Preamp with processor loop

NeilGabriel

I am looking at a couple pres that hype having a processor loop. I gather that you can run the signal from the pre to processor and back to the pre? or pre to processor out to amp? How does this work with 2 channel v. 5 channel? Don't get it, as you can see! Thanks.

Ricardo

I guess you are talking about a 2 channel pre with HT bypass? They are used when you want to have your HT and 2 channel integrated in the same system (using the same L/R speakers and amp for these speakers).
You connect the HT receiver/processor L/R output to the HT/bypass inputs on the 2 channel pre, and the pre's output to the L/R amp.
Then you use the rest of the 2 channel pre inputs for your 2 channel sources, CD player, DAC, TT, tuner, etc.
If you want to listen to 2 channel, you select the source in the 2 Ch pre, and you'll be using the L/R speakers. If you want to listen to the HT you select the loop/bypass, and the signal will go from the HT receiver/processor to the L/R speakers.

NeilGabriel

Thanks. I drew a picture! I assume the pre is passive when used in HT bypass then?

Ricardo

Right; unity gain when set to HT Bypass.

adam2434

What preamps are you looking at, if you don't mind my asking?

I'd also like my next one to have a HT bypass.

NeilGabriel

Adcom 750 (thinking about upgrading from 565).

tcrossma

NeilGabriel wrote: »

Adcom 750 (thinking about upgrading from 565).

That's the pre i'm likely getting as well. I was just eyeing a Proceed Pre-2 (also with an HT bypass), but I think i've decided to go with the Adcom.

NeilGabriel

Ricardo wrote: »

I guess you are talking about a 2 channel pre with HT bypass? They are used when you want to have your HT and 2 channel integrated in the same system (using the same L/R speakers and amp for these speakers).
You connect the HT receiver/processor L/R output to the HT/bypass inputs on the 2 channel pre, and the pre's output to the L/R amp.
Then you use the rest of the 2 channel pre inputs for your 2 channel sources, CD player, DAC, TT, tuner, etc.
If you want to listen to 2 channel, you select the source in the 2 Ch pre, and you'll be using the L/R speakers. If you want to listen to the HT you select the loop/bypass, and the signal will go from the HT receiver/processor to the L/R speakers.

A couple years ago, I used a source switch/selector box so I could select either my 2 channel amp or HT amp to run the front speakers. I am sure this would curl the toes on some.

adam2434

The more I think about it, processor loops (like the one on that Adcom) don't make total sense to me either.

The Adcom's processor loop has an "in" and "out". So does that mean you have to connect the "out" to your amp? If so, would you have to switch the amp's ICs from the processor loop out to the main preamp out to get the signal to your amp when you switch between 2 ch and HT. If that were the case, there would be no benefit vs. just switching the amp's ICs from your HT pre to your 2 ch pre.

Or does the main preamp out get the signal from the processor in, but with a bypass of the gain and tone circuitry?

tcrossma

adam2434 wrote: »

The more I think about it, processor loops (like the one on that Adcom) don't make total sense to me either.

The Adcom's processor loop has an "in" and "out". So does that mean you have to connect the "out" to your amp? If so, would you have to switch the amp's ICs from the processor loop out to the main preamp out to get the signal to your amp when you switch between 2 ch and HT. If that were the case, there would be no benefit vs. just switching the amp's ICs from your HT pre to your 2 ch pre.

Or does the main preamp out get the signal from the processor in, but with a bypass of the gain and tone circuitry?

The amp gets connected to the pre-amp with the HT bypass. The pre/pro's (or AVR) front L/R plus your 2-channel sources get connected to the pre-amp.

The benefit here is that at the touch of a button you can bypass the pre/pro (or AVR) completely and have your sources route throught the pre to the amp. The signal never touches the pre/pro.

adam2434

tcrossma wrote: »

The amp gets connected to the pre-amp with the HT bypass. The pre/pro's (or AVR) front L/R plus your 2-channel sources get connected to the pre-amp.

The benefit here is that at the touch of a button you can bypass the pre/pro (or AVR) completely and have your sources route throught the pre to the amp. The signal never touches the pre/pro.

Hmmm, I thought the purpose of an HT Bypass is to bypass the 2 ch pre's circuitry so that you get an untouched L/R signal from the HT pre-pro or AVR to the amp.

This make sense if the pre has a bypass input that simply shunts the signal right to the pre's main output (bypassing all other circuitry).

I am just unsure that a processor loop (like what's on the Adcom 750) works the same way, since it is a loop that has an "in" and "out", more akin to putting another component in the preamp path.

Ricardo

Right; that processor loop with an input and output sounds more like it's used to add an external processor to the signal, like an equalizer.

tcrossma

HT bypass is "unity gain". When enabled, it just passes the signal straight through without any gain so your processor can control the volumn of all channels.

I'm not exactly sure what you're wanting out of it, but it does exactly what I need it to, which is to allow me to add a 2-channel pre into my HT system.

When I want to play 2-channel sources I can go directly to the pre and avoid my AVR. When I play movies, it goes from my AVR->Pre->Amp.

adam2434

tcrossma wrote: »

HT bypass is "unity gain". When enabled, it just passes the signal straight through without any gain so your processor can control the volumn of all channels.

I'm not exactly sure what you're wanting out of it, but it does exactly what I need it to, which is to allow me to add a 2-channel pre into my HT system.

When I want to play 2-channel sources I can go directly to the pre and avoid my AVR. When I play movies, it goes from my AVR->Pre->Amp.

Right, we're all on the same page regarding HT bypass.

My question was regarding the processor loop on the Adcom 750, which does not appear to have the same function as a HT bypass.

tcrossma

adam2434 wrote: »

Right, we're all on the same page regarding HT bypass.

My question was regarding the processor loop on the Adcom 750, which does not appear to have the same function as a HT bypass.

Ah, ok. I thought they were one and the same thing. I thought HT Bypass, SSP loop, and Unity Gain were all just different terms for the same thing.

NeilGabriel

Does the Adcom have both HT Bypass and the loop. The rviews I read decribed it as a way to integrate the 2 channel into the HTR set up, ala the HT bypass. I do know some pres have set ups to allow an equalizer or other sound processor to muck with the sound. So, does the Adcom 750 have both? I need to go pull their manual. Anyways, I might get another B&K ref 20 (great prices used). I thought it sounded great in my 2 channel before I put it into HT setup.

adam2434

NeilGabriel wrote: »

Does the Adcom have both HT Bypass and the loop

GFP-750...no, just the processor loop, which was really designed to loop a signal to and from a Pro Logic processor, back in the day.

Off topic, but researching the 750 brings me back to my 1st HT in '93 or '94. My Sony ES stereo receiver had a processor loop (Sony called it "adapter"), which I connected to an outboard Kenwood Pro Logic processor that powered the center and rear channels. I still have that (useless) processor boxed up in the basement.