Our concerns about numbers, harmonics, distortion, square waves, THD, measurements

[mosfets]

Originally posted by Bob Cordell
The MOSFET amp you bought surely did not have 0.001% THD at 20 kHz. The spec you are referring to is almost certainly 0.001% at 1 kHz (assuming you recall it correctly). This very different, and much easier to achieve. It sounds like you have possibly fallen into the trap of 1 kHz THD specs.

Cheers,
Bob

I do not recall it being a MOSFET amp I do not recall it listed at .001% at 20kHz either. I do not recall falling in a trap. I guess I don't remember any of those things...weird

Any who, I'm just saying I don't pay much attention to specs like I once did. I think I can easily handle 1% THD without much bother. I would love to spend time studying the different harmonics in distortion, though. I envy guys like you Bob, who have dedicated so much effort and time to such things.

I love reading this stuff!

[andy_c]

Originally posted by Lumba Ogir
My understanding says that the value of simulation in that regard is zero, because the conjugate variables, position and momentum of a moving particle cannot be determined simultaneously. In other words, spectral components are not traceable at any given time instant.

FFT analysis in SPICE gives the amplitude and phase of each individual harmonic (IOW, a full spectral analysis). It's not just a THD thing. You can do IM with it too - it's just a bit more effort. If you have questions about what it can and cannot do, just ask.

[Rafael L]

Very good Andy has done a good job in this forum with simulators

In the graph fig. appears as the measurement IMD , two different frequencies are applied to input, 60Hz and 7Khz (Standard default SMTPE) the residual near the fundamental 7KHz is the product IMD (highlighted yellow in Figure).

[Miles Prower]

Originally posted by mosfets
I do not recall it being a MOSFET amp I do not recall it listed at .001% at 20kHz either. I do not recall falling in a trap. I guess I don't remember any of those things...weird

Given the time you bought it, and the description of how it sounded, I'd bet that it was indeed a MOSFET amp. I have one of those as well. It's sitting out back, and at least being useful as a home for field mice. The sound was gawdawful.

Seeing that no OPT is cheaper than the cheapest OPT, designers of these abominations simply adapted the SEPP-type output stage that works quite well with BJTs to MOSFETs. It's not a good idea, being that "complimentary" N-Channel / P-Channel devices are a good deal less "complimentary" than NPN / PNP pairs. For MOSFETs, use one type or the other, but not both in the same circuit.

Connect them to an OPT or use a Circlotron-type OTL final. Also, keep 'em well away from Class B operation. These thingies have hideous cross-over behaviour.

[destroyer X]

about this subject...the thread is exausted..the interested ones to comment have already made.

So, let the thread rest in peace and remember that i feel gratefull about your cooperation.

bye.

Carlos

[Pingrs]

Originally posted by ostripper
.options plotwinsize=0

is the same as

QUOTE]Originally posted by ostripper
turn off all "compression" in "control panel/compression"[/QUOTE]

isn't it?


Brian.


http://www.diyaudio.com/forums/showt...78#post1124278