The Steel Guitar Forum

Although I'm no "expert", I surmise (perhaps incorrectly) that Jim is talking about strings. They have changed, although I think there are still good strings being made. Jim, please enlighten us.

I know that I haven't tried to address every single aspect of tone production here. Of course, it's way more complicated than just pickup/effects/amp interactions. Tone is the product of every single variable, including player technique and its interaction with picks (or lack thereof), strings, guitar, pickup(s), cables, volume pedal, effects, amp, and speakers. I thought we were trying to isolate and discuss pickup/effects/amp issues here, leaving all other variables fixed.

Dave, it sounds like you took my comment a bit personally. When I said experts, I didn't mean that sarcastically. I wasn't referring to you or anyone here, or anyone specifically although in my view you and some others here certainly do qualify as experts in the field, much more so than myself.

No, at the risk of appearing somewhat ornery, I prefer not to reveal the item I was referring to, for several reasons.

One, I'd really like to find out just how long it's going to take before someone in the guitar/audio clique will finally see it and say something.

Another reason is I don't want to encourage people to make any kind of modification that they may botch up, or maybe they might even prefer the modern mud sound and then it'll be too late.

Also, when I mentioned what I found to some friends and other players many years ago, a few good friends listened to me and found I was right. Many others looked amused and more or less told me to go play outside.

That's because what I'm talking about is so simple anyone should be able to see it. The manufacturers surely know but don't care. Apparently, the rest must not care too much either or it probably would not be the common practice among manufacturers.

That's why I'll sit and wait until someone realizes and then makes a big deal out of their "discovery". <font size="1" color="#8e236b"><p align="center">[This message was edited by Jim Phelps on 06 October 2005 at 05:00 PM.]</p></FONT>

Jim your're killing me.

Brad

Are you talking about the instrument or the amp or other?

Brad

It can be all of the above.

Sorry, I shouldn't even have said anything, up to now I've resisted the temptation and I had no intention of starting a guessing game.

It's such a simple thing I think it's just a case of overlooking the obvious. I would think that someone else must have seen it, I'm no expert or genius, but it makes me crazy that so far no one else seems to pay any attention to it. It's become a pet peeve of mine, but I really don't think anyone other than some of you tech-types would care.

No, that's not accurate.... what I mean is probably only a few people would pay attention, most people can hear the difference when I a/b the difference for them, but most musicians don't even believe me if I just tell them without demo'ing, so I only usually mention it to a few friends. I guess it's just too simple for some people to believe it. There's also no money in it, it's not any kind of invention, just a change in many of the new electronic products and in audio uses it affects the tone.

Although I haven't had the chance to examine a lot of new steels, my guess is you wouldn't find it there, so steels are probably OK as far as the thing I refer to.

Everyone with a little electronic knowledge would know the electronic theory concerning this, but maybe no one is paying attention to some basic areas of application.

Don't let all the knowledge of impedance, reactance, frequency, etc. cause you to overlook the simple things. <font size="1" color="#8e236b"><p align="center">[This message was edited by Jim Phelps on 06 October 2005 at 05:53 PM.]</p></FONT>

Security!!.......


Brad

Jim, I assume no offense meant, none taken. But I really am no "expert" in electronics - my E.E. specialty is control systems and signal processing, which involve a lot of math but a lot less hands-on electronics than one might think.

There have been a lot of changes in the way electronic items are built. Wave-soldered PC boards, choice of circuit elements like resistors and capacitors, use of ICs vs discrete components, electronic vs. mechanical or electro-mechanical switches, chassis-mounted pots and jacks, carbon-comp vs. plastic-element or other pots, the way tubes are made, transformers, solid-wood vs plywood vs particle board in cabinets, and much more, have changed. Guys like Eric Johnson insist they can tell the difference between old-style batteries and alkalines in effects pedals. Every one of these things has the potential to change tone, even in an amp otherwise designed to old specs. To the point that up until I started playing pedal steel in the late 90s, I almost never used anything newer than 70s or 80s tube guitar amps, which used older construction techniques. Most frequently, I used blackface or earlier Fenders. I'm not sure I ever completely isolated what I don't care for in a lot of newer amps, so I'm really curious what it is you're talking about.

<SMALL>Jim Phelps: That's because what I'm talking about is so simple anyone should be able to see it.</SMALL>

<SMALL>Sherlock Holmes: The surest way to hide something is to put it in plain view.</SMALL>

Really, if you've discovered something, please clue us in. I promise I won't tell you to go play outside.

Someone please introduce the winding capacitance factor, the wire size, and the winding style. These were all different in the "old time" pickups (as well as the magnet types/sizes/shapes)...hence the difference in the sound (frequency spectrum from the pickup). Think resonances and Q.

