Class D is just Dandy!

Hi @merrillaudio

Welcome. I'd like to ask you a few questions about what you pointed out.

However as with all transistors, there is a lag between the command to switch and the actual full switch. This is call the dead time. This has been reduced over the years with faster transistors and also limited with feedback. But it is fast. Hence the apparent speed of Class D also.

Sorry, could you be mistaking "switching time" with "dead time?"

As I understand, you are talking about switching time. How long to go fron on to off, or vice-versa.

I think "dead-time" is a little different. As I understood, the problem with bi-polar PWM amplifiers (uses + and - V at the transistors) is that you must NOT have the positive and negative sides on at the same time. This affects both efficiency and distortion. I link Wikipedia and a B&O brochure discussing it. (The PDF is a little easier to get).

https://granitedevices.com/wiki/Dead-time_distortion

http://www.icepower.bang-olufsen.com/files/solutions/iceedge_brochure_final_20150624.pdf

By the way, this issue with multiple transistors being on at the same time plagued Carver for many years. :) but in his case, he was switching among multiple voltages of the same polarity. Eventually it was solved by reducing the switching speed.

Best,

E

FYI,

Found some good references re: Damping factor and speaker sound quality and posted here:

https://forum.audiogon.com/discussions/measurements-clearly-explained

Best,


E

@toddverrone, You may be confusing 'Active' bi-amping with bi-amping. 

Bi-Amp - 2 amps wired to the speakers LF and MF/HF binding posts using the internal passive crossover.

Active Bi-Amp - Putting an active crossover in between the amps and the preamp. In this case, it's highly recommended to remove the crossover in the speaker and wire the drivers directly to the binding posts. This adds a level of complexity you may or may not like because you have to know crossover point of the MF/HF and LF drivers. 

Fortunately, my VT-80 outputs equal watts in 4 and 8 ohms load with 26dB gain which made it bit easy to coordinate. I tried few Class D amps that had very high damping factor or high gain settings (obviously they didn't quite gel as they over-powered the tube amp). While it's only been couple of days with THOR mono's in my system, I am throughly enjoying their more than adequate bass slam. In my system, the key was to attain just the right amount of low end without overwhelming the mid's and high's. So far I have not notice any coherence or speed mis-match issues.  

PS: I am glad to hear that you're enjoying your setup. 

In the professional world, "bi-amping" a single speaker system is always active, meaning it uses an active crossover before the amps.  Multi-way active speakers also use this type of crossover.

Only in the consumer world is there a question of whether or not to use a crossover when bi-amping, hence the confusion.

Far too many types of crossovers further confuse this, because while most line-level crossovers are "active" or powered, a rare few are passive.

Best,

E