe it is true? That's why people need to do a blindfolded test to really truly let their ears decide. I submit to you that it's in people's minds that a cable that costs four times as much and has a few pF/per foot less capacitance is so immensely better.

actually i've never done a blindfold test between cables

but i have rolled down my volume control and noticed that it gets muddy. "muddy" not "thick" or "heavy". Simply cutting highs makes something sound muddy.

and even if there's not noticable difference, all those little things all over your sound combine to make a significant difference

even so, i personally don't think $50 is reasonable for any guitar cable, even a 0mF cable

V2, V3, V4 etc, are the outputs of your opamps. The diagram shows the resistors, R2, R3, R4 that mix the outputs into the following buffer (the op-amp shown in the diagram)

OHHHHHHHHH okay,

yeah then that's what I was describing.

so it will work, with the resistors. K thanks!

as long as the signals dont travel through the resistors anyways...

For goodness sake yes - that's exactly what I said and provided the diagram for above. You are describing a mixer !!

But your diagram had resistors before the op amp. I'm saying if a resistor was after each parallel voltage follower. Surely they wouldn't act the same way.

I agree, it's mostly hype. Just like hi-fi speaker wire and guitar cables. And a good many other things, too.

WOAH i disagree there. Cable capacitance does play a role in guitar tone; you lose high end, especially with the volume pot turned down.

psw, do you mean that the signal produced by part A (pickup A in series with voltage follower A) will try to run through part B? I don't think a signal can enter the output of a opamp.

Unless, as I was thinking earlier, signal A entered the output of voltage follower B via opamp B's inverting input. Would this happen? And could it be stopped by adding resistors after each voltage follower?

Let's try it this way. An "ideal" voltage source has zero impedance. If you connect two zero impedance voltage sources that are different in voltage, the voltage difference divided by the impedance (zero) means it would try to deliver infinite current. In the real world, this is not a good thing. They will NOT "average each other". They MIGHT try to destroy each other :-) except that built in protection in opamps and the fact that they are less than ideal voltage sources, might save them. They will both try to control the voltage to the value they want, and as that is different - they cannot both succeed. How's that for interaction?

hmm, thats exactly what i was afraid of.

sorry but i still don't understand your "If you connect two zero impedance voltage sources that are different in voltage, the voltage difference divided by the impedance (zero) means it would try to deliver infinite current." Do you mean voltage follower A would try to deliver infinite current into the output of the voltage follower B?

now what if you put a resistor after each voltage follower, and THEN brought them together. Then the impedances would not be zero. Would that produce "A+B"?

oh and long pots distort a bit smoother than short ones, but they lose some high end.

HAHA jk

Newbie to the guitar building world, just curious about the above mentioned topic, I'm assuming standard pots are for non carved tops and long pots are for carved tops. Excuse my question I did a search and couldn't find a topic on it. Any info would greatly be appreciated.

Thanks

that would be correct

well, technically depending on thick vs thin. but carved tops are generally thick and noncarved have thin wood top.

You really can't connect ideal voltage sources together. There needs to be some resistance, otherwise interaction due to loading will occur.

hmm i'm not sure i'm understanding your explaination here. What is "interaction due to loading" referring to? What is loading what?

You have 2 low impedance sources in parallel, why would the 2 voltages not just average each other?

Well...a voltage follower is just that...there is no gain...so...ummm...A & B...if that makes sense....

but there is theoretically infinite current gain, that's how the voltage follower has low output impedance

...right?

and why would there be distortion, if a pickup's signal is only a few millivolts and I supply the opamp with +-9v?

It's hard to give an answer or opinion without knowing what your real world proposal or thinking is.

If for instance as I assumed earlier (but not confirmed) A and B are pickups and one is being buffered...you will have on the buffered pickup the equivalent of a low impedance active pickup given...

there is infinitely high input impedance and infinitely low output impedance.

so...it will accept any input and give out an exceptionally low output...

