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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
robert1976
75 posts
 
@georgehifi
Pro’s=
More watts.

Con’s=
Worse damping factor
Higher output impedance (has relevance to damping factor)
Lower stability (especially into low impedance’s)
Current ability is reduced (especially into low impedance’s)
Higher distortion.

Whether these con's are a real, audible issue depends on the amplifier in case, no?

Looking at the Luxman's M-900u specs, doesn't it still have great specs when used as a monoblock?

Sure, damping factor and current ability take a hit. But 600/1200/2,400w into 8/4/2 ohms and a damping factor of 300+ still sounds pretty good.

Please explain if you disagree, I'm kinda new to this :)
georgehifi's avatar
georgehifi
10,312 posts
 
Please explain if you disagree, I’m kinda new to this :)
Just search Google "cons of bridging amplifiers" or "disadvantages of bridging amplifiers" there’ll be pages and pages to read.

Looking at the Luxman’s M-900u specs, doesn’t it still have great specs when used as a monoblock?
If they put them in print, only the ones they want you to see.

Almarg (rip) will also tell you the cons. https://forum.audiogon.com/posts/1762093

Cheers George
audio2design
1,351 posts
 
I would say many comments made here are made by people without a deep understanding of amplifier design and are just parroting comments made by others without deep amplifier design knowledge.

Potential advantages of bridged amps (if properly designed for the purpose).

- inherent cancellation of even order distortion products which can be especially beneficial at low power (biggest advantage)

- reduced distortion by reducing voltage swing allowing devices to operate over more linear ranges of operation


- improved power supply rejection ratio


- related to above, better rejection of IM and THD products from audio modulation of the power supply 



georgehifi's avatar
georgehifi
10,312 posts
 

All you have to do is read techs with far more savvy than you on the subject in Google, and now your even saying you’ve got more than Almarg (rip) as well, your are a genius!!! well self proclaimed one at best
audio2design
1,351 posts
 
"techs"? ... That's laughable.

I have read some of Almargs posts. Intelligent and knowledge guy and sorry that he passed before I could interact with him, but yes, on amplifier and audio technology based on his own writings I have more likely significantly more knowledge. However, as he alluded in his post George which likely went over your head is a balanced amplifier design of which a special case of a bridged design.

However, a mistake made by many, and I believe by Almarg but maybe he was just simplifying for the likes of you was the belief that you must have perfect gain matching on both channels which is not at all true. Gain mismatch shows as offset, it does not in itself make a distortion product hence why the benefits of 2nd order cancellation and power supply / power supply modulation rejection carries through as does the benefit of reduced voltage swing as it relates to distortion.
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