[RonK]

This message is for Curt or anybody who knows how the AV pass through works. Curt mentioned that the LLC-A and the LLC-IR will have an AV pass through to work in cordination with an existing HT system but that additional gear would be required. What additonal gear is required?

[lo mein]

This message is for Curt or anybody who knows how the AV pass through works. Curt mentioned that the LLC-A and the LLC-IR will have an AV pass through to work in cordination with an existing HT system but that additional gear would be required. What additonal gear is required?

With the A/V By-pass, you can use your existing A/V processor/receiver, and also by utilising the superiour main 2 front channels power amps and loudspeakers - if you have a nice 2 channels music system already - to drive the front main L/R channels; while retainning the full functions of your A/V processor/receiver, and use the A/V processor/receiver to drive the center, and rear channels, plus the sub-woofer.

It acts as a bridge between your 2 channels music system, and your A/V system.

Usually, a high quality 2 channels music system is vastly superiour than most A/V system, that also do double duty for 2 channel music reproduction.

You can get the best of both world without spending too much money, and space, than two completely seperated dedicated systems.

Alex

[jcoat007]

So what you would typically do in this scenario is take the pre-amp outs from your home theater receiver and plug them into the HT pass-thru in's on your 2 channel pre-amp.  Then use the pre-amp outs to your front 2 ch amp and hook your your main speakers to this amp.  When the HT pass-thru is engaged, you bypass any volume control that is in the 2 ch pre-amp.  This allows you to control volume from your HT receiver when watching movies.  

With this kind of set-up you can have your DVD/VCR/TV/Sat Dish etc... all hooked up to your HT receiver.  Then you can have sources such as a turntable or high quality CD player hooked up to the 2 channel pre-amp without going through the HT receiver.  You can even use the DVD player as a transport to a stand alone DAC (from the coax digital out on the DVD player) and use the optical out on the DVD player to go the HT receiver for watching movies.  

The possibilities are endless.  

Steve

[RonK]

So it looks like the only extra gear required is two additional cables that run from the AV receiver to the preamp.

[jcoat007]

If you have an external amp that you are already using, then yes.

[Curt]

Hi Guys, I do have some thoughts on this one. For all the experts out there please excuse the depth I go into but, guess I got carried away. I've been thinking about this one for a while.

A long one...

Using your two channel gear as the front left and right channels in your home theater (HT) or other type multi-channel system.


What is a preamplifier pass-through?

Customers request a preamplifier feature they call “HT Pass-through” or “A/V Pass-through”. It is believed that this feature allows an easy and seamless insertion of a two channel audio system into a HT system.

IRD simply calls this feature an “HT” input. It’s just another source connected to the two channel preamplifier. The HT position is selected with the source selection switch.

The HT input has one difference from the normal source inputs, the HT input receives no gain (0dB) nor attenuation (0dB). This is where the name pass-through comes from. When the HT input is selected the two channel preamp simply acts as a unity gain buffer.

Using the two channel system as L&R channels in the HT can improve the sound quality of the HT system, save money and minimize the number of HT components.

The problem is that this basic HT input feature may not be ideal for every HT system.

Some two channel systems may do better and mate more seamlessly into a HT system using the two channel preamplifiers independent gain or attenuation capability.

Exactly how does the HT input work?

When you have a preamp with an HT input all that is required, to add your two channel gear to your HT system, is one set of interconnect cables.

The source of the HT input signal comes from the HT receiver’s decoded front L&R analog output RCA jacks. These are line level signals that are ready to be sent directly to a power amplifier.

Simply connect the receivers decoded front L&R analog output RCA jacks to the two channel preamps HT input RCA jacks, like any other source, using a set of standard interconnect cables.

The signal gain and volume control functions are preformed directly in the HT receiver before being sent to the two channel preamplifiers HT input. The HT remote control controls the systems audio volume.

When using the two channel preamplifiers HT input all the preamplifier functions are bypassed and it acts as a unity gain buffer driving the two channel systems amplifiers with the front L&R channel program content supplied by the HT receiver.

The HT receiver normally has built-in amplifiers, or other amplifiers may be used, that drive the center and rear channel loudspeakers which completes the HT multi-channel system.

Sounds simple, what could go wrong?