If I run out the jargon and equations and attending explanations most will be bored" to death", and those that object to "technical" and PSG in the same room will be offended.

Ed, these certainly all come into play. But ultimately, don't all these things get reflected in the frequency response of the pickup? Of course, one needs to look at the complex frequency response to get everything. I do agree, inter-winding capacitance is important and seems to often get overlooked.

Of course, there are people like Lindy Fralin, Jerry Wallace, and Jason Lollar who really do "make 'em like they used to", to the extent possible - I guess nobody uses Cobalt steel magnets for Charlie Christian pickups. I've used a bunch of Fralin Strat-style pickups, wound to old specs, including scatter-winding, and calibrated magnets. I defy anybody to sonically separate a batch of them from a batch of "real" ones in a blindfold test through the same guitar and amp. I say a batch because pickups wound the old way are not perfectly consistent, IMO. I don't consider that a problem - it's called individuality.

David M: Yes, all the itty bitty items sum up to make the total pickup output capability...capacitance is one, resistance is one, inductance is another etc. The thread topic is labeled "pickup tone and impedance loading" so it seemed that comments re anything impedance related was appropriate. In my estimation, the capacitance vs. winding characteristics had not been brought up.

Then someone asked why the old time pickups sounded different...one reason is/was in the winding details. Old time pickups were also quite microphonic till they anchored down the windings.

Winding capacitance kills the highs just like "impedance loading" does, so it seems reasonable to know how to control the capacitance in a winding.

The languages of electronics 101, mechanics 101, properties of materials 101, etc. are foreign languages to most pickers. One does not need all this "stuff" to be able to play, but it sure helps on the design end.

The designer has to figure out what is in the head of their client/market and reduce it to product, so terms like good tone, bad tone, dry tone etc. are ambiguous. The answer to the problem is to reduce it all to a picture of what each likes/wants. Your Urbana reference "charts/curves" are a good start. Get the FSA output from a Buddy Emmons, John Hughy, etc. instruments pickup and relate curves (repeatable) to sound and sound vs time.

I spent a day ath Jim Palenscar's NORTH COUNTY STEEL shop in Oceanside Ca last week. He has lots of different steels and PSGs. A good bit of the time was spent comparing their different sounds (by ear alone) and philosophising about what made the differences. Using the FSA on them would allow the visual (as opposed to verbal/mathematical) capture of their characteristics, loaded and unloaded in various ways.

We need a paradigm shift re the way we describe the attributes of the PSG to take it into the future...those that are traditionalist won't care.

All the Forum folk have computers so they have the basic device for the instrumentation (oscilloscope/Frequency Spectrum Analyzer/etc) and data processing when setup with software that costs less than a pickup. Want to see the results of the impedance loading of pickups and other frequency vs time and environment issues all thru the "system" (strings thru speaker output)...get into this arena.

The "individuality" comment is cute...I take it as a euphemism for "can't make two alike".

Hey James Moorhead, you asked how a Twin and a Peavey would be affected by this. Well with a very simple, pot-pedal and no effects pedal setup, the pickups would see 150kOhms (full volume on the v-pedal) into a Nashville amp and it would see about 340kOhms into a Twin. Big tonal difference right there. The lower impedance of the Peavey would be getting way down into that range where lots of highs are lost, as Keith Mentioned about 150k. The Twin's higher impedance keeps it up there at 340k or so allowing lots more highs from the same pickup.

Brad

Ed, you've reminded me of another aspect to this topic that I'd like to learn more about. I'm sure that Bill Lawrence could answer this for us in under 2 hours. From my listening, it seems that the lower load impedances not only cut the highs of the pickup, but also seem to reduce or at least change the intensity of the resonant peaks of the pickup's spectrum. It sounds like the characteristic voicing of the pickup changes. I think that there are two primariy peaks in a pickup, one wide one being roughly in the 750Hz range and another sharper peak typically but not always in the 2.7kHz range. I left a conversation with Bill Lawrence with those notions, but they're not real clear in my memory.

I wonder if the changes in loading actually effect the amplitude or frequency of these resonant peaks.

Anyone????

Brad

Brad; Yes, there are several things at work here re load values. The buzz word is damping. The pickup has a primary resonant frequency curve, thcenter frequency of which is determined by the Inductive and capacitive reactance in the winding. The capacitive reactance (for a given number of turns)can be varied by the wire size and style of winding. The Inductive reactance for a given number of turns can be varied depending on whether the winding is around the magnets or the return poles.

The flattness/broadness of the curve is a function of the "damping". The damping is related to the Resistance/reactance ratio. External loads add to the damping factor, costing in both high frequency response and output amplitude.

The symbol Q is used to define the narrowness of the resonant peak...narrow = high Q, flat/broad = low Q. A Dobro has a relatively high mechanical Q.

