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Audiophile Home Theater Overcoming obstacles in blending two channel
and April 2011
I remember
the first time I tried to create
an audiophile home theater... it was before I started Decware and I was
given a good Denon Home Theater Receiver as payment against a bad
debt. I used great speakers for the front two channels and
experimented with a variety of things for the rest. It was OK for
watching movies and by most standards probably sounded pretty
good. Of course the real test is to remove the TV and try serious
two channel listening with the same system and it was always a sobering
reminder of why my two channel system consisted of Single-Ended Triodes
and a good source as opposed to a cheap DVD player. It's easy under these typical conditions to
take the attitude that home theater and two channel just don't
mix. You have one or the other, or keep them in separate
rooms. Then when you consider that big screen TV sets placed
between your loudspeakers ensure compromised imaging it's pretty easy
to build a case against having any success of blending the two. Nevertheless, I got my hands on a DVD player
with discrete outputs for each channel that was actually listenable
when playing CD's so I got the great idea to hook up my tube amps to
all 5 channels, which I did. This takes the Denon 5.1 receiver
out of the picture and it should sound pretty good. I set
it all up and put a good movie in and put my TV between the speakers
and had an interesting
problem. The TV was a bit small, the room was set up for
imaging and sound-stage in a big way for two channel use and now
suddenly the movie was imaging so big and so well it made the TV seem
like a tiny spot in the middle. It was so distracting in fact
that it became impossible to follow what was going on in the
movie. I had to restart it more then once after realizing I
forgot to watch it... so wrapped up in the sound I was. I quickly gave up because it was impossible
to focus on the movie. I put the Denon back in and with the
two-dimensional boring performance it brought to the table, I could
once again watch the movies. My conclusion was that a big screen
would be required if I were ever going to make this work. At that
time projectors were not an option and a big screen TV would be too big
to move from between my speakers when I wanted to listen to two channel. Years later I set up a small studio in my
garage, a free standing building, where I found myself spending a lot
of time listening and recording. After the first several years of
weekly recording sessions I started using a HiFi VCR as a live two
track machine as an inexpensive way to have analog masters that came
directly off two room mikes. We hooked up a black and white video
camera to it figuring why not, and found listening to these tapes and
watching the video was really enjoyable after a session. Since we're out there watching these videos
all the time anyway, it might be fun to set up a home theater and watch
a few movies out there. Well times changed and now flat screen
TV's were just becoming available. I wanted something large
enough that a room full of people can see and of course I wanted a
great picture so I started to look at plasma sets. After
realizing I wasn't going to spend five grand on a TV I looked into
projectors and was pleasantly surprised to discover they had come a
long
way and had gotten affordable. In fact for less than 1/3 the
price of the Plasma I would have liked to have owned, I was able to get
a higher resolution picture that was over twice as large with the
projector. Projectors are the answer because it allows
you to set up your room for two channel, ie., nothing between the
speakers but empty space and perhaps some diffusers so that you have
maximum sound stage depth and focus. The worse thing you can do
is to put a reflective flat surface between your speakers if you want
stable and focused imaging with good depth. So you simply do one
of two things; Use the wall behind the speakers for the screen
and cover it with drapes during two channel use, or if you have
diffusers on the wall behind your speakers (like you should) you
simply pull a retractable screen down from the ceiling when you want to
watch a movie. So this is what I did out in the studio where
I had an excellent setup for two channel playback. Basically I
set up an ideal test bed to explore the potential of audiophile home
theater. In this studio, every speaker and every amplifier
Decware makes is tested 7 days a week so it would be easy to try
multiple different types of speakers, amplifiers, cables and so on. We set up the system based on two decent DVD
