The volume pot – what is the right resistance and how does it affect the sound of a guitar pick-up

Posted on 1 CommentPosted in Guitar in general, Guitars

In forums I often read questions about different volume pots and the best value they should have. A normal Fender Strat pot has 250 kOhms, but 1MOhms (=1000 k Ohms) is used on Telecasters, while Gibson often uses 500 kOhms. And then there are the no-load pots,  so all in all it seems there is some confusion about what to use best, and what effect a different pot value will have.

To start with, pots of all values will do the same in a guitar: adjusting the volume from 0 % to 100 %. Their value has (almost) nothing to do with the resulting highest possible volume, nor has it to do with the ‘volume curve’ that describes how fast the volume changes from 0 – 100% (the so-called taper, which is described with terms like linear or logarithmic). There is only one thing affected by the pot resistance: the height of the pick-up’s resonance peak. So, what on earth is this?

The resonance peak

A guitar pick-up normally consists of a coil around some magnets. Such a construction does not have a linear sound – which means not all frequencies are transduced at the same volume. Instead, there is normally a certain frequency that appears much louder than all others – this peak is called resonance peak, its frequency is the resonance frequency. Note that frequencies higher than the resonance frequency are hardly transduced at all (they become lower with 12dB per octave), see the following image:

Picture courtesy H. Lemme

The height of this peak and the exact position of that resonance frequency depend on the pick-up’s construction details.Stronger magnets might have a higher resonance peak, while a metal cap of a Gibson humbucker or telecaster neck pick-up dampens the peak. Generally a pick-up with more windings has a lower resonance frequency. It also depends on the guitar cable since a shielded cable – and guitar cables are always shielded – behaves like a capacitor, and a capacitor shifts down the resonance peak. A Fender Stratocaster pick-up for example has its resonance peak at about 7 kHz without guitar cable, but just about 3 or 4 kHz (!) with an average guitar cable – the longer or thinner the cable, the lower the resonance frequency.

If we now put a resistor in parallel to the guitar pick-up – this is called ‘load’ – , it will decrease the height of the resonance peak, in other words it will dampen the peak, see the following graph:

The volume pot load can drastically change the frequency response of the pick-up. Read below why this however often hardly matters within your setup. (Picture courtesy H. Lemme)

A volume pot divides the signal voltage produced by the pick-up in accordance to the pot position. But no matter which the position the pot is at, the load is always the full resistance of the pot , and thus this value will dampen the resonance peak.

What does it mean to my guitar sound?

Damping the resonance peak means that a part of the treble range is decreased, so we have less treble. Note however that the resonance peak itself is not a ‘natural’ thing but an artefact caused by the pick-up. Seen from this perspective a dampened resonance peak will sound more linear, thus maybe more natural. In fact the resonance peak causes a certain colour to the sound – typically a presence boost that can help to promote clarity, but also can lead to a harsh sound (ever had aching ears from a clean Fender pick-up at high volumes?).  So dampening the resonance peak can sound bad or good – depending on the situation and of what you are looking for.

Which value for which sound?

Especially for clear sounds, I like the sweeter sound of the dampened resonance peak better than that harsh, trebly sound. For this reason I prefer a smaller value of the volume pot. Years ago I tried out 1 MOhms pots in a Strat which I found terrible. However, this value might be okay for a Telecaster since the metal cap of the Tele neck pick-up dampens the height of the resonace peak anyway, and dampening it even more might overdo it. On the other hand those typical squealing, microphonic noises of a (sometimes poorly waxed) Telecaster pick-up usually get worse with a high pot value, in fact that whistling feedback will typically start directly at the resonance frequency of the pick-up, so a smaller value might mean less pick-up feedback (which must not be confused with the wanted ‘string feedback’).

The ‘no-load’ pots work like an off-switch at the last part of the rotary. They are intended to be used as tone pot and cannot really be used as volume pot, so let’s forget about these here.

The low input impedance of the Morley volume pedal will make the guitar sound sweeter at all volume positions because it adds an additional load to the guitar pick-up. The load of your effect devices can make the difference between a 250 or 500 kOhms volume pot almost non-existent.

Now forget about all this again because…

The volume pot is not the only part which puts a load (= a resistance parallel to the pick-up) on the pick-up. Also the input resistance of the first device that follows the guitar in the signal chain adds to the total load (and if the first device is a passive device, the input resistance of the next devices will also put more load on the pick-up). To be concrete, both loads will not simply add (in the sense of 250kOhms + 500 kOhms = 750 kOhms) but will follow the formula for resistors in parallel: R-total = (R1 * R2) / (R1+ R2) , with R1 and R2 being the two resistor values. Thus e.g. a 250 kOhms and 500 kOhms will result in a total load of 166.7 kOhms (note that the total is less than the individual values of the two resistors used).

