Tubes on top and Class D on the bottom

Mfsoa, you may not be realizing that the question concerned pairing an amplifier rated at 300 watts (into the 4 ohm impedance which the speaker has at low frequencies) with an amplifier rated at 3.5 watts.

Please see my earlier post regarding the implications that would have. Essentially, it would convert the 300W amplifier into little more than a 7W amplifier (7 rather than 3.5 due to the fact that the woofer section's nominal impedance is 4 ohms, while the impedance of the mid/hi section is nominally 8 ohms).

It seems the only safe way is to buy a separate tube power amp for the top and use a PVC on one or the other to level match. Correct?

Tom, using a pvc is certainly a way that it could be done. A fixed resistive attenuator having the right values might also be readily available off-the-shelf, or else could probably be obtained customized to your requirements.

But given my earlier point that the fraction of the M300's power capability that could be utilized would be limited by the voltage swing capability of the lower powered amp, I think it would only make sense to choose a tube amp with a fairly hefty power rating. In that case you may very well be able to find an amp which, besides being a suitable choice sonically, would also be a close enough gain match to not require any special matching provision.

Best regards,
-- Al

I was wanting to do the same thing with my 4jr's and I emailed a few people on this site and got great advice and sold the m-300's and bought a Moscode 401hr which was exactly what the doctor ordered. It's also fun because you change the sound easily with tube changes. This is one fantastic amp with the 4jr's. Sorry I couldn't answer your question but I thought you might want to look into this.

Good luck
Gary

Thanks for all the information. Still experimenting....

FWIW there are tube amps that go full power to 2Hz...

20Hz response with zero squarewave tilt is thus possible. So I would not use the 'response to 20Hz' issue as an argument against tubes, just say'n...

Atmasphere, thanks for your reply. I am thinking that tube amps that go below 20 Hz with authority are expensive. At what price range do they start?

Tom