last word on my last post

[tonequester]

tonequester here.

I posted a reply on the increase of resistance with increased frequency at 10:58 tonight. I received an e-mail from t-boy telling me that one can't reply to a
reply, that it just goes to him. he told me that if I would look at that Arrl hand book that I had recently received, under components, I would see that resistance does not change with frequency. If anyone looks on page 19 of that book, under Skin Effect, they will find out that resistance does indead increase with frequency, due to that very effect. My mistake was in not considering the terminology "high frequency" to be anything other than high audio frequency. The action of Skin Effect causing electrons to
congregate on the surface of a conductor at radio frequency, is what causes the resistance to increase. In my post "reply" to Enzo, I give examples of the consideration of this effect for several circumstances. One source(which I identidied) was a wire manufacturer who's graphical "curve" chart showed increased resistance at 10khz, and hugh
increase at 100khz. I know this is above the frequency of a 24 fret guitar at standard tuning(including harmonics). However, the increase can be shown. There are other examples, and the statement that "resistance increases with frequency" is used in other contexts as well. One being power transmission at 400hz for compuiter mainframes.
The statement is FACT. I just stupidly assumed that high frequency meant high AUDIO frequency. After listing the sources and qouteing the pertinent information, I admitted MY mistake, and re-phrased my question. However, once again, beyond a doubt, resistance does increase with high frequency. Even the experts disagree on what frequencies this becomes relevant at. I found speaker wire manufacturers at odds over this. That being said, this will be my last post. If one cannot answer their critics with
relevant and truthful information when asked for it, I have no further use for the forum, nor intend to waste my time. I thank all who have been so kind and generous to share with me what you have to offer. tonequester.

[Steve Conner]

Hi Tonequester

You are right that resistance of real conductors increases with frequency because of the skin effect. This sits uncomfortably with electrical circuit theory, which only considers resistance in idealised lumps known as resistors, whose resistance is the same irrespective of frequency. For instance, the popular Spice simulation software doesn't support a frequency-dependent resistor, and this makes it hard to model eddy current effects in guitar pickups.

(FWIW, the resistors you buy from the electronics store are pretty close to ideal over the audio band, except maybe the big wire wound ones which can have considerable inductance. This is not the same thing as frequency-dependent resistance.)

The frequency at which skin effect becomes an issue depends on several things. In magnetic materials like iron, there is huge skin effect even at 60Hz, which is why we don't make power cables out of iron. The iron parts in guitar pickups develop eddy currents that are subject to skin effect, so it is right there in your guitar (and does affect the tone)

As far as the rest of the circuitry inside guitars and amps is concerned, you can forget about skin effect. Even at the highest audio frequency, the resistance of the wires is almost the same as at DC, and still negligible compared to the impedances of the other components.

I build Tesla coils as well as guitar amps, and I'm used to using copper brake line and copper sheet as conductors to carry hundreds of amps at 200kHz. As km6xz points out, you use a hollow pipe because the centre of a solid conductor would carry hardly any current, so it might as well be left out.

[J M Fahey]

Dear tonequester, you received accurate and useful information about your doubts, yet you choose to ignore or misquote it.
I must self quote:

VERY short answer: forget all about skin effect.
Even the name.
Absolutely irrelevant in MI amplification.

Now, ask yourself:
"what are we talking about?
a) Music Electronics (other name for "MI amplification") ... or ....
b) Radio Frequency/Switch Mode Power Supplies/Plastic foil soldering machines/Medical shortwave/Ultrasonic cleaners/Radar/Microwave ovens/high speed data transmission lines/CATV

Take your pick and see whether my suggestion applies or not.

Also, you got a lot of us talking about and explaining skin effect, fully knowing it does not apply in your case.

Quoting Steve Conner:

As far as the rest of the circuitry inside guitars and amps is concerned, you can forget about skin effect. Even at the highest audio frequency, the resistance of the wires is almost the same as at DC, and still negligible compared to the impedances of the other components.

