Why there are so many diverse Tube Screamers?

Recently, I realized that I had never built a Tube Screamer before. This gap must be filled. It also makes sense to figure out which Tube Screamer I need and which is better for you. After all, if you play an electric guitar, then you probably need it in your life!

The Tube Screamer is probably the most popular of all guitar pedals. Especially if you count in numerous clones, mods, and pedals built based on the Tube Screamer circuit.

The scheme has proven to be so fitting that it suits most styles of guitar music, from light rock and blues to the heaviest styles with eight-string, low-tuned guitars.

The Tube Screamer has a nice-sounding overdrive of its own, ready for the clean channel of a pedal platform. It can also help to overdrive a vintage amp.

Or it can make the sound of a modern high-gain amplifier more focused by emphasizing the desired frequencies and preventing the amplifier from choking and squealing due to an excess of unwanted frequencies. And ensure the notes are legible while maintaining the warmth of the solo.

The legendary green pedal with a rectangular button and the number 808 in the name entered the market in 1979. Its name did not contain the phrase "Tube Screamer." It was produced not by Ibanez but by another Japanese company, Maxon. It continued to make the OD-808 and OD-9 for Ibanez and under its own brand.

Maxon employee Susumu Tamura not only developed the circuit and case for the Overdrive OD808 but also came up with the name Tube Screamer Overdrive Pro, which is already for the Ibanez TS808.

Today, early examples of the Maxon OD808 and Ibanez TS808 are highly collectible. This screenshot from Reverb shows the prices that are considered not that high. However, there's always a chance to find it in a pawn shop or local market.

Like most guitar pedals and amps, the Tube Screamer's circuit was not designed from scratch. Enthusiasts of guitar electronics and analog synthesis love to disassemble the products of their colleagues and improve or rearrange something in them to create unique devices based on what they have learned.

In 1977, the Roland BOSS Corporation, also from Japan, released the OD-1 overdrive pedal. Let's look at its diagram, starting from the power stage in the lower left corner.

The power socket is connected through diode D4 and resistor R15. Together with capacitors C11 and C8, R15 forms a U-shaped power filter.

Why is diode D4 needed? To protect against reverse polarity, the circuit has a Zener diode D5. It also protects the pedal from overvoltage above 11 volts. Diode D4 does not act as a rectifier either since the pedal is designed to be powered by a DC adapter.

In the post about the legendary BOSS DS-1 distortion, we've already seen precisely this power supply circuit. And we have found out that this is not just a filter or additional protection but also an analog simulation of the voltage drop of a 9-volt molten-salt battery. This stage is found in many early BOSS pedals, improving the tone.

We will not show the bypass JFET circuit since we discussed it in the same article. It's precisely the same, and many enthusiasts don't like it, preferring true bypass instead.

True bypass with LED indication can be implemented using a 3PDT foot switch. You can get by with DPDT if you use the Millennium bypass indicator circuit described in the post on Brown Sound in a box.

The virtual ground, indicated in the diagram by a diamond, is formed by resistors R7 and R8. They have equal resistance values and divide the supply voltage in half. Capacitor C3 grounds the virtual ground for alternating current.

The input and output buffers on transistors Q1 and Q2 are the usual emitter followers.

An overdrive section is built on the operational amplifier U1A, and an active filter is made on U1B. Most of the first BOSS OD-1 pedals used Raytheon's RC3403ADB quad op-amps.

But sometimes, you can find a copy with the uPC4741C chip from the Japanese company NEC. This is neither a counterfeit item nor a refurbished pedal, but a genuinely original BOSS OD-1. Known examples with uPC4741C were produced in 1978.

Roland/BOSS then stopped using the quad op-amp as a dual op-amp, and later pedals contained the 4558 IC with different indexes.

What does the 1977 BOSS OD-1 have to do with it when we're talking about the 1979 Maxon OD808, you might ask? Just have a look at the OD808 diagram.

As you can see, these two schemes have a lot in common! Several components have been swapped for different values compared to the BOSS OD-1. Capacitors C5 and C6 have been added; C9 has been removed.

The D3 diode was also excluded, so clipping became symmetrical instead of asymmetrical. And most importantly, the R14 tone control has been added. It started as a pedal with two knobs; now it has three.

This time, BOSS studied Maxon's overdrive and, in 1981, released the SD-1 Super Overdrive! Here is its diagram.

Some call this practice stealing ideas, but BOSS, Maxon, and Ibanez ultimately benefited from it, as did the guitarists and listeners. The more different pedals with different nuances, the better!

Next came the TS9 and many other Tube Screamers and overdrives from various manufacturers. My pick is the MXR ZW44 circuit.

This is a Zakk Wylde signature pedal; at its core, it is still the same Tube Screamer. Or rather, SD-1 Super Overdrive because the limitation here is asymmetrical.

I enjoy the range of tone, gain adjustments, and how Tube Screamer's volume control affects the amp's overdrive. You can get a lot of different sounds and fine-tune their shades.

Without Tube Screamer, the amp responds to the gain knob input differently because it is the overdrive pedal that determines the frequency bands that will be emphasized. And this is the primary purpose of the pedal.