Volume Adjustment

Okay . . . found CD Test track on Spotify (something like decibel.org from Amazon for free).

Used a 1,000 hertz test tone and it appeared that each Volume increase from 52 to 53 to 54 increased the volume by 3 dbs. 

So am guessing the MA-252, not being a high priced amplifier with a large volume knob like those on a Pass Labs amp, had compromised volume adjustment to about 3 db per volume control display. 

 Makes me recall what my Dad would say, “Poor people got poor ways.”

Uncle.  Over and out ! 

Ask Mac I seriously doubt the 3db step in right…. 

Also w test tones and a decent SPL meter you are ahead of many here….. 

The McIntosh MA252 does not use an old-style rheostat for volume control. Instead, its electronic attenuation system (reflected in the volume display) follows a logarithmic attenuation curve. As a result, the volume increase per step is not uniform; in some regions, each step may represent a larger change than in others.

It is quite possible that the 52–53 transition crosses one of these regions where the attenuation curve changes slope. My Cambridge Audio Azur 851A integrated amplifier has a similar type of volume control behavior, and I can also notice a slight jump at certain points on the dial.

On my system, the jump is noticeable but still within expectations. If you feel the step change is unusually large compared to normal behavior, it may be worth raising the question with McIntosh for confirmation.

I had an ARC preamp that had a blown shift register and it created what you are describing