[Gold]

"Discrete" as in resistor ladders (or other single components) - or do you mean 4 AD ICs per channel?

I'm not sure but I know there were no AD IC's that gave anywhere near that performance in the early 90's.

[living sounds]

I'm not sure but I know there were no AD IC's that gave anywhere near that performance in the early 90's.

Late 90s, but still, yes. The best chips today are not as good as the AD-2.

[iampoor1]

I wonder if they rolled a custom A/D converter using an FPGA? That might be what's under the heatsink....Might explain the "discrete" aspect too IE: They designed it out of discrete gates in the FPGA 

[living sounds]

I wonder if they rolled a custom A/D converter using an FPGA? That might be what's under the heatsink....Might explain the "discrete" aspect too IE: They designed it out of discrete gates in the FPGA 

There's not much room under these heatsinks. The ICs are really small.

[mhelin]

Currently AKM's AK5578EN (8 ch A/D) for an example can be configured to parallel it's all eight converters for 130 dB SNR (112 dB THD). You will still need two chips for 2-channel conversion to get that SNR.

https://www.akm.com/akm/en/product/datasheet1/?partno=AK5578EN

[living sounds]

Currently AKM's AK5578EN (8 ch A/D) for an example can be configured to parallel it's all eight converters for 130 dB SNR (112 dB THD). You will still need two chips for 2-channel conversion to get that SNR.

https://www.akm.com/akm/en/product/datasheet1/?partno=AK5578EN

Yes, today you can get even better performance from a SAR chip. I'm still waiting for a commercial product for pro audio.

But the AD-2 came to market in 1998.

[JohnRoberts]

Currently AKM's AK5578EN (8 ch A/D) for an example can be configured to parallel it's all eight converters for 130 dB SNR (112 dB THD). You will still need two chips for 2-channel conversion to get that SNR.

https://www.akm.com/akm/en/product/datasheet1/?partno=AK5578EN

Yup... 3dB for every doubling so 1-2 is 3dB, 2-4 is 6db, 4-8 is 9dB... not nothing but they would need to go to 16 for the next 3 dB.

JR

[edit] another strategy available to increase resolution as convertors get faster and faster is more over sampling.  If the convertor is fast enough that you can capture multiple samples within a single output sample interval, those samples can be averaged together to improve resolution following a similar rule (3 dB per doubling). I have used this inside digital meters with modest A/D resolution. Since I didn't care about aliasing (in a meter data stream) I combined together multiple samples at lower than sampling theory wants for frequency integrity to realize more meter resolution.  [/edit]

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