Eric,
Our precision ladder steped attenuators put only 2 low noise resistors in the signal path at any one time. A typical 40 position step attenuator puts 39 resistors in the signal path... all the time. The Purist LLC-P noise floor has been measured at <-130dB which is quite good. Check some of the other gears specs.
The more resistors there are (and their location in the circuit) the higher the noise level is since noise components are additive. Also, the more resistors you have the larger the combined tolerance error is which makes channel level matching, over the volume range, more difficult.
Another point, with fewer resistors (2 vs. 39) there are also much lower parasitic capacitance and inductance effects. These parasitics effect the attenuators frequency resoponse (the total resistance value is important here also) and at times makes audible differences at higher frequencies.
I won't even go into the total resistive value concept of the ladder or series step attenuator here because that is another completely different topic, in our case also a circuit topology topic, and would deserve it's own thread.
How do they sound... well as we all seem to agree, most times less is better in audio. This is just such a case.
I have heard people mention things like removing a viel from the speakers, less grunge, more air, better dynamics... everyone seems to have their own words and opinion.
For me they simply sound cleaner, less colored and both channel levels match very well over the entire volume range wich seems to keep the image very stable and centered.
I tried a very popular well made 24 position series attenuator before and it really did color the sound quite a bit. It also seemed to noticably cut down the higher frequencies which made the high end seem a little too thin for me.
All in all the ladder step attenuator is a known superior solution to a series step attenuator. But, the trade off is a ladder does cost more and IMO it's worth it
