The CSP3, as it is known, is a feedback-free Single-Ended-Triode preamplifier recommended with any Decware amplifier or any brand or type amplifier.  It is compatible with literally everything because it has adjustable output voltage (0~25V).  
 
Don't go away, we're not done yet.  This is wonderful sounding OTL headphone amplifier for use with dynamic headphones and ideal with higher impedances.  In fact it was originally designed to be just an OTL headphone amp, but then we realized everything was there except the jacks to make it into an equally stunning preamp, so that's what we did.
 
For headphones it can be configured with the correct jacks to be used with either 1/4 inch, 4-pin XLR or dual 3-pin XLR headphone cables, your choice.
 
For people serious about transparency, liquidity and drive.  Since it can be dialed-in for any type of amplifier, low or high power, tube or solid state, it is very popular in solid state circles for those looking to get some tube warmth and better imaging and dynamics from their system.