geniuses help- pre into pre--gonna blow up?

The speaker connection idea is not necessarily a bad idea. However, you may want to consider building yourself a mechanical A/B break before make box to switch the speakers from one amp to the other depending on what you want to listen to. That way you will avoid any unwanted impedance changes.

the 501 monoblocks unfortunately are not auto- sensitive and require manual switching which is too cumbersome.i connected the 135 prepro main outs to the processor in on the ref3 and the home theater pass through worked for about 30 minutes then the tv audio came through the center channel and lightly in the mains as well---in any event, that config doesn't solve my problem as the tubes are on all the time which is what i'm trying to avoid. sounds goofy but could i connect two sets of speaker cables to my main speakers, one from the monoblocks( tt to ph5 to ref3 to monoblock) and the other from the ht multichannel amp(prepro to multichannel ) to same main speakers?

No, he needs to save his money for the Ref. 3, periods, commas, etc. . . are a luxury he can do without.

You can do easily exactly what you are trying to accomplish where you are running both preamps (the MX 135 and the Ref. 3) into the same amplifiers (assuming it has two inputs (ie. one balanced and one single ended) and is auto sensing between single ended v. balanced. Under this scenario, the risk is that you can only be sending a signal from one preamp at a time (if you mistakenly send signals from both preamps into the amp at the same time - you will not like the results).

So the question is - if you are the only person who would ever turn on the Ref. 3 and you don't leave it on so that somebody can come along and turn on the Mac Pre, then you can do this with a higher degree of confidence.

I have two kids and a wife and I would not feel comfortable with this. You can of course use the HT bypass of the Ref. 3, but I believe you are correct in that in HT bypass, the tubes are active in the Ref. 3. There are other good tubed pre-amps that allow you to not power up the stereo preamp when in HT mode - Cary in particular. However, in my opinion, the Ref. 3 is a better preamp than the Cary preamps - but that is a matter of personal taste.

The only thing you wrote that I understand is can you take preamp out, to line in on another preamp. It's fine. That's basically what HT bypass is, except HT bypass bypasses volume and gain stages. If your preamp doesn't have HT bypass, you can use any line level input. Just be careful about the volume levels the first time you turn it on.

You may want to think about buying some punctuation and capital letters next time you post . . .