You want to put it in numbers?
OK, let's do it, so you really see what you are nitpicking about:

Guitar with 500K Audio volume pot.
Set on around "7" where both halves of the track have 250K each.
*If* the pickup is a low impedance (active) one (to simplify the model in your favor), the pot behaves as if both halves were in parallel, meaning the source impedance is 250K/2=125K
You use Steve Conner's favorite cable (680 pF?)
You start losing highs above 1870Hz.
Well within the audio band, your guitar will sound dull compared to the sound with volume on 10.

Solution?:
a 220pF cap from wiper to hot will restore and even increase brightness. <<<this is what you should have asked
Why?:
its effect can be explained from 2 sides, which end up meaning the same.
a) being in parallel with the upper half of the pot track, it lowers its impedance.
220pF have a 125K impedance at 5790 Hz, about the highest frequency at which a guitar speaker still has some audible output, so this cap is starting to compensate the brightness loss.
b) since the pot is not only a simple resistor in series with the signal (as calculated above) but also a voltage divider, any cap in parallel with the upper half will not only compensate loss but even *boost* highs (relative to the attenuated signal), so the clearly audible of adding such cap will be perceived as *increasing* brightness, hence its "bright cap" nickname.

So far we have been solving an "MI world" problem with "MI world" concepts.
Let's introduce "skin effect" and see whether it modifies our results ... or not.

Suppose the guitar pickup is connected to the volume pot with an abnormally long (always tilting assumptions in your favor) one foot of 20 AWG wire.
I chose this value to make for an easier nicely rounded calculation, in fact the wire will be shorter and its effect even smaller.
From wire tables: 1000 feet of #20 gage wire=10 ohms ..... so:
1 foot has 10/1000=0.01 ohm
Applying skin effect, and supposing resistance goes up by a huge 30% at the frequencies mentioned
1 foot has 0.01 ohm x 1.3=0.013 ohms.
So that 250000 ohm upper half , instead of 0.01 ohms in series , now has 0.013 ohms in series because of skin effect.
Yes, *one* component of "upper resistance" has increased by a whopping 30% ... so what?.
The actual variation of such "upper resistance" has been from 250000.01 to 250000.013 ohms.
In percent = 0.000012%
Would the "absolutely irrelevant" label apply?
Or: "still negligible compared to the impedances of the other components"?
I bet it would.

And mind you, all this is *considering* the skin effect.

If so, why all that fuss, scientific papers, etc. about skin effect?
Because if you are designing, say, the output tank of a 6 meter band transmitter, made out of 10 turns of #12 Gage solid round copper, the skin effect resistance will, say, double or quadruple its DC resistance (which may be, say, 0.01 ohms) and *there* it means an important increase in losses.
But we are not talking MI stuff there !!!!

[Tom Phillips]

In addition consider that this forum provides free advice. This sometimes involves a long discussion to clarify the questions / problem to be solved. The free advice often requires significant time on the part of the participants. Time that they could spend working on their own personal projects or working their profession earning a living.

The discussions are cordial a majority of the time. After you get to know their on line personalities, even the feuding members are often entertaining. In fact, if this were a TV sitcom, they would be an essential part of the cast.

It takes some time to work out the details of a topic in some discussions such as your recent, next to last, post. It takes time to calibrate the members so that you know how credible the information they post is. If your skin isn’t thick enough to “take it” here then it is likely that you run into the same feelings elsewhere.
Best of Luck,
Tom

[Chuck H]

Tom... You've offended me. I'm posting to the moderator and running away somewhere to drink too much before going home to beat my cat in an attemt to relieve frustrations that you have caused. Everything is your fault.

[rjb]

Tom... You've offended me. I'm posting to the moderator and running away somewhere to drink too much before going home to beat my cat in an attemt to relieve frustrations that you have caused. Everything is your fault.

