Sharing a subwoofer between a Stereo and HT combination.

First, disregard option 1 of adding a stereo amp — you don’t wanna leave the AVR’s preamp section in the stereo pathway so either an integrated or separates is the way to go. You should share what sound characteristics are most important to you and you’ll get better recommendations for one of those.

Set the HT as a 5.0 and make sure the fronts are set as full range to use the Stereo as the front L/R with HT bypass.

Can’t quite wrap my head around what you’re doing here. I think the easiest solution might be to have a sub that can use more than one connection at once and use one for stereo and another for HT and optimize for stereo. Another option would be to get a 2:1 RCA switch and manually switch input for stereo and HT.  Just some initial thoughts and hope it helps. Best of luck.

Until you have more room to work with...what about a great sounding pair of headphones? Fidelity wise this might be your best band for the buck.  

@soix 

First, disregard option 1 of adding a stereo amp — you don’t wanna leave the AVR’s preamp section in the stereo pathway so either an integrated or separates is the way to go. You should share what sound characteristics are most important to you and you’ll get better recommendations for one of those.

Adding a stereo amp would be a way to migrate to separates for stereo and allow a gradual transition. Easier to audition amps in the system to decide the sound I like best.

Included some sample devices that I liked for a sound reference. Heard the Hegel H390 with Revel Performa3 M105s. My present front and center are Ascend Acoustic Sierras that are similar to the Revel Performa3 M105s.

From what I have, am pretty happy with the overall tonal character. Would like the mids a little stronger; more soundstage depth and height; and better separation of the instruments.

@soix 

Can’t quite wrap my head around what you’re doing here. I think the easiest solution might be to have a sub that can use more than one connection at once and use one for stereo and another for HT and optimize for stereo. Another option would be to get a 2:1 RCA switch and manually switch input for stereo and HT.

Sub can use more than one connection, but easiest is speaker level from the stereo and RCA LFE from the HT, but then the sub would get both signals when using HT bypass from the separates. Will see if that can be controlled in some manner from the sub maker. RCA switch on the LFE to the sub may be the only way to go.

Adding a stereo amp would be a way to migrate to separates for stereo and allow a gradual transition. Easier to audition amps in the system to decide the sound I like best.

Well, the only problem is the crappy pre section of your AVR won’t allow you to hear all that’s going on.  If you’re gonna do that I’d highly suggest auditioning a stereo pre with it so you better know what you can expect out of it.  I’ll make an exception — you can buy this with total confidence that it’s a near SOTA amp and can pair any number of preamps in the future and get unreal sound.  BTW, IMHO this is overpriced by at least $500, which is probably why it’s been on the market for a while, so should be some wiggle room on price, shipping etc.

https://www.ebay.com/itm/145476002357

Or you can just get it all done at once and get a good integrated.  Here’s a nice, reasonably priced Hegel H390, and by adding this everything will significantly improve on every level. And if not, you can turn around and sell it for little/no loss — almost kinda like a cheap in-home trial, which is kinda nice.
https://www.audiogon.com/listings/lisb81fd-hegel-h390-solid-state

Here’s a good review just fyi…

https://www.soundstagehifi.com/index.php/equipment-reviews/1365-hegel-music-systems-h390-integrated-amplifier-dac

If I’m you I’d drive a hard bargain on that McCormack and bask in its glory until you can find a good stereo pre that mates well with it.  Then again the Hegel is no slouch and a much easier proposition, and either way you’ll be on another planet sonically.  Just a couple suggestions FWIW. 

I have the same sub array for three different systems on the same room., one surround and two stereo. Just get a decent quality switch and maybe some level balancing electronic pots.

