Well, with a disclaimer that many factors go into the sound of a system and so your mileage may vary, but there is no competition between my Virtue Two amplifier and my Outlaw 7100. The Outlaw has more power and I now use it for my center and surrounds but my l/r av123 strata minis are powered by the Virtue Two.

Regarding the "digital" amps (not really digital, that's a misnomer), I discovered an Audioholics article on Class D amplifiers that was enlightening. The article states it's possible for a Class D amp to sonically excel (probably by some small margin) a Class AB amp (the classic type including the Outlaw amps), my impression was the Class D amp will be much more expensive. Typical Class D amps (which includes the T-Amp) have two main things going for them. They extract the most watts per supply volt (very good for mobile audio), and they have greater efficiency which means the power supply, heat sink, and overall chassis can be smaller (or you can pack more into a receiver or HTIB chassis). The power consumption will get them an Energy Star rating. The T-Amp and audiophile Class D amp reviews and comments mention "tube sound" as the major attribute, likely due to similar high frequency impedance characteristics. Other aspects of the sound quality all seem inferior to Class AB, and there's some serious concern about EMI related to the high frequency switching.For my money, I'm sticking with Class AB amps, even if that does brand me as an energy hog. I love my 7700.

I saw early subwoofer publicity on the Emotiva web site and that's all I know about their subwoofers. However, after some months of research, I decided to get Rythmik Audio servo subs. I'm delighted with their musical performance, and they can still shake the house on movie LFE. I certainly recommend Rythmik to anyone in the market for a near $1000 sub.

Bill

It depends on the digital amp, certainly. The benefits of size, heat rejection, and energy consumption (all of which relate back to the greater efficiency) can be very appealing, but I'd have to have a decent payback from the energy consumption and cooling load before I parted with my 7500.

There have been some very good digital amps built, from what I've read, but typically you have had to pay more per watt - sometimes a lot more - to offer comparable performance (as seen with something like Axiom's eight-channel amp, although some older examples have an even more extreme cost differential). The cost penalty is narrowing, I think, but there can still a pretty decent differential. Dvenardos' Virtue Two is an example of this: the 7100 sold for something like $900 and offered a total of 700 watts at 8ohms (just under $1.29 per watt), while the Virtue 2 offers up to 60W per channel for two channels at a price of $500 (or 40W per channel for two channels at $380, depending on the power supply you get). That's actually a pretty good price for a high-performance stereo amp, but it's still somewhere between $4.17 and $4.75 per watt. There are several reasons for the price difference, but using a digital chip while still rivaling good class A/B amps is likely a significant contributor to the extra cost per watt.

As usual, gonk hits the nail on the head.
I used to think that you could look at the specs of an amp and pick out the best amp, but I have found that in reality that is not the case. There is a big difference between a high quality "stereo" amp and a standard class a/b amp. I really love my Outlaw 7100 and there is no competition between the 7100 and a receiver. The Outlaw 7100 was my first real "wow" upgrade, but there is an equally impressive upgrade for two channel with a really good "stereo" amp and, as gonk says, you have to pay for it. For HT, there is absolutely no reason to look anywhere besides Outlaw (I have not heard Emotiva) and, in my opinion, Outlaw is THE name in price/performance.

Don

not to sound like an emo fan though you could wait to see what the xpr line amps will do once released..

as for digital I don't think we will benefit from it any time soon given that sony has been using a half breed system since the 1990's..

essentially I think if we went to a complete digital amp I would say we would end with power amps avr amp sections like sony which end being underpowered machines..

from what I've heard emo specs tend to be a reserve estimate of what the amps can do, unsure what outlaw states for their amps whether is reserve estimate or not...

digital amplification isn't all it has cracked up to be from what I've seen..

Digital amplification has been maturing steadily for a number of years now. Companies like Rotel and Axiom (among others) have proven that quality amps can be built with this technology, and there are undeniably both size and efficiency benefits to be had. The significantly greater efficiency means that the amps produce much less heat, which in turn means you need much less resources dedicated to heat rejection (heat sinks, etc.). That reduced heat rejection means you can build the amps smaller. In really big systems that operate frequently - which mainly relates to commercial installations - there can also be savings in HVAC equipment first cost and utility costs from both the lower amp power consumption and the reduced cooling load.

The trick is achieving at least equal sound quality at a price that justifies the amp. After all, in a typical residential environment the utility cost savings will amount to much less than a commercial facility, meaning the payback will be pretty painfully long if the only benefit is utility cost savings. If the cost savings comes at a reduced sonic fidelity, it becomes rather pointless.

Will I run out and buy new digital amps when they arrive? No, I don't think I will. I have seven channels of very nice amplification already sitting in the cabinet. They do a very fine job already. I don't have any current plans to make a change in that regard. When that day eventually comes, I will most likely look at digital amps, though. Much like LED lighting, the concept greatly appeals to the HVAC engineer in me, but I want the implementation to be satisfactory rather than settle for the novel concept of efficiency alone.


