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Re: Use which high Effiency Speaker with which company Tube Amplifier by Using Digital X-Over to Bi or Tri Amp Speaker

Hi Sanjaysahani!

You wrote:
[a lot of things about analog vs. digital sound]

On the loudspeaker issues, I'd like to recommend that you peruse my site at www.PiSpeakers.com . There are a lot of other excellent sites, but this one has some great information. You might enjoy reading the technical papers at the bottom of each page. I would suggest the Pi Alignment Theory and the JBL sound design papers.

Also on the issues of loudspeakers, remember that this is arguably the place where most sound reproduction inacuracies occur. They're electro-mechanical systems - in fact, electro-mechanico-acoustic systems. So we have the greatest "chance for error" here.

If you want to get the most accurate signal, it is my opinion that most of your focus be on the loudspeaker system. But the best motors you can afford, and put them in a cabinet that is aligned for linearity.

I'm not going to debate the merits of different cabinet types, because I don't want to "start something." But I think its safe to say that bass reflex and acoustic suspension systems are generally considered to offer more linear response, and horns provide better efficiency. There's a performance trade-off with each, and the loudspeaker designer attempts to limit his compromises.

On these forums, I've seen excellent examples of builders that have been able to exploit a design's merit while minimizing its compromises. Some get close to removing the "weakness" of the design type's "charactersitic compromize."

So you decide what's best for you.

I'm not a big fan of attempting to keep phase "right." If you run a loudspeaker in an anechoic environment, it might be reasonable. But in the complex environment of the "real world" - we have an incredibly complex phase interrelationship. Even considering that the line of site energy is stronger - and placing the listener in a "sweet spot" - one must be careful to keep priorities straight. That is, unless one enjoys "counting the number of angels on a pin."

Many do enjoy this, and my "hat's off to them." Sometimes it's fun, and sometimes it's even productive. But just consider the issue, and whether it is realistic to place emphasis on it, for your system installation.

That brings me to the point of the electrical components. You've mentioned digital, semiconductor and tube signal devices.

Remember that the world is analog. The only reason we've made digital devices is because they are easier to work with. It isn't because they are better. The results obtained by digital equipement of a given cost are often better - these days - because digital devices are so much cheaper to make.

But just 20 years ago, we computer guys could built the same digital equipement and didn't because it was cost prohibitive. So times have changed. Now, we can build a circuit that will sample an analog audio signal sufficiently to get a reasonable representation of the signal. That makes our job very easy - we can manipulate the signal with computer algoritms against the representation of the signal.

We do it 'cause it's easy. We can do almost anything we want with the same set of microprocessor chips. No analog devices are required.

But remember that - for the purist - the best way to have done this would have been with an analog computer . Amplifiers - tube or semiconductor - are nothing more than analog multipliers. Frequency controls are integrators and differentiators. They provide a perfectly analog function to a perfectly analog signal.

Now then. Down into the "yukky" parts of all these devices. Analog devices can often be exceeded in quality by digital devices of the same cost. This is mostly because an analog device needs some pretty big parts to do some of the same things that a digital device can do with in microcode. It's the same sort of evolution that moved us away from tubes and into semiconductors.

The point is that you can do all the same things with any of these three technologies. These are advantages and disadvantages of each, and the places where a particular technology are often compromised are where you should place your emphasis.

Whether your front end is digital or analog - your presentation to the loudspeaker motor will be analog. Your input to the system (at the microphone in the recording studio, at least) will be analog. So your "main amplifiers" will be analog.

If you're running tube gear, you should take pains to ensure that bandwidth is high enough. Tube amps tend to offer less bandwidth than semiconductor amps. You'll also want to make sure you have enough current to drive your chosen loudspeakers, because tube amps are high impedance devices that some call "voltage amps." Current output from these devices is relatively low.

Tube amps tend to create odd-order harmonics when clipped, which contributes to the "tube sound." They also enter clipping fairly "gracefully" - having a much more "smooth clipping" - if I can say that - than do transistor amps. Up to the point where the system reaches the limits of the power supply, the tube amp will provide non-linear gain as it approaches clipping. This too, contributes to "tube sound."

If you're running semiconductor gear, you have some of the same shortcomings of bandwidth, but its typically limited to the lower frequencies. They may be DC coupled - which gets around this - but there's probably gonna be a coupling capacitor in the systems somewhere. That coupling capacitor will set your low frequency limit.

Bipolar (trasistor) devices present even-order harmonics at clipping, which is what gives them the "transistor sound." They also "hit clipping much harder" - in that they provide linear gain up to clipping, and then cleanly stop providing gain. There is no "smooth transition" as is the case with tube amps. These two effects are what give a bipolar amp its own distinct "sound," and it is these, I suspect, that are particularly annoying to lovers of fine tube gear.

But with either type of amplifier - or "analog multiplier" - you will have all the issues of biasing and coupling and clipping, etc. If it's a "single ended tube" or class A amp - you must have the stages bias' set to the centers of the operating ranges of the devices, or you will clip prematurely. With "push-pull" stuff, you must have some bias so that zero crossing is smooth.

You will want to make sure that the power supply has a purely DC voltage, with no ripple. That's one place where "AC hum" comes from, and in the "old days" - was the most likely canidate for its cause. Its also very common to have ground loops and unbalaced signals getting electromagnetic coupling from AC power. Those are often just a result of bad installations. Just make sure all "grounds" connect to a single source, and ensure that all signal and ground connections are of good quality.

Even when running digital front ends to all this stuff - you will now have a great degree of freedom in "signal processing" - but it still all comes down to the same basic fact that the better quality you can obtain is determined by what you can afford. You can make great sound with any technology, if its done "right."

So no matter which of these devices you use - you pretty much will be only limited by your budget. You just gotta buy good stuff.

Wayne


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