Wattson Classic Electronics

ECN-06-16-2008-001

This Engineering Change Notice was issued to address problems with specific Wattson Classic SuperFuzz products during production. All Wattson Classic SuperFuzz products produced since this notice was issued will already have the described changes. All Wattson Classic SuperFuzz products produced and shipped before this notice was issued do not have the described changes.

If your Wattson Classic SuperFuzz does not have these changes you are not required to modify your pedal as described here, nor should you return your pedal to Wattson Classic Electronics to have it modified. Your pedal was determined to be in proper working order when it was manufactured. However, if you believe that your pedal is affected by the problems described here then contact us at support@wattson-fx.com, and we'll determine if a warranty repair is needed. If you choose to make these changes yourself then we will not void your warranty, provided the changes are made by a competent technician, and no damage is done to the product in the process.

The following Wattson Classic SuperFuzz pedals were shipped from the factory before this notice was issued, and do not have the modifications described here:

Serial numbers 0000NC through 0021NC

Serial numbers 0022RC through 0027RC

Serial numbers 0029RC through 0050RC

Serial numbers 0052RC and 0053RC

Serial numbers 0055RC through 0068RC

The following Wattson Classic SuperFuzz pedals were shipping from the factory after this notice was issued, and do have the modifications described here:

Serial number 0028RC

Serial number 0051RC

Serial number 0054RC

All serial numbers from 0069RC and up

History

The Wattson Classic SuperFuzz features a tone stack consisting of capacitors C12 and C13, and resistors R24 and R25. The tone stack creates a notch filter which is engaged when the "Tone" switch is set to position "2".
During the development of the SuperFuzz it was noted that the crossover spikes generated by this tone stack were lower in amplitude on the prototype product than those which were measured on the Shin-ei tone model product. It was determined that changing the value of C12 from 0.001uF to 0.002uF helped to restore the amplitude of these spikes, and improved the accuracy of the tone in switch position "2" with respect to the Shin-ei tone model.
When the first PCB prototype was produced it was fabricated using a 0.002uF capacitor for C12. During testing, it was noted that the circuit produced noticeable bursts of oscillation between 12Khz and 16Khz when the "Tone" switch was in position "2". The oscillation presented itself as "chirps" which were most noticeable when muted chords were played. These bursts were supressed when C12 was changed back to 0.001uF, so it was decided that C12 would be 0.001uF in the production models.
During the course of production it was noted during final testing that specific production units still exhibited the oscillation in position "2" of the "Tone" switch, even with a 0.001uF capacitor in C12. The specific units that exhibited this problem were S/N's 0028RC, 0051RC, 0054RC, and 0069RC. These pedals were set aside during production, but production was stopped at S/N 0069RC so that diagnostics could be run.
During diagnostics it was determined that the oscillation was coming from transistor Q1, which is configured as a high gain preamplifier with stabilized bias coming from emitter follower Q2. The original Shin-ei design had a small capacitor C2 in parallel with the collector resistor R5 on Q1. The purpose of C2 is to compensate for the internal capacitance of Q1, and prevent regenerative feedback from causing oscillation. The original value of C2 was 0.002uF, which was sufficient with the 2SC828 (and similar) transistors used in the original circuit, but not enough to always supress oscillations with the NTE123A transistor used in the Wattson Classic SuperFuzz. Increasing the value of C2 to 0.0047uF was sufficient to stop the oscillations.
A subsequent subjective tone comparison was made between the modified circuit and the original Shin-ei tone model. It was determined that the tone in position "2" of the "Tone" switch was slightly muted at higher frequencies on the Wattson Classic SuperFuzz compared to the Shin-ei tone model. Now that the oscillation problem had been dealt with, C12 could be changed back to the previously modified value of 0.002uF. It is our subjective opinion that the result is a more accurate aural reproduction of the original tone model.

Details

Capacitor C2 is changed from 0.002uF to 0.0047uF. Capacitor C12 is changed from 0.001uF to 0.002uF.
This change is applied to S/N's 0028RC, 0051RC, 0054RC, and all pedals from 0069RC and up.
This change is considered minor, and does not significantly affect the functionality or usability of existing products already in the field. No recall will be issued, however, customers will be notified of the change.