The ideal situation is when all of the HT loudspeakers have the same efficiency level & sound characteristics and all the amplifiers used have the same signal gain & sonic characteristics.

Small SPL adjustments for component differences and room conditions can be made with the HT receiver normally in the amount of about +/- 6dB. Even if this is all the adjustment required the adjustment system may not be ideal and many times can adversely effect the systems sound quality.

If you can get a HT system up and balanced correctly using a maximum of +/- 3dB of the receivers available adjustment you will have a great or almost perfect setup.

The problem is when the loudspeakers or the amplifiers used in the system are farther apart than +/- 3dB. This may mean you will not get the best sound. This is often the case when integrating a two channel system into an existing HT system.

The largest differences can be in power amplifier gains which can vary from as little as 18dB to as much as 40dB. An ideal HT system would use all the same type of amplifier.

Loudspeakers efficiencies are usually pretty close but can also vary more than 3dB. Placement and room effects also create SPL differences.

Matching the output SPL of all channels trying to use only +/- 3dB of HT receiver adjustment is what may go wrong when mating a two channel system with a HT system or building a HT system from scratch.

Is there another way?

The pass-through was invented because it is virtually impossible to set a gain of 0dB (x1) with a normal preamplifier.

The reason for this is that it is impossible to set a potentiometer with any degree of accuracy or repeatability, even if there is a silk-screen marking on the faceplate. Most preamps use a potentiometer type level control.

If you could easily adjust the two channel preamplifiers gain to 0dB (x1) you could put the HT input into any standard source input and it would be exactly the same thing as using the HT “pass-through” input function mentioned above.

Some argue that they would not want to do this because they may turn the HT system off forgetting to turn the two channel preamplifiers volume control down. They worry that when they turn it on next time, without checking the volume control, they may damage their loudspeakers at power up. This does seem a bit careless and not like the normal audiophile but, it is one more knob to remember at turn on–off time.

So what do you do if your system SPL levels don’t match close enough or you like to swap components often and never know what you will have next?

Well, with a step attenuator the 0dB (x1) gain problem is completely solved. A two channel preamp can easily be set to 0dB or any other gain required.

This also solves the problem of seamlessly matching the two channel loudspeaker SPLs to the HT systems other loudspeaker SPLs for any system and keeping the <= +/- 3dB rule to achieve the optimum sound.

This is a very expensive solution but, if your two channel system has a step attenuator why not use it to your best advantage?

Just remember to turn the volume down when you turn your system off.

**********

Comments?

[byteme]

Curt, that sounds like the ideal solution.  However, wouldn't it be somewhat similar to run things like I've got them hooked up?  I have a Sonic Frontiers SFL-1, the pre-outs for the main two channels run into the Aux1 input, the only 2 channel source I've got run into the "Direct" inputs on the SFL-1.  When I calibrated the 7.1 system after adding the SFL-1, rather than using the receiver's (Denon 3802) +/- 3db gain I simply used the SFL-1 volume control for the mains and marked it with a small piece of tape.  When watching TV or movies now, we simply flip the direct/normal toggle to normal and turn the volume to the tape mark.  I realize this is probably somewhat a stopgap fix - but nearly anything beats using the 3802 for a 2 channel pre!!

I'm looking very forward to hearing more about your Purist and Sabai, especially since the first person to post a review here compared the Purist to a SF SFL-1 Signature and said it blew it away!  Any chance you'll offer the Sabai w/o the Phone stage?

[Curt]

Curt, that sounds like the ideal solution.  However, wouldn't it be somewhat similar to run things like I've got them hooked up?  I have a Sonic Frontiers SFL-1, the pre-outs for the main two channels run into the Aux1 input, the only 2 channel source I've got run into the "Direct" inputs on the SFL-1.  When I calibrated the 7.1 system after adding the SFL-1, rather than using the receiver's (Denon 3802) +/- 3db gain I simply used the SFL-1 volume control for the mains and marked it with a small piece of tape.  When watching TV or movies now, we simply flip the direct/normal toggle to normal and turn the volume to the tape mark.  I realize this is probably somewhat a stopgap fix - but nearly anything beats using the 3802 for a 2 channel pre!!

Exactly what I said. Yes, this is very similar. Good thinking!

