Regular readers of this blog might know my first article about the different behaviour of Mark Knopfler’s Ernie Ball volume pedal compared to recent Ernie Ball models. In short: In the 80ies  a different poti was used that caused a completely different sweep curve than later ones (see diagram below).

Knopfler’s pedal changes volume drastically over the first part of the pedal sweep range. This allows him to perform the violin-like fade-in notes he is famous for with much more intensity than the new pedals.

Also, during the last part of the pedal sweep – from middle to full – Knopfler’s pedal changes the volume only moderately which means you can adjust the overall volume of the guitar much more precisely than with the new pedal. Let’s say you want to set the level to something like 80% (which Knopfler often does), the new models require a pedal position  that must be accurate to a tiny fraction of an inch, just a bit more and you are instantly at 90%, a tiny bit less and you are at 70% or even less. I found this extremely difficult to perform with your foot while playing and singing. Knopfler’s pedal can be rolled back for an inch to have the desired level, half an inch more and you might have 85%, half an inch less and you are still at let’s say 75%, so it is much easier to adjust.

Again:

Old style: great change in the first, small change in the second half of pedal sweep –> great for fade-ins, great to adjust volume
New style: small change in the first, great change in the second half of pedal sweep –> less intense fade-ins, difficult to adjust volume

Knopfler himself is aware of the problem so his roadie Ron Eve (or was it already Glenn Saggers?) just bought the remaining stock of the old potis from Ernie Ball to have replacements for all times.

My findings and measurements in detail

I have examined Ernie Ball pedals from the last decades but almost all had the new type of volume curve. I just managed to find one from 1986 which seems to behave like Knopfler’s, while my 1989 is already wrong. Surprisingly both the 1986 and the 1989 have an Allen Bradley poti, both made in Mexico. Later they came with a Canadian poti, today with one from Japan (custom-built by Tocos). I took a lot of measurements to see what really happens (diagram below), and found that all the newer potis behave almost identically.

Unfortunately the original poti is no longer produced . Allen Bradley was sold in the 80ies and soon stopped making them. The original type is – as I found out – extremely sought-after, in other words almost impossible to get. In addition, Ernie Ball changed some details of the pedal itself – e.g. to accommodate the new potis which have metrical threads instead of inch threads – so a direct replacement is often impossible anyway. Since these potis were all designed for heavy-duty usage (“extended life”), replacing it with some ordinary poti wouldn’t be a good idea – and possibly not easy anyway.

The taper switch on some newer Ernie Ball pedals

Ernie Ball reacted to the situation and implemented a switch which enables two different volume curves, something that seems like a solution. However, my measurements showed me that it in fact changes the curve, but not really to what it was with the old poti. If you look at the diagram you will see what I mean. Besides, with the additional 220k resistor the taper switch puts in, you will lose a bit more treble, too (by the way, this is the reason you cannot simply increase the value of the resistor to make the curves more similar).

Quote from the Ernie Ball website FAQs on the problem

Q:I recently had you guys rebuild my older EB Volume Pedal and the new pot does not distribute the volume like the old pot did. Is this correct?
A: We have used at least 4 different companies to custom-build our potententiomers since the pedal’s inception in the 70′s. Since 1998, we have been using Tocos pots, which we feel are among the very best available today. However, they do have a different “sweep” than the older pots do. On top of the fact that potentiometers in general have very wide tolerances, the fact that upon rebuild we are removing one vendors pot and replacing it with another, there will be some obvious differences in the pedal’s sound. Here’s the scoop: we no longer stock the pots of old, not only because we can’t get them, but also because we do not think they are as consistently good as the Tocos pots. The Tocos pots are the most consistent, high quality pots we have tested. With regards to the sweep changing, that is due to modern day pot manufacturing techniques that are used across the industry.

In my first article I described that I swapped the cable from the guitar and to the amp on my pedal, so I got a curve closer to the old ones. This however had a technical drawback: you lose a lot of treble when the pedal is not at full position (much more than you normally do), so it was not really a solution.

Measurements

Without being a technician, you can see huge differences in the diagram. On the horizontal axis we have the pedal position, on the vertical we have volume output. The 1989 Allen Bradly (red) and the Canadian  poti used in the 90ies (blue) have almost identical curves. This is only slightly changed with the taper switch (green).

The yellow curve is the original poti style, and the orange curve is the 1989 poti after my modification (see below). Believe me, I myself am very pleased with my result , and don’t forget that potis differ due to tolerances, so even two identical models will not measure 100% identical.