players with discrete outputs for each channel and jumped in with both
feet. Our original motivation was to watch music videos and
concerts which we did - with mixed results. Regrettably there
were more than several that simply didn't sound good. When this
happened, we would explore every possible option including different
amps and or speakers or DVD players until we found some way to make it
sound good so we could watch it. Often the amount of bass was an issue, or
that the bass simply didn't blend well with the rest of the
sound. Often the sound was harsh or thin. Often the
engineers had wild ideas about how they should distribute the sound to
5.1 speakers and had us shaking our heads in disbelief several times. This was about the time that I decided if I
had to use one more poky on-screen setup menu I was going to start
shooting things. We had already figured out that some movies
sound better in stereo and some sound better in 5.1 but some sounded
dreadful either way. You see, it's what they put where that
makes it work or not work. Many movies or music videos would try
to do all the vocals from the center channel and all the music from the
fronts which does not sound right. Others would blend both music
and vocals on the center and use the main speakers for only ambiance or
effects and that doesn't sound right either. Some would have
sound come from the rear channels only on occasion, which is also less
than realistic. So you need a way to access every channel and
if you don't like the sound of it, you pull the signal for it from
somewhere else. In our case this meant about an hour or sometimes
two hours re-arranging how the gear was hooked up. Then when you
finally get a usable sound from the movie or even perfect the temporary
satisfaction is burst when you put the next movie in because now
everything has to be set up differently. A
preamp or analog control center will have to be built so we can
accomplish all of these configurations and adjustments on the fly without having to unhook anything. You can't run around the room and adjust the
volume on each tube amplifier for very long without growing tired of
it, and you can't use a solid state receiver to control things as it
would completely ruin the sound quality, so there is no other solution. The right preamp would allow us to hook all 6
channels from the DVD player to 6 different amplifiers and have all the
knobs in one spot. Of course making such a preamp is complicated
and making it good enough to be left in during two channel playback
would make it even more challenging. If I find myself having to
take the preamp out of the loop to get the best sound on two channel
playback there would be no point to this project for me. I had to
combine both Home Theater and 2 channel in the same space because it
was the only space for either that I had at the time. This would be interesting, because many
nights by the time we got the movie to sound good, we were too tired to
watch it. Having the ability to adjust the volume and sources for
every channel from one device was going to be a God send. You
see, the pre-flight check on your DVD player via the on-screen set up
menus where you adjust the levels of each speaker with pink noise is
almost worthless. The movie will determine how loud each speaker
plays at any given point and assuming your have all the levels matched
before the movie starts, you can be reasonably sure something will be
too loud or too quiet. How many times have you stuck your head by
the rear channels to see if they're on? Hard to tell considering
many movies don't put any sound out on the rears except in certain
scenes. How many times have you wanted to adjust your sub woofer
and found that's impossible unless you wait for the first explosion to
occur in the movie, and of course being either too loud or too quiet,
it's back to the on-screen set up menus again and about that time you
press the wrong button and end up at the main menu having to start the
movie all over again! You get the idea... so I pondered the circuit design for a new preamp for several weeks until I figured out a way to accomplish cross channel mixing without the sound of one channel effecting the other. The main front channels would be used as my main two channel system and I didn't want to ever hear the sound of those front channels change when other channels were engaged or switches were thrown. Then there was the other consideration, and
that is that very few DVD players are considered "audiophile grade" so
what can we do to make the DVD player sound better? Up till now
we ran three ZBOX's on the output of the DVD player to make it sound