Chuck, you just caused me to crack a rib from laughing so hard. You will be hearing from my attorneys shortly.

[tboy]

I'm a little confused, and I feel as though I've been misquoted. Just to be clear, here is the email I sent to tonequester:

Hi Larry,

The email notices you get from the forum aren't meant to be replied to. They're just a convenience to let you know that someone posted a reply on the forum. If you reply to one of these emails, it just comes to me, rather than the person who posted the reply.


Thanks,


tboy






On Aug 10, 2012, at 9:46 AM, larry Boydston wrote:

On Fri, Aug 10, 2012 at 1:03 AM, Music Electronics Forum <staff@music-electronics-forum.com> wrote:

Dear tonequester,

Enzo has just replied to a thread you have subscribed to entitled - attenuation experiment, lack much theory, would like opinions - in the Music Electronics forum of Music Electronics Forum.

This thread is located at:
attenuation experiment, lack much theory, would like opinions

Here is the message that has just been posted:
***************

Well here, let me confuse you further. It is one thing to reduce the sound level without changing the overall freq response, but your ears are not linear either. Go google up "fletcher-munson curves" to see how your ear responds. That is why stereo receivers have a "loudness" button. The less loud a sound is, the more limited is your ears' response to it.

And remember that in a guitar amp, the single largest variable in tone is the speaker. And once more, speakers are not linear either. They are mechanical systems, and can respond differently when run at polite levels versus when they are run LOUD.

Please be sure you understand the use of the term frequency here. A-sharp is a note, it has a frequency, same with B-natural. And all the others. The frequency is the note, or vice versa. All your EQ and tone controls and speaker effects change the frequency RESPONSE, meaning that in one system, given a dead even input, maybe the A-sharp comes out a bit louder than the B-natural, while in another system the B-natural comes out a shade louder than the A-sharp. However, in none of them is the B-natural turned into an A-sharp. If your guitar is in tune, and you change amp and speakers, the guitar will still be in tune, even if the tone is different. Frequency is the notes, frequency response is the relative loudness of each note compared to the others. Your tone controls or your attenuators or anything else that changes the sound will not change the frequency of the sound, it will change the frequency response of the sound. SO an active circuit can boost a frequency relative to another, not boost frequency. You turn up the treble control you get more treble, not different notes of treble.

I had an Ohmite wirewound rheostat, brand new, checked out for accuracy at 25 Ohms. I tried this alone(adjustable power resistor).

HOW did you try it? If you put it in parallel with a speaker, it won;t have a lot of effect, put it in series with a speaker it will have a larger effect.

Resistors are fine attenuators - electrically. WHy do they sell fancier things than resistors? Because they can. Every one of them touts itself as the best in some way. But really, the amplifier and speaker work together, they react to one another. An amplifier reacts differently to a speaker than it does a resistor. Those fancier attenuators have L and C elements addded in to make the amp react more like it does to a speaker, because a speaker is not a pure resistance.
***************


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tonquster here.

