Can someone explain a pre-amp with HT bypass?

[Thebenz]

My question here is that if you have a 5.1 speaker system, I'm not understanding what a HT bypass or passthrough does for you on a 2 channel preamp?

Chris

[Stereo-head]

Can you give me the name and make of the pre amp so I can get a look at it?

[Kal Rubinson]

It lets you use the 2-channel amp and speakers for the front L/R of your 5.1 system.

[Thebenz]

ok. right now, I have a pioneer elite receiver and a separate 2 channel amp. So I could buy a pre-amp and have it integrated with my HT receiver? So the preamp would have to be on when I watch movies through the receiver then?

[MyPal]

Originally Posted by Thebenz

ok. right now, I have a pioneer elite receiver and a separate 2 channel amp. So I could buy a pre-amp and have it integrated with my HT receiver? So the preamp would have to be on when I watch movies through the receiver then?

Yes...the pre-amp would have to support unity gain or HT passthru. I believe all current McIntosh pre-amps do.

[Thebenz]

I think I understand this now because I wanted to integrate a mcintosh preamp with my HT. My Elite receiver has 7.1 pre-outs on it. I'm using the 2 channel amp right now for my L/R fronts so, if I purchase a pre-amp, the 2 channel amp will have to be dedicated to the pre-amp or can I use that amp for both units? That's where I'm confused. Or is it easier to get an integrated amp with pass thru? I guess the connections is where I am getting confused here.

[Kal Rubinson]

Originally Posted by Thebenz

I think I understand this now because I wanted to integrate a mcintosh preamp with my HT. My Elite receiver has 7.1 pre-outs on it. I'm using the 2 channel amp right now for my L/R fronts so, if I purchase a pre-amp, the 2 channel amp will have to be dedicated to the pre-amp or can I use that amp for both units?

The amp will be used for both purposes and that is the exact point of HT Bypass.

Take a look at the Parasound P7 or JC-2-BP preamps for info.
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[jeffkrag]

Originally Posted by Thebenz

I think I understand this now because I wanted to integrate a mcintosh preamp with my HT. My Elite receiver has 7.1 pre-outs on it. I'm using the 2 channel amp right now for my L/R fronts so, if I purchase a pre-amp, the 2 channel amp will have to be dedicated to the pre-amp or can I use that amp for both units? That's where I'm confused. Or is it easier to get an integrated amp with pass thru? I guess the connections is where I am getting confused here.

Here is the point of HT Bypass in a preamp.

When you integrate a separate 2 ch preamp into a mch setup, you simply take the L/R outputs from your HT processor and run it into the preamp, then the preamp feeds your amp. Your 2 ch source would run directly into the preamp, then out to the amp. No issue there. Just turn on your source, press the appropriate input on your preamp, and listen to music

However, when listening to a mch source that runs into your processor first, then into the preamp, you now have two active volume controls. Without getting too complicated, you would need to set the preamp volume to "unity gain," set up your levels and EQ, then, every time you listen to mch music, you would set the preamp to this unity gain level so you have a constant output and don't mess up your levels/EQ (and probably sound quality might be a little impaired).

A preamp with HT Bypass allows the mch signal to pass through unaffected by volume control or anything else, by essentially creating the unity gain scenario and bypassing it's own volume control. Typically, you simply engage the source input on your preamp that corresponds to the L/R connection from the processor, and you are in business.

Now, the only tricky part is that there are several different ways to engage HT Bypass, depending on the preamp. Some preamps do just what I said in the previous sentence, you simply switch to the input on the preamp taking the L/R feed from the processor. Other processors do it even more simply, by having an HT Bypass button that you simply press to engage HT Bypass, regardless of selected input. Some, like some Mcintosh preamps, do it in what I believe is a little more complicated fashion. (Mac guys can correct me if I'm wrong here) With Mac, you cannot engage HT Bypass any other way but via a 12v trigger, so when you turn on the processor, it triggers the Mac to go into Bypass. However, when you turn off the processor, it turns off the Mac, which you must then turn back on if you want to listen to 2ch music. I haven't used a Mac pre, so I'm simply going by what I've read on these forums.

Hope this helps.

[wpascoe]

I just replaced a Parasound Halo JC-2 with H/T bypass with a McIntosh C2500, which also has H/T bypass.

They work the same way. No need for a 12-volt trigger to turn on the bypass feature of the Mac.

To add the 2-channel preamp to an existing multichannel H/T system, simply take the Front L/R outputs from your current multichannel preamp or pre-pro (which you now have going to the Front L/R inputs on your amp) and plug them instead into the L/R inputs on the 2-channel preamp with bypass. The L/R outputs on the 2-channel preamp are then plugged into the L/R inputs on your 2-channel amp.

When you're listening to the 2-channel rig, you don't have to have your multichannel amp and pre turned on -- they're not in the signal path, so there's no need for them. Just select the proper input for your source, and play.

When you want to listen to multichannel, you turn on your multichannel amp and pre, and then engage the bypass function on the 2-channel preamp. Both the JC-2 and the C2500 do this easily -- in each case, you designate one set of inputs on the back of the preamp as your bypass inputs. Any time you switch your input selection to that designated input, the preamp takes the signal from that input and passes it straight through the box, with no messing around. The gain exiting the box to the amp is the same as it was when it entered the box through the designated bypass input. That's "unity gain."

On the JC-2, there are six small lights in a row along the bottom of the front panel. Each glows blue when the source it's connected to is the selected input. But when one of them is used as the bypass input, and that input is selected, the light glows orange. It's easy to see from your seated position whether you're in bypass mode or not.

On the C2500, there's a two-line LED display in the middle of the front panel. It tells you what input you've selected on the top line, and shows your volume level on the bottom line. I use an Integra DHC-80.2 as my multichannel pre-pro, so I've labeled its input "Integra" (a nice feature of the C2500 -- naming your inputs, not available on the JC-2 because there is no LED display on its front panel). When I want to watch TV, or a movie via AppleTV or my OPPO player (all three of which input to the DHC-80.2), I simply turn everything on, set the source select on the C2500 to "Integra," and away we go.

By the way, I had a similar experience to Kal's when he was reviewing the Integra DHC-80.2. If I remember correctly, Kal discovered a bug in the Audyssey XT32 Pro software as he was trying to map his room, and it took the software guys a bit of time to figure out how to patch it. Well, I bought my new C2500 16 days ago -- the first day my dealer had it in the store -- and couldn't get the H/T bypass function to work. To make a long story short (I've posted the full story over at Steve Hoffman's forum), it turns out I was the first C2500 purchaser to identify this software glitch. It took the Mac engineers a week to develop and double check the patch, but my unit has now been updated and is working flawlessly.

[chessman]

wpascoe, welcome aboard!