Now the great news

Coming from a family of engineers, I could not sleep (well not really ) before I found a solution for the problem. I finally managed to modify my two pedals to behave almost 100% identical to the old poti style, and this without any drawbacks, like the need to use (and first to find!) some low-quality poti with a similar curve, or to build in active electronic components that require a battery and introduce noise. The ease of use, look  and reliabilty of the pedal is not decreased in any way! The modification was  very tricky at first (you need inch allen keys that are difficult to get here in Europe,  or you constantly wish for thinner but longer fingers to operate things inside the pedal) and required a lot of experimenting (including making myself a little tool), but finally I got it done. I was really surprised about how close my modification is to the original curve (see diagram).

If you want me to modify your pedal (should work with all Ernie Ball types, at least for the common 6166 and the 6180 Junior pedals), I will happily do so. I thought it is fair to charge you the same fee as you pay for a repair at Ernie Ball – US $ 55 or 42,- € via PayPal (and what I do is more work than what they do, plus for some pedal models they even charge you US $ 75.)  Shipping: You pay shipping to me (Germany), I pay shipping back within Germany, within the EU it is  plus 5,- € . If you are from outside the EU, please ask for details before since customs seem to make handling rather difficult. Also ask for alternatives if you don’t want to use PayPal.

Use the contact form of this blog for first communication. I will reply via email then!

BTW, I will leave in your original poti which means if it is already scratchy, it probably will still be after (although one of mine was cured for some reason after the modification . I also can open your poti when scratchy to see if I can clean it inside, please inquire for details in such a case.

Update: Check the MK-guitar.com shop for our stock of Ernie Ball pedals that are already modified.

"Buy me a beer" - donate for the site via PayPal. Or buy a backing track in my online shop :)

Related articles

• Some new thoughts on the Ernie Ball volume pedal
• Mark Knopfler’s Morley Volume Pedal
• Mark Knopfler’s Ernie Ball Volume Pedal – and how I use mine

On the recent Get Lucky tour I became aware of a little technical detail I had never paid attention to before: I was sure that the guitar cable coming from the guitar would first go into the Ernie Ball volume pedal and then back to the area on the right side behind the stage where Mark Knopfler’s effect rack and amps are placed. Instead, I observed that a long cable leads directly from the guitar to where the amps are. In other words, the input amp of the effect rack (or some other) seems to be the first part in the signal chain. Here the signal is boosted to line level, then (before or after the other effects in the rack) it seems to go back to the volume pedal in the front area on stage, and back to the effect rack again from where it runs to the amps.

I always wondered why Mark’s volume pedal behaves different than the Ernie Ball pedals  I have tried out (the response curve seems to be totally different, see here for more). Maybe Mark’s pedal really has a different poti (like some rumours say), or it just reacts differently because it works on a much higher signal level (after the first gain stage in the effect rack the signal becomes “active”, which means more level and a lower impedance). Theoretically it is also possible that Mark uses the version for line levels of the Ernie Ball pedal, which has a 25 kOhms poti instead of the 250 kOhms of the standard version.

I tried my pedal with a low impedance signal to see if it makes any difference: it did not, but I could not test with a higher level yet.

Another consequence of this signal path is that the long first guitar cable surely changes the colour of the tone. The longer a cable is, the higher its capacity which means it moves down the position of the pick-ups resonance frequency peak. It acts like a small capacitor put into the circuit. This way the cables capacity can easily shift the resonance peak of a standard Fender pickup (normally at about 6 kHz) to something like 3 or 4 kHz, which means that glassy high end at 6 kHz is reduced and the “presence” frequencies at 3-4 kHz are boosted.

"Buy me a beer" - donate for the site via PayPal. Or buy a backing track in my online shop :)

Related articles

• Ernie Ball volume pedal modification to make the taper like it was with the old Allen Bradley poti
• Mark Knopfler’s Morley Volume Pedal
• Mark Knopfler’s Ernie Ball Volume Pedal – and how I use mine

After the other article about Knopfler’s Ernie Ball volume pedal, this time I want to feature the volume pedal he played before, which means during the Dire Straits days until the end of the Making Movies tour in 1981. The pedal I am talking about is the silver Morley Volume Pedal.

Morley made a whole range of effect foot pedals, including a very popular wha-wha or even models with built-in flanger or delay. All of these could be used as simple volume pedal as well. Knopfler’s model, simply called “VOL”, was just the ordinary volume pedal.

The unique thing about those Morleys was that they did not use a poti  but a photo resistor instead. The advantage: potis tend to make noise after some years of usage, the photo resistor will not, no matter how much you use or even misuse it (dusty or smoky stages, humidity etc.)

What sounds rather complicated was in reality an extremely simple circuit: a small bulb  – the one behind the red jewel light that is also used as power indicator – shines on a photo resistor (LCR) which lets the guitar signal pass as long as it receives light. When you roll back the pedal, a piece of black cloth is pushed between the bulb and the photo resistor which reduces the volume of the guitar accordingly. That’s all! Well, the simple ideas are often the best

The bulb (right) shines on the LCR (center), if this is not covered by the cloth

As the bulb needs electric power, the pedal is powered via mains line voltage, no external 9V adaptor like modern pedals! Since the power indicator bulb is part of the circuit, it means when it blows the pedal is dead. Fortunately replacing the bulb is simple and cheap.