G'day Chuck.Thanks for the return on the "one too many project' ! Headphones aren't really a concern. My set-up(HT-1R) with
speaker emulatro/headphone jack, and 32 Ohm headphones with 20hz to 20,000 hz response don't teally sound bad. They DO sound different from the sound coming out of the Weber cv8a 8" Alnico I put in the Blackstar. Since giving up on Blackstars warranty crap, and re-tubing/speaker change, the amp has zero tone issues for me. I still don't like the fact that on the clean channel at full volume there is no sign of. overdrive/clipping/distortion/added sustain.this s contrary to what i was told by Blkackstar's chief technical engineer. Change channels, and immediately you hjave very noticeable distortion. There was supposed to be a smooth transition between fully craked clean channel and the
high gain channel at low volumes. On the high gain channel (actually Blackstar says this channel is not "high gain") a 40% increase in volume causes the distortion to be "so much thrash metal dissonence in my opinion. The headphones react much the same way.However,
more than that it just seems that they have a high degree of "brightness'.Although 20hz-20,ooohz sounds great, I,ve seen no graphical representation of just how linear that response is. perhaps the phones merely do a better job on the high mids and up. The tone is not untolerable though. it is really amazing what different tubes can accomplish. i did a lot of study to arrive at my choices to replace the cgeap Sovteks tht originally came with the amp. I ended up with an Electro-Harmonx 12 ax7 gold pin for the pre-amp position, and a JJ 12au7 gold pin for the output tube position. This change caused an immediate improvement in tone at all volume levels. When I installed the Weber speaker the tone became immeditely "warmer" or"browner" just as their description of it had stated. The Blackstar is as good as it's gonna get cause I'm not about to touch anything else inside that 90% s.s. mess. I'm heading toward that MOD 102 all tube build, and when I have completed it, there will be a great deal offered on one Blackstar HT-1R/modified-tubes and speake). The tubes ran me $45.00 and the speaker was $50.00. I'll probably tale $100.00 for the amnp that retails at $259.95-$299.95. If I can't get that, I'll go as low as $50.00, or I'll junk it for parts. Thanks for the replies and everything that you've sent me.I stilll need to print off the circuitry and set down to ponder it well.
I always think best setting down, and do my best back-pedaling on my feet. I hope you have a great day doing what you like best.
tonequester.

[tonequester]

tonequester here.


You might be "a yankin'". If not, your forgiven anyway. You are one of several that post and reply without ego. I've learned a lot from your correspondence, without your
questioning my integrity. I'm thankful for that. I don't know if you've read all correspondence concerning my original post. The only thing I tried to do in reply to Enzo, was to demonstrate that I did not pull a simple statement out of my a__. I'm now being accused of being "thin skinned". I very well may be. I am not, nor have ever claimed to be anything other than a beginner, that's for sure. However, I am not a complete idiot. I'm not going to post anything new. I have learned some good things here, as previously stated. It's a shame that one of the things that I've learned is that the forum serves as an ego trip for more than a few. People that want to quote a certain textbook(knowing that I own one) should read the WHOLE book before they do so. They should especially read page 19. Now, if I am "thin skinned", this can only be found out by "trial". If I am put on trial, it's only natural to defend myself, meaning my source information as this is what has happened here. I really am not thin -skinned. I think that this "affair" is about the biggest "Hoot" I've had in a long,long time. In my admitted lack of theory, I ask a simple question in a poorly chosen manner. Nobody even attempts to answer my question. Instead, folks seem to get rather "tweaked' about the matter. The more I try to extricate myself(Sheeeez ! Like pulling out of Vietnam) the deeper the incoming B.S. gets. rjb is laughing so hard that he might bust a rib. I'm so laughed out that I've had to re-type this whole reply. The only problem is that I'm pretty sure that the "laughers' are in the minority. I've always tried to thank everyone that was good enough to reply to my posts, especially the ones that were really helpful. My Mama didn't raise an ill-,mannered buffoon, just a plain buffoon. Chuck, if you're not a "yankin", then either you turn on a man faster than Jeckyl became Hyde, or you just "blow with the wind". Facts can be both cursed, and denied. They still remain....facts. Slap rjb on the back , I think he,s chokin'. Have a fine day Chuck !
tonequester.

[Tom Phillips]

Tom... You've offended me. I'm posting to the moderator and running away somewhere to drink too much before going home to beat my cat in an attemt to relieve frustrations that you have caused. Everything is your fault.

Chuck,
I would be deeply saddened if you beat the cat. I suggest that you take a trip to the land of rocking horse people and eat some marshmallow pie. That always makes me feel better.
Tom

[big_teee]

Chuck,
I would be deeply saddened if you beat the cat. I suggest that you take a trip to the land of rocking horse people and eat some marshmallow pie. That always makes me feel better.
Tom

I always get distracted when It Envolves the Kitty!
T

[Chuck H]

Ok, ok... I was just kidding of course. I didn't think it was in THAT poor taste. Big_teee, please don't become so distracted as to have an accident. One lawsuit a day is enough.

