Newbie here. I'm upgrading a rack-o-parasound gear from 1999 to a new Integra 9.8 (yes - actually have one!) and need to pair up am amp. I read the other posts from HTBloggingGuy (and others) re his noise issues with the 7700, and his option to stick with a B&K. I like the B & K too, but Edward almost has me convinced to get a 7700 (cheaper, even considering shipping to AK).

My internet research on amps, however, leaves me with a bunch of questions about amp classes. I've read the Wickapedia explaination of different amplifier classes (A, A/B, D, G, H). My basic understanding is that A and A/B "traditional" amps are not very efficient and run hot, but most forums (AVS, HTSpot, Polk, etc.) conclude they are pretty much the best preformers overall if you can handle the heat and the weight. Not sure I agree, but all I've every used is a Parasound HCA 806 class A/B six channel.

The "hybrid" designs, like the 7700, use different kinds of technology that I don't understand (something to do with rail switching and a bunch of microfarads), and I don't think I need to. I know there are some very bright electrical engineers on these posts who may be able to distill this into 5th grade english for us idiots.

Anyway, seems like most people are happy with the 7700, so I assume the hybrid amps perform well, but I'd still like to know if anyone has switched from a class A-A/B amp to a hybrid, and if they notice a difference.

Thanks for any info!

The model 7700 is a traditional class A/B liner design. This type will yield better sound quality than any of the other classes except for class "A" types which are very rare and expensive (and extremely inefficient).

Class "G" is a rail switching type which uses a lower power supply rail up to a pre-determined output, then switches to a higher voltage set of rails. This switching is never perfect, but the point of switching is usually placed at a high enough level that is is inaudible over the signal.

Class "D" amplifiers are digital - technically they use pulse width modulation. They are very efficient, but there are several problems with this type of amplifier, not the least of which is a high amount of ultrasonic clocking signal which cannot be filtered from the output.

The Outlaw amps are extremely well made - Buying the 7700 is a real no-brainer of a choice.

Class D amps are just a different type of switching amp and are not digital amps...this is a misnomer.

http://en.wikipedia.org/wiki/Electronic_amplifier#Class_D

The 7700 is not a hybrid design at all but is a full differential A/B amp.

For the most part, I agree that it is well made, unfortunately I think they made some compromises to the power supply section of the amp that result in unwanted issues in some instances as has been noted in my review.

Personally, if you like the B&K, I'd stick with that unless the difference in price is large (>$500). You should be able to find them for at least $2250 if not lower.

Uh....pulse width modulation IS a form of digital processing. "Digital" encompasses more than just PCM, Sigma-Delta modulation or other variants. "Switching" by it's very nature is one of several digital processes.

I'd love to hear more about these "unwanted issues" about the power supply. I'm pretty familiar with the circuitry of that amp.

BloggingITGuy had an unfortunate problem with the 7700 that he couldn't resolve. There are lots of us who have them (with no issues) and love them.

Here's a great article on class d http://sound.westhost.com/articles/pwm.htm

Unwanted issues being things like transformer noise loud enough that you can hear the transformers humming from 7-8 feet away from the amp.

The B&K 200.7 does not suffer from this problem at least not in my experience. They chose to compromise on amount of heat sinks instead. Both amps sounded about the same to my ears.

The Outlaw probably has more actual power, although I only say this since I had to adjust each channel down about 7db, which might just be a factor of sensitivity of the inputs on the 7700.

Home theater amplifiers today are designed to have as close to 28dB of voltage gain as possible (this is also the THX target gain). I know for a fact that the Outlaw amps hit this target pretty closely. What you experienced is more of a case of the B&K amp being around 7dB more sensitive than is standard. An amplifier having more or less gain is neither good nor bad, but the target is 28dB for compatibility's sake.

Toroid transformers in general will hum when fed 120 volts AC that has high amounts of harmonic distortion on the line. The 2nd harmonic distortion is especially bad in this respect because it is non-symmetrical, and as a result causes a DC shift on the AC waveform which, if bad enough, can saturate the core. At the very least, DC on the core eats up the capacity of the transformer to supply the required current.

Fed clean AC, a transformer will not buzz or hum.

Unfortunately, commonly available power conditioners and filters will do nothing to eliminate distortion on the AC line. To do that, you need to use a power regenerator, which is expensive and in any case, not recommended to use with a heavy load such as a power amplifier.

Perhaps you should read my blog post on the subject to get up to speed on what I went through: http://itmanager.blogs.com/notes/2007/12/200-watt-home-t.html

Please note that my experiences are based on direct, repeatable observations of two separate Outlaw 7700 amps, 2 separate B&K amps and my old Kenwood amp. Out of those, only the Outlaw had the problem of the humming transformers that could be heard from my listening position.

