Paperw8, I think you may have misread Herman's comment. Note that he did not say that the gain of a preamplifier is fixed. He said that "the gain of almost all active STAGES is fixed." That is a correct statement, as are the rest of his comments, IMO. The statement in his post that "the gain of these amps is fixed" was clearly a reference to amplifier STAGES, when considered in the context of the surrounding paragraph.
It is certainly possible to design an active stage whose gain can be directly varied by the setting of a potentiometer, and where the maximum gain setting is greater than 1. An example would be an op amp stage with a pot in the feedback loop. However, that "would be extremely unusual" (to use Herman's words) in a quality audio design.
Regarding preamps that provide independent level settings for each input, to allow similar settings of the main volume control to be used for sources having significantly different output levels, it obviously makes sense to not refer to those controls AND to the main volume control as "volume controls," which would lead to confusion as to what was being referred to. So it would make sense in that situation to refer to the controls at the input as attenuators or input level controls. But those controls and the main volume control are doing the same thing, just at different points in the signal path, and with different kinds of adjustability.
In Mark's case, I believe he is saying that there are three controls involved -- one in the power amp, a main volume control in the preamp, and an "attenuator" in the preamp, perhaps providing a few discrete attenuation settings that affect all inputs equally (i.e., the attenuator is "after" the source selection function in the signal path). To be able to utilize the main volume control in the preamp at higher settings, which was his original question, I don't think it is possible to say in general if it would be better to lower the setting of the control in the power amp, or to increase the attenuation setting in the preamp, or both, as there are many design-dependent variables and unknowns involved. In some cases it might not matter at all. Experimentation figures to be the only way to tell.
Regards,
-- Al
It is certainly possible to design an active stage whose gain can be directly varied by the setting of a potentiometer, and where the maximum gain setting is greater than 1. An example would be an op amp stage with a pot in the feedback loop. However, that "would be extremely unusual" (to use Herman's words) in a quality audio design.
Regarding preamps that provide independent level settings for each input, to allow similar settings of the main volume control to be used for sources having significantly different output levels, it obviously makes sense to not refer to those controls AND to the main volume control as "volume controls," which would lead to confusion as to what was being referred to. So it would make sense in that situation to refer to the controls at the input as attenuators or input level controls. But those controls and the main volume control are doing the same thing, just at different points in the signal path, and with different kinds of adjustability.
In Mark's case, I believe he is saying that there are three controls involved -- one in the power amp, a main volume control in the preamp, and an "attenuator" in the preamp, perhaps providing a few discrete attenuation settings that affect all inputs equally (i.e., the attenuator is "after" the source selection function in the signal path). To be able to utilize the main volume control in the preamp at higher settings, which was his original question, I don't think it is possible to say in general if it would be better to lower the setting of the control in the power amp, or to increase the attenuation setting in the preamp, or both, as there are many design-dependent variables and unknowns involved. In some cases it might not matter at all. Experimentation figures to be the only way to tell.
Regards,
-- Al