TubeScreamer+ Project - Part 5: Seeing Sound

INTRODUCTION

A few weeks ago, I became curious what sound passing through the TubeScreamer+ would look like. Fortunately, I have two cell phones, and the cables in hand already. I used a Samsung Galaxy s4 mini and an app called ToneGen for tone generation. As the scope, I used a Google Nexus 5x with an app called Oscilloscope. I also used a screenshot app to capture the images of the scope. Between the two phones, I have the pedal connected to each phone using two cords and two adapters (1/8" stereo-to-1/4" mono). Next, I fired up the apps, and started sending a nice clean tone (about 1000hz) from the tone generator to the oscilloscope.

NOTE
For those that did missed my earlier posts during the building project, refer to a photo of the pedal below. The H/L switch under the GAIN indicates High and Low. The original Tube Screamer TS-808 used the H position. The L position activates a capacitor mod that ends up giving the output much more low-end (for a heavier rock style). The lower switch describes two different distortion methods. The left side (with the diode symbol) is the original asymmetric diode clipping style used in TS-808. Flipping the switch to the right changes the clipping technique to one that uses both transistors and diodes.

A CLEAN SIGNAL

Above is the clean signal. The peaks and valleys are symmetrical, and have a nice logarithmic bow. In addition, the distance is exactly the same from one crest to the next. These are all traits we would expect to see from a signal generated by a tone generator.

THE ORIGINAL SOUND

In the image above, we see the effect of running the same clean signal through the pedal. Notice the nice even curves now have a slight shark-fin look. The audio for this would sound significantly distorted, and somewhat high-pitched.

ADD A CAPACITOR MOD

The capacitor mod (flipping the top switch to the right) shown above shows an increased amplitude but the wave is shaped slightly differently, as well. In audio terms this would sound similar to the previous, but with more low frequencies (for that heavy rock sound).

A CAPACITOR MOD WITH LESS TONE

In this image, you can see the effect on the wave of changing only the tone control in the upper left corner. I dialed the tone down to about 50%. The wave now has a slightly more subtle curve in the crests and valleys. Audio-wise, this translates into the same low-end distortion from above but as though someone threw a blanket over the speaker. Much of the higher frequencies have been filtered out.


This was a really fun exercise. I want to do more playing to see how different clipping styles compare, and how changes in the GAIN affect the shape.

PART 1 ~ PART 2 ~ PART 3 ~ PART 4 ~ PART 5