Officially Class A

muralman1 · 15th March 2002, 12:33 AM

I just bought anX150 for my Apogee Duetta Signatures. A buddy bought a Llano Trinity 200 (200 watts/side) the same time. At an apogee site <http://audioworld.com/cgibin/sw/foru...Group&number=1> there has been an ongoing hot discussion whether the Llano is truly Class A throughout its rated power using moderate heat sinks that don't get hot. Randy White, the designer insists it is. After a phone conversation with Randy, one member came back with this to report:
Just got off the phone with Randy White. His amps run pure class A to rated power. They run cooler because the new MOSFETs he is using have a much lower impedence than usual. Even so the Amp idles at 300watts/Ch. The Trinity 200 that is. These Amps have an efficiency of 66% at full power. Not bad at all. Of course it stinks at Idle but what the hey, how many of us listen at Idle.

What say you?

grataku · 15th March 2002, 01:21 AM

me sez,
now I know why I don't hang @audioworld.com.

66% eff. is too high for class A.

AudioFreak · 15th March 2002, 01:38 AM

unless of course it uses dynamic bias.....

my guess, It aint class A @ rated output.

Lisandro_P · 15th March 2002, 01:44 AM

Quote:

Originally posted by AudioFreak
unless of course it uses dynamic bias.....

my guess, It aint class A @ rated output.

This increases efficiency, but nowhere up to 60%! I agree, it's probably class A at lower output levels and AB at full output.

muralman1 · 15th March 2002, 02:16 AM

What about Randy White's assertion that highly efficient Mosfets are largely responsible for the Class A rating?

AudioFreak · 15th March 2002, 02:34 AM

Quote:

Originally posted by Lisandro_P

This increases efficiency, but nowhere up to 60%! I agree, it's probably class A at lower output levels and AB at full output.

Well push pull can be just under 50% so i wouldnt right it off totally.

Quote:

Originally posted by muralman1
What about Randy White's assertion that highly efficient Mosfets are largely responsible for the Class A rating?

Has almost nothing 2 do with it sorry. Pure Constant Bias Class A cannot be over 50%.

I guess althought unlikely, it's also possible Randy's amp uses a tracking power supply.

Lisandro_P · 15th March 2002, 04:36 AM

50% is the theoretical maximum. But i dunno, actually i never got to think how much the dynamic bias thing improves efficiency, though i'm almost sure it's not 10%.

A schematic for that amp would be nice... anyone?

hagtech · 15th March 2002, 04:55 AM

The lower impedance of the FETs has nothing to do with the amount of heat dissipated in a class A or class AB amplifier. It's only marginally meaningful in switching class D types.

Even if you meant "thermal" impedance. The answer is the same. Hogwash!

If dynamic biasing is used, then it is possible to achieve higher efficiency, but FET impedance is irrelevant.

Jim Hagerman

muralman1 · 15th March 2002, 04:09 PM

You can take a look at the Trinity 200 at:

http://www.whiteaudio.com/page2.html

I will be listening to the Trinity in comparison with my Pass at my place very soon. I will post my findings.

grataku · 15th March 2002, 08:33 PM

Muralman,
don't bother. Noboby here cares.

15th March 2002, 12:33 AM	#1
muralman1 diyAudio Member Join Date: Mar 2002	Officially Class A I just bought anX150 for my Apogee Duetta Signatures. A buddy bought a Llano Trinity 200 (200 watts/side) the same time. At an apogee site <http://audioworld.com/cgibin/sw/foru...Group&number=1> there has been an ongoing hot discussion whether the Llano is truly Class A throughout its rated power using moderate heat sinks that don't get hot. Randy White, the designer insists it is. After a phone conversation with Randy, one member came back with this to report: Just got off the phone with Randy White. His amps run pure class A to rated power. They run cooler because the new MOSFETs he is using have a much lower impedence than usual. Even so the Amp idles at 300watts/Ch. The Trinity 200 that is. These Amps have an efficiency of 66% at full power. Not bad at all. Of course it stinks at Idle but what the hey, how many of us listen at Idle. What say you?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
I now officially hate M-Audio	SY	Everything Else	95	3rd August 2007 05:12 PM
How about a round-up of Class A kit power amps, or collectable vintage class A?	Brisso57	Solid State	4	14th February 2007 10:30 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

15th March 2002, 01:21 AM	#2
grataku diyAudio Member Join Date: Dec 2000 Location: -	me sez, now I know why I don't hang @audioworld.com. 66% eff. is too high for class A.

15th March 2002, 01:38 AM	#3
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	unless of course it uses dynamic bias..... my guess, It aint class A @ rated output.

15th March 2002, 02:16 AM	#5
muralman1 diyAudio Member Join Date: Mar 2002	What about Randy White's assertion that highly efficient Mosfets are largely responsible for the Class A rating?

15th March 2002, 04:36 AM	#7
Lisandro_P diyAudio Member Join Date: Oct 2000 Location: Argentina	50% is the theoretical maximum. But i dunno, actually i never got to think how much the dynamic bias thing improves efficiency, though i'm almost sure it's not 10%. A schematic for that amp would be nice... anyone?

15th March 2002, 04:55 AM	#8
hagtech diyAudio Member Join Date: Mar 2002 Location: Hawaii	The lower impedance of the FETs has nothing to do with the amount of heat dissipated in a class A or class AB amplifier. It's only marginally meaningful in switching class D types. Even if you meant "thermal" impedance. The answer is the same. Hogwash! If dynamic biasing is used, then it is possible to achieve higher efficiency, but FET impedance is irrelevant. Jim Hagerman

15th March 2002, 04:09 PM	#9
muralman1 diyAudio Member Join Date: Mar 2002	You can take a look at the Trinity 200 at: http://www.whiteaudio.com/page2.html I will be listening to the Trinity in comparison with my Pass at my place very soon. I will post my findings.

15th March 2002, 08:33 PM	#10
grataku diyAudio Member Join Date: Dec 2000 Location: -	Muralman, don't bother. Noboby here cares.