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Thread: Stereo Pre-amp with HT Pass Thru. Can someone explain this?

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    MLO owner/operator TomDac's Avatar
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    Default Stereo Pre-amp with HT Pass Thru. Can someone explain this?

    I've read several posts on Audiogon forums regarding getting a good stereo pre-amp that has a Home Theater pass thru, which would give me the best of both worlds (HT & 2 channel).

    Can someone explain how this works? Thanks.
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    Tom,
    As far as I know this feature would be the same in any preamp that offers stereo as well as switching to a Home Theater Processor.

    Here's how it goes; for two channel listening and considering that you have a surround sound processor connected to the preamp, this bypass feature would allow your two channel music to go from your source, such as a CD or Turntable directly through the preamp and on the main two channel amplifier. This avoids always having a surround sound processor in the chain between your sources, preamp and the main amplifiers for the least amount of equipment in the connection.

    In the Home theater setup, this feature would allow you to switch your preamp to route the incoming two channel encoded home theater signal from your DVD or video source through the Preamp and off to the surround sound processor. Then the two front main surround sound processor outputs would go back into the preamp and then off to the main front amplifiers, the remaining surround channels out of the surround sound processor (the rear, sides, and sub) would go to their respective amplifiers sans the preamp. With this connection you are adding another component into the chain of equipment and hence more chance of "coloring" the sound. Doesn't matter to much for movie soundtracks but could for critical two channel music.

    So in short, the bypass is there to avoid unnecessary additional equipment (surround processor) being connected in the audio chain thus avoiding additional coloring of the sound. When you want to listen to surround sound switch out the bypass and your processor becomes added into the chain of equipment and active for movies.

    Note: My ARC LS-15 does not have a bypass feature, something which I am disappointed with. In order for me to listen to surround movies, I elect to physically re-connect the processor between the preamp and amp each time I want to watch a movie. When I do my critical two channel listening, I physically remove the surround processor by disconnecting the cables. Even though my processor has a bypass feature built into it (note I said the processor not the preamp) the signal still goes thru untold amounts of IC's (integrated circuits) which I do not want to have in my signal path during critical listening...less is more

    Sam

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    The HT Bypass also gives you universal volume control when using your Surround Processor. I do this in my setup and it works great.
    .............

  4. #4

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    I dont see the reason for such a feature on a stereo preamp. Why would you not just run your DVD player or sat/cable box into the processor digitally? If you want to listen to it through the stereo preamp, send analog. Am I missing something here?

    On a integrated amp, I can see the HT bypass coming in handy....send the front preouts from the processor to the HT input on the integrated, and when you watch something in surround sound, you simply bypass the preamp section of the integrated and use its amp for the front channels. Volume controlled by the processor.

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    Senior Member Jeff Zaret's Avatar
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    Tom & Sam,
    My pre has a HT Bypass.) They way it works is you plug in devices in to your surround processor directly. Now, let me say this, you can still plus devices in to your preamp and use it as before but it will be affected by the HT Bypass function.

    What happens is this, the devices which are plugged in to the surround processor, CD, DVD, etc ,are controlled by the surround processor in regards to selection, volume and dare I say, ......tone controls. The "front L&R" output from the processor go to the preamp to the HT Bypass inputs. From this point the preamp is still connected to your amp(s). There can be other variations from the surround processor but I will avoid that explanation for simplicity.

    Typically what is done at this point, is the surround processor, the preamp and amp(s) are on, one would switch the pre to HT Bypass and on the surround processor select the input desired.

    In reality what happens is the surround processor (if it is designed well) will not process anything when sending the information back to the pre. The bottom line here is convenience. You have one source for volume instead of multiple sources. The surround processor controls those functions and the pre understands this and is used as a pass-thru to the amp.

    Again this is simplified but I hope this clearer.


    Jeff

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    Quote Originally Posted by Audiophiliac View Post
    I dont see the reason for such a feature on a stereo preamp. Why would you not just run your DVD player or sat/cable box into the processor digitally? If you want to listen to it through the stereo preamp, send analog. Am I missing something here?
    Yes you can do either connection as you mention. But when you have your digital into your Processor, where do you connect from there to hear sound from your mains???

    The HT passthrough uses the connection from the Main/Front Channel Pre-Outs of the Processor.

    So when you adjust the volume level on the Processor, the volume on the Pre Amp (with HT Passthrough) is not needed. This alleviates the need for volume matching between the two.