I kind of live in the same world as you do. Started with a Marantz sr5015, added a MM7025 amplifier for the left and right to improve SQ. That was a good move until I got a INNUOS pulse mini. That was a nice upgrade from the HEOS streaming app on the Marantz. Wanting to take the stereo game up a little more I started looking at pre-amplifiers with home theater pass-through and subwoofer integration. The best solution that I could find on the market currently is the Anthem STR pre-amplifier and power amplifier. Currently awaiting its arrival will report back after a few hours of playback. Good luck in your search

I’m in the same boat as you, and right now I’m running an integrated amp with ht bypass 2 ch and ht/w sub config. I’ve tried line level for the sub on the integrated, but then the ht wasn’t right. So when I wanna run the sub, I’ll listen through the ht bypass, otherwise I run 2 channel without sub. It’s a little sacrifice yes, but  not much where I’m gonna go buy 2 separate subs to add for 2 channel.

I added the same external amplifier that @gkelly did and got favorable results using my Yamaha RX-A2080 AVR. I have since upgraded to the Yamaha RX-A6A AVR (just deployed yesterday) and so far the same favorable results.

Even though the Marantz specs out the same as the AVR it is dedicated 2-channel power and not sharing things with the AVR innards. I disagree with those that feel the pre in a well-made AVR is terrible. Mine has been quite engaging.

My dual subs are driven from the pre out on the AVR and I listen in straight mode when doing 2-channel stereo so that he subs stay engaged (on a Yamaha in Pure Direct mode it turns off the sub channels). The room correction in the Yamaha also helps figure out the room and blends the subs and the speakers for both HT and 2-channel.  I would try this way first and determine what you think. I was able to get the Marantz used at half of the list price.

My advice is to audition a Marantz processor and external amps.

I haven't gotten to listen to all Japanese HT brands but I've heard some that really sounded thin by comparison to Marantz or high end processor brands.  Marantz is the cheapest I know of that consistently sounds good. 

Mind you, I have a Luxman (Japanese) integrated and it sounds great.  There's something about certain inexpensive HT processor brands that just don't sound that full.  Oppo BD players however sounded excellent. 

My 3.1 mixed setup has been rock solid for the past three years.

- Denon 4700x running in pre-amp mode

- 3 channel power amp (ATI 523NC)

- Parasound P6 for front channels on the bypass input. Sub out from Denon to the Sub Bypass input. Sub Bypass is a great feature, it operates the same as the L/R bypass with sub output and crossover/level management controlled by the P6 for stereo inputs and by the AVR for HT play via bypass input. One note on the P6, the internal DAC isn’t great and I experienced great improvement inserting a separate DAC.

All components are in a console and controlled by universal remote. I only need to get up to change the CD.

Running a separate Pre was critical for my use case, because I like to watch sports on mute and play the stereo at the same time.

I went through the same upgrade path recently. Unfortunately, I don’t have a separate music room. I started with an amp powered by the pre-amp output from the AVR. It was better, however, your eventual goal should be to remove the AVR from the chain for stereo listening. I did this with a used node streamer (not using the internal dac), fed into a DAC with volume control and HT inputs, and then into the separate amp (AHB2). This is not an end game system, but it will be a huge step up from the AVR being in the loop and interfaces well with HT use. Used nodes are cheap and are a great stepping stone. You are already close to having the amp. The only part missing is the pre-amp dac function.

I decided on the DAC3 HGC paired with the AHB2. The DAC3 combines a DAC and volume control, as well as inputs for the signal from your AVR. And, you can output the sub signal from your AVR into the subs directly, or the DAC3 has a second set of analog outputs that you can feed into the subs. Having the analog outputs from the DAC to the subs is nice because you can then use the subs with stereo music as well as when using the AVR. It is a well made, versatile device, which measures great. And, it has a headphone output - music through headphones is amazing as well. Finally, you can add a tube preamp in the future, and just use the DAC3 as a DAC.  

Your are on the right path.

Similar desire to the OP - this worked for me:

Parasound zpre3 preamp (https://parasound.com/zpre3.php).  IMO, much smaller than it looks in the picture.

The preamp is connected to the amplifier for the left & right speakers.   Also, from the AVR, the front l & r preouts are connected to the  Parasound preamp.  (So, you need an AVR with preouts and an external amp for the front speakers).