Even before companies like Sony, Pioneer, and Panasonic started using digital amp tech in their receivers, receiver amps were underpowered compared to separate power amps. The biggest problem was always the size of the power supply, with heat rejection being second in line (probably a very close second for class AB amps). When they moved to digital amps, they still had limitations on the power supply side. They also had no incentive to try to improve that when all their competitors were going to make deceptive claims about receiver amp power. (Ratings of 110W and 130W look good on spec sheets, and the note about being for just one channel driven are always small, easy to overlook, and often meaningless to the average consumer.)

Makers of separate power amps are in a different circumstance. If they're going to build a digital amp, they're going to have to do it right. Folks have asked Outlaw about digital amps for at least five years now, possibly longer. I think it's safe to say that Outlaw hasn't offered something yet because they wanted to do it right.

I think the reason why nobody has bothered with digital amps in context of power amps is because you can only 2/3rds of of the power from a digital amp..

look at sony's spec sheet as an example, they report 110-130 watt on some of their digital hybrid amp sections..

in reality a 130w system 105-110w is the effective output, try and use the rated spec power and watch a fried circuit board in your near future..

a 110w system will have the effective output of 85-90watt range try and use the rated wattage output and watch the circuit board fail...

that is the price of a digital amp hybrid..

I doubt a full digital power amp could push the same power output that the traditional power amps we use today do.

I would expect a 20-35% power reduction on a digital amp.. in regards to the rated output of the suggested maximum output of the power amp in question can produce.. if you follow sony's example for the last 25 years..

a pure digital or a hybrid digital amp is a lost cause to produce..

I don't know that this statement is accurate. From what I've researched, there can be digital amps that can handle higher power ratings. As some examples, there are the two Axiom amps (like this one) several Rotel amps (like this one) that can do 200W and more.

I thought I would add my $.02 to the conversation, so here goes.

First of all "Digital Amplification" is a misnomer, it is actually Class D amplification that is being discussed here. Although the "Digital Amp" name is becoming common place to refer to Class D it is misleading. Granted they often contain a great deal of "digital" circuitry as part of the design. However the thought that you are amplifying a digital signal just makes no sense. So what do you get bigger 0s and 1s! Furthermore, the input signal is an analog signal as is the output signal and nowhere in the path is there and ADC or DAC circuitry.

No in regards to the efficiency of a Class D amplifier (now this is really stretching my memory back to my college studies taking Electrical Engineering) in theory they are 100% efficient. But like most things theory and reality are often not in line with each other so as a practical matter good Class D amplification is easily over 90% efficient and some of the better ones are claiming in the mid 90s. The reason they are so efficient is a simple matter of electrical physics. A Class D amp (also known as a switching amp) is nothing more then a very high speed switch. The frequency at which it turns on and off is generally 10 to 20 times the highest audio frequency it will reproduce. In order to remove this very high frequency signal the output will have a purely reactive (i.e. no DC current due to a resistive load, it's a purely capacitive and inductive load) low pass filter designed to allow only the audio signal to pass. The majority of the time output circuit is either on or off. When it is off, there is high voltage across the output, but since the circuit is effectively open no current can flow. When it is on, it is a zero resistance path across the output so infinite current could flow, but since there is no voltage (you can't develop voltage across 0 resistance)then no current actually flows. In either case, no power is consumed since Power = Voltage x Current.

Now this begs the obvious question, how does power get transferred to the speaker? Remember the reactive load across the output? Not only is it used to filter out the very high frequency signal created by the rapid switching, but it is used to effectively transfer the audio signal to the speakers. Capacitors and inductors are both devices that store energy. They are either being charged or discharged depending on the switch state (on or off). Again in theory, capacitors and inductors hold there charge indefinitely. They require a resistive path in order to discharge. Well conveniently, the speaker attached to the output provides that resistive path. And I think we all know the rest of the story.

The only other question that hasn't been answered; how is the audio signal used to modulate the switching circuitry so that the final output is an amplified version of the input signal? Without going to deep into that whole process, and there are certainly many different ways to accomplish the task, I will just give you a simple explanation. The basic concept is called Pulse Wave Modulation(PWM). This might be where the idea of "digital amp" comes from in that the PWM circuitry could certainly be called a digital circuit. So without going into the nitty gritty of PWM lets just say it is this PWM circuits that turn the output switch on and off. This does not occur at a steady frequency. It is the varying times that the switch is in either the on or off state the creates the audio frequencies that drive the speakers. The longer that the output switch is in either the on or off state the greater the voltage swing seen at the output, i.e. louder. The difference in the on pules times vs. the off pulse times controls the output signal going in a positive or negative direction. The rate at which these pulse difference are generated is what determines the audio frequencies being output.

OK, now that I took a little trip down memory lane from my EE days, let me just say I am all for the growing acceptance of Class D amplification. After all, it's been around for a long time. Hell, it's been used by a large number of Audiophiles, though they might not know it. Most of today's powered sub-woofers are using Class D amps for driving those big ole speakers! But seriously Class D has a lot going for it:
1) Over all smaller design for same power
2) Less expensive components, therefor same price should get you better quality
3) Far more efficient, so it produces less heat
4) Less heat means small (or no) heat sinks which leads to 1 and 2 above
5) Due to its inherent power capabilities they should handle low impedance loads (2 ohm speakers) as easily as conventional speakers

Therefore, I would love to see Outlaw come out with a Class D based amp!