better, and it does. So what I decided to do is build an 8
channel preamp where 6 channels are used for home theater and the
remaining two channels are for hi-fi. The hi-fi channels will
serve double duty and handle the front main channels during movies but
with different circuitry. Then on the 6 movie channels I'd
incorporate the ZBOX circuit right into the preamp but kick it up a
serious notch by using tube rectification and tube regulation on each
channel. That's something the ZBOX does not have, plus the
absence of the extra cables and power cords can only improve things
further. (ZBOX technology puts back the even
order harmonics that are continually stripped out of the music my solid
state devices including the DAC chip itself.) Once these ZBOX circuits fix the sound from
the DVD player, the signal is passed on to another triode gain stage so
that we have more than enough control and dynamics to work with the
vast majority of amplifiers. As you can see it's hard for me to
build anything that's just for myself. In the back of my mind is
always the thought that if it works and I really like it I might decide
to manufacture it. The next trick was going to be a way to move
the inputs around. There will be 4 pair of front main inputs so
we can have 4 sources. I expect two of them to be used with the
DVD player and the other two for my good 2 channel sources. On
the first pair of inputs we'll connect the Front Left and Front Right
from the DVD player. (the
Center, Sub, Left Rear and Right Rear from the DVD player will also be
plugged into their dedicated jacks on the preamp) On the second
pair we'll hook up the Left and Right stereo outputs from the same
player. This way I can mix the remaining 4 channels (center, sub,
rears) from either input when the soundtrack isn't pleasing. When
a soundtrack in a movie is all screwed up, you'll be able to down-mix
to
any channel from the Left Front and Right Front inputs OR the Stereo
Inputs that will have all the information in them. Depending on
how the soundtrack is mixed and decoded depends on which way works
better. Then we need a bridge switch for each of the
remaining 4 channels, so we'll install one for the Center and Sub, and
one for the Rears. This way we can switch the inputs for these
channels from what's coming direct from the DVD player's
Center/Sub/Rear outputs TO what ever is coming out of the main
channels. For example, movie starts and there is no rear channel
information except for some occasional noise effects. Most
annoying. Find the bridge switch for the rear channels and flip
it. Problem solved. Now you have signal going to the rear
channels at all times creating ambiance for the front channels.
Another example, center channel holds most of the movie and the main
front channels only play on certain scenes. Again, most
annoying. Fix, flip the bridge switch for the center/sub channel
and switch the front mains to the stereo inputs. Problem again is
solved. This also allows you to complete your
adjustments before the movie even starts. How? As you know
most previews that you watch before the movie starts are not in 5.1 so
there is no way to know how loud your center channel, rears, or sub
will be until after the movie starts. Well, now you can simply
flip both bridging switches and have the sound come from all your
speakers and then simply adjust the levels of the center/sub and rears
to your liking. Then return the both bridging switches to
their previous position and enjoy the movie in 5.1. No more
waiting for a bomb to go off in the movie to find out if your sub is
working and set to the right level. Since we're talking about subs, we found out
fairly quickly that having a separate volume control for the center
channel and the sub woofer was a mistake. In virtually 100% of
every test, we observed that the sub woofer level must always be
proportional to the center channel level. If the center channel
is raised in level, the sub must come up with it, and visa versa.
So we tied the two together with a single control and it made life much
simpler with one less thing to think about... By this time things are working extremely
well. We're batting 100% now with every movie and every music
video, all adjustments are easily made on the fly, usually before the
movie even starts, during the previews. If part way through the
movie we want a bit more rears, bit more center or a bit less fronts,
it's so easy, just 3 simple knobs. No more pausing the movie or
trying to find the light switch. Of course there was a nice side effect from
all this. During serious two channel listening, I found out how
easy it is to add a touch of center channel which is kind of fun.
