Originally Posted by Trepidati0n
I apologize since I keep forgetting to post here you need to be incontrovertibly correct and then back it up with a dozen PhD papers which have been blessed by Danley and the blood of a rare Chinese chicken raised in Brazil and slaughtered in a Greek temple was offered to Mohamed.
No sh!t. People have casually said on many occasions that the clones are class H and no one calls BS. But, state the obvious, that it isn't class H and have to be stripped searched and interrogated for pages. But, yes, this is the norm around here to get a point across for the benefit of those who rarely post but want to know.
Originally Posted by J_Palmer_Cass
Semantics and BS come into play here. There is no official Class TD amplifier topology. For that matter, some people claim that there is no official Class G or H amplifier topology.
Wiki and the link below say that Class G amplifiers use a rail switching power supply, and Class H amplifiers use a "voltage tracking" power supply. Aside from the power supply, then you can apply whatever class amplifier that you want to with AB being typical.
LG makes up their own name for an amplifier that uses a "voltage tracking" power supply and a Class B amplifier and names it TD. Some of the LG amplifiers are straight class D amplifier that "emulates Class TD" ( a made up LG class). Not sure what that means exactly either.
The bottom line is that the amp is not class H. The rest of the discussion is, as is usually the case, irrelevant.
The 2nd posted link shows the difference between the class TD and H, D, etc., in simple diagram form. Should make it clear to the usual suspects.
The confusion comes from the typical poster on these forums who basically knows little about amplifiers but loves "Wiki" and "Google". Wiki has no information about class TD and LG isn't so stupid as to try to spell out its patent in marketing brochures, so Google will be of no help either when it comes to a drive-by version of amplifier topology.
Another probable source of confusion is that LG calls their power supply a class D amplifier, or, in other technical writings, more specifically, a Tracking Class D Voltage Provider, which it technically is. There's nothing new about the idea of using a class D amplifier as a power supply. Bob Carver calls his similar design "Tracking Downconverter". It tracks the input, but the efficiency increase comes from the same principal as the LG design. They both also have the ability to deliver extremely high current as voltage requirement drops (as the impedance of the load being driven drops).
I have tried to mention this before but some objected that it was BS or whatever. In any case, a typical amp has a power supply that offers its full voltage all the time which high voltage is lost in heat through the transistors that are receiving that full voltage when there is low or zero input, which is the case with music program and especially the case with a sealed, L/T'd HT subwoofer. They also are less able to provide high burst energy for the transients typically found in music program.
Class H simply uses multiple supply rails, one for low V situations and one for high demand situations. It switches between the rails accordingly, saving energy lost to heat = increase in efficiency vs a standard linear amp.
The LG (and Carver and BASH, etc.) amps arrange for the single rail power supply to 'track' either the input (Carver) or the output (LG) signal and deliver only the voltage needed. Therefore, less energy lost to heat = higher efficiency than class H. The 6V headroom is cited because the supply is never at zero V. When in input is zero, the supply is 6V and it stays at +6V to max voltage.
Both of them received patents which have run out and, to my knowledge, have not been renewed. Neither of them is class H.
LG's test results show efficiency equal to class D, especially at 1/10 to 1/3 power. Competing amp companies have show their own test results that supposedly prove that LG's efficiency claim is not true. The difference in results relates directly to the type of test being used. LG uses something like 33ms on/66ms off input cycle (in an attempt to approximate music program, and other amp companies have other varying ratios of on/off times for the same reasons) and the 'dis-provers' use steady state sine wave input into a resistive load.
It should be a common sense deduction that the savings against energy loss comes from the tracking supply offering only the voltage required for music program, as a %, will change when the input is steady state at maximum output.
Class TD does not equal some class D amps in efficiency but for the purpose of HT amplification it definitely does and with higher SQ in my opinion and by my own test results.