Will changing gain affect frequency response?

Right,  I wouldn't call F-M curves "psycho-acoustic" as your knowledge or lack of it has no bearing on the perception. It's more of an ear-sensitivity issue. 

If you remember equipment with a  "loudness" switch, or dial, they were meant to compensate for this known effect, and some speakers are deliberately tweaked along those lines to make it seem like you hear more detail at lower volumes.  Well, you DO hear more detail, but it also means at higher volumes you get exaggerated treble and/or bass. :)

Best,


Erik

Psychoacoustics is the scientific study of sound perception. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound (including speech and music). It can be further categorized as a branch of psychophysics.

Loudness is the characteristic of a sound that is primarily a psycho-physiological correlate of physical strength....

Hi Eric - I'm using psychoacoustic as defined above applied to the perception of loudness quantified by "phon".  Because of how we perceive sound, varying dBs are required to support a constant level of loudness across a range of frequencies.  Each F/M curve is dB (Y) as a function of frequency (X) for one level of loudness (constant phon). 

I suspect what I'm hearing (if real!) might be a function of electronics, not a function of the "hearing response" (one aspect of which the F/M curves are describing).    

Well, I'm in no way arguing F-M. Of course, they are old, and may need updating, but the principle has been around and used for a long time. :)

Best,

Erik

Hello again, Erik.  Thanks for your time considering this.  I'm not arguing the F/M curves either....more a case of not sure they explain what I think I hear when gain is increased but volume reset to the original level.  

Ghosthouse, yes, you're right that the Fletcher-Munson Effect will not cause a change in perceived tonal balance if the volume at the listener's ears remains constant.

Regarding your original question, yes it does seem conceivable that changing how the overall system gain is distributed among the various circuit stages that are in the signal path could affect perceived brightness.  Although without knowing the details of each of the designs that are involved a more specific explanation would be speculative at best. 

For example, Atmasphere has pointed out in a number of past threads that very small amounts of certain harmonic distortion components (e.g. the 5th, 7th, and 9th harmonics) can affect perceived brightness.  Changing the signal levels that are processed by the various gain stages that are involved could conceivably affect the degree to which those distortion components are generated.  Erik mentioned another example, which is that impedances might change, depending on the specific designs.  If the output impedance of a component were to change significantly, and is relatively high, its interaction with cable capacitance could affect treble response to a perceivable degree.  And it seems conceivable that changes in impedance at internal circuit points could also affect the treble, depending on the specific designs. 

Best regards,
-- Al