My kitty is seventeen years old and taking two medications. One for thyroid problems and an antibiotic for her bad gums that are a result of failing kidneys. a problem exacerbated by the thyroid meds. She's stone deaf now and yowls in the middle of the night from dementia. But she is still my sweet kitty and beating her is, of course, unthinkable. If not unjokeable.

[tonequester]

tonequester here.

Who says you can't" yank a yanker" ? f.y.i.-Bipolars talk too much. Narcotics are the only med that seems to help(high doses), but damned if they won't give me any.
t-boy is in on the joke. He feels he's been mis-quoted. I wonder why he didn't post the "quote" in it's entirety. Someone creative could take bits and pieces from this entire post and turn it completely serious. I'm a "dyed in the fur" cat lover. I have a 3 year old Maine Coon cat. he's hugh and doesn't reach maturity until 4 years of age. I'm sorry for the health problems your kitty suffers. 17 years old means sge's part of the family in a big way. You wouldn't "yank me" on the cat ? Naaa ! You'd have to be a real fur-ball to do that. Kitty's in my prayers.
tonequester.

[tonequester]

tonequester here.

I hope you are not too serious about all of this, as I believe most of ti has been a joke from the start. On my original post, the thing about resistance/frequency was an off the cuff reference that unfortunately I did not then know concerned the "Skin effect". I truly had read the controversial statement a number of times, in a number of places. none of these were from forums or blogs, which I would have been very wary of. I found it strange that everyone seemed to concentrate on my admitted arror,while not one person chose to even try to answer the crux of my post, which was seeking to determine why there is treble loss when a guitars volume control is turned down. Enzo, the first to reply, stated : "Where did you understand that from ? Resistance is not reactive and has no frequency component." " There must be more to the concept you propose." He goes on to say : A cap across a volume control is what we often refer to as a brightmness cap." That's definately to the point, if not blunt, but it does not answer my question. The info I gave Enzo was the best I could, and he asked for it ! You say "you want to put it into numbers" ? Who gave you that mistaken notioin. I don't need numbers to verify what I have learned about skin effect, during the search for Enzo's requested info, and which prompted me to amend my original post. You say "You got a lot of us talking about skin effect(and i like the way you italicised the rest to point out my DEVIOUS PLAN), fully knowing it does not apply in your case. I cannot make you or anybody on this forum do anything. I can't make you mad, you can let yourself get mad. I canm't make you post or reply, YOU make that choice. Your lengthy exposition on SKIN Theory was wasted on one whoi admits to not understanding it but at the most basic level. I doubt that you understand it fully.
As for "all that fuss",once again I responded to a request from Enzo in the best manner that I could, period.One thing that I know for sure, is that my original question, and it's subsequent
re-phrasing have yet to be answered.Simply put : Why does turning down the volume control begin to cause a loss of treble(and I darned sure know it's NOT because of the Skin Effect).
I hope that you aren't taking all of this in a bad way. I don't want anybody to be upset. It all started as a poor choice of words by me, a beginners mistake. Sadly, it concerns a subject where there are varying ideas(by far theoretically) in my observation. It can be frustrating for a truly experienced electronics "tech' to have to deal with a beginner's misconceptions.
It is equally hard for a beginner to be "talked down to" on a regular basis, not to mention when a group of these same people, along with experts in their electronic background, to disagree among themselves and get all P.O.'d about such a small matter. Forget the volume control explanation as well. I'll keep on using the "bright" cap, knowing that it works, ignorant about why it is nesessary(in my opinion). I here that this is the oldest forum of it's kind. I can't help but wonder how many people have "run, not walked to the nearest exit" during it's existance.
Arrogance does not have to go hand in hand with knowlege, and those without such knowlege deserve patience if they are willing to make the attempt to learn. We are not all Einsteins.

