Preamps w/HT BYPASS that works when preamp is OFF.


I have spent quite a bit of time researching this issue here and on other fora. I have been looking for a thread that lists the stereo preamplifiers that have home theater (or "cinema," as some manufacturers call it) bypass that works while the preamp is turned off. I think this list would be very helpful to those who have hybrid systems, which seems to be the majority of audiophiles.

I will start the list with those that I know operate this way, either through personal use or through research on the internet. Please feel free to add to the list, but please limit your contributions to the preamps that meet the criteria above. I will break down the list into two parts: Preamps that have XLR HT bypass input and preamps that have RCA HT bypass input only. Please indicate next to the model listed whether it is tube or solid state, fully-balanced or not.

PREAMPS WITH XLR HT BYPASS INPUTS:
Cary SLP-05 (tube, fully-balanced)
Cary SLP-2002 (tube, fully-balanced)
Modwright LS 36.5 (tube, fully-balanced)

PREAMPS WITH RCA HT BYPASS INPUTS:
Supratek Chenin (tube)
Supratek Chardonnay (tube)
Rogue Perseus (tube)
Gill Audio Alana (tube) [HT Bypass available by request]
Aesthetix Janus (tube, fully balanced)
Aesthetix Calypso (tube, fully balanced)

If you know through personal experience that any of this information is incorrect, please feel free to suggest corrections.
asindc
Cary SLP98 has HT bypass when the unit is off. It must be specified that it has this feature.
Macdadtexas,

I believe it is only the F1 version of the Cary SLP-98 that has HT bypass, but I agree that it should be added to the list. ADDITION:

PREAMPS WITH RCA HT BYPASS INPUTS:
Cary SLP-98, F1 version (tube)
CORRECTION:

PREAMPS WITH RCA HT BYPASS INPUTS:
Modwright LS 36.5 (tube, fully-balanced)

I had previously listed this in the XLR category. Its HT bypass is single-ended only.
What good is it unless the unit defaults to the HT bypass when off? Otherwise you'd have to turn it on, switch to HT by[pass, then turn it off right??

I ask as I am currently looking to add a solid two channel preamp to my HT and use an HT bypass, but can't see how the 'when off' part is important, and also can't see how tube gear does it unless it is just a straight wire across the in to output....
The Dodd Battery Powered Preamp HT bypass works when the unit is off.
Kennyt:

I know that the Carys' HT bypass works when the unit is powered off. They default to HT bypass automatically. I cannot speak for the others on this list.

The benefits of "powered off" HT bypass:

1) Saves on tube life if it is a tube pre. Not a big difference, but a difference nonetheless.

2) Saves on electricity. Same idea as #1.

3) Saves on heat. Same idea as #1 and #2.

4) Prevents possible ground loop hum from being introduced into HT system by having it interact with the preamp while it is on. I have experienced this before.

5) The security of knowing that the preamp is not processing the HT signal at all. Some might prefer that, but I do not.
ADDITION:

PREAMPS WITH RCA HT BYPASS INPUTS:
Dodd Battery Powered Preamp
Kennyt:

I will add another reason for wanting to leave the preamp off. The only reason I have a hybrid system is because I don't have the space for separate systems (I would imagine that is the primary reason why most do not). I prefer to think of them as two separate systems occupying the same room, with the only thing in common between them is the utilization of the amp(s) and speakers. In addition to the reasons stated above, I see no reason why I should have to turn on the preamp to bypass it, especially when it is not necessary.
The TAD 150 Signature has RCA HT bypass - work with the preamp off (or on, though I can't imagine why anyone would want to leave it on).
Updated list:

PREAMPS WITH XLR HT BYPASS INPUTS:
Cary SLP-05 (tube, fully-balanced)
Cary SLP-2002 (tube, fully-balanced)

PREAMPS WITH RCA HT BYPASS INPUTS:
Modwright LS 36.5 (tube, fully-balanced)
Supratek Chenin (tube)
Supratek Chardonnay (tube)
Rogue Perseus (tube)
Gill Audio Alana (tube) [HT Bypass available by request]
Aesthetix Janus (tube, fully balanced)
Aesthetix Calypso (tube, fully balanced)
Cary SLP-98, F1 version (tube)
Dodd Battery Powered Preamp
TAD 150 Signature
The VAC Standard PreAmp LE I had had HT passthrough and worked when powered off.
You can only these used now but it was a great PreAmp.
Don't most folks keep their pre on all the time, I do.
Unless your pre draws a lot of power off the wall, I can't see shuting off the pre. That being said, why do you feel you need to turn off the pre when using HT bypass ?
drjoe
Don't most folks keep their pre on all the time,
Tube pre, yes. SS pre, no
.
Drjoe:

Some people turned off their equipment when not in use, so it seems pointless to have to turn the preamp on just to bypass it. I do understand why some choose to leave their preamps and amps on all the time, but I have a relatively small space that gets too hot to leave my equipment on. And as Bdgregory noted, there seems to be no benefit to leaving a SS preamp on.
Don't most folks keep their pre on all the time,

Tube pre, yes. SS pre, no
well what I wrote is exactly the opposite of what I meant. I turn my tube preamp off, leave my ss preamp on.
Bdgregory,

I understand your point, though I will point out that some don't want to leave tube preamps on because of tube life issues, while others do because they stay "warmed-up" that way.
"can't see how tube gear does it unless it is just a straight wire across the in to output...."

That's pretty much how Supratek does it. A wire from the HT inputs to the HT bypass toggle, to the output. The tube output goes to the other pole of the HT bypass toggle. Flick it one way = HT, the other = the tube output.
Sorry guys, I was thinking ss preamp but didn't say so.
I leave my ss pre on all the time. It is true, that leaving a tube pre on all the time is going to affect the tube life. I don't leave the power amp on all the time. My
electrical bill would go up significantly.
However my ss power amp sounds best after 2-3hrs warmup No trouble with HT bypass in my case as pre is on all the time.
drjoe
quick comment on the aesthetic calypso - i've spoken to aesthetix directly about this and they confirmed that the calypso's HT bypass will not work when the unit is off or in standby mode. the calypso must be fully powered up for the HT bypass to function.
I'm the one (maybe even the only one) who's done the HT bypass on the Gill Alana.

Gill Audio can tailor the Alana to have Balanced and/or Single ended inputs and/or outputs for anything you want by using high end transformers for the conversion SE/Balanced conversion. The Alana itself is single ended.

As mentioned, my Alana passes the HT signal straight through unless it is powered on. When it's powered up, it will play from the other inputs. I hope this provides some clarification as it seems most Alanas are custom configured based on the system it's installed into.

FWIW, David Gill made several changes to my Alana to better match my SS power amps. This made a HUGE improvement to an already very impressive pre. Right now, it's getting updated to the latest spec (I think it's called mk III).
Lector Zoe. Single ended tube pre, does ht bypass when off. Interestingly, it bypasses all input signals when off! May come in handy if source had volume control...
I leave mine off because 1960's Amperex 6922s dont come cheap!
Sony TA-P9000ES SS, RCA (5.1 bypass!)
Some Audio Valve Eclipse/Eklipse's.