What is the PT2399?
The PT2399 is an Echo Processor IC produced by Princeton Technology Corporation. This 16-pin integrated circuit (IC) is responsible for producing echo and time delay in many boutique guitar effects circuits.
Complete with an onboard VCO (Voltage-Controlled Oscillator), two Modulator/Demodulator active low-pass filters, and two op amps, the PT2399 is a convenient echo-producing device. One just needs to use a handful of resistors and capacitors to build a basic delay circuit.
PT2399 Pinout
The PT2399 comes in a 16-pin integrated circuit package. You can purchase it in through-hole or surface-mount footprints. Either way, both versions have the same pinout, shown below.
| Pin | Description | Pin | Description |
|---|---|---|---|
| 1 | Vcc – Positive Power | 9 | OP1-OUT – Op Amp 1 Output |
| 2 | REF – Analog Reference Voltage | 10 | OP1-IN – Op Amp 1 Input |
| 3 | AGND – Analog Ground | 11 | OP2-IN – Op Amp 2 Input |
| 4 | DGND – Digital Ground | 12 | OP2-OUT – Op Amp 2 Output |
| 5 | CLK_O – System Clock Output Pin | 13 | LPF2-IN – Low Pass Filter 2 Input |
| 6 | VCO – Voltage-Controlled Oscillator | 14 | LPF2-OUT – Low Pass Filter 2 Output |
| 7 | CC1 – Current Control 1 | 15 | LPF1-OUT – Low Pass Filter 1 Output |
| 8 | CC0 – Current Control 0 | 16 | LPF1-IN – Low Pass Filter 1 Input |
Are there PT2399 alternatives?
There is no known direct replacement for the PT2399.
That said, you can choose to design an echo circuit using alternate methods. Some examples include bucket-brigade devices and DSP chips (like the FV-1).
Which pedals use the PT2399?
Here’s a list of pedals that use the PT2399 Echo IC:
- JPTR FX Kaleidoscope – Youtube | Reverb | eBay
- Caroline Guitar Co. Megabyte LoFi Delay Computer – Youtube | Reverb | eBay
- Dr. Scientist Sunny Day Delay – Youtube | Reverb | eBay
- Polarbear Effects Young Hearts V2 – Youtube | eBay
- Potar Design Devices Noise Ensemble – Youtube | eBay
Where can I purchase a PT2399?
The PT2399 Echo IC is readily available from the following sources:
| Sources for the PT2399 Echo IC |
|---|
| Amazon |
| eBay |
| Smallbear Electronics |
| Tayda |
You may also be interested in 16 pin IC sockets for mounting.
What is the Delay Time Range for the PT2399?
According to the datasheet, the PT2399 can produce echoes from 31.3 ms to 342 ms.
How do I adjust the Delay Time?
You can adjust the delay time by changing the resistance between pin 6 and ground. As the resistance on pin 6 increases, so does the delay time.
The datasheet for the PT2399 includes a table linking the delay time and the resistance value.
What is the Total Harmonic Distortion (THD) for the PT2399?
The PT2399’s THD is based on the resistance at pin 6 (the same resistor used to set the delay time). The table in the PT2399 datasheet was used to create the plot below.
As the resistance on pin 6 increases the distortion also increases, which manifests as a degraded, glitchy echo signal.
Meet the Author:
Hi, I’m Dominic. By day, I’m an engineer. By night, I repair and modify guitar effects! Since 2017, I’ve been independently modifying and repairing guitar effects and audio equipment under Mimmotronics Effects in Western New York. After coming out with a series of guitar effects development boards, I decided the next step is to support that community through content on what I’ve learned through the years. Writing about electronics gives me great joy, particularly because I love seeing what others do with the knowledge they gain about guitar effects and audio circuits. Feel free to reach out using the contact form!
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