Exploring the PT2399 Delay IC: The Heart of Analog-Style Digital Delay
Introduction
When it comes to building delay pedals, one chip stands out for its balance of simplicity and versatility—the PT2399. This IC has become a go-to for both DIY enthusiasts and pedal manufacturers looking to create warm, analog-style delays with the reliability of digital technology. In this article, we’ll dive into what makes the PT2399 special, how it works, and why it’s such a popular choice for delay effects.
What is the PT2399?
The PT2399 is a delay IC designed by Princeton Technology. It’s technically a digital delay processor, but its simple architecture and inherent noise characteristics make it capable of producing analog-style delay sounds. With a delay range from 31ms to 340ms, the PT2399 covers everything from slapback echoes to longer, ambient delays.
Key features:
Operates on low voltage (5V – 9V), making it ideal for guitar pedal designs.
Provides simple control over delay time using external capacitors and resistors.
Offers warm and musical repeats, thanks to a natural lo-fi character.
Easy to integrate into a circuit, with minimal external components needed.
How the PT2399 Works
At its core, the PT2399 is a digital echo processor that converts the analog input signal into a digital signal, delays it, and then converts it back into analog before outputting the delayed signal. While it’s a digital IC, the architecture is designed to sound warm and analog, largely due to the way it handles signal degradation at longer delay times.
Digital sampling: The PT2399 uses a sample rate to create the delay, which is governed by an external clock circuit. The lower the sample rate, the longer the delay time.
Analog-like tone: While it processes audio digitally, the PT2399 introduces a slight amount of noise and aliasing, which gives it a natural “dirty” quality. This is one reason why it’s often favored by pedal builders looking for vintage, lo-fi delay sounds.
External control: The delay time is set using external resistors and capacitors. This allows for a wide range of creative control in pedal designs. Additionally, other parameters like feedback and wet/dry mix can be manipulated with relatively simple circuit additions.
Advantages of the PT2399
Warm, Analog-Style Delay: Despite being digital, the PT2399 excels at delivering warm, slightly degraded echoes that are reminiscent of classic analog delay units. As the delay time increases, the signal naturally loses high-end detail, creating a tape-like sound that many guitarists love.
Simple Circuit Design: The PT2399 is easy to work with, requiring only a few external components to function. This makes it a favorite among DIY pedal builders and hobbyists who want to add a delay effect without dealing with complex circuits or expensive components.
Affordable and Reliable: Compared to traditional analog delay chips like the Bucket Brigade Device (BBD), the PT2399 is much more affordable and easier to source. It’s also more reliable in terms of noise performance and consistency.
Versatility: Whether you’re looking to build a short, slapback delay or a longer, more ambient echo, the PT2399 is capable of covering a wide range of delay times. This flexibility makes it a great choice for pedal builders who want to offer multiple delay sounds in one unit.
Challenges and Limitations
While the PT2399 is a great chip, it does have some inherent limitations, which are part of its charm but also something to consider depending on your project goals.
Noise at Longer Delay Times: One of the most significant trade-offs of the PT2399 is the increased noise and aliasing at longer delay times (above 300ms). This results in a noticeable degradation of the signal, but for many, this adds to the chip’s appeal by introducing a “vintage” character.
Limited Delay Time: With a maximum delay time of around 340ms, the PT2399 doesn’t reach the extended delay times offered by some digital processors. This makes it more suitable for short to medium-length delays.
Not True Analog: While the PT2399 delivers an analog-style sound, purists seeking a true analog delay may still prefer BBD chips, as the PT2399 does use digital processing. However, the character of its sound is often enough to satisfy fans of vintage tones.
Popular Pedals Using the PT2399
Many commercially successful pedals have been built around the PT2399 due to its ease of use and warm delay tone. Here are a few popular models:
tre_audio DIRTY DELAY: Known for its lush, warm repeats, this pedal uses the PT2399 to create a musical delay that works well in both clean and overdriven settings.
Ibanez DE7: The DE7 is a highly regarded delay that uses the PT2399 chip to achieve both clear digital delays and warm, analog-like echoes, making it a versatile tool for any guitarist’s rig.
Conclusion
The PT2399 delay IC offers a fantastic balance of simplicity, affordability, and warm, analog-style delay tones, making it a favorite in the world of guitar effects pedals. Whether you're a seasoned pedal builder or just starting out, the PT2399 provides an easy way to add lush, musical delays to your circuit.
Are you ready to dive into the world of delay pedals? Check out our DIRTY DELAY and DELAY pedals featuring the PT2399, and start crafting your perfect delay sound today!
The DIRTY DELAY Pedal is a mashup of two awesome effects, a classic overdrive and a delay, in one pedal! The Overdrive circuit in the pedal is an asymmetrically soft-clipping Overdrive, while the Delay is a versatile echo machine. A selector switch allows you to choose either Overdrive or Delay or both simultaneously. The DIRTY DELAY is great for that larger-than-life arena rock sound or for adding delay to a massive solo to make it sound ever more…. massive.
Delay Pedal lets you add echo to your guitar or synth signal from 60 ms to 1.5s of delay time. This can take your signal from a rapid spring-like echo to long canyon-like echo. By cranking the Repeats knob, the Delay will go on seemingly forever.
The pedal features controls for the number of Repeats, the length of Delay, and the amount of Mix of the original guitar signal with the delayed signal. A true-bypass footswitch helps to keep your tone pure when the pedal is not in use. Delay runs on 9V DC Negative Center power and consumes 85mA.