Placette pre amp

I assume that the author of this thread has triode monoblocks from Legend Audio and I dare do dissapoint the author that these amps will loose some of its performance if driven by passive stage. These monos have low sencitivity and relatively low gain. The great deal of detail and dynamics may dissapear if the source with high output(~3.V on the output) isn't used.
CD players with volume control can have a sufficient output voltage for your amplifier but won't you use different components as well?

There are several options for you:
Pass Aleph P(hard to find though) that has switchable gain and can be used as an active and passive preamp as well in case if you will have high output source(can be a phono too).
BAT VK50 is one of the best preamps for the money spent. It's excellent performer with triode and SET amplifiers and has a remote.
EVS volume pot or even Creek OBH12 passive remote stage can also be coupled with existing non-remote preamp.

I'm the passive folk too but there are certain conditions must meet before you'll get into no-preamp listening. Most of SET and Triode amps have a low sensitivity and will loose a great deal of dynamics when coupled directly with the source. There is one more condition but usually it's the only consearn for solid states which is impedance compatibility. There are a few technical differences that I want to describe as a former engineer:

Triode amps need in average 4...5x higher input voltage than tetrode push-pulls due to a lower gain. If insufficient voltage is applied to the input(lower than offset) the triode enters non-linear operation and will operate with the great deal of distortions(especislly on low volumes)

Tetrodes have their characteristics more linear and usualy more sencitive amplification components. On most of tetrode operated amps the input voltage of .4 volts is enough to drive them. If the specs say that input sencitivity of the tetrode amp is 1.2V and you will drive it with just .4volts on input most-likely you will just loose the rated power of the amplifier with remaining linear non-distorion operation.

To my experience SET and Triode amps should be best driven with 20dB gain amps not excluding the solid state(MOSFET) or hybrid designs.

Creek OBH12 is indeed a nice product for the price and can be a great addition to any non-remote preamp.