I'd also be willing to bet $5500 that the Integra Research RDA-7.1, a very similarly designed amp to the 7700 would not have the same issue in my home.

As it stands, I can only recommend the 7700 to two kinds of people...those who can't get a similar or better amp for around the same price, or those who need an amp they can put into an enclosed rack.

All others would be better off, in my opinion, going with a different product.

For what it is worth, I've watched the 7700/7500 forum since it was set up in 2005 or so (before I even got my 7500) and have not seen transformer hum as a common malady. Like several others, I have placed my ear against my 7500 and not heard anything. I can't explain why both amps' transformers reacted adversely to your installation, but I hardly consider it endemic to the design.

I don't doubt your experiences. Some transformers are more prone to being influenced by high AC line distortion than others. I _do_ know however that the transformers in the 7700/7500 are not built to any lower of a standard than those from any other manufacturer - there were no "compromises" involved in it's manufacture for cost reasons.

I'm also quite sure that if you placed distortion analysis equipment on your AC line, you'd see that you have abnormally high amounts of harmonic distortion in your location. This mainly comes from the pole step-down transformers, and is aggravated by heavy loads from people who share that transformer or ones upstream.

If it was such a universal problem, everybody would have the exact same experience, even those with clean AC service. The fact that the problem is as scarce as it is and that there are many who don't have this problem, points to the quality of your AC line.

The B&K amp you have is simply more tolerant of line distortion, nothing more.

I can only make conclusions based on my own observations with the products. I could have tried amps ad infinitum, but my 30 day trial with the B&K was running out so a decision had to be made.

Also as I have noted before, these were both (I think) B-Stock amps and as such might have been returned by others for the same reason? I don't know.

At the end of the day, it cost me $450 extra to try the Outlaw amp in my effort to really want to like it. But after spending the $350 to get the dedicated power circuits installed to isolate out that problem I still had the issue and had to send the amp back, which cost me another $100.

So when someone asks "hey what do you think of the Outlaw 7700?" I will chime in and say good amp, but...

And while I can't wholeheartedly endorse the product, the risk to try (~$100 for most people) is relatively low.

Running dedicated circuits in your home will do absolutely nothing to eliminate distortion on the AC line - it originates in the pole transformer or at points upstream from there - the distortion is already there on the line that enters your house.

The fact that the B&K amp is more tolerant of line distortion speaks to the fact that Outlaw made a compromise on the product, which is usually done to keep costs down.

Either that or it's a problem inherent in using such large transformers.

Take your pick.

And you can't tell me that they didn't make compromises on the design to keep cost down. There's REASONS why an amp like the Integra Research RDA-7.1 is $5500 retail vs the Outlaw and most of the difference has nothing to do with the distribution chain.

Running dedicated circuits will eliminate distortion on the AC line coming from other sources within the home.

It's interesting how you keep telling me what I already know from DIRECT OBSERVATION.

No product is perfect, so you have to pick your poison. I chose mine and you chose yours and now AlaskaHT can choose his knowing the risks.

Actually it has _everything_ to do with the distribution chain! Internet only companies avoid middlemen markups and can sell a product for less money as a result. You may not believe it, but it's very true.

A far as the quality aspect, all I can say is that I am more familiar with their manufacture than you'll ever know......

Actually, a dedicated circuit will only help with providing adequate current. The only way to get rid of distortion from sources in the house is to either move it to the other leg of the service (so if the compressor in the fridge is on leg A, you want to power the amp from a circuit on leg B) or to put in an isolated ground system. In commercial installations where there are sensitive electronics (computers) that can get irritated by noise from things like variable frequency controllers, we put in separate IG panels and even transformers because the noise produced by the drives (and other things, but I'm picking on drives because I'm usually responsible for them being in the building in the first place) affects more than just their own circuit or even their own distribution panel.

Direct observation with AC line distortion measurement equipment? I don't think so. To properly and completely trace any problem requires the proper test instrumentation and the knowledge to use it.

Running dedicated AC lines in your home will usually eliminate EMI/RFI sources of interference, which is also a form of distortion, but not the low-harmonic series distortion I've been talking about. That distortion comes from _outside_ your house, and you have no control over it. You can also reduce or eliminate interference by running your audio/video equipment from one of the other phases of AC that services your house. In some cases, the other phase of AC will have less harmonic distortion than the one you're using.

For circuits which are run from the _same_ phase, there is no real suppression because the circuit breakers are the only barrier between the different pieces of equipment which are drawing current from that phase. In this situation, power line conditioners are useful to filter out EMI/RFI on the line before it enters your equipment.