[tonequester]

tonequester here.


Tom, if this were a t.v. sitcom we'd be the first "un-reality" sitcom in history. I understand the time it would take to gather, share, and sort info for the best answer to a post. However, this did not happen with my post. It was rapid fire, shoot from the hip all of the way.I also understand that it's free. No excuse for "brow-beating" or the complete ignoring of the major question posed, so one and all can throw in their two cents on a subject that I quickly found on my own was inapplicable to my situation. I've copied averything that has been posted/replied to, from both posts in it's entirety and I read it more as a tradgedy than a comedy. it's a comedy of error... in fact, opinions, and a good example of ALPHA MALE SYNDROME.
If the whole thing doesn't die down soon, I won't be heard from again. this is possibly just what some may wish. It's no problem to make a strategic re-treat when it's no more than
a hassle, and wasted time anyway. The one's who may wish me gone, would be the ones that have always been overly critical, and provided the least contributions in useful information. So, there's a bonus in leaving if I choose to do so. I'm getting too old for B.S. That's why I can go overboard, when know that I'm being spoon-fed as much.I belong to three other forums and have NEVER had one single problem with anything.These are music forums, they tend to be free-thinkers and don't care much for theory, out side a few who are into music theory. it's mostly about the joy of music and it's creation. It;s too bad it can't be that way here. Have a good day.....tonequester.

[Tom Phillips]

Ok, ok... I was just kidding of course...

Yep. I knew that Chuck.
Attached is a photo of my shop cat checking out a new arrival.
Cheers,
Tom

[J M Fahey]

To your question:

have yet to be answered.Simply put : Why does turning down the volume control begin to cause a loss of treble

the answer, both conceptually and with the Math to really know what we are talking about was:

the pot behaves as if both halves were in parallel, meaning the source impedance is 250K/2=125K
You use Steve Conner's favorite cable (680 pF?)
You start losing highs above 1870Hz.
Well within the audio band, your guitar will sound dull compared to the sound with volume on 10.

And it was posted 21 hours and 12 posts behind (more if we count the parallel thread where this one was unnecessarily split)
Any *other* doubt?

[tboy]

t-boy is in on the joke. He feels he's been mis-quoted. I wonder why he didn't post the "quote" in it's entirety.

Apparently I missed something somewhere, as I have absolutely no idea what you're referring to. I posted the entire text of the email I sent to you, which included a quote of the entire text of the email you sent to me. If you believe I left anything out, you're more than welcome to post it here.

[tonequester]

tonequester here.

I have all posts and relpies in print. tonequester.

[J M Fahey]

tonequester here.

I have all posts and relpies in print. tonequester.

Meaning?

[Enzo]

TQ, tboy's message to you was not an insult. What he was trying to tell you was that the messages you get from the forum telling you someone responded to you are not correspondence from the member. It is just a flag to you that the forum holds responses. Further it also tells you that you will only get the one notice, whether there is only one response to your last post or 20 responses. All that message to you meant was, you got at least one response, so you ought to go look. If 20 people post in response, you won;t get 20 notifications, you'll just get the one.

If I responded to a post of yours, you might get an email telling you that "Enzo responded" but if you try to reply to me with that email, it won't get to me. SO that notification was pretty much simply "you've got mail."

[tonequester]

tonequester here.

I wish to put this post where it belongs. I have already done so with the first related post. I want to thank Chuck H and rjb for their efforts to keep things humorous and in perspective. I won't mention the other replies. I realize this could go on and on, but if it does it will be without my participation on any level. If there are those who wish to continue it, that is their choice. I won't know if they do or not. I consider it a "dead letter'. I will delete notification by e-mails concerning the two related posts. I've learned a lot from both posts, some has been good to know, some belongs where I intend to put it(virtually). I know one thing for sure, the longer it drags on in the fashion it has grown in, the more it shows the participants character. Please, let it go. I have.