A document, called Errata.doc has been published here : Errata - Google Drive
The document correct errors I may have made in various projects I have worked on.
The document is to be updated.
Please, report all errors and problems.
The document correct errors I may have made in various projects I have worked on.
The document is to be updated.
Please, report all errors and problems.
Something more has been published in the other thread, called " A Buffer for Class AB Amplifiers ". Here is the link :
https://www.diyaudio.com/forums/solid-state/361346-buffer-class-ab-amplifiers-2.html#post6839283
The post contains some explanations and two schematics, is on page 2 and is called : " Buffer for Class AB Amplifiers with Adders "
Please, use the other thread, " A Buffer for Class AB Amplifiers ", for comments.
https://www.diyaudio.com/forums/solid-state/361346-buffer-class-ab-amplifiers-2.html#post6839283
The post contains some explanations and two schematics, is on page 2 and is called : " Buffer for Class AB Amplifiers with Adders "
Please, use the other thread, " A Buffer for Class AB Amplifiers ", for comments.
Machine Gun Noise :
I have done some additional investigation, as, previously, mentioned. I will publish an additional document. For now :
The direct circuit works OK in mono! No machine gun noise. Rbe improves the sound. The machine gun noise is present in stereo. Most likely, the reason is fast switching with high current, which, loads the power supply and capacitors and, occasionally, proliferates from one channel to the other.
I have done some additional investigation, as, previously, mentioned. I will publish an additional document. For now :
The direct circuit works OK in mono! No machine gun noise. Rbe improves the sound. The machine gun noise is present in stereo. Most likely, the reason is fast switching with high current, which, loads the power supply and capacitors and, occasionally, proliferates from one channel to the other.
The direct push pull circuit and the machine gun noise have been investigated. The circuit has been made to work. A document, called " Machine Gun.doc ", has been published. Please, scroll down to the " Addendum " and read a page and a half only, except when interested in more information : https://drive.google.com/drive/folders/19EGkuJHapxfTlS9T0iIIMLXz-E-U9-1r
I suggest adding zobel networks to the output terminal of each amplifier - something like 8R2 in series with 100n connecting the output to ground.
Consider the inverting input of your amplifier is a summing junction which samples the mix of signals at your output terminal going to and from the loudspeaker with those going to and from ground via the zobel network.
Comparatively to some extent the speaker return signal is the wicked witch and ground return signal is the fairy godmother.
Thank you! Excellent advise. I have tested your suggestion with a 10 Ohm Zobel resistor ( I do not have 8.2 Ohm ) and 100nF Zobel capacitor. Works Ok and no load resistor is necessary, although, a large value would not hurt. I have updated the document accordingly and corrected some errors.
I have been reluctant to use capacitors and used only resistors. However, I guess, a Zobel network would not hurt with these values, which give a good impedance at 20KHz, ten fold the speaker resistance.
I think, the Zobel network would try to introduce a phase shift and, therefore, non linearity ( hopefully, very slightly ), but, the circuit would cover for this.
Also, there would be some consumption of the current with which the amplifier IC regulates directly, but, this is very slight at 20KHz and under.
Surely, Zobel is the way to go. And, yet, I think, Sziklais, best, not be used at all. True, save some voltage, but, this isn't worth. However, Sziklais may be a good idea for power supply, where, an amplifier and a Sziklai can provide each of the supply rails ( positive and negative ). Since this is a power supply, there would be tons of capacitors thereafter and the Sziklais would not oscillate.
Anyway, thanks for the suggestion. I may use this in the original amplifier circuit ( with other tricks, because, even a standard capacitor with not so low ESR did not work ).
Please, keep posting!
A new thread, called Oscillations, has been posted, where Oscillations and simple weapons against them are discussed.
Here is the thread :
https://www.diyaudio.com/community/threads/oscillations.383752/
Here is the thread :
https://www.diyaudio.com/community/threads/oscillations.383752/
A new document, called " Offset with Amplifiers.doc " has been written. Please, note, I have not made the schematics, yet, but, I intend to make and test the circuit.
Here is the document :
https://drive.google.com/drive/folders/1I-gJFsjT1I2w7QNfagujAo1DXqRQrGxG
Here is the document :
https://drive.google.com/drive/folders/1I-gJFsjT1I2w7QNfagujAo1DXqRQrGxG
A new document, called " Offset with Adders.doc " has been written. Please, note, I have not made the schematics, but, I have made similar.
Here is the document :
https://drive.google.com/drive/folders/1I-gJFsjT1I2w7QNfagujAo1DXqRQrGxG
Here is the document :
https://drive.google.com/drive/folders/1I-gJFsjT1I2w7QNfagujAo1DXqRQrGxG
I have decided to publish a document, called, " Standard Schematics ", which, describes the standard schematics of amplifier and transistors stage. I, usually, do not like writing a document on standard or other people's schematics, but, this document helps with non standard, own schematics. Of course, I could not resist to publish some non standard, own, original schematics as noted in the document.
Here is the thread :
https://www.diyaudio.com/community/threads/standard-schematics-class-b-and-class-ab.384847/
Here is the thread :
https://www.diyaudio.com/community/threads/standard-schematics-class-b-and-class-ab.384847/