Another useful strategy is to use one of the balanced power transformers from companies like Equitech, although this solution is costly.

BloggingITguy and Altec -- thanks for the comments! I really do appreciate the diverging opinions. Altec mentiones that the 7700 is a traditional A/B linear design, which I think is what the B&K is. Maybe these amps are more similar than I thought. BloggingITGuy -- did the 7700 get as warm as your B&K?

Thanks again guys!

No, the 7700 did not get as warm as the B&K, which is why I can recommend it for use in an enclosed rack whereas I would not recommend putting the B&K in anything other than a well ventilated rack.

I did not need test equipment to tell me that something was wrong with the Outlaw amps. I compared them to comparable amps from another manufacturer that did not have the same problem.

Most people will not have "clean" power coming from the street, there will always be artifacts of one sort or another. Therefore, it's important in my mind, at least, to get equipment that does well under normal conditions and not just on a test bench in a lab under ideal conditions.

The B&K performed better under normal conditions (normal in this case defined as my home, which is the only space that I personally care about) than the Outlaw.

THAT is direct, repeatable observation. You can dance around it all you want, but that's what happened. Why it happened, is quite frankly, immaterial. The fact that it did happen, was to my mind unacceptable which is why I have a B&K amp in my rack and not the Outlaw.

You may have different experiences with the Outlaw than that, which is fine, but I can only report on MY experiences so that others know what problems they might expect to have.

Like I mentioned before, I don't doubt your experiences, and yes, the B&K amp probably is less influenced by line distortion. They may also pot their transformers, something that is impractical in the 7700 because of available space.

However, you are doing a real disservice by proclaiming a blanket condemnation of the Outlaw amplifiers for reasons that have more to do with compatibility in your particular case than any flaw of the Outlaw amplifier. As has been noted elsewhere, the vast majority of people have no transformer issues whatsoever with these amps. If it was really a problem, it would manifest it's self with everybody - clearly that is not the case.

I don't remember making a blanket condemnation about Outlaw nor their amps. All I have done is note my experiences with two 7700 amps vs two B&K and one Kenwood amp.

Obviously, you have not read what I have written on my blog or elsewhere in regards to Outlaw.

However, when push comes to shove and someone asks which they should buy the Outlaw 7700 or the B&K 200.7, assuming they can get the B&K 200.7 at or near same price as the 7700 AND they aren't going to be putting it into an enclosed rack, there is no doubt in my mind that for most people in that circumstance that the B&K will be the better amp for them.

And enough people have complained on the forums about the same or similar issues that it does raise some questions about the design of the amp.

However, as I stated before there's very little risk (about $100 in shipping if Outlaw is still offering free shipping on the 7700) in trying out the 7700.

And seriously, pointing out that you may have problems with humming transformers is hardly condemnation of the product.

At any rate, again, I stand by my original statement above. In my opinion, the B&K is the better buy at or near $2k.

By the way, middlemen add markup, but I know that the Integra Research costs authorized retailers somewhere between $3000-3500. There is a difference for that price vs the Outlaw 7700's price tag of $2149 and it has nothing to do with distribution.

Perhaps I should have saved up and tried out the 7900 instead, as it doesn't seem to have the same issues (at least no one's complained about it yet), but ~$2k was my budget and as such ended up with the B&K. Which as I have said, again, in my opinion, made compromises in more acceptable areas (heat reduction) vs design of the transformers. Oh and if you by potting the transformer you mean putting a metal "shield" around it, yes, that's exactly what they did with the B&K.

At any rate, I think we've given AlaskaHT more than plenty enough information to make an informed choice.

Well, obviously we'll just have to agree to disagree on this issue.

By potting, I meant either the mu-metal shielding or epoxy encapsulation. Either of these or a combination of both are very common.

If it becomes a big enough issue, I'm sure Outlaw will implement one or these approaches in the future.

I've got two setups here; 7500/990 and an older (but goodie) BK ST202 amp/Conrad Johnson Sonographe pre-amp (for vinyl)....at times, my 7500 is dead silent, other times it hums, likewise, the BK does the same thing. I can almost set my watch for times it will do it....usually around dinner-time, early morning, etc.,i.e., when there is a high demand for power in my area. After trying different outlets, isolating cords, cable, etc, I just write it off as a less than ideal feed from my local power company....it is not annoying enough to give up the 7500's superb performance, or the older BK for that matter.

You are absolutely correct as to the source. The line distortion varies with the load placed on the utility transformers in your area. If you were unfortunate enough to be near a heavy manuacturing area, you would get this noise every time a large motor or something similar started was running.

I'm fortunate in that I live in an area where I never experience line distortion. Power outages every time the wind blows or it rains, yes. Distortion, no. :p