BBD Selection Guide and Reference Table
BBD Selection Guide and Comparison Table

Introduction

There are a number of different BBD chips currently in production, and many more "legacy" chips that have long since been discontinued but you may still find NOS (New Old Stock) or even chips pulled from old equipment. There are also a lot of fake and bad chips sold in the gray market. Here we will talk about only current production parts from reputable and well known manufactures.

There are two primary families of BBD chips, the 300X chips and the 320X chips. They use different supply polarity and voltage levels but otherwise operate the same way. Within each family there are a series of models that offer different number of stages, delay time ranges, clock frequency ranges, etc.

BBD Clocks

There are two common clock chips that can generate the 2-phase clocks required by all BBD chips. The two clock chips correspond to the two families of BBDs. The MN3102 is a clock chip for 320X family BBDs, and the MN3101 is a clock chips for the 300X family. The two clock chips are similar except for the polarity and magnitude of the supply voltage they require.

The MN3101 is long since out of production, but we make a pin-compatible replacement module, the CT3101 that can be used with any 300X BBD chip. Technically the CT3101 could also be used with 320X devices by reversing the ground and supply voltages, although the Coolaudio V3102 clock chip is available and matches the 320X BBD power supply arrangement. Note that the V3102 cannot be used for 300X BBDs because it does not support the higher power supply voltages.

BBD Selection

There are a number of criteria to consider in selecting a BBD. First, it must supply the proper delay times for the effect desired (e.g. echo, reverb, chorus, flanger, etc). Beyond that the design decisions are based on system design parameters like power supply voltages, and performance requirements like minimum S/N ratios. The table below compares key design parameters of current production BBDs.

BBD
COMPARISON		 MN3009 MN3007 MN3008 MN3005 V3207 V3208 V3205
Series 300X 320X
Manufacturer Xvive Xvive Panasonic Xvive Coolaudio Coolaudio Coolaudio
Stages 256 1024 2048 4096 1024 2048 4096
Max Supply -15V -15V -15V -15V 10V 10V 8V
S/N Ratio (typ) 88dB 80dB 78dB 75dB 73dB 71dB 60dB
Clock Freq kHz 10-200 10-100 10-100 10-100 10-200 10-100 10-100
Delay mSec 0.6-12.8 5.12-51.2 10.24-102.4 20.48-204.8 2.56-51.2 10.24-102.4 20.48-204.8
Clock Chip CT3101 CT3101 CT3101 CT3101 V3102 V3102 V3102

As can be seen in the table, the 300X series has the best S/N ratio for a given clock frequency and delay period because it's higher supply voltage gives it more headroom (dynamic range). If the system is running at 9V then the 300X series may not provide much advantage as the dynamic range is reduced.

In general the 300X series is more expensive, but can provide significantly better S/N and is the only series that includes a 256 stage device (3009) for very short delay times. Note that the V3207 can achieve a shorter delay than the corresponding MN3007 because it supports a clock of 200kHz.

So in general, if the system power supply is less than 10V or the design is price sensitive, the 320X series may be the best solution. If a high S/N ratio is desired or very short delay times then the 300X series may be preferred. Note the S/N ratio of any BBD may be improved by support circuitry such as a compander (V571 or similar).

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