If you use a normal pot pedal, then your pickup sees 500kOhms and also whatever follows the pot pedal. For example, if you use a pot pedal into an RV-3 which is 1Meg, you get 333kOhms of a load that the pickup sees. Anything after the RV-3 doesn't matter because it's buffered from the pickup by the active circuitry in the RV-3. If you use a pot pedal into an old LTD or Session 400, you get the same because those amps are also 1Meg (or 1000kOhms) at the input. If you use a Hilton pedal or Hilton Digital Sustain, your pickup sees 1Meg. That helps account for the high fidelity and extended frequency response you get in that situation. If you use a Black Box your pickup sees 450kOhms.

What you can find is that the tone of the pickup itself is very sensitive to the loading. Low impedance will give a darker mellower tone and higher impedance will give a clearer, brighter tone.

Many of the Peavey amps use a relatively low input impedance of 220kOhms. The Nashville 400, 1000, and 112 have this. If you use a pot pedal into the Nashville, you get a load of 153kOhms. That's quite low. If you plug into a Nashville using their 3-wire hookup, you get 220k, still kind of low. If you use a pot pedal into a typical delay or reverb pedal and then into the Nashville, you get 330kOhms.

There is a tremendous tonal difference between 153kOhms and 1Meg, and you'll experience more of the difference when using hot pickups. It's amazing how much tone shaping takes place right there, before you ever hit a preamp or equalizer. Sometimes if you've lost highs by having too low of a load, it's really hard to get them back with the preamp. And if you try, you may find that you just can't regain that sparkle, you just get hiss from the electronics.

I think I need to get out more....

If you've ever heard the clarity gained by just adding an RV-3 or DD-3 pedal to a rig with a pot pedal into a Nashville amp, this helps explain the brightness gained. Your were feeding an amp input impedance of 220kOhms but by adding the pedal, you change that value to 1Meg.

Seriously, I'm gonna get out more.

Brad

Just a though.

Remember also that, with a lot of windings and a magnetic field in the pickup, inductive impedance of a pickup is large, so pickup impedance goes up with frequency. If this doesn't see a very high input impedance, high end is lost more severely than low end. Don't be mislead by the "20 KOhm resistance" of your pickup windings. In the high frequency range, the actual complex impedance may be many times higher than the D.C. resistance. The old 'rule-of-thumb' in tube amp design was to present a 1 MegOhm input impedance. Old Fender amps like the Twin Reverb have that value in the #1 input. Back in Physics and E.E. labs, old high-input-impedance vacuum-tube-volt-meters (VTVMs) were routinely preferred, over solid-state units, for measurements where it was important to minimize loading effects.

Yes...maybe you can 'splain all that to the audience here.

Twin Reverbs?

bob

Brad

Also, I noticed what you said. When you get down around 150kOhms, a lot of tone gets lost. I notice that it really starts to clear up around 300k and by 450k it's pretty open. Up above 600k and on up it really sparkles. Also, the hotter the pickup, the higher the load impedance needs to be to get clear tone. Vintage, "underwound" pickups can get away with much lower impedances and still sound bright.

If you scroll down to the "Electric Guitar Pickup Measurements" link, you'll find useful frequency response curves for an assortment of Strat and P-90 pickups on page 8. The magnitude of the complex impedance near the resonant peak is near 1 MegOhm. I believe there are 3 basic effects going on here. The DC resistance is about 6-8 KOhm. As frequency increases past a few hundred Hz, inductive reactance increases, and this increase becomes very rapid as the resonant peak is approached, between 4 KHz and 10 KHz, depending on the pickup. Then, past the resonant peak, capactive reactance from inter-winding capacitance now shunts the signal, reducing impedance. The exact shape of this curve and the resonant frequency depend on the number of windings, magnet material and strength, geometry, etc. It's pretty hard to make simple generalizations about how changes will affect this curve. Even given a constant geometry and magnetic material, more windings raises inductance, capacitance and resistance, so it's not exactly obvious what the overall effect will be, but one thing is that it generally does lower the high end and broaden the resonant peak. A stronger magnet raises inductance, which sharpens the resonant peak. Bill Lawrence seems to be one of the few pickup makers to 'tailor' his pickups using this kind of technical approach, although there are other good-sounding pickups. The point is that I don't think it's possible to simply say "more windings always means less highs", but clearly, many modern pickups sound different than old pickups. Either way, it is clear that even a high-impedance amp loads down a pickup at some frequencies, and that is going to affect the amplified tone.

