Even if there were engineering issues, forty years is more than enough time to solve them. Not to be a curmudgeon, but I suspect most of what is being engineered in wire and linestages are differences marketed to different tastes.
This statement is false to the best of my knowledge. Any designer worth their salt is doing the best they can.
This engineering issue is in fact solved. There is a reason why passives don’t always work- it has to do with the interconnect cables and what the source is. The engineering issue is that its usually a Bad Idea to have a volume control driving an interconnect cable. It is also true that sometimes you can get away with it. Sometimes the control acts to reduce the effectiveness of the output coupling capacitor in the source device. So as you turn the control down from full volume, you get a reduction in bass. This phenomena has been documented for decades. That is why you rarely see volume controls at the output of electronics without some sort of buffer from the interconnect cable, unless the interconnection is known to be very short.
I agree entirely, move my equipment to another room and the result could be entirely different. Or bring another set of ears in and they may hear it differently to myself.
I think you will find that this has nothing at all to do with the room and everything to do with your equipment!
Here’s how it works. The source has an output impedance that must drive the interconnect cable and the input impedance of the amplifier. The source impedance is not always linear with frequency- quite often it is considerably higher at 20Hz than it is at 1000 Hz (look up the measurements on various CD players, phono sections and the like and you will see this quite often). The source drives a cable, which then is connected to the PVC. The output impedance of the control often **appears** low, since quite often its the wiper of the control and at low volumes its close to ground.
But from the source point of view things are different. If the control is all the way up, the source drives the interconnects and the amplifier directly. As you turn the volume down though, the source has to go through an increasingly higher resistance to get to the amp. If the source already has a variable output impedance that is higher at lower frequencies, the fact is that the ratios of the control vs the output impedance means that the source simply isn’t going to make as much voltage at those frequencies where the output impedance is higher (like in the bass).
Result: lack of bass impact (a tilt towards the high end) results. People report this all the time; now you know why it happens.
It can be avoided by an output impedance that is linear with respect to frequency. The problem here is that to do that often requires a larger output coupling capacitor in the source (which pushes the rolloff down to a point below human hearing). A larger coupling cap often means additional coloration on the part of the cap itself (increased inductance accompanies increased capacitance as capacitors are rolled into a cylindrical shape). On top of that, the designer has to avoid an overly-large coupling cap that might allow the bandwidth of the circuit to exceed the power supply’s low frequency bandwidth (else low frequency instability can occur which can manifest as IMD, muddiness, even thumping). So there are constraints on how large the output coupling capacitor can be.
This means that this conversation will continue for some time, as people will continue to encounter variable results; its 100% equipment dependent.
At least now you know why it happens.
