Highly recommend csmip-ip-s, and maybe modern import step/dir servo drives instead.
Or use the drives you have in step/dir mode with the csmio-ip-s.
Very easy, fast, good, done.

I have seen lots of threads about analogue-> s/d conversions.
Past 14+ years.
And some few really clever people got them to work really well (Mark V. was one, 8+ years ago).
Via custom electronics they made (cheap, but I could not design them), lowpass / bandpass filters, tuning, etc.

Look;
You have a bob .. a converter .. a drive .. tuning .. motor.
Thats 4 pieces of kit in a row, and no easy way to detect noise, hum, non-linear response, accuracy etc. etc.

Alternatively, a csmio-ip-a would drive them directly.
And one of the smartest most capable guys I know uses it with great results. Real VMC, with auto toolchanger and analogue servos.
He also has an csmio-ip-s like mine, on a small lathe.

I am pretty sure the drives You have can work extremely well.
Could.

But I also think that You will suffer and struggle to get them to work, and the results are likely to be far from close to optimal - vs what they could do technically.
Usually, bobs have electronic problems of all sorts.
Limited speeds, responses, noise, non-linearity, functioning etc etc. and these mostly only appear at high speeds aka servos.

After trying 12+ combos for 10+ years, I ditched all that and imported new ac servos myself and cslabs controllers.
Right choice.

You can get new small 400W servos for 290€/axis, more or less, EU, all in.