Tubes are 'naturally' high-impedance devices, while solid-state is 'naturally' a low- to medium-impedance device. But it is possible to make a high-impedance solid-state amp, so I don't think that's the complete answer - there's more to it than linear amplification.

My own experience is that solid-state gets harsher more easily when pushed in the high-end region. Tubes are more forgiving, hence there's a smaller penalty for pushing in the high-end. There is a tradeoff between clean and powerful low-end and sweetness in the top register. Another change from 40 years ago is speakers. Modern high-power speakers are more able to clinically reproduce with high fidelity. Even the high-headroom old Altec-Lansings and JBLs sound different than modern clean speakers. These speak to the nonlinear aspects of amplification. Distortion is not always evil, even for a PSG, IMO. The standard was "it should sound good", not "the specs should be so-and-so."

But part of the change may be changing tastes. It seems that nobody wants to hear it, but many consumers of popular music these days are turned off by the 'high whining' sounds of the high strings of a PSG. When playing around my part of the world, that kind of high-string playing is tolerated in very limited doses by fellow musicians and audience alike. That's true whether using a tube amp or a solid-state amp, although I get more complaints when pushing a solid-state amp like that. Most popular music these days is bottom-heavy, and this is often even exaagerated in live performance. Most people I know get annoyed at a piercing steel, or Telecaster for that matter.

[This message was edited by Dave Mudgett on 06 October 2005 at 07:59 AM.]

Brad

quote:

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...many consumers of popular music these days are turned off by the 'high whining' sounds of the high strings of a PSG. When playing around my part of the world, that kind of high-string playing is tolerated in very limited doses by fellow musicians and audience alike.

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Well, to be honest, I sorta concur with that hypothesis. However, the biggest complaint heard around here about tone is usually something like..."that pot sucks the highs out", or "it has no sparkle". So, my (hopefully) logical question is..."What is really going on here?"

Am I the only one who notices that most guys that complain about not having enough highs have their "bright" switches off, and set their treble controls around "4"?

Strange, isn't it?

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The "real deal" is better 99% of the time.

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I agree 100%. Once you lose the "air" in the sound of a pickup, trying to get it back is like trying to put the genie back in the bottle. Remember that frequency response includes both amplitude and phase components. It's possible to EQ out amplitude response differences pretty accurately, but I believe that phase is much tougher.

And don't get me wrong on my earlier comment - I like both bright traditional and less-bright modern steel sounds. I'm not a vintage nazi. One of my favorite sounds ever is the sound of Curley Chalker playing darker-tinged jazz on an MSA through a Session 400. Or Pat Martino playing jazz guitar through a Polytone or Acoustic Image amp.

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Artificially created highs...

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Uhh...I don't really understand that phrase. Neither a pedal or an amplifier can "create" anything! They can only process what's already there. All a bright switch does is remove highs that already exist when you turn it to the "off" position. A treble control does the same thing. When you turn it down, you're merely attenuating the highs that are already there.

quote:

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Once your pickup loses highs, there is no way to get them back, unless you re-create them artificially.

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One "replaces" highs by adding via EQ. Yes, a bright switch or passive treble control is passive, but if you normally set it lower and now set it higher, then you are "adding" to the high-frequencies over your nominal setting. One could also do it via active EQ. As far as the amplitude frequency response goes, one can correct more or less at will.

Brad

There is another very BIG reason that todays instruments don't have the sparkle that the instruments in the "old days" had, that I discovered about 15 years ago. I'm still waiting for the experts to say anything about it, in all that time I still haven't seen a thing and it truly amazes me.

[This message was edited by Jim Phelps on 06 October 2005 at 03:50 PM.]

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".

[This message was edited by Jim Phelps on 06 October 2005 at 05:00 PM.]

Brad

Brad

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.

[This message was edited by Jim Phelps on 06 October 2005 at 05:53 PM.]

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.

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

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

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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.

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

Anyone????

Brad

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!

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