Am i going to blow everything up..... ?

Hi There

I currently have a ROTEL surround processor with a ROTEL 5 chanel 120w amp for home theatre fun. These are driving JMLab Colbalt series speakers.
These sound great but I want to add a 2 Chanel Valve Amp to my system to listen to audio / CD / turntable (when i get one..). I am considering the Shanling SP80C monoblocks.

SO my questions are:

Can i hook up the Valve Amp to my ROTEL processor as Zone 2 so that i can control everything from one location.

Can i hook up a turntable to my ROTEL processor, there is no phono in, but i presume i can use a preamp and use the tuner or tape inputs.

Will the JMlab Colbalt 815's sound good with a valve amp (2*45w) class A/B

and the big questions: Can i continue to use my JMLab front speakers with 2 amps plugged into them ie the valve amp and the surround Amp, or do i need to keep switching the cables, or is there some other trick (a filter or something). I am not sure if i will damage something by having on amp off and the other playing, or the risk of having both amps on at the same time (but one with no signal)

Thanks for any help you can give me


Your surround processor should work as a preamp for the amp you are considering. However, please be sure to check that the output impedence of the processor is much less (e.g., 5-10 times less) than the input impedence of the amp.

Chances are that you will not be able to use the surround processor for the turntable. You will likely need to purchase a phono preamp. The output signal of many cartridges are much smaller than the output signal of other devices such as a dvd player, tuner or cd player. Phono preamps are often necessary to boost the signal sufficiently for a line preamp (or processor) to utilize. Further, phono preamps are also designed to handle the output impedences of various cartridges -- you will need to check and potentially adjust settings once you select the cartridge and phono preamp.

Others can speak better to two amps feeding the same speaker, but I would be cautious about that since the closed loop would also mean that each amp is feeding the other amp. Even if the power is off on one amp, there may be some complete circuits in that amp via the speaker cables and output stage of the amp. Other audiogoners may have experience and knowledge here that refute my concerns, but I would be very careful with driving a speaker with two amps unless there's a switch to disengage one of the amps speaker wires while the other amp is active.

There are a number of systems fellow Audiogoners have listed that combine both two and five channel listening in one system. You may wish to peruse some of those systems for some ideas.

If memory serves, one option is to utilize only three channels of the surround sound amp (rears and center) and use two channels of the stereo (e.g., valve) amp all driven by a single five channel processor (i.e.,preamp). That requires some thought to amp matching, but many processors allow for separate volume controls per speaker pair so the volume matching could be pretty simple. It does mean that two channels of the surround amp go unused. When listening to music, simply switch the processor to stereo mode (this may still require a separate phono preamp).
Hi Ozfly, thanks for the response. I thought about just conecting the fronts to the valve amp and ignoring the surround amp, but i am a little worried about the difference in tone / flavour and speed response between the 2 amps. I guess worse case i just switch the wires each time. You don't know of some sort of in line unidirectional filter that would stop the circuit from reversing? Or some sort of auto switch...hmmm more internet searching...


Tony, you may want to contact some of the folks who have both HT and stereo systems listed in the virtual systems area (I'd start by browsing the HT part to see who does both). They may have some great tips for you.

The tone and flavour are what needs to be matched to some degree. Since you have matched speakers and the preamp and source are the same, the amps themselves may not impact the sound as noticeably as you might think (especially while watching HT, where the primary focus is visual).
At 8 ohms and 91db the 50 watt Shanling monos should work well. The Shanling has it's own high quality volume control so you may want to think about a high quality switcher with three or more inputs? One for the the Rotels L+R pre-outs and another two for cd and phono pre-amp. This way you could bypass the Rotel and use the Shanling volume control for two-channel cd and vinyl play back.

Don't worry about the Shanling sounding different from the Rotel amps for Hometheater...It will still be just as fun IMO.