What remains is this picture, an ordinary nfb system.
The reactances -j1.246*10^6Ohm and +j18.85*10^-3Ohm are omitted, or rather one is practically a short circuit, while the other is much too high impedance to play a role.
The reactances -j1.246*10^6Ohm and +j18.85*10^-3Ohm are omitted, or rather one is practically a short circuit, while the other is much too high impedance to play a role.
What does your contribution have to do with the topic, the subcontext quad 405: Mesh equations, voltage dividers and possibly two voltage dividers (which could form an electrotechnical bridge)? Nothing!
greetings,
HBt.audio
(please do not feed)
Dear @jan.didden and dear @johnnyx
please explain to us correctly the mechanism that eliminated! the non-linearities, takeover distortions ... etc. here in the picture.
Many thanks in advance, I would also be grateful if you would not title me lightly.
Yours sincerely,
HBt.audio
please explain to us correctly the mechanism that eliminated! the non-linearities, takeover distortions ... etc. here in the picture.
Many thanks in advance, I would also be grateful if you would not title me lightly.
Yours sincerely,
HBt.audio
Dear Mr. Anonymous,
I have posted several explanations and links to external studies and papers at the beginning of this thread.
It is probably more efficient if you would just read those instead of me typing it in all over again.
Jan
I have posted several explanations and links to external studies and papers at the beginning of this thread.
It is probably more efficient if you would just read those instead of me typing it in all over again.
Jan
Supplement:
The vectorial addition of the string currents at the summation point (| Iload |) should result in the I_Load * Z_Load being spectrally pure, i.e. cleaned of all errors.
I hereby ask you to publicly describe this process in detail.
The vectorial addition of the string currents at the summation point (| Iload |) should result in the I_Load * Z_Load being spectrally pure, i.e. cleaned of all errors.
I hereby ask you to publicly describe this process in detail.
My name is not interesting, but if you address me by my forum nickname or my initials H. Bt. you are doing everything right.
You are evading Mr. Didden!
I have all the documents on the subject myself, long before I typed the first letters in this forum. It is therefore completely unnecessary to refer to the *.pdf documents.
#
It's all about thinking for ourself and not consuming. You can be sure that I have fully understood the subject matter.
Sorry,
HBt.
(I'll retire now, everything has been said.)
Reading through some of the linked to papers and posts, it seems CD had a lot of detractors over the years and ultimately, the system loop gain would be the limiting factor on just how close to a 'piece of wire with gain' (Walker's famous aphorism) could be achieved with the technique.
But, the most important contribution of Walker's design was that all the fiddling around with setting the OPS bias and DC offsets could be dispensed with at a stroke, and distortion reduced to below audibility threshold levels. This allowed Quad to churn out amplifiers in production that required no adjustment and/or trimming. They just worked well straight off the production line and continued to do so over the life of the product.
As they say, 'Perfect is the enemy of the good' and the Quad 405 got the balance just right.
🙂
But, the most important contribution of Walker's design was that all the fiddling around with setting the OPS bias and DC offsets could be dispensed with at a stroke, and distortion reduced to below audibility threshold levels. This allowed Quad to churn out amplifiers in production that required no adjustment and/or trimming. They just worked well straight off the production line and continued to do so over the life of the product.
As they say, 'Perfect is the enemy of the good' and the Quad 405 got the balance just right.
🙂
red and blue: currents in classB output stage
black: output current of classA driver
green: amp output voltage
low output inside classB dead zone:
high output:
black: output current of classA driver
green: amp output voltage
low output inside classB dead zone:
high output:
I admit that the Quad 405 presents an interesting picture in its implementation. We could also say it's food for thought. And it is precisely this material that raises questions.
HBt.audio
(not "Mr. Anonymous", please don't fed)
😉
IIT Bombay
And a quasi-school experiment, a typical laboratory experiment, carried out by four Indian students, or first-year students, 2007.
Dear Bernhard,
would you reveal the values of the components used in your virtual test, THD -120dB is great.
thx
HBt.audio
And a quasi-school experiment, a typical laboratory experiment, carried out by four Indian students, or first-year students, 2007.
Dear Bernhard,
would you reveal the values of the components used in your virtual test, THD -120dB is great.
thx
HBt.audio
After staring at the schematic for 1 minute, this is my understanding:
Reduced to the most basic principle, bridge aside:
Starting from very small output levels, the classA amp works alone via the resistor, as the unbiased output transistors are there only for decoration.
When the output level increases and said transistors start conducting, they alternatingly take over most of the part of the current, due to the low impedance connection to the load, controlled by the classA amp.
Still, from there on the classA amp continues to deliver a constant "last maximum" current because of the Vbe drop of the output stage.
In other words, until the classB stage starts conducting, the classA current increases to a maximum of Vbe_classB / R_classA_out and remains constant from there on.
Documented in post #373
Reduced to the most basic principle, bridge aside:
Starting from very small output levels, the classA amp works alone via the resistor, as the unbiased output transistors are there only for decoration.
When the output level increases and said transistors start conducting, they alternatingly take over most of the part of the current, due to the low impedance connection to the load, controlled by the classA amp.
Still, from there on the classA amp continues to deliver a constant "last maximum" current because of the Vbe drop of the output stage.
In other words, until the classB stage starts conducting, the classA current increases to a maximum of Vbe_classB / R_classA_out and remains constant from there on.
Documented in post #373
Maybe it could benefit from some rework.
1, the driver stage BD139/140 also lacks bias.
2, the opamp needs to provide current for both the resistor and the output stage.
3, the circuit does not work as intended because the magic C is missing, so THD is not optimum.