The pedal way is extremely long. This means you can control the volume precisely, but you have to move your feet quite a lot. You get used to this, I have no problems with it. You can adjust how quickly or slowly the pedal reacts with a screw that changes the position of that black cloth. And you can adjust how easily the pedal moves with the two screws that hold the pedal. The whole thing is very stable, you can rest your foot with a lot of weight on it without problems.

One thing that is remarkable is that the pedal changes the sound, even when pushed down completely (full volume). This is due to the – compared with other guitar gear – extremely low input impedance which dampens the resonance peak of any passive guitar pick-up. It sweetens the sound of a Stratocaster pick-up. Without it that Dire Straits sound would definitely have been harsher.

"Buy me a beer" - donate for the site via PayPal. Or buy a backing track in my online shop :)

Related articles

• The Dan Armstrong Orange Squeezer compressor – Did Mark Knopfler really use it?
• Mark Knopfler’s Ernie Ball Volume Pedal – and how I use mine
• Gear on one of the first Dire Straits gigs on the Clapham Common bandstand
• Gear on Dire Straits’ first TV appearance at Old Grey Whiste Test
• Calling Elvis chord analysis – Major, minor, no-third, power chords
• Mark Knopfler licks around the 7/9 chord

Mark Knopfler has used a volume pedal almost since the very first beginning of his career. He does not only use it to adjust the overall level, but also for his characteristic volume swells that make a note fade in just like a violin. In short, he hits the note with the pedal all the way back to remove the attack, then presses it down to fade in the note.

For the first years he used a Morley volume pedal, but later he changed to a model by Ernie Ball. This is common knowledge that can be found everywhere in the internet.

I bought one of these Ernie Ball pedals many years ago. However, I found out that mine basically does what it is supoosed to do, but in detail there seem to be some differences to the way Knopfler’s pedal works. Over the years I had some good opportunities to watch him operating the pedal on stage, and I noticed that he often takes volume back to let’s say 70 – 80 % of the pedal way (100% = all the way down, full volume), and the volume of the guitar becomes slightly lower (maybe also 70 – 80% volume).
When I set mine to 70 or 80%, the volume is considerably lower, maybe just 50%. In other words, mine changes the volume quite a lot as soon as you take it back just a bit. This makes it rather hard to set the volume to the desired level, one fraction of an inch too much and it is too low.

I also noticed that he can create very ‘fast’ volume swells easily, which means the attack is filtered out but the note comes in quickly. When I do it, the volume comes in slowly, I have to press it down a rather long way – and very fast – until the note really cuts through.

It seems that the poti in Knopfler’s pedal behaves differently than in mine. The behaviour of a poti can be displayed as a curve, see this diagram:

Mine behaves like the blue curve (comes in slowly while the last inch of the pedal way changes a lot) whereas Mark’s rather does the opposite (red curve).

I found the solution in an interview with Mark’s guitar tech Glenn Saggers. He said that Mark is only happy with a particular poti that Ernie Ball once used, but which is not installed in later models anymore (some recent models allow you to change this curve by the way). They even gathered a supply of that old potis in case it worns out and must be replaced.

I later tried a second and even a third Ernie Ball pedal, but all of them had the same curve as mine.

One day I accidentally found a solution that works for me, without having to buy a new poti or to spend any cent at all (and I admit I had no idea where to get such a poti). I swapped the input and the output jack because I accidentally plugged the guitar cable into the amp jack (output) of the pedal and the cable to the amp into the guitar input jack. And voila, it behaved exactly as I want it to do.

There is one side effect of this which I have to mention. This way the pedal swallows some treble end when not pressed completely down (all potis do so but this way the effect is a bit extremer). However, this is no problem for me since the softer tone fits nicely to low volume, while full volume cuts a bit more. If you use one of these and have the same problems, try it out and let us know what you think about it.

Update: I recently found out how to modify all those Ernie Ball pedals with the wrong curve (basically all after the mid 80ies).

"Buy me a beer" - donate for the site via PayPal. Or buy a backing track in my online shop :)

Related articles

• Mark Knopfler’s Morley Volume Pedal
• The Dan Armstrong Orange Squeezer compressor – Did Mark Knopfler really use it?
• The Hotcake overdrive pedal
• Mark Knopfler’s Guitar Rack of the 2008 Tour
• Mark Knopfler’s effect rack of the Making Movies tour in 1980/81
• Ernie Ball volume pedal modification to make the taper like it was with the old Allen Bradley poti