Your plot of the "small speaker distortion at 1 KHz", reveals some (lower level) spectral lines which are not harmonics of the fundamental. Any idea what produces them?
Kurt
This is rubb and buzz. I comes from imperfect glue joints, noise in the suspension, iron dust or hairs in the airgap etc. A little bit also comes from my generator. I used a simple M-Audio Transit soundcard.
The highest of this side distortions is 74dB under the main signal. I am not sure if i can hear that. Funny enough rub and buzz is audible if you crank it. Until recently there was a women in every serious loudspeaker factory that checked every spaeker with a loud sine sweep. A terible job only for people with iron health. The latest Klippel System that costs a fortune claims to make that unnecesesarry but i am not 100% convinced. Fix a little bell to the membrane of the speaker you measure and you here the bell ringing loud all the time whereas the first and second harmonic on the analyser show the same result as without the bell. The ear seems to be superb to pick up noise that escapes conventional analysers.
Hi Damon,
That's wonderful if the SPICE tutorial in the book helped you get going with LTspice. It's a great tool that I know from experience can be very helpful in gaining insight and refining circuits.
When you enter a value like 2 mA (the way we would write it in a sentence), for LTspice you need to enter it as 2mA with no space. Also, the thing that counts is the "m", so if you wrote 2m for a current source that would signify 2 mA as well. Also, be careful of resistor values in the megohm range. 2M will not work. You need to write 2Meg. If LTspice sees an m or M, it thinks milli.
Cheers,
Bob
all units are normally tagged on to the value.
5lbs, 4inches, 25degC, 2pair, it's the way we technocrats do it.
5lbs, 4inches, 25degC, 2pair, it's the way we technocrats do it.
p23, The Ideal Transistor. 2nd para:
infinite current gain, infinite input impedance, infinite output resistance.
Really? This confuses me.
infinite current gain, infinite input impedance, infinite output resistance.
Really? This confuses me.
No Andrew, Bob is actually correct and the way it should be written is with a space, e.g. "2 mA". I think it's also stated to be written that way in British Standards. Most engineers do it wrong!
Bob,
I know you are busy, but could you post one of the SPICE models for the complete amplifier from your book? I have been reading the book, and have been re-acquanting myself with SPICE modeling (it has been ~10 years), and I would like to start to dig in with a working model.
Thank you for your book!
Edward
Hi all,
I have finished Intro + Ch1 & Ch2.
A very good read.
I particularly like the way Bob talks us through these early topics.
I am amazed at how well he ties all the disparate nuggets together into a coherent whole. Decades of titbits are coming together, some for the first time.
I look forward to reading the rest and expect my Christmas present to be the "knowledge" and not the physical book, as I had first thought.
Thanks Bob.
I have finished Intro + Ch1 & Ch2.
A very good read.
I particularly like the way Bob talks us through these early topics.
I am amazed at how well he ties all the disparate nuggets together into a coherent whole. Decades of titbits are coming together, some for the first time.
I look forward to reading the rest and expect my Christmas present to be the "knowledge" and not the physical book, as I had first thought.
Thanks Bob.
Sorry but could you reexplain this bell stuff. It should ring because of the main signal , no ?
JPV
Hi Andrew,
The ideal transistor is a chunk of transconductance, namely a voltage-controlled current source. This goes against the other common view that a transistor is a current gain device. If you look at the hybrid-pi model, you see a transconductance as the active element. Everything else in the model is essentially unwanted departures from the ideal.
Cheers,
Bob
Hi Edward,
Glad you liked the book!
I'll try and put an amp sim up this afternoon.
Cheers,
Bob
Hi Ed,
Here is an LTspice file for one of the amplifiers discussed in Chapter 3. Let me know how you make out with it.
BTW, I fly to Denver tomorrow for RMAF, so I may be out of touch for awhile.
Cheers,
Bob
Not everyone likes the book
Well, it had to happen sooner or later. In the spirit of balance and transparency, I've posted my first bad review on Amazon below. Thought you might be interested in seeing a different view, now that many of you have seen the book:
________
By Ray de Velder
Owners of the excellent books of Douglas Self and Ben Duncan, will not benefit much from Cordell's book because it mostly repeats the information disclosed by Self and Duncan, but not as well. For amplifier basics, Douglas Self's books are very thorough, and Ben Duncan adds more information to include commercial designs and alternatives to the conventional art, as well as many useful references. In contrast, Cordell's references seem to be restricted, and mentions very little of various innovative commercial designs.
His understanding of more complex amplifier systems seems lacking in some areas, e.g. higher order poles, and class-D amplifiers. For example, he does not mention (maybe because he does not know) that conventional class-D amplifiers (with -ve feedback) or the self-oscillating systems he mentions, intrinsically produce distortion, even if the electronics is assumed perfect. Further, he fails to mention that this intrinsic distortion can be cancelled and indeed is so very successfully in several commercial products.
He also "measures" distortion using Spice. In the real world these "measurements" are unrealistic.
_____
I'm a bit puzzled by the class D comments, but that is a big subject whose surface I have only scratched. Maybe I missed something there. If one of you guys can articulate in more detail what he may be referring to that would be helpful. Or maybe one of the guys on the class D forum can set me straight. There's always the second edition to think about.
Cheers,
Bob
Well, it had to happen sooner or later. In the spirit of balance and transparency, I've posted my first bad review on Amazon below. Thought you might be interested in seeing a different view, now that many of you have seen the book:
________
By Ray de Velder
Owners of the excellent books of Douglas Self and Ben Duncan, will not benefit much from Cordell's book because it mostly repeats the information disclosed by Self and Duncan, but not as well. For amplifier basics, Douglas Self's books are very thorough, and Ben Duncan adds more information to include commercial designs and alternatives to the conventional art, as well as many useful references. In contrast, Cordell's references seem to be restricted, and mentions very little of various innovative commercial designs.
His understanding of more complex amplifier systems seems lacking in some areas, e.g. higher order poles, and class-D amplifiers. For example, he does not mention (maybe because he does not know) that conventional class-D amplifiers (with -ve feedback) or the self-oscillating systems he mentions, intrinsically produce distortion, even if the electronics is assumed perfect. Further, he fails to mention that this intrinsic distortion can be cancelled and indeed is so very successfully in several commercial products.
He also "measures" distortion using Spice. In the real world these "measurements" are unrealistic.
_____
I'm a bit puzzled by the class D comments, but that is a big subject whose surface I have only scratched. Maybe I missed something there. If one of you guys can articulate in more detail what he may be referring to that would be helpful. Or maybe one of the guys on the class D forum can set me straight. There's always the second edition to think about.
Cheers,
Bob
Bob,
Thank you. I have downloaded the file and unzipped it. It appears that everything is in order. I will try to run is later - must work now :^)
Enjoy the RMAF!
Best regards,
Edward
Seen it? Damned Amazon isn't shipping my pre-order until December! Bastards! 🙁
Still looking forward to the book.
I find many things in your book that i do not find in Selfs or Duncans volumes.
To include measurements of all described designs whould make the page size double i am afraid.
To include measurements of all described designs whould make the page size double i am afraid.