what's to be bridged

Monoblocks are very different than bridging an amp.

Monoblock amplifiers only pass the signal from one channel to one speaker. No bridging involved. There is only one channel.

Bridging an amplifier only helps to make one channel stronger. You sum the channels by bridging them. A 100 watt 2ch amp becomes a 200 watt single channel amp. But not a monoblock. In in practice you actually get more than the sum of the two channels. In the case of the GFA555 that would be 600 watts the GFA555 is a beast of an amplifier.

The main difference between the two is sound quality. A bridged 2ch amplifier will have more distortion than a dedicated single channel amplifier.

You have a third option with two of these amps also. It is called bi-wiring. That is when you take both channels and drive the highs with one side and the lows with the other. You would replicate this on both speakers. Which looks like this:




I have never heard a 555 bridged so I do not know how they sound that way but they do sound quite good in stereo.

Bridging will increase output in watts but because the 2 channels are summed (added together) the load the amp see's is cut in half which is not a good thing if you are trying to drive speakers less than 8 ohms.

It also impacts sound quality. It's not recommended simply because the marginal gain you get in watts usually doesn't justify the issues of driving less than 8 ohm speakers and the lower sound quality.

That said the Adcoms are beefy enough to drive less than an 8 ohm speaker load when bridged. It's still not recommended but you can certainly experiment if you don't believe us.

If you have SDA's you can't run bridged stereo amps.

H9

TNRabbit wrote: »

GENERALLY, bridging an amp WILL increase output, but USUALLY at the expense of sound quality. This is particularly true when bridging into low Z (ohm/impedance) loads.

Bi-amping is USUALLY a much better use of 2 amps & is less stressful to the amps as well. It's especially useful when you are stressing a single amp into speakers that are a difficult load or inefficient.

Pay attention to the capitalized words.

If you Bi-amp it's preferable to use an active crossover to get the best possible results.

H9

Mono blocks are also considered better due to cross talk ( channel leaking info into another channel is an easy way to kind of understand it) and also it allows the transfomer and power supply to be dedicated to only 1 channel, thus it helps lower distortion, noise, and other unwanted things that you can get from bridging. Mono's will tend to be more expensive due well double of everything.

McIntosh will have mono blocks like the 501 and the 1.2KW etc. A pair of 501's even on the used market will still run 5-7K for a pair. Once again though you have double of everything, thus increasing cost etc.

Normally if you want, doing a good 2 channel amp (stereo) is a good way to go when starting out. If you then get more into the hobby mono blocks can be looked at but once again would require a large budget and other associated gear. I would not recommend getting 501 amps to power a system but then use a cheap DVD or CDP or pre amp and speakers to run the rest of it.

I get the feeling my amps (Cambridge-Audio 840W) were designed as mono amps, and made stereo for mass market. Mainly because the bridged mono output is greater than double the stereo output.

One of my first upgrades after about 6 months of getting the new Cambridge pre-amp/amp (840E/840W) combo was to add a second amp. My unscientific impression was two amps in bridged mono mode was better than one in stereo mode. The sound was clearer and more detailed, and I was able to set the pre-amp 15-20 db lower than in stereo, yet still get the same volume.

Although I bought this gear ‘in the dark’ from Audio Advisor, it turns out every review I have seen has been overwhelmingly positive.

"This information is critical to obtaining the ultimate performance of the 840E/W combo. The power yielded by each amp in either stereo or “Mono Bi-Amp Mode” is 200wpc into 8 Ohms, 350wpc into 4 Ohms. However, when the entire amp is mono bridged it becomes 500wpc into 8 Ohms and a whopping 800wpc into 4 Ohms. For those seeking a capable stereo amp for general purposes one 840W will suffice. However, those looking for high quality solid-state amplification will want to move to the “Mono Bridged” mode, that is, obtain two of these units. The performance elevation is such that it is easily merited."

“Even though these are solid-state amps their design makes them run really hot; now I refer not to their thermal nature, but rather their sonic nature. I will state this in the most forward manner: If these amps did not sound so good I would nod a polite “Howdy-Do” to them and send them on their way, writing a “they’re fine” summary. But they are not fine, they are sizzling, nay, searing in performance! If they raise the room’s temperature, they most certainly raise my desire to hear them. Their sound is commensurate to the thermal energy they produce. As the heat of the sun draws us outside to bask in its rays, the hot performance of the 840W’s draws me to them.

The big deal is the proprietary “Class X-D Technology” which is said to, “eliminate crossover distortion at low signal levels. Cambridge Audio explains that the crossover point is “actively displaced”, which, “creates a region of pure Class-A operation where the crossover zone would otherwise be before moving into an enhanced form of Class B at higher levels.” If I guess correctly, the Azur 840W creates its own nano-black hole for crossovers, which explains the phenomenal energy output.

To explain the Nano-Black Hole Amp concept (or Class XDNBH), I asked Matthew to clarify. I was only mildly disappointed to learn that the amp does not produce a Black Hole. It does something nearly as wondrous: it makes the crossover point disappear! In reality it gets displaced; it is only gone if you look for it in the wrong place. Displacement of the crossover point has been a method tried for years in amplifier design in order to eek out more operation in Class A and less in Class B. The key here is a transition at much higher levels and less abrupt than conventional Class A/B designs. One of the tricks (Cambridge is not divulging all of them) is using a second generation circuit where the displacement current is modulated by the audio, but outside the feedback loop. This does not occur by DSP, but purely an analogue process. ”

http://www.dagogo.com/View-Article.asp?hArticle=321

Anyway, I love these amps. Whether at 70 db playing string quartet music, or Lady Gaga at 95 db, they rock. If this is the distortion caused by bridging then give me more.