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.
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.
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.