You have a tube buffer, but it would seem to be not a bandaid style anymore like a buffer seprate, you have the real thing due to the tube preamp, its directly in the signal just as well as a buffer would be, mostly it is for a fix on thin sounding solid state equipment, so what you are experiencing is exactly what you should be. Only other thing is that it is possible the impeadence changed with your cd using the buffer, now the preamp is already a similar impeadence signal as well..Tubes rule