Have a question about ADCs or DACs? Ask our Expert, Nick Gray

Hi Nathan,

Let me make clear from the beginning...I am not Nick :>)  I am sure he will reply with a well thought out answer.

However, being in the audio business, your post caught my attention.

My immediate response is to use an associative or content addressable memory.  There are not many simple AM or CAM devices on the market. Those that are one the market are more sophisticated and typically used in high speed search and pattern matching applications.

Since you say you have only an 8 bit converter and need only 256 bits, one could take a small EPROM that had an 8 bit address bus and for each address location program the EPROM memory at that location with whatever HOH data you wanted instead the data at the A-D output.  For each possible A-D value, you could then have an alternative HOH value stored in EPROM memory which would be output to the digital amplifier instead.

You would use a standard EPROM programmer for this task. 

In operation, you would wire the EPROM to output data synchronously with the output rate of the A-D.  Depending upon the converter used, there should be an output synchronous with the 8-bit output.  That synchronous output would be used to enable the READ operation on the EPROM.  It would probably have to be delayed so that it would only cause the EPROM output after the A-D outputs were stable on the EPROM address lines. Otherwise, you might introduce data changes to the audio amplifier which would be basically interpreted as noise.  The delay sould be on the order of microseconds, not milliseconds.

You could try this out on a bench setup, and if the HOH data were fairly consistent over a large group of listeners, you may be able to put the HOH data in a custom memory chip (if production volumes are high enough), or put it in one time programmable ROM, or even a small FPGA.

Good Luck,

Ken

Hi Nathan,

Let me make clear from the beginning...I am not Nick :>)  I am sure he will reply with a well thought out answer.

However, being in the audio business, your post caught my attention.

My immediate response is to use an associative or content addressable memory.  There are not many simple AM or CAM devices on the market. Those that are one the market are more sophisticated and typically used in high speed search and pattern matching applications.

Since you say you have only an 8 bit converter and need only 256 bits, one could take a small EPROM that had an 8 bit address bus and for each address location program the EPROM memory at that location with whatever HOH data you wanted instead the data at the A-D output.  For each possible A-D value, you could then have an alternative HOH value stored in EPROM memory which would be output to the digital amplifier instead.

You would use a standard EPROM programmer for this task. 

In operation, you would wire the EPROM to output data synchronously with the output rate of the A-D.  Depending upon the converter used, there should be an output synchronous with the 8-bit output.  That synchronous output would be used to enable the READ operation on the EPROM.  It would probably have to be delayed so that it would only cause the EPROM output after the A-D outputs were stable on the EPROM address lines. Otherwise, you might introduce data changes to the audio amplifier which would be basically interpreted as noise.  The delay sould be on the order of microseconds, not milliseconds.

You could try this out on a bench setup, and if the HOH data were fairly consistent over a large group of listeners, you may be able to put the HOH data in a custom memory chip (if production volumes are high enough), or put it in one time programmable ROM, or even a small FPGA.

Good Luck,

Ken