Now mixing a passive pickup with an active pickup is notoriously troublesome and the control pots are likely to need scaling back to work properly for the active, but not for the passive...if you buffer after the controls...you are likely to induce noise and scratching from the high pots.

A common strategy with opamp designs is to bridge the input to ground with a 1M or so resistor, this gives the input a 1M input resistance similar to the impedance of a guitar amp. This is just one of the many little design subtlties with working with circuits and guitar impedances.

Again...not sure I am understanding the application...

SO...opamps are often regarded as cold...at the least "overdone". If you find a diagram from a data sheet say of the inside of an opamp...TL071 and family being very common...you will see that it is chock full of diodes, caps and resistors and quite a few transistors.

Now...a transistor will give you the same effect, high input, low output...do you really want the guitar signal going through all these extra components? Well...maybe you do...it will give a very cold solid state kind of sound perhaps (different opamps have different characteristics) however, a design like the tillman or fetzer uses a single transistor and a few components to keep it happy, to provide the same kind of effect but a warmer "tube like" distortion characteristic. This may be even more desirable.

Really horses for courses I guess...and again depends on the application and what kind of effect you are trying to achieve. Personally, I don't mind opamps for some things and once you start wanting to add variable gain (by altering the feedback ratio) or tone controls or adding numerous stages (a TL072 is a dual opamp in the same size pack for instance and is often easier to work with than the single 071 for the same price even if you only use half of it!)...they also have their own bias circuitry inside that gets rid of pesky biasing trimpots and stuff...they do have a tendency to draw a bit more power, but then it is very little anyway so it hardly matters that much...with more complex circuitry that might have active tone controls (cut and boost) or overdrive (added diodes to produce clipping as in the tube screamer and such) or other processing...there is a lot to be said for opamp circuits.

I am not following however the application that your question is asking...generally, you would buffer all of the pickups or signals A & B I suppose, either collectively or individually, or both (as in a mixer circuit) due to potential issues with mismatched impedances, control problems and loading issues.

There can also be issues with "popping" when active circuits are switched in and out of a signal...so say you have two pickups and one is active, selecting the non active pickup may well generate a mini power surge that will be loud through a wall of marshalls!!!

pete

OK yeah let's say A and B are pickups. And lets say they both have voltage followers on their hot leads. And they are in parallel. Would the output of this circuit be simply A+B? Or would the two voltage followers affect each others' performance?

oh, then consider the same circuit using transistors instead of opamps. Would the output be A+B?

Hmmm I'm not trying to use them for any distortion, so "tubelike breakup" isnt important, but other than that, how would an opamp make a signal sound "cold"? .....Limited bandwidth?

and by the way, I'm not just asking all this just for one specific application, it's mainly about a deeper understanding about how opamps work. I KNOW how opamps work, but to know and to understand are entirely different

I have read many places that vintage guitars had cloth-coated wires connecting the components. Does this DO anything differently than plastic coated wire? Or is is just for people who are **** about vintage replication and identification?

One place said that cloth wires were individually shielded by the cotton. Isn't cotton nonconductive?

I am confused.

Answers?

dude did this website just bleep out the word that starts with a cr- and ends with a -azy?

The "shielded" thing...they probably mean insulated...one thing about cloth covered wire is that the cloth can be pulled back and soldered...then the cloth pulled back over the join...but yes it is an authenticity thing like using exotic vintage caps as much as anything.

soooo many questions!

that pulling cloth over the joint thing sounds cool...

do i ask too many questions?

it's only because i love guitar electronics!

Use of opamps for active guitar circuitry either as a buffer or with a few extra components and a preamp (the same thing but with gain) is very common although many prefer the sound of the discrete transistor circuits such as the tillman or fetzer. Opamps are the lego blocks of the electronics world...but your guitar signal is going through a lot of circuitry inside those little black chips.

As for your second question...I don't really follow...it seems that you are suggesting having one pickup A buffered with another signal B non buffered going to the guitar output...probably not a good idea...as you google quote will have told you...there are massive impedance differences.

