In this new article about delays, we will take a closer look to the first technology : the tape echo. We will learn a little more about the different technologies, and how they work. It will allow us to better understand what makes their unique sound, so popular today ! follow our tone quest the different recording mediums The idea of a tape echo is to record a signal on a medium. So first we will look at the most common types of medium technologies. the reel to reel tape It is the first medium that was created, and probably the most used. It is also the one we have in mind when we think about analog delay ! Two rotating reels drive a magnetic tape. First, a recording head records the signal on the tape. Then the tape passes in front of a reading head located a little further away. This head will read the signal that has been recorded, creating a delay. This is the technology used in early tape echoes like the Maestro Echoplex or the Roland Space Echo ! The reels and magnetic tape of a Maestro Echoplex EP3. the magnetic drum A little rarer, it is the technology used by the Binson Echorec. Here, no tape, but a magnetic wire that is wound around a metal disc. The working principle is the same, with recording and reading heads. There is less mechanism, and it also avoids the risk of tape breaking or being dislodged from the reels ! The drum of a Binson Echorec. We can see the very light magnetic wire wrapped around ! the oil can delay An interesting technology, which also intended to create a delay without using tape ! A brush was used to scrub the surface of a rotating disc coated with oil. By scrubbing, it created electrostatic charges in the oil. The advantage of using oil is that it can store a charge for a relatively long time. Then, a second brush placed further away collected these charges, to transform them into a sound signal. So we use the storage of electric charges instead of a magnetic medium to create our delay. We could almost say that this is the precursor of the BBD ! This technology had a unique sound, producing a delay with a slight mix of reverb and vibrato. Among the famous oil can delay, we can find the Tel-Ray Adineko, Fender Echo-Reverb, or Morley EDL. VOX has even developed a mechanism working on the same principle but without using oil ! This is the VOX V807 Echo Reverb Unit. tel-ray adinekovox v807 echo reverb unitthe inside of the tel-ray adineko and the vox v807 showing the mechanism. the working principle We will first explain how the 2 main elements of the recording part work : the tape and the magnetic heads. The magnetic tape is a plastic tape coated with a microscopic ferromagnetic powder. This means that the particles of this powder can become permanently magnetized when another magnet passes close to the tape. It can therefore be seen as a tape covered with lots of small microscopic magnets ! A magnetic head is an electromagnet. Basically, it is a magnet whose magnetic field strength depends directly on the electrical signal that it receives. By placing a head in front of the tape, we will be able to magnetize the particles on the tape, depending on the electrical signal we send to the head. We’ve just recorded our signal on a medium ! But what if we want to restore our signal and listen to it again ? Well, the advantage of an electromagnet is that it also works the other way around ! So if we put a second head after the first one, the magnetic field created by the particles of the tape will generate an electric current in the head, which we will be able to recover to do what we want with it. a good explanation of how magnetic tape works. So we’ve just created a player-recorder ! This is the main principle used in tape echoes. The distance between the 2 heads and the speed of the tape makes that the signal requires a certain time to pass from one head to the other, which creates a delay, and thus an echo effect ! the electronic part Come on, let’s hang on, we’re going to introduce the most complex part : electronics ! Of course we’re not going into details to keep it understandable. Instead, we’re going to try to build a diagram with blocks. That will allow us to understand how it works and what makes it characteristic sound. So we’re going to start with a simple diagram and then add blocks to it as we go along. first diagram As we have seen, the principle of tape echo is to record the input signal on a tape, and then play it back to create a delay. So we can imagine a first diagram like this one : amplification Since the recording head needs a signal strong enough to magnetize the tape, we will need to amplify the signal first. In the same way, the read head only produces a very small signal, which needs to be amplified as well. So we’re going to integrate two amplifiers into our diagram. In addition to these 2 amps, we will generally find a buffer at the output, and a preamp at the input. We will talk about it later, but this preamp is an important part of the tape echo sound since it will act directly on the dry signal. So we get this diagram : feedback loop Then, to get more repetitions, we will add a feedback