High output dacs/CD players

The Kora Hermes tube DAC puts out 5v or the regular 2v.

For most power amps 2v input is close-to-peak voltage. Anything higher than that has to be attenuated. Very often there is no need for active preamp for that reason. Just make sure that you have input impedance of the poweramp ~10x output impedance of passive preamp and output resistance of the passive amp should not be less than 5k. Another words look on the specs of the passive preamp along with its resistor and potentiometer values.

Marakenetz:
Thanks for your info. I try to keep myself working below the output resistance of the passive at 1k. But, with such an arrangement, there is not enough gain. I'm using the Aleph 1.2 amps whose input imp is 10k. Thats where the problem is. Any solution? I feel the only way is to use something like the theta gen V who gives out 6.6V, and that would give me addt. approx 10dB extra gain. So, now, I can back off the passive and stay at output resistances like 100-300 ohms.

You really do not need a high output DAC for it to work with a passive preamp. What is much more important is correct impedance matching of DAC output/preamp/amp combo. Cable selection is also important. You won't be able to use long cables at all.