Analog delay how does it work

A fast rate means a slapback delay, a long rate means a long delay time. Applying another low-pass filter helps reduce the clock noise and smooths out the signal for dynamic range expanding. The signal response is now very similar to the original input signal but has a darker tone as it has passed through two filters. This feedback is what creates the trailing echo effect. Too much signal fed back into the circuit leads to oscillation — that awesome space-ship effect that is a signature sound for analog delays.

There is much more to an analog delay than mojo, or the number written on a BBD chip. My Account Login. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits.

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We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. Digital will be easier to edit in the studio than recording direct to tape. The pedal converts your signal into digital as it enters the pedal and converts it back to analog when it leaves that pedal.

The accuracy of this analog-to-digital-to-analog ADA conversion differs with every delay pedal. Ideally, you would want a high conversion rate to preserve most of your original signal. There are plenty more details that separate the two, this blog was just meant to introduce the concepts. There is definitely a place in music for both and there are situations in every genre of music where you would want one or the other. This is very similar to digital audio though it is technically still analog.

The major difference is that the amplitude of digital audio is quantized to fit a certain value in a certain bit-depth bit, bit, etc. The amplitudes of the BBD are continuous, meaning they are not quantized to the nearest digital byte.

So the BBD, controlled by a clock whether the clock is analog or digital , is analog even though it samples audio. Aliasing is defined as the misidentification of a signal frequency, introducing distortion or error.

As we can see, it is possible to have a clock sampling rate that is too low to capture the audio signal accurately. We could have a situation like the second illustration where a much lower frequency signal is sampled rather than the true waveform. Like having a sample rate that is too slow, we could also be trying to sample audio with frequencies that are too high.

This is true of digital signals and BBD delay circuits. To avoid aliasing, the Shannon theorem states that the sample rate clock frequency must be at least twice as fast as the highest frequency of the input signal being sampled. Unfortunately, we have to strike a balance in a BBD.

A faster clock yields more accurate results but has shorter delay times. A slower clock will get us longer delay times but will cause unwanted aliasing in the signal. That is why BBD delays are limited in their delay times. A few hundred milliseconds will generally be the point at which aliasing makes the delayed signal too distorted to use.

The anti-aliasing filter is a simple low-pass filter that removes any harmonic content from the incoming signal that would not respect the aforementioned Shannon theorem. The trick with this filter is to have it set to not interfere too much with the original signal.

This, again, is part of the reason why analog delays have limited delay times and a rather dark sound. The waveform outputted from the BBD will resemble the input signal but will have discrete jumps in amplitude. This means there are sharp jumps in amplitude and these square-like steps are a cause of distortion and saturation. Oftentimes, this saturation will show up as increased harmonic content and even as the introduction of new harmonics.

This filter also works to rid of the clock ticks that are inherent in having a clock signal running the BBD. To further condition the signal for the BBD, most analog delay pedals will have a compressor before the BBD and the anti-aliasing filter and an expander unit after the BBD and reconstruction filter. The capacitors of the BBD and the clock are inherently noisy. So first, the signal is compressed, which reduces the dynamics of the signal and increases sustain by bringing the quieter parts of the single closer to the louder parts of the signal in terms of amplitude.

The compressed signal which sounds different from the dry signal passes through the anti-aliasing filter, BBD, and reconstruction filter. It picks up noise and gets EQed significantly in the process. The expander at the other end acts to undo the compression by increasing the dynamic range. As it drops the quieter parts of the signal back down to their natural level, it also drops down the noise.

So although it seems like the expander and compressor are only there to undo each other, they are actually cleverly included to improve the signal-to-noise ratio of the delayed signal dramatically. This looks a lot cleaner. Now that we understand how the delay circuit works, we can finalize our understanding of the entire system. To further condition the signal, analog delay pedals will generally have a high-shelf filter at the input and a low-shelf filter at the output.

The high-shelf at the input will boost the treble of the signal and recover noise in the BBD and overall delay circuit. The low-shelf at the output will effectively cancel out the high-shelf at the input and restore the original signal tonality.

The tone of analog delay, whether achieved by actual BBD chips or by emulation, can be defined as dark, warm and nuanced. Its first iteration was introduced all the way back in Analog delays are inherently flawed. We can see that by how many extra circuits are required just to get a decent sound. The filtering, compressing, expanding. Rather than using tape or the BBD-based analog delay circuits mentioned above, digital delay pedals utilize digital signal processing DSP to create their delay effect.

As we can see, the main setup is similar to the typical delay pedal. The difference is the digital signal processing unit s. With DSP, we can achieve results that are beyond the capabilities of tape and bucket-brigade devices.

Digital delay circuits can have extremely long delay times and can repeat the same sound back indefinitely without any signal degradation other than the losses from the ADC and DAC.

Digital processing is beyond the scope of this article. The main point here is that digital delay pedals are extremely versatile. Early digital equipment may have suffered from the conversions from analog to digital and back to analog.

Of course, purists would argue that any conversion degrades the signal. Pick your poison! Digital delay is often cherished and criticized for being bright, clean, clinical and exact in its reproduction and delaying of the original audio signal.

The Boss DD-8 link to check the price on Amazon is a fantastic example of a digital delay pedal. All of this can be programmed digitally to mimic the sound of these non-digital devices.

So we can get these old-school effects in a new-school stompbox. The Strymon TimeLine link to check the price on Amazon is an excellent example of a digital delay pedal that can emulate both analog bucket-brigade and tape delay tones. The Dunlop EP Echoplex link to check the price on Amazon is a digital pedal designed to emulate the sound of tape delay.