I'm interesting add on another tube amp use with my 990/7125 on main speaker Q&A
1. How 990 work well with tube amp.
2. Should I get Integrated Amp or Stereo Power Amp?
3. I use 990/7125 for HT, how I hook up another tube amp to my main speaker?
Thanks

There should be no issues with using the 990 with a tube amp. However, it seems an integrated would not be a good choice as its preamp section would be redundant. So a tube power amp would be the way to go. You'll need to make certain it has enough output to drive your speakers. What are you using for your mains?

With reagrd to hooking it up, you'd just unplug your FL and FR outputs from the 990 that currently go to the 7125 and send them to the tube amp to power your mains. The 7125 would be used for your surrounds, center channel (and rear surrounds, if you have a 7.1 set up).

Long-time forum regular soundhound (who unfortunately hasn't had time to drop into any of his old Internet haunts over the last couple years due to work load) has an Outlaw 950 feeding a closet full of tube amps - last I heard, it was still working very nicely for him. The 990 should work just as well as the 950 did. Just treat it just like a solid state amp when connecting it to the 950 and the speakers. As Videodrome says, there's no need for an integrated amp since you already have volume control and switching at the 990.

One question does occur to me: will this be separate from the home theater, or will the tube amp handle the front speakers all the time (stereo and multichannel listening)? If it's separate and you will still have the left/right pre-amp outputs going to the 7125, we have a slightly different issue. You may want to consider a switch box between the 990's left/right pre-amp outputs and the left/right amp inputs of the tube amp and 7125.

Thanks Videodrome and gonk
I use Martin Logan Clarity for main.I want use tube amp for listen music 2 ch and 7125 for HT,
gonk can you give me detail about a switch box what's kind and where I can buy.

So you want to use the same speakers with different amps at different times? That could present a few challenges. Purely from a wiring perspective, we're talking about two switch boxes: one between the 990 and the two amps, and another between the two amps and the speakers. That leads to a separate issue, though: it is not wise to tube amps without a speaker load in place - unlike solid state amps (which typically include protection circuits), tube amps operating with no speaker load can suffer damage. You'd need to have some sort of dummy load in place to keep the tube amp under control when the ML's were switched over to the 7125. Have you considered using the tube amp all of the time?

If you get an integrated tube amp and don't use the 990 as the pre for 2 channel music, Niles Audio has a 2 amp to 1 speaker set switch box. The spec sheet does not state that it keeps the non active speakers under a load, so unless an integrated tube amp includes protection similar to a SS amp, you still have the issue of running the tube amp accidentally without a speaker load. The companies contact information is in the link, you could contact them to see if it does keep the switched speakers under load.

Yes, I want to use the same speakers with different amps at different times, can I use speaker selector with Dual audio source capable with A/B switch supports one or two amplifiers.