In the "old times", when amplifiers were tube types, input impedances (Zs) were high = 1 meg, pickups were scramble wound with large wire, there were things called output transformers that coupled the signal from the output tubes to the speakers. These had lots of turns of wire, hence inductance, capacitance, reststance, and all the things that go with the territory including a freq' response curve that was a function of loading. They also had a thing called overshoot, just before the high frequencies started to drop off. Overshoot meant that the output at the high freq end of the spectrum increased just before it started to fall off. The amount of "damping" applied decided the final sound.

Pickups have the same effect and the amount of damping determines the spectral output of a given pickup. Look up "damping factor" in an electrical engineering handbook. Semiconductor apmp (most) do not have output transformers, hence a different speaker damping coefficient in most cases. They also generally have a wider frequency response curve than the tube amps...see "transient response" in the electrical eng' handbook.
This output coupling function may be a large part of the "tubes are warmer" syndrone.

If you kill the highs in a pickup you will also kill the attack on the low strings, and the "string separation" as it tends to be called. I think that the attack function is best handled in the pickup, and its loading rather than try to restore/control it by turning up the treble control. The buzz words here are "transient response, harmonic content, phase relationship, and Fourier transform".

Will stop now so as not to infringe upon Bill L's reputation re time.

If you ask either of us what time it is we tend to tell you how to build a clock!

So, if I want to figure out what kind of load
my pickup is "seeing"....I can just stick a
cord into my amp, preamp, etc. and measure
the resistance at the other end of the cord
(from hot to ground) with my meter? Will
that give me a rough idea?

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JG, your meter may load enough to effect the reading. In the old days, you needed a VTVM to make an accurate measurement. JP

Hmmm, methinks you all might benefit from a quick trip over to the "Tone-Stack Calculator". That neat little program lets you change both the input and output load the tone-stack sees, and then view the resultant changes in frequency response.

Try it. You might find the results verrry interesting!

Anyhow, to me, EQ is EQ, no matter where you do it. Every single change you make to the sound is nothing more than an EQ change. So, when you change a cord, a pickup, a pedal, an amp, or a speaker, or anything else (even strings) to get a different sound, all you're really doing is altering the EQ. If we remove the "sustain" and attack variables, and you give me enough EQ, I can make <u>any</u> guitar sound like any other guitar (that's of similar design). No, no amount of EQ will make a Gretsch Country Gentlemen sound like a Stratocaster, (the overtone structure is too different), but it will make a Tele sound just like a Strat or an SG. Or, it will make an Emmons sound just like a Sho~Bud, or vice-versa.

If, on similar instruments, you take sustain and attack out of the picture, EQ is all that's left to differentiate the sound.

Indeed, EQ is not only everything, it's the <u>only</u> thing! And if you don't believe it, then you've never fooled around with a good active graphic equalizer.

I can tell.

You guys are way above my head.

You guys are way above my head.

Well gentlemen, I've read all of the info from everyone here. Now I have a simple question I want to ask. I just use the basics for Psg. LDR volume pedal,RV-3 delay and Fender Steel King amp usually. Here's the question. In order to get that smooth, pure and clean Psg tone, what items would you recommend? By the way, I'm adding a black box shortly to my set up. Thanks for any suggestions.

Jay...nice looking gear there, and a nice looking environment.

Re the meter...I assume that you mean an Ohm Meter because you say resistance. The answer to your question is maybe. Resistance as measured with an Ohm Meter is a DC (direct current) measurement. Impedance is an AC (alternating current) measurement. Resistance and Impedance are equal when the frequency in the AC is 0 Hz.

If there is a reactive component(capacitor/inductor or??) in the chain your Ohm Guesser will just read the ohms, not impedance. Dc does not pass thru a capacitor (except for leakage) so a capacitor in series with the leads will not let your meter see what may be on the other side. If the capacitor is in parallel with the leads, its impedance to ground (which is frequency dependent) will not be seen. Same kind of thing for inductors in the circuit.

If the chain is purely resistive, then Resistance = Impedance (at 0 Hz).

Donny H: The most popular circuit design/analysis program that I know of is named SPICE (or one of it's offsprings). It handles transients (think attack).

The FSA approach lets you see the harmonic content of the vibrating string or strings as a function of time (attack, steady state, and sustain); you can even see how the harmonics fade in and out because of string rotation, which is a function of how you excite the string (for the "it's in the hands people"), and how the string is terminated.