The only difference is that a pot and a piece of tape are not "exactly" repeatable. A Ladder step attenuator is exactly repeatable, everytime.

[randog]

byteme, can you walk through your solution once again? I have an Odyssey Tempest pre that I was going to send to Klaus for HT bypass, but I'd like to try this other option first. I have an Outlaw 1050 for HT duties.

What I hear you saying is to run the main speaker pre-outs from the Outlaw to the Tempest aux inputs. But I lose you as far as calibrating the volume control for the mains in HT mode. You speak of a direct/normal toggle. What is that?

Thanks,
Randog

[byteme]

Randog,  

Sorry, I was speaking specifically to a feature of the Sonic Frontiers.  It has a special input and toggle to select it which bypasses amost all of the electronics in the preamp, making it nearly passive in nature.  I use that input for my digital source.

For your standard preamp without this "direct" input do exactly as you said, pre-out from the receiver for the mains to the Aux (or any other except phono) input on your preamp.  When you want to watch TV or HT then you (obviously) select that input and put the volume to the marked place.  For calibration, what I did then was set the mains volume via the preamp by ear, and then used Avia or the built in receiver/pre/pro level setting and my Radio Shack SPL meter.  If the mains were off, rather than adjusting the level via the receiver/pre/pro I adjusted it using the preamps volume.  Once the levels are set and even, I put a small piece of tape on the volume knob and the face of the preamp (cut the corners off electrical tape in a triangle shape) so I can easily put the volume almost exactly (that was for Curt   ) where it needs to be for everything to be level.

If I didn't explain this right (chances are!) let me know!  I find this to work out very well, because each of the speakers are probably within +/- 1-1.5db anyway and it was VERY easy to explain to my wife.  Who was already hacked off enough that she has to turn on the amp and premap anyway!!

[Rob Babcock]

You explained the pass thru very well, Curt.  My only question at this point is, do your IRD preamps all have this feature? Or does only the Audiophile & Sabai have it?  By that I mean an "HT" or "Pass Through" input.  I've recently been looking around for a preamp & this feature is high on my list.

One note I'd like to add on your explanation of why unity gain is sometimes more practical that a Pass-thru.  Most recievers allow you to change the individual channel level, at least mine does.  One could use this to balance the volume to compensate differing input sensitivity level, etc.

BTW, how will the Sabai compare sound wise, and is there an ETA?

I know you're a busy guy, so I appreciate your time.

[Rob Babcock]

Sorry, I shoulda read more carefully before I asked.  I see now which models have HT pass thru.  Still curious when the Sabai will be out, though.

[Curt]

Hi Rob,

The HT pass-through (X1) feature comes in the Audiophile LLC-A and the Sabai LLC-S.

The purist LLC-P does not have a dedicated HT pass-through but, any input can be set to unity gain (or any other required gain) very easily with the volume step attenuator. The Purist was designed to be our reference standard, the best sound possible at this time, and we find extra bells and whistles do effect sound quality.

All our preamps can use any standard input for the HT system and then match the 2CH system to the HT system with the precision step volume control. With the dual capability of Audiophile and Sabai, you can decide what way works best for your system then use that input method.

Rob, the HT receiver adjustment does allow you to change individual channel levels but may not be enough at times to match a high-end 2CH system while also performing listening room acoustic adjustments. I found this out the hard way a couple years ago, the receiver adjustment is normally only around +/- 6dB. In addition, the receiver at extreme level adjustments may affect the sound quality of those channels.

Your idea of using the receiver level adjustments for balance control is very good. Balance only requires a couple of dBs and should not degrade the sound quality. This is an excellent way to adjust for the room acoustics and is what I believe the adjustments were really designed for. I do not believe the receiver adjustments were designed to make the larger adjustments sometimes required to match high-end 2CH systems into a HT receiver system.

IMO a HT pass-through is most needed in preamplifiers that have resistive pots, that are unpredictable and not easily reset to any exact desired level with any precise degree of repeatability. Step volume controlled preamps do not really require the HT pass-through feature.

Sabai is not far away but, I do not have an exact ETA.

I just got back from holiday last night and we will have a meeting to updating our remaining E1 series component schedules later this month for publication on our website. There is very little to do on any of the new components and we have all the parts in stock now at the factory.

It’s just some final testing then production and documentation but, this will take some time.