Simple Symetrical Amplifier - Page 5

Nico Ras · 6th August 2011, 11:48 AM

Odd order artifacts is a little on the high side. H3, 5, 7 and 9 contributes most of THD. Increasing the quiescent current to around 1.2 amps does change the order to even and lowers THD from 1.6% to 0.4%

Nico Ras · 6th August 2011, 11:49 AM

Sorry I should have qualified it, at an output swing of 24V peak.

buzzforb · 6th August 2011, 11:52 AM

Is this simmed or built and tested? I understand the two can be quite different.

Nico Ras · 6th August 2011, 11:56 AM

Hi Buzzforb, it was simulated in microCAP. And yes, in practice it could be several orders of magnitude worse.

AndrewT · 6th August 2011, 12:00 PM

Quote:

Originally Posted by Nico Ras

.........Increasing the quiescent current to around 1.2 amps does change the order to even and lowers THD from 1.6% to 0.4%

Quote:

Originally Posted by Nico Ras

.... I should have qualified it, at an output swing of 24V peak.

this is 84W of output dissipation for a maximum ClassAB output of 36W and about 24W of ClassA into 8r0.
You are suggesting a very high bias ClassAB amplifier.

Nico Ras · 6th August 2011, 12:04 PM

Hi Andrew, as I have said the artifacts are very high and odd order while running it in class AB, in other words low quiescent current.

Pushing it into class A works nicely and all the odd order stuff goes away. In my opinion it will make a rather nice class A amp.

Nico Ras · 6th August 2011, 12:14 PM

Class Ab @ 1 kHz fundamental

Nico Ras · 6th August 2011, 12:29 PM

Andrew, the efficiency of class A is very low, power loss can be as high as 75% that is why high power class A is not that popular simply because the power supply and heat sink is uneconomical in relation to output power. But it does sound nice, so the toss-up remains whether irritating the neighbors is more fun than listening to music.

alex mm · 6th August 2011, 12:55 PM

...... few minors changes , and you can see the new PCB rev.1.1

It was my plesaure to do this board , but can be layout again if not ok

Alex.

Nico Ras · 6th August 2011, 01:30 PM

Hi Lazy Cat, any reason for using power transistors. In fact you can use the same small signal devices throughout. Alex are heat sinks necessary, these transistors hardly dissipate 50 mW.

Other than that, you laid a great board Alex!

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6th August 2011, 11:48 AM	#41
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	Odd order artifacts is a little on the high side. H3, 5, 7 and 9 contributes most of THD. Increasing the quiescent current to around 1.2 amps does change the order to even and lowers THD from 1.6% to 0.4%

6th August 2011, 11:49 AM	#42
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	Sorry I should have qualified it, at an output swing of 24V peak.

6th August 2011, 11:52 AM	#43
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	Is this simmed or built and tested? I understand the two can be quite different.

6th August 2011, 11:56 AM	#44
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	Hi Buzzforb, it was simulated in microCAP. And yes, in practice it could be several orders of magnitude worse.

6th August 2011, 12:04 PM	#46
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	Hi Andrew, as I have said the artifacts are very high and odd order while running it in class AB, in other words low quiescent current. Pushing it into class A works nicely and all the odd order stuff goes away. In my opinion it will make a rather nice class A amp.

6th August 2011, 12:29 PM	#48
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	Andrew, the efficiency of class A is very low, power loss can be as high as 75% that is why high power class A is not that popular simply because the power supply and heat sink is uneconomical in relation to output power. But it does sound nice, so the toss-up remains whether irritating the neighbors is more fun than listening to music.

6th August 2011, 01:30 PM	#50
Nico Ras diyAudio Member Join Date: Nov 2005 Location: Amanzimtoti - East Coast of South Africa	Hi Lazy Cat, any reason for using power transistors. In fact you can use the same small signal devices throughout. Alex are heat sinks necessary, these transistors hardly dissipate 50 mW. Other than that, you laid a great board Alex!