loop to it. This loop will return part of the delayed signal to the recording head. The signal will be delayed a second time before coming out again, then a third time, etc… high frequency oscillator We’ve got a near-functional tape echo ! But it’s still missing an essential element. If we keep it like that, we will soon have a problem. Once the tape has done a full rotation, we’re going to re-record and replay over the audio track we’ve already recorded. And so we’re going to get a mix of tracks that will overlap with each new revolution of the tape. So we need to erase the tape before each re-recording ! The most common way to do this is to add a recording head that will be connected to a high frequency oscillator. This high frequency signal (above the audible spectrum) will disorient the particles on the tape, erasing the signal that was recorded. This signal is simultaneously sent to the recording head. It will allow the head to operate correctly in its linearity range and thus avoid possible saturation. This is called the bias. So the signal from the recording head is amplitude modulated with a high frequency signal. But to avoid recovering this high frequency signal, we will also place a low-pass filter on our read head to recover only the audio signal. optional elements We finally have a tape echo that works ! Now we can also add some elements that we find in some famous tape echoes. As on the Binson Echorec or the Roland Space Echo, we can find several read heads. This allows to create more complex delays with irregular repetitions by disabling some heads or by changing their spacing. Or simply create subdivisions easily. On some tape echoes, a tone circuit can also be found after the read head. This allows to change the tone of the repetitions and make them more or less dark. Here we are, we have a complete schematic that includes the main elements of the most famous tape echoes ! the characteristic sound of tape echoes After studying how a tape echo works, we will be able to better understand what makes its sound characteristic. the modulation We’ve already mentioned it in the first article, one of the characteristics is modulation. The mechanism is not perfect, and the tape speed may vary slightly, causing pitch variations. This brings a slight vibrato more or less fast on the repetitions, or even a chorus effect when it is mixed with the dry signal. Speed fluctuations also make the repetitions slightly faster or slower, making them less regular. artificial modulation on a vinyl. the tape saturation Tape saturation is caused by the recording system (tape and heads) which is not perfect and causes losses, but also by all the electronics around it. Each block (amp, mixer, filter…) will bring a slight coloration and saturation to the sound. This saturation is very subtle, but will be added at each new path in the circuit, that is to say at each re-recording-replay cycle on the tape. So the tape saturation comes from wanting to make a copy of a copy of a signal. The more copies are made, the higher the saturation becomes. The same thing happens in the studio with tape recorders, when you mix on a new tape all the tracks that were recorded on separate tapes. example of significant tape saturation due to the use of tape recorders. the preamp We started talking about it in the electronic analysis, the preamps of the tape echoes are an essential component of the sound ! They act directly on the dry signal, even before the repetitions. So we were able to use tape echoes as a simple preamp to boost the signal before going to the amp ! These preamps could add texture and warmth, and change the frequency content of the signal. On top of that, tape echoes were not intended to be compact and integrated into a pedalboard powered by 9V batteries. This meant that the circuit was generally powered with higher voltages. The result was more headroom, which means a very rich, less compressed sound with more dynamics. Nowadays, some companies reproduce these preamps in an effect pedal size, to get a warm boost that brings additional texture to the amp. maestro echoplex ep3binson echorec 2roland space echo re-201three tape echoes known for their preamps, which many manufacturers nowadays integrate in their effects pedals. our research on a modern tape echo In conclusion, this technology is really interesting and unique, so much so that we have been wondering whether it is possible to develop it again today. But after studying it and doing a lot of research, we concluded that it would be too complicated. For the electronics, some of the components used in the old tape echoes are no longer produced. It is therefore complicated to reproduce a perfect copy of a legendary tape echo. On the other hand, nothing prevents us from creating our own circuit with modern components ! But the problem comes essentially from the mechanical part and the recording medium. As this technology is no longer widespread today, manufacturers of magnetic tapes and heads have become scarce, making mass production of a new complete tape echo difficult. don’t miss the upcoming articles !