You know the first stereo invented was actually three channels. A
mono summed center channel and a left and right. Now you can
recreate this at will. Also found out that blending a touch of
sound to the rears for ambiance almost always enhances the
experience. The trick to doing this without screwing up your
imaging is moderation. Very tiny amounts are needed. It may
take several minutes for you to find the right levels, usually just a
tease that you can't really hear unless you put you ear up to the
speaker. Now that these levels are set, your going to instantly
want to hear it without the additional speakers so you can compare the
sound with and without, but if you turn the levels back down, you'll
loose your settings! Enter the Master Volume control for the Mixed
channels. After you have added that delicate amount of center,
rears or both, you simply turn them up and down as a group with the
master control. This lets you hear your two main channels by
themselves and then the stuff you added in comes at the turn of the
master. The master makes it possible once you've got the ratio of
center channel to rear channels set where you want it, to adjust these
added channels as a group up or down, independent of the front channels
which have their own volume control and can not be effected by anything
else on the preamp. So the Master control was also implemented
and that completely satisfied all of the needs we had for this rather
radical preamp. I built a production prototype and put it into
service and have used it every day since for listening to music, and
almost weekly for watching movies. That was in 2001. It is
now 2011 and I have never once during that time had an issue, desire to
tweak, desire to add a new feature or change it in any way. I've
simply just used and enjoyed it for 10 years. This how I know
it's good, because those who know me will tell you that if there's
anything I don't like the sound of, it either leaves the building or
goes under the soldering iron until I like it. I'd like to also make the observation that
with an all tube system, and serious speakers for the fronts center and
rears (all exactly equal in importance contrary to popular belief) the
fidelity of good movies is stunning. A CD has to try damn hard to
get close. Imaging is unreal, and yes if you turn of the
projector so there is no video to look at the sound is so 3D and to
proper scale that it's like no one even turned the projector off.
Simply amazing. So this approach requires a source player,
ie., DVD or BLURAY player that has 6 discrete outputs which also means
it will have an on board decoder. Can't have one without the
other. This will be fed directly into the Zen Ultra Preamp I just
discussed and it will feed your tube amplifiers for each channel.
No HDMI cables to poison the sound, no nasty solid state
receiver/processors to ruin it either. This can not be done any
other way. If you're using a computer as your source, get a 5.1
channel 24 bit USB DAC and hook it directly to the preamp. Be
warned however that Windows will constantly change your sound
settings. There will be sound setting for the DAC, sound settings
for the computer's DSP which must be off, sound settings for the Movie
player software, and your default computer's sound settings. They
will all overlap and other programs that have nothing to do with movies
will randomly change these settings. The result is lots of
frustration and a few occasional happy accidents when everything was
accidentally set right. Bluray is definitely where it's at sound
quality wise, at least as I write this. I've seen several good
Bluray players, that in front of this preamp will give more than usable
fidelity. I researched if such a preamp as this existed
before I finished mine in 2001 and the closest thing had none of the
features and was packed with circuit boards and op amps despite the
fact that it was tubes. Now 10 years later I searched again, and
nothing has changed except that the few I did find are around $7500,
have none of the features, packed with boards and being sold for 1/2
price to get rid of them. That's not going to happen with this
one, as you've probably figured out by now because it actually solves all the problems and
is good enough for the hard core SET guys needing a full time, fully
transparent preamp. Hopefully this will encourage those of you
who love serious two channel setups but also enjoy movies but only have
one room. Of course for those who are steadfast against polluting their wallpaper with vibrations from home theater, this preamp is highly desirable as a two channel only piece where you can run a bi-amp or tri-amp system with complete control over each amplifier OR set up 3 combination's of your favorite tubes and have basically 3 different preamps to listen to on any given night! A tube roller's dream machine for sure. The tube regulation is used as a filter to
reduce ripple by 10 times and block all the grunge that makes it into
your equipment's power supply via the wall outlet and power
cords. The result is as good or better than adding a power
generator, such as the PS AUDIO power plant to name one. Grain
free, and black backgrounds as though you were listening in the middle
of the night, anytime come standard with this approach. Nice to
save a few extra thousand by not having to buy a power generator, and
forget about most power conditioners, many make the sound worse. This is also a preamp I tend to leave on the vast majority of the time and so far I've only changed tubes twice in 10 years. It uses 8 6N1P or 6922 tubes, a rectifier tube and 4 Voltage Regulator tubes. A nice bonus is watching it turn on as the VR tubes wait to ignite until the preamp heaters are warmed up and then they fire on independently. Turning it off is about 5 times cooler because the VR tubes will go off and then come back on and then go off several times over about a minutes time. You'd have to see it to appreciate it.
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