This is the reason why in a real-life set-up the value of the volume pot might become irrelevant. Let’s say the first effect device has an input resistance of 100 KOhms (they normally have a few hundreds, but there are some like a Morley volume pedal, or an Orange Squeezer compressor that are even below 100 kOhms) . Exchanging a 250 kOhms volume pot for a 1 MOhms pot (= 1000 kOhms) will result in a mere change from 71 to 91 kOhms of the total load, and it is this total value that matters.

So, only if you go directly into a high impedance input (high load), e.g. a tube amp typically has 1 MOhms, you will get a major change of the resonance peak height.

Years ago a friend of mine had a ’71 Stratocaster which sounded absolutely great. Besides being very resonant, it sounded sweeter, less harsh, when directly A/B compared to other Strats, going directly into the amp. And we had an original ’62 Strat which for some reason sounded harsher than normal. In fact the volume pots had been replaced on both of them, the ’71 had a mere 100 KOhms, the ’62 had something I measured to be about 800 KOhms.

Conclusion

* The value of the volume pot affects the tone because it has an effect on the height of the resonance peak.

* A smaller value might sound sweeter and not neccessarily duller than a higher value, which might sound harsh in some situations.

* It is the total load that matters – not alone the value of the volume pot. This is why exchanging the pot can have almost no effect, at least it is nothing I use to worry about.

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The Schecter Story: Schecter Guitar Research – Dream Machines – The Van Nuys Era

Posted on 28 CommentsPosted in Guitars, Mark Knopfler gear, Vintage guitars

In the 80ies, Mark Knopfler was probably the most famous user of Schecter guitars. He bought several Schecters in 1980 at Rudy’s Music Stop in New York, mainly because he was looking for a guitar that was easier to play and better suited for the high demands on the road than the vintage Fenders he played before. Also his former girl-friend played a Schecter which he said was much better than his Fender guitars.

So what was the story behind the Schecter company?

Schecter Guitar Research started around 1976 in Van Nuys, California, when David Schecter opened his repair and custom guitar shop. He soon started to produce his own quality guitar parts which were intended to replace some stock parts on common guitars. Especially the Fender Stratocaster and Telecaster were the ideal guitar to be hot-rodded, since all their parts could be replaced much easier than with the laminated constructions that Gibson used, and the quality of Fender guitars was possibly at the lowest in the Fender history.

We got it all - a Schecter ad from 1979

Because of their background as supplier of upgrade parts, Schecter soon was mainly known for

(a) exotic woods

Unlike Fender who build their guitars from rather common woods (ash, elder, maple,..), Schecter specialized in beautiful exotic woods, like Shedua, Koa, Cocobola, Pau Fero, Mahogany, Rosewood, Purple Heart, or figured maple (necks), or Red Oak, Paduak, Zebrawood, Teak, Koa, Anjico, Imbuya, and many more (bodies). As you see, trading with protected tropical woods was not an issue in the 70ies yet.

All necks were one-piece which means they did not have a separate fingerboard (as Mark Knopfler’s red Tele had, but this was a very late model). They had 21 frets, 22 frets were a later trend started by heavy metal guitarists in the 80ies. If you upgraded your guitar with such a beautiful exotic wood, you don’t want to hide it behind a solid finish, consequently the typical Schecter guitar was bare wood, or an oil finish, although laquer was offered for additional charge.

exotic woods for necks, from left to right: Pau Fero, Shedua, Cocobola

(b) brass hardware

In the seventies it was common believe that a guitar should ideally be rather heavy in order to have a lot of sustain. Surprisingly today many players prefer light-weighted woods, and talk rather about tone than sustain. One way to improve sustain – which means how long a note will last – was to replace the steel hardware with brass hardware. For this reason not only Schecter but also Mighty Mite – the second big parts supplier – and Fender themselves offered brass hardware as an upgrade in the late 70ies. Fender even released an upgraded Stratocaster with the model name The Strat in 1980 that came with a brass bridge, a brass nut, and matching brass knobs. By the way, Schecter also supplied the big manufactureres like Fender and Gibson with parts, so possibly some of the brass master series parts by Fender were actually produced by Schecter.

(c) beefed-up pick-ups

In the 70ies, there were hardly any high-gain amps, again something that was more a child of the 80ies. Nevertheless, the first amp manufacturers or amp repair specialists were successful with offering high-gain mods, e.g. the first Mesa Boogies based on a Fender circuit that was modified to have more distortion. Another way to increase the distortion abilities was to replace the stock Fender pick-ups with overwound pick-ups. This was what DiMarzio started in the early 70ies. Instead of the common 7,000-8,000 windings you simply put much more on a Stratocaster pick-up. This way the pick-up became louder and had less treble but more mids. The drawback: you would loose the original Strat sound which was great for clear sounds. Here David Schecter came in with the invention of the F500T pick-up, the first successful tapped pick-up. Tapped means that the F500T was a beefed-up pick-up with almost twice as much windings than a standard Fender pick-up, but it had a tap after the normal number of windings, so you could “switch off” the second half of the coil so to say. For this reason the pick-up did not have the normal two cables but three (ground, half coil, full coil). The pick-up coils were switched by three mini switches with three positions each (tapped, off, full), instead of the Fender 5-way switch.

