no volume control

OK, now I get it. so my recommendation would be USB out to DAC. DAC output to passive pre. since it does not appear that you need a source selector, I would recommend the Lightspeed Attenuator which you can buy from member Georgelofi. do a search to read the long thread about the LSA which is considered to be one of the true high end bargains out there. I've had one in my system while by main pre was out being upgraded. Cost difference about 20X, sound quality difference not all that much.

If you can tell me what the output impedance of the MF dac is, and also what the input impedance of the Rotel is, I can tell you if the Lightspeed Attenuator is suitable for your system.

Cheers George

Audio output impedance of dac is 50 ohms and input impedance of amplifiier is 33k ohms/1.0 volt.

Hi Sugar1. The 50 ohms drivability from your MF dac will easily drive the combined load the Lightspeed Attenuator and Rotel amp and the 1v sensitivity is also a great figure to have

Cheers George

Thanks for the information as I have been thinking about what direction to take to control the volume output as it seems so many directions to take and the lightspeed attenuator sounds like a good fit. I was looking to replicate sound to be somewhat in the middle between solid state and valve amplifcation. Could you verify this and also how to go about a purchase.
Thanks:
Gary