    This is also very convienient for those with HT Recievers that have power driving abilities. You just Pre Out the - mains to HT Passthrough and let your main power amp handle the duties for the main speakers - instead of a possibly inferior power section of the receiver.

    Does this make it clearer?

    Dan
    .............

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    Senior Member Rich's Avatar
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    One thing to be aware of is that you want to select a preamp with a home theater bypass that has "Unity Gain." As I understand it, this is the feature that allows the volume level for your mains to be controlled solely by the Surround Processor when in bypass mode. There are some models of preamps that don't support Unity Gain.

    Some models of preamps even allow a complete pass-through for the home theater signal, meaning that your two-channel preamp doesn't even have to be turned on when you are in multichannel mode, allowing the surround processor to be your sole preamp. I don't recall the name they give to this feature.
    Rich

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    Quote Originally Posted by Rich View Post
    One thing to be aware of is that you want to select a preamp with a home theater bypass that has "Unity Gain." As I understand it, this is the feature that allows the volume level for your mains to be controlled solely by the Surround Processor when in bypass mode. There are some models of preamps that don't support Unity Gain.
    Rich...Good point...

    Dan
    .............

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    Forum Administrator twich54's Avatar
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    Quote Originally Posted by DTB300 View Post
    Rich...Good point...

    Dan

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    Quote Originally Posted by Rich View Post
    Some models of preamps even allow a complete pass-through for the home theater signal, meaning that your two-channel preamp doesn't even have to be turned on when you are in multichannel mode, allowing the surround processor to be your sole preamp. I don't recall the name they give to this feature.
    This would be the type I would look for. Then hook up all the things you want to listen to in 2ch to that...ie. Turntable, high end CDP, etc. Everything else (DVD, Sat, LD, etc) would plug into the HT processor. When you want 2 ch. just turn on the preamp alone and the power amp(s) for the mains and off you go. When you want to go surround sound, turn on the HT processor, the mains, the surround amp(s) and the source you are watching and the TV and off you go there. Never even turning on the 2ch preamp...signal just passes right through properly attenuated by the HT processor and on to the amps for the mains!
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    Senior Member amey01's Avatar
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    Quote Originally Posted by DTB300 View Post
    The HT Bypass also gives you universal volume control when using your Surround Processor. I do this in my setup and it works great.
    If you don't mind a bit more of a sound quality drop with surround sound (let's face it - who cares about movie soundtracks), any preamp can be used this way - just set the volume to an easily identifiable setting (like 12 o'clock or "50" or whatever) and calibrate the surround processor to provide balance at that preamp setting.

    Now, whenever you want to use the surround processor, put the preamp on its input and set the volume to the calibrated level - now you can control everything through the surround processor.
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    Quote Originally Posted by amey01 View Post
    Now, whenever you want to use the surround processor, put the preamp on its input and set the volume to the calibrated level - now you can control everything through the surround processor.
    While this works (tried it), it just does not provide that cohesive surround sound field which the HTPT gives you - IMO.

    Better yet, to not deal with all of this, just buy a top of the line Pre/Pro and do away with the other pre all together.

    Dan
    .............

  13. #13

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    Pass Labs preamps are awesome and they give you pass through as well as Unity. This is how my main system is set up.

    My mono blocks go into the preamp and then from that into the processor. I turn it to unity an that's it. It works flawlessly.

  14. #14

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    Quote Originally Posted by DTB300 View Post
    While this works (tried it), it just does not provide that cohesive surround sound field which the HTPT gives you - IMO.

    Better yet, to not deal with all of this, just buy a top of the line Pre/Pro and do away with the other pre all together.

    Dan
    In my opinion there is no way any pre/pro can sound as good as a good analog preamp. They put to much stuff into pre/pros that mess with the sound. My McIntosh and Cary Pre/Pros don't even come close to my Pass Labs preamp.

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    Quote Originally Posted by Diamonds View Post
    In my opinion there is no way any pre/pro can sound as good as a good analog preamp. They put to much stuff into pre/pros that mess with the sound. My McIntosh and Cary Pre/Pros don't even come close to my Pass Labs preamp.
    Did not say it was better (just used the phrase - "better yet")...just showing all the options available out there.

    I also would not part with my ARC Pre. Two Channel is my priority in my setup with MCH available but not the most critical.

    Dan
    .............

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