Jay, if you have a good, high-impedance voltmeter and the input section is coupled only with resistors, it may work OK. I read very close to 1 MegOhm on my old Fender tube amps, which are resistively coupled. But my Peavey solid-state amps are capacitively coupled. As Ed says, you need to make AC impedance measurements. Here's a simple explanation of a reasonable way to measure input impedance in this case:
http://www.sunynassau.edu/users/schoenf/refshts/measzin.htm

A bit more detail is given here:
http://ist-socrates.berkeley.edu/~phylabs/bsc/PDFFiles/bsc1&2.pdf

The upshot is that the input impedance may be a function of frequency. In addition, if the input signal is large, it may also be a function of the input signal level. One generally makes these measurements with sufficiently low input voltage levels that the input circuit is not overloaded, i.e., runs in its linear region.

Brad, the load may change the overall frequency response of the combined pickup-impedance, Zp(jw), and load input-impedance, Zi(jw), system. One can view the pickup as a Thevenin equivalent circuit, with the voltage induced in the pickup coils, Vp(jw), as the voltage source and Zp(jw) as the pickup Thevenin equivalent impedance. The load is directly connected to these, and we're concerned with the voltage dropped across the load input, Vi(jw). This is a simple voltage divider, and Vi(jw) may be computed for any angular frequency w as:

Vi(jw) = {Zi(jw)/[Zp(jw)+Zi(jw)]}*Vp(jw)

or = {1/{1+[Zp(jw)/Zi(jw)]}}*Vp(jw)

This is the voltage transfer function form. You can see that the pickup drops significant voltage signal at frequencies where |Zp(jw)| is not very small compared to |Zi(jw)|. If the load impedance varies with frequency, it distorts the effect of the pickup frequency response.

Ed, of course pickup makers need to understand how the various design parameters affect the pickup voltage generated and the frequency response of the coil. I think that guys like Bill Lawrence have this well in hand. I agree with you that serious measurements across lines of pickups would be useful to establish a baseline for players and designers of equipment.

I know that it is often difficult to do this, but it would be useful to translate such technical ideas into descriptions that are meaningful for guitar or steel players. I don't think most players are going to ever think in terms of frequency responses or transfer functions. They need something simple and intuitive to help them decide if a pickup, pedal, effects unit, or amp will sound good with what they have.

As far as input impedance goes, I believe it is well understood that everything in the signal chain should be low-output-impedance into high-input-impedance as much as possible, unless one wants to muddy things up. Some people do - e.g., jazz and blues guitarists often do that intentionally.

Donny, I've used plenty of EQs. As you say, EQ doesn't add attack or overtones that aren't there, nor do they equalize the many nonlinear things involved in the sound. They can also mess with the linear phase response and add a lot of noise of their own. Used judiciously, they can be very useful, but I don't like using them to make large changes in guitar sound. It may make a Les Paul or SG with HB credible in a single-coil context, but I've never heard anybody really make one sound exactly like a trad Tele to my ears.

Billy, from what you're saying, it sounds like you should be in good shape. You don't say what steel/pickup you use, but the LDR volume pedal specs say the input impedance is 410 KOhms in full-frequency input, and 100 Ohms output impedance. The RV-3 and Steel King both have input impedances of 1 MegOhm. I assume the RV-3 also has a very low output impedance. If it were me, I would probably try running into the RV-3 first, to take advantage of its 1 MegOhm input impedance to buffer the pickup, then into the volume pedal, then into the Steel King. But it may not make that much difference - all these devices have fairly high input impedances. In addition, noise generation may be a bigger issue than input impedance. It's important to have things that raise the noise floor, like compressors and overdrive, early in the chain so they can act on the cleanest possible signal. When in doubt, try different orders and see what sounds better. That is always the acid test for me, regardless of frequency responses, input and output impedances, transfer functions, or any amount of mathematics.

Thanks Dave, I use the S-12U Carter with a XR-16 p/u. Very clean even w/o effects.

Brad, forgive my lack of electrical knowledge. But is the loading on a Peavey or Fender the same on both the high and low inputs?

I'm not Brad, but the input impedance specs for a NV 400 are:

Preamp, high-gain input (no pad): 220K Ohms
Preamp, low-gain input (-10dB pad): 44K Ohms
Patch Input: 220K Ohms
Power Amp Input: 22K Ohms

I think other recent vintage Peaveys are similar. BTW, Brad - on my Session/LTD 400 manual, it says input impedance is 330 K Ohms, not 1 M. The circuit diagram indicates both inputs are the same on those.

Input impedance specs on classic Fenders like the Twin Reverb are:

Input 1 (Higher gain): 1 M Ohms
Input 2 (Lower gain): 136 K Ohms

The Steel King has only one input, 1 M Ohms according to the manual.

<SMALL>The "individuality" comment is cute...I take it as a euphemism for "can't make two alike".</SMALL>

That's true. Ever try to make a coil? Even with the proper equipment it's somewhat difficult to make two the same. Especially if you use fine wire. Forty gage will break with a single gram of tension. (Don't ask me how I know that!)