Integrated amp and home theater

Discussion in 'Archived Threads 2001-2004' started by Patrick_T, Dec 20, 2001.

  1. Patrick_T

    Patrick_T Agent

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    Ok,

    I currently have a rotel RA-972 integrated stereo amp running a pair of thiel cs1.5s. I plan to slowly upgrade this system to the point of having a full home theater setup. My RA-972 has pre-out jacks, no pre-in jacks. Now, if I were to purchase a processor and a 3-channel amp to drive the 3 fronts, is there any way I could, at least for the time being, use the integrated amp to power the rears? If I hooked the pre-outs of the rear speakers from the processor into an input such as "cd player" into my integrated I forsee a problem. With this setup both the processor and the integrated would control volume of the rears. So, would it be possible to say, set the volume control on my integrated at a certain level (all the way up, half way up, etc...???) and then calibrate using the processor? Would this setup, as long as I kept the integrated amp's controls untouched, allow me to effectively gain the use of the integrated amp's amp section?

    Thanks for any help

    Patrick Toomey
     
  2. Darin H

    Darin H Auditioning

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    I have an RA-972 that I use when listening to CD's. I have my Yamaha reciever pre outs connected to the Rotel's aux imput for when I need 5.1, bass management, etc. I just used my SPL meter to find the spot on the Rotel's volume dial that matched the other speakers powered by the Yamaha. It takes a few more seconds to get ready to watch a movie, but it is worth it to me to have the much improved stereo performance from the Rotel. My music to movie ratio is about 90/10.
     
  3. Saurav

    Saurav Cinematographer

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    Does your integrated amp have preouts and main-ins on the back connected with a jumper? My NAD integrated does. If you have this, then it's simple - just disconnect the jumpers, and take the interconnects from your processor and feed them directly into the main inputs. If you can't, then your only solution is to mark the point on the Rotel's volume dial where you get unity gain, like Darin said.
     
  4. Patrick_T

    Patrick_T Agent

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  5. Darin H

    Darin H Auditioning

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    I am no expert, and there are people here who I am sure can tell you WHY this works, but I will tell you my experience.

    Let's say I choose to calibrate at 60dB on my RS SPL meter. I use a test tone, and set the Rotel volume where the main speakers read 60dB and the center and surrounds read 60 as well. If I then set the SPL meter to 80, all I have to do is turn up the volume on the Yamaha reciever to change volume. Once my Rotel is set, (about 10 o'clock for me) I don't have to touch the Rotel volume setting.

    Hope that helps.
     
  6. Patrick_T

    Patrick_T Agent

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  7. Saurav

    Saurav Cinematographer

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    I think Darin and I are saying the same thing. I agree, there are probably individual level controls for all the channels. However, that doesn't matter - you can set the receiver's level to something fixed and then adjust the Rotel so that you get the same level from those 2 channels as the others. Or, you can pick a volume level for the Rotel and then adjust the receiver's internal levels so that all channels balance out. Either way, you have to find a fixed combination of the receiver's levels and the Rotel's volume control position, that gives you the same gain for those 2 channels as you have for the others. Then, the receiver's main volume control will correctly adjust all channels.
    Actually, my "unity gain" statement was probably incorrect. Let's see what's happening here.... you have 2 preouts on your receiver that you are connecting to line level inputs on the Rotel. Is that correct? Let's assume that it is... in this case, that signal is already amplified/attenuated by the receiver's preamp section (or, it goes up and down with the receiver's volume control, it's not a fixed-output tape-monitor-like signal). So, the receiver's preamp is "in the loop" for these 2 channels.
    What do you need to do next? You need to ensure that your Rotel's combined amplification, for its preamp and power amp stages, is exactly the same as the amplification provided by just the power amp section of the receiver. In other words:
    Ensure that (Rotel pre + Rotel power) = (Receiver power)
    That way, your signal for these 2 channels will go through:
    Receiver pre + Rotel pre + Rotel power
    And for the other channels, it will go through:
    Receiver pre + receiver power
    And your gain in both cases will be the same. Does that make sense?
    How do you test this... that's a good question. An SPL meter should work, or a voltmeter, if you have one that can measure AC voltages at KHz frequencies accurately. You'd need to generate a tone and measure output at the speaker terminals for both your receiver's channels, and your Rotel's channels. You probably want something like a 1KHz tone, because amplifiers tend to be not so linear at very low and very high frequencies. Of course, that means you need a voltmeter that can handle 1KHz sine waves. With an SPL meter, it's the same thing, make sure they both produce the same output.
    I hope that's clearer now [​IMG]
     
  8. Darin H

    Darin H Auditioning

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    I think that Saurav explained this much better than I did. When I calibrate my system for watching a movie, it required using the volume control on both the rotel and the receiver so that R,C,L,LS, and RS all read at the same level on my SPL meter. I then just use the receiver's volume control to adjust system volume. I have put a small piece of tape on the rotel so I know where the volume knob needs to be so I don't have to use the test tone and SPL meter each time I switch from a CD to DVD.

    I should note that I don't use my sub with 2ch. listening. It is connected to the receiver. It is set to match the center and surround speakers driven by the receiver. That way when the rotel is at the "tape mark" everything is at the correct level.
     

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