The assembled Schecter F400T pickguard often sells for over 1,000 € on ebay

The Dream Machines

After a few years Schecter was very successful and their product range had grown so that they actually had each part of a Fender guitar in their catalogue. So it was nothing but the next logical step to offer complete guitars. These were put together by one of their qualified retailers (e.g. Rudy’s Music Stop was one of them), and marketed as Dream Machines. The five Strats (red, red, blue, sunburst, plus replacement sunburst) and the black Tele were Dream Machines. The red Tele as well, but he got this about 3 or 4 years later.

Schecter Dream Machine

Some more detail difference between a dream machine and a stock Fender (except the points mentioned above): two strap pins at the bottom (Schecters were often heavy, and this way the player could change the balance by using one or the other pin), metal pickguards, only two knobs (one volume, one tone), treble-bleed capacitor to reduce treble loss when reducing volume (similar to the telecaster circuit), two long-life plastic conductor potis, and sometimes no fingeboard dots.

The end of the era

About 1983 Schecter was sold to – officially – a group of Texan investors, who moved over the business to Dallas, Texas. They still offered parts and complete guitars, but the quality was apparently different to what it was before. Here is an inofficial insider story I read in a forum:

One of the laeding sales guys at Schecter had origins in the ‘meat-packing industry’ – some weird people who made obscure deals. Before being accused of spreading false rumour, I prefer to quote the following:

“They basically write contracts to people that wanna save money on their meat purchases, by buying 1/2 a cow, and getting the cut and packed into convenient sizes. Don’t have a freezer big enough? They’ll sell you a freezer too, just sign the contract. Then they sell the contract to a finance company. If they get too many complaints, they simply move their operation to another county or another state.

Apparently, Shel didn’t use their investment money very wisely, and the meat-packers were getting pissed. I don’t know whether it was before, during, or after this problem, but at some point, Dave [Schecter] decided he had enough and split (or was forced out; that part is still unclear to me), leaving the company in Shel’s hands. At some point the meat-packing investors decided that they had had enough, too.

One night. around midnight, they showed up in meat delivery trucks at Schecter after the place had closed, broke the locks, went in, and grabbed everything they could grab: guitars, pickups, winding machines, office furniture, everything that wasn’t bolted down (and a few things that were), loaded their trucks and split – for Dallas, Texas.”

So according to this source, the whole Schecter Californian shop was robbed out and the inventory sold from Dallas. This would explain why the Dallas era guitars still have many identical parts while other parts seem to be from other sources, and the overall quality was lacking.

Later the name Schecter was sold to a Japanese investor who moved back the company to California. The new Schecter company made many original models,aiming mainly at the heavy metal scene. It seems besides the name this company has nothing to do with the original Schecter company.

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Fender discontinued the 150 super light strings

Posted on 4 CommentsPosted in Mark Knopfler gear, Misc

After almost 40 years, Fender recently dropped the 15o SL strings from their product range. For me bad news because the 150 SL (pure nickel, 008, 011, 014, 022, 030, 038) are the strings of choice on most of my Stratocasters.

08-strings had their popularity peak surely some decades ago. They were favoured especially among country players since thin strings made all those fancy banjo-style rolls and licks easier and faster. When players like Stevie Ray Vaughn promoted  heavy strings, 08 became rare and were often no longer on stock in most smaller shops.

I started to experiment with strings thinner than 09 amost 20 years ago. Two things I especially liked about them were the thinner g- string because with vintage-style Strat pick-ups (staggered pole pieces) an 016 always seemed too loud for me compared to the 011 b-string, and I like the sound of the thinner wound strings, especially the d and a strings.

It was however just a few years ago that I got a hint that Mark Knopfler might have played 08s on the early Dire Straits stuff.

By the way, Fender also dropped the 010-038 set some time ago (010, 013, 05, 026, 032, 038) which I personally liked better than 010-013-017… .

At least I don’t have to worry about not getting 08 nickel wound strings anymore because Fender still have them with that bullet end at a slightly higher price (3150 SL). I also noticed that they still have the 09, 011,015, 024, 032, 040 set (originally known as 150 extra lights, the strings Mark played on the Making Movies tour) which are now denoted as 150XL, while 150L is now 09,011,016,024,032,042.

Knopfler himself has meanwhile moved to heavier string as we know, and plays 010s (or heavier) on most of his electric guitars now. At least on Sultans of Swing and Romeo & Juliet he still played a signature MK Strat with 09s, but even on these songs he tried out 010s on the last tour.

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