Blameless THD

nicholas1113 · 16th January 2010, 08:37 AM

Hey
I really need some help with my high THD ... i really dunno what happen to my High THD can anyone help me giving me some advise with 10hz THD is 0.0006% .. but i simulated a 73% for the Blameless power Amplifier.

I really need some help since I have stucked.

Below is the Blameless.asc and also the Diagram of the THD result .
Mind everyone for the help!

ClassB(THD8ohm).txt
121212123.JPG

jaycee · 16th January 2010, 09:18 AM

add .options plotwinsize = 0 to your spice diagram. also you will have to simulate at a small timestep like 0.05u.

Post your LTSPICE .ASC file and we can help more

megajocke · 16th January 2010, 09:39 AM

The models used were not included so I couldn't test your simulation but with a simulation length of only 15ms you are not going to get any information on the 10Hz distortion.

godfrey · 16th January 2010, 10:26 AM

This gives sensible results:

.four 0.01kHz V(OUTPUT)
.tran 0 500m 100m 0.1m

h_a · 16th January 2010, 11:18 AM

Well, the output clearly shows he's simulating 10kHz, not 10Hz. That's a much more reasonable number.

Likely you're DC-operating points are completely banana.

Always distrust the computer.

Have fun, Hannes

megajocke · 16th January 2010, 11:25 AM

Oh, that's right too. There is a mismatch between the signal source which was set to 10 Hz and the .four command set to 10 kHz.

nicholas1113 · 17th January 2010, 11:45 AM

Quote:

Originally Posted by h_a

Well, the output clearly shows he's simulating 10kHz, not 10Hz. That's a much more reasonable number.

Likely you're DC-operating points are completely banana.

Always distrust the computer.

Have fun, Hannes

What does it mean by DC-operating points are completely banana?
How does it know ?

nicholas1113 · 17th January 2010, 11:46 AM

Quote:

Originally Posted by jaycee

add .options plotwinsize = 0 to your spice diagram. also you will have to simulate at a small timestep like 0.05u.

Post your LTSPICE .ASC file and we can help more

I have post the .txt file and you can change to .asc .
thank you

nicholas1113 · 17th January 2010, 11:52 AM

Quote:

Originally Posted by godfrey

This gives sensible results:

.four 0.01kHz V(OUTPUT)
.tran 0 500m 100m 0.1m

Ya man ... the THD is lower but it should be 0.0006% in the BLameless ..
IS the input voltage frequency should be same as 0.01K for the command of
.four 0.01kHz V(OUTPUT)?
Are they the same?

h_a · 17th January 2010, 01:07 PM

Quote:

How does it know ?

Any amp you want to simulate you need to know very well first. You need to understand how it works and what the DC-working points (currents, voltages) are. Otherwise you cannot be sure that the results are worth the time you needed to generate them. A simulator does not replace basic understanding of the circuit.

However, first you should read the wikipedia-article on distortion

I'm sure then it's more clear what signal to put in (1kHz) and what to analyze for (1kHz).

Have fun, Hannes

16th January 2010, 08:37 AM	#1
nicholas1113 diyAudio Member Join Date: Nov 2009	Blameless THD Hey I really need some help with my high THD ... i really dunno what happen to my High THD can anyone help me giving me some advise with 10hz THD is 0.0006% .. but i simulated a 73% for the Blameless power Amplifier. I really need some help since I have stucked. Below is the Blameless.asc and also the Diagram of the THD result . Mind everyone for the help! ClassB(THD8ohm).txt 121212123.JPG

16th January 2010, 09:39 AM	#3
megajocke diyAudio Member Join Date: Jan 2003 Location: Solna	The models used were not included so I couldn't test your simulation but with a simulation length of only 15ms you are not going to get any information on the 10Hz distortion. __________________ The bewitching snivvie is dulcet paragon.

16th January 2010, 11:25 AM	#6
megajocke diyAudio Member Join Date: Jan 2003 Location: Solna	Oh, that's right too. There is a mismatch between the signal source which was set to 10 Hz and the .four command set to 10 kHz. __________________ The bewitching snivvie is dulcet paragon.

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16th January 2010, 09:18 AM	#2
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	add .options plotwinsize = 0 to your spice diagram. also you will have to simulate at a small timestep like 0.05u. Post your LTSPICE .ASC file and we can help more

16th January 2010, 10:26 AM	#4
godfrey diyAudio Member Join Date: Nov 2009 Location: Cape Town	This gives sensible results: .four 0.01kHz V(OUTPUT) .tran 0 500m 100m 0.1m

16th January 2010, 11:18 AM	#5
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Well, the output clearly shows he's simulating 10kHz, not 10Hz. That's a much more reasonable number. Likely you're DC-operating points are completely banana. Always distrust the computer. Have fun, Hannes

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