2. amps-preamps
  3. 148670-2497

Bridging an amplifier

I recently watched a YouTube video, a few years old, that featured Flemming Rasmussen, the highly regarded founder and engineer for Gryphon (now retired I believe). Flemming was speaking of his class A monoblock amplifiers in the Antileon Evo, Colloseum and Mephisto. Flemming was expressing his disdain for Monoblocks that are actually 2 internally bridged amplifiers, (such as DNA 500,Clayton M300s and also class A Luxman that can be used as Monoblocks in the BTL mode (bridged tied load), calling these types of Monoblocks inferior and not true Monoblocks. He claims dedicated Monoblocks where all push pull transistors are paralleled, are vastly superior to summing the two channels via bridging (antiphase summing). I’d love to know if most audiophiles and engineers agree with Flemming. I have owned and found both the DNA Monoblocks and Clayton M300 Monoblocks to sound excellent, and a friend uses two M-800A Luxman class A amplifiers in bridged tied load mode (BTL switch) with great clarity and power. Thank you for your thoughts!
audiobrian
millercarbon's avatar
millercarbon
12,531 posts
 
Well as Austin Powers put it, "Everyone likes their own brand."

On Wall St its called talking your own book.

A psychologist would probably see it as evidence of cognitive dissonance.

Me, I just see it as way too simplistic. You hear a guy talking like that, you just know he's taking something in which a zillion different aspects interact and boiling it down to the one thing. Which you know is nonsense. Which is why Austin Powers pee joke isn't irreverent, but accurate and very much to the point.
auxinput
2,920 posts
 
Hmmm, from what I understand, the concept of using a stereo amp in bridged-mono mode is really no different than a true monoblock. They both use "antiphase summing" where one amp board pushes while the other amp board pulls. They both have to use push-pull transistors arrays where one set of transistors is pushing the positive side of the waveform and the other set pulls for the negative side of the waveform. However, stereo amps cannot normally support low impedance loads. For example, DNA 500 is a stereo amp that supports 500 watts into 8 ohms or 900 watts into 4 ohms. When bridged, I suspect that you do not want to run a load under 8 ohms.


The Luxman is designed with higher current, but again the impedance capability is halved when bridged. However, they support 1 ohm loads in stereo and 2 ohm loads bridged.


A dedicated monoblock usually has a power supply design that can adequately support low impedance loads (such as 4 ohm or lower). Based on what I can find, that Clayton M300 is a true monoblock.
audiobrian OP
184 posts
 
Hi millercarbon & auxinput 

Thanks for your input. I guess I’m still not fully understanding the difference between a ‘true’ mono-block vs bridged monoblock....maybe I’m getting stuck on terminology. I thought it was more than a robust power supply? BTW, the Clayton M300s have been described as a bridged Balanced Class A design with essentially two M100s internally bridged in each monoblock....guess I need to read a little more about paralleled vs bridged amplifier designs.
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