OR...I might be completely misunderstanding the application you are proposing here.

If you are designing things, I'd suggest doing a bit more homework than google or use an existing circuit as a starter...there are some good tutorials around also on this subject.

Be aware also, that the control pots and such generally need to be changed to much lower values...again, because you now have a completely different impedance change.

However, many have simply added a buffer at the output and run the guitar through that...generally improved highs as you eliminate cable capacitance effects...

pete

What does all the cicuitry inside an opamp do to the sound that makes it any worse than transistors?

I know that the impedance difference will cause one signal to be much more prominent, but what I am asking is: Does B affect the operation of the op amp? I was thinking that maybe since B is tied to the output, and therefore the inverting input, B would become obliterated by itself and there would be no trace of B in the final signal. Does that make sense?

And also, does the impedance of B change how B affects the op amp operation?

I have read many places that vintage guitars had cloth-coated wires connecting the components. Does this DO anything differently than plastic coated wire? Or is is just for people who are **** about vintage replication and identification?

One place said that cloth wires were individually shielded by the cotton. Isn't cotton nonconductive?

I am confused.

Answers?

An Op Amp Voltage Buffer, a.k.a. Voltage Follower, is when you connect the output of an op amp directly to the inverting input. The voltage at the noninverting input is copied directly to the output. But there is infinitely high input impedance and infinitely low output impedance. Google it for more info.

So here's the Question:

Say you've got a voltage source, "A", before the Voltage Follower. In parallel with all of that, you've got another voltage source, "B". How does B affect the operation of the voltage buffer? Would the 2 voltages just be added? Would the total output just be equal to B or A? Would B invade the inverting input and get saturated?

I ask because I am considering using op amps in some active circuitry in my guitar.

It was about a year ago, so my memory is sketchy. I remember them being pretty bright with lots of treble, but not much more. There are a lot of demo videos on YouTube that give a fair representation of the sound.

yeah but to demo something yourself is so much more informative, ya know?

I played one of the Taylor hardbodies once. I'll say this. The pickups sound different. They weren't particularly to my liking, but they certainly weren't bad. The neck, on the other hand, felt amazing.

yeah when i test drove one, i didn't get to play it through an amp. How would you say they're different? brighter, warmer? midrangier? more/less attack?

Problem is the switches are not independent of each other, 1 on, all on, 1 off all off. Can anyone help me wire this? Thanks

Do you mean that the volume/tone knobs are not independent?

That will happen, to where when you turn the tone down for one pickup, it effects the others. There are ways to wire around that. Is that what you're talking about?

p.s. How many knobs are there on the guitar?

i haven't used that particular amp but IME its the "contour" of the midrange ie max =mid scooped, min= mid humped, in your case probably used to adjust the overall mid shape then the parametric EQ provides more focused adjustment.

So you mean it's like just a "mid" control? My amp already has one of those. It's called "mid".

Or "contour" it like a "Q" control for the mid knob?

My Mesa 5:50 combo amp has a single knob that is called "Contour". The manual and website says it "adds the power of a graphic EQ to your amp". That doesnt exactly tell me what it does.

All I know is, my sound is better, thicker, ?heavier? when I have the contour knob all the way up, so I keep it that way.

My amp already has a parametric EQ, so it's probably not a bass, mid, or treble knob, so...Can anyone tell me what the knob DOES?

These Taylor solidbody "3/4 size pickups";

are they just mini humbuckers? Is there anything different about them? The website said they were revolutionary, but they seem to be just mini humbuckers.

Has anybody opened them up or found an article showing what's inside?

I'm not sure...but you are asking the wrong forum...try...[url="http://www.diystompboxes.com/smfforum

oh. sorry. i guess this forum is just for on board guitar electronics?

i'll try that site

Anybody have a schematic for an EHX Micro POG? I can't find it anywhere.

Does anybody know even where I could get it?

I hate when I can't find schematics.