I am glad to have gotten into the Forum and saw this topic. This is a question I have been inquiring about for years to varied individuals/techs. I did learn of the possibility of the plug in to the Equalizer board a couple months ago. I have installed one, 6 years ago, but they are no longer available. I have upgraded many PS1 engines with ERR, both steam and diesel. I am happy with the sounds in them from ERR, but they are more common Big Boy, F3s, FEF, etc. and have more generic sounds. However, I have five PS1 turbines and the DD40X I wish to retain the proto-sounds as they are. I have wondered why, when Lionel had their early sounds provided by the same type of chip that PS1/QSI sounds were using, how difficult would it be to provide an "interface" to keep proto-sounds with TMCC control. As with many others, I wish to use only one system, TMCC, and wish to retain the unique sound functions of specific engine types. In my case, this would be great, specific sounds of the various turbines I have, not to mention the PSA functions. Also, the costs and complexity of changing to PS2 is another reason, for myself, to remain with TMCC as my one operating system. I run my PS2 and PS3 engines with this and with no difficulty, at least to the point of I am satisfied with the results.
Again, very glad to hear of this, hope it comes to a rewarding fruition.
Jesse TCA