The AVR and the Parasound pre-amp are both connected to the same subwoofer.  The Parasound preamp is connected to the line-in on the sub, and the AVR is connected to the LFE inputs (Rythmik sub).

So, the two-channel setup and surround setup share the same amplifier, front speakers and subwoofer.  The zpre3 has Home Theater Bypass, which provides some protection against having the AVR and preamp active at the same time.  I use the two-channel setup with a CD transport, digital streamer, and a DAC.  No turntable in the system.

I disagree with those that feel the pre in a well-made AVR is terrible. Mine has been quite engaging.

@larryincmh I’m sure it sounds fine, but you should still try a good stereo pre as it’ll make a sizable improvement, and you won’t know what you’re missing until you hear it. Years ago I inserted a good stereo preamp that relieved 2-channel duties from my Rotel prepro that was likely better than the pre section of your AVR, and the performance increase was substantial across the board. Pre sections of AVRs are hugely compromised by poor power supplies, noisy electronic and digital signals, and low quality parts — in short, they’re designed to do a lot at a low price point hence all the necessary compromises. When all those compromises are removed with a stereo pre it’s very easy to hear the improvement and very well worth at least trying.  One of the most important things I learned while reviewing audio equipment is preamps matter, and matter a lot.

Thanks to all replies. It looks like there are 3 solutions, but with some restrictions.

1. Parasound Halo P6 preamp, and the Parasound Hint6 both have 2 sub line level or LFE bypass inputs as well as the HT bypass inputs. Will check them out at the local dealer. It does limit the choice of integrated or pre. Thanks to @frl for pointing that feature out.)

2. Rythmik subwoofer has both line level, and LFE inputs. In HT bypass, the Line level would be active from the 2 channel integrated or pre, and in HT the LFE would be active. Both can stay connected at the same time. (Approved by Rythmik). Does limit subwoofer choice. Thanks to @tommyr1963 for pointing this out.

3. Anthem STR pre also offers subwoofer HT bypass, but at the loss of other analog inputs. @gkelly is trying that route. Hopefully he will post his experience.

I am not including the use of added switches to select input for the subwoofer. A choice I want to avoid, and haven’t looked to see if any offer remote control or other means to switch them. I guess a unity gain preamp could fill that role, but a lot of wire to solve what should be a simple problem.

Will do some hearing comparisons of the Parasound products. Will also see if they have any of the Anthem to demo (they are an Anthem dealer). I’m inclined to replace my existing sub with a Rythmik and choose other components for the 2 channel sound I am looking for. Will see what listening to the Parasound and Anthem choices reveal.

  Ha ha , I’m having flashbacks. I went down this road , but I had a large living room. By the time I threw in the towel I had a Yamaha RX-V amp, Sony Blue Ray, JBL 4312A mains, Klipsch Heresy II rears, Klipsch RC center and sub. Also a Panasonic Plasma an Oppo 105 and Sound Anchor stands. Super Audio CD’s and DVD concerts were particularly enjoyable, plus no neighbor issues. I was able to go back and forth between surround and stereo with a button on the amp, you would hear a loud click. I did not experience any sub integration issues.                                                                                                        At this point I lost interest and bought a modest tube integrated and paired it with the JBL’s , the dvd player and the sub. I used that for about 2 years and then thought low powered tubes and single driver. I went to a Rogue RP-1, Had Inspire, and Zu Omens. I purchased a Schiit Bifrost Uber to top it off. I then played with cables and rolled tubes for the next few years. I’ve added a Thorens TT, Schiit Yiggy and a Richard Grey power filter. So my wisdom to share is that my little system is VERY enjoyable for low level late night listening.  When I’m in the sweet spot it’s more enjoyable than my Audeze headphones. And if you buy any of the Rogue items you listed pull the JJ’s and pony up for some Telefunkens they are a must. Today I rotate a small 60 wpc DYI SS amp and enjoy absolute Mid Fi bliss. Cheers, Mike B.