Then take a screenshot and post a *.png - which simulator are you still using?
Absolutely correct and MC12 is kind enough to let us know the actual border of the tolerable maximum modulation swing / range of excursion.
At this limit, you can see what delta the BIAS miracle really delivers before it switches to AB-B operation.
And that is not Iq + Iq = 2 times Iq, but 808mA plus 324mA = 1.132A ... I leave it to the reader to decide whether this is 10.25W or 5.13W.
In any case, this simulator reveals in the most diverse ways what everyone actually knows. But marketing people are beating about the bush, till today.
However, we should also point out that the MF-A1 naturally complies with the old hi-fi standard.
HBt.
The whole thing has a certain tragic comedy, because the amplifier works and its sound is great, but unfortunately it is not a 100% fully-fledged 1 + 1 = 2, 2*Iq pusher and puller. I didn't expect the new name 3/4 + 3/4 = 1.5 to be so incredibly accurate.
😎
Are we still waiting for @m0rten ?!
THD_10k
looks the same as THD_1k
0.006% _ 10W
0.03% _ 17W
Use R23 to set the positive DC offset of the upper half and R11 to set the negative DC offset of the lower half of the circuit. R22 and R5 are the same size for this purpose at 15k each. After R13 & R10 now connect the halves, this should result in an Iq of <1.3A but >1.1A. Only now do you increase R5 until the output node is set almost exactly to zero volts.
Genuine class A operation is now guaranteed up to 7W, as a push pull A interpretation it is more than 15W ... one can explore this vague definition even further.
But, as @wahab rightly pointed out, A is not necessarily the golden seal of quality.
I think this very simple modification of the forefather is quite respectable - and that with only 4 BJTs "in the signal path" and the frowned upon VA-OS.
HBt.
THD:
10 W(rms, 8R)
-84.4dB
1 W(rms, 8R)
-96.5dB
Bandwith:
delta_f > 200kHz
These specifications meet every conceivable HiFi standard. There is also sufficient dynamics, even for a small party. The schematic from posting #68 would then be my next reboot of the A1, v2.1 !
@m0rten,
as always: everything looks great.
greetings,
HBt.
10 W(rms, 8R)
-84.4dB
1 W(rms, 8R)
-96.5dB
Bandwith:
delta_f > 200kHz
These specifications meet every conceivable HiFi standard. There is also sufficient dynamics, even for a small party. The schematic from posting #68 would then be my next reboot of the A1, v2.1 !
@m0rten,
as always: everything looks great.
greetings,
HBt.
Just a question:
Is this design converging toward a finite goal, or will it continue to change ad infinitum?
I subscribe to the thread and will check if a design for production materializes...
🙂 morten
Is this design converging toward a finite goal, or will it continue to change ad infinitum?
I subscribe to the thread and will check if a design for production materializes...
🙂 morten
That's a mean question,
because although everything is finite, there will always be evolutionary steps in one direction and the other.
Mod 1, as version 1.1, is independent and therefore ready for the prototype, the zero series. Mod n+1, i.e. the preliminary version 2.1, is currently nothing more than an exemplary exercise. And should slowly close the MF-A1 topic. In the Hanseatic thread I will show how to establish an independent BIAS using a current mirror. Here then are the ac & dc control circuits or loops 100% separated from each other.
tpc
But,
"3/4 + 3/4" remains unchainged as it is in the initial posting #1.
Of course I would be happy if @jxdking doesn't remain the only other developer in this thread.
regards,
HBt.
I thought you have pretty much figured out. Using current mirror alone gives you a big boost on the THD figure. Add Miller compensation to make it stable as I showed. Regarding the feedback network, I prefer the original one. You might have another idea.
I theorized 800ma should be minimum current. In the real life, you probably want 1a.
If you want a class A amp and occasionally can do class AB, that’s an excellent design.
TBH, I am not the class A guy. I can’t manage the heat.
I theorized 800ma should be minimum current. In the real life, you probably want 1a.
If you want a class A amp and occasionally can do class AB, that’s an excellent design.
TBH, I am not the class A guy. I can’t manage the heat.
THD_100Hz:
Consists solely of H2, 0.01%_1W & 0.035%_10W. Could one wish for a more beautiful brushstroke in an acoustic picture?
#
Version 1.1 is competing to claim the "utopian THD" for itself, v2.1 does not.
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For the original MF-A1 !
In retrospect, I was able to understand your comment. I now know what you wanted to say. And you are right, Iq < 0.8A is not sufficient for Mr. Tim de Paravicini's construct.
Typo
the mentioned schematic is in post 65 (not 68). 65 is version 2.1.
@m0rten
device of R29 is min 1W type -> the same as R28 & R27. Maybe someone can willingly give valuable tips for the pcb layout. Where has Nico Ras gone?
THD_100Hz
THD_1kHz
THD_10kHz
Mission "utopian THD" has been fulfilled.
Which says absolutely nothing about the potential sound character of Version 1.1 .
Iq < 1.3Adc
1W, 1kHz, n=9 -> -114dB THD
#
To be honest, the fast version 2.1 is not really worse than the overkill version. This is due to the Darlington and the higher negative feedback voltage.
Everyone has to decide for themselves which modification path they want to take. Frequency compensation also plays a very important role here, the theory and implementation of which is certainly not easy to understand and implement.
The most sensible solution is always the most elegant and the simplest.
Bye,
HBt.
THD_1kHz
THD_10kHz
Mission "utopian THD" has been fulfilled.
Which says absolutely nothing about the potential sound character of Version 1.1 .
Iq < 1.3Adc
1W, 1kHz, n=9 -> -114dB THD
#
To be honest, the fast version 2.1 is not really worse than the overkill version. This is due to the Darlington and the higher negative feedback voltage.
Everyone has to decide for themselves which modification path they want to take. Frequency compensation also plays a very important role here, the theory and implementation of which is certainly not easy to understand and implement.
The most sensible solution is always the most elegant and the simplest.
Bye,
HBt.
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I still don't know if any of the PCBs are reaady for production and I don't know if any of them would make a decent amplifier.
I still call this PCB/schematic combo for #98 (old thread). Is this design still in debate? Is it good? (on paper, I know...)
Will there be more changes in the near future?
If yes, I will come back and check later.
Changed R29
I still call this PCB/schematic combo for #98 (old thread). Is this design still in debate? Is it good? (on paper, I know...)
Will there be more changes in the near future?
If yes, I will come back and check later.
Changed R29
just combine the findings ...
THD_1k, 10W -> -126dB
THD_10k, 10W -> -98.4dB
THD_100Hz, 10W -> -132dB
So there really is a winner in the game of optimal dimensioning.
There you go, here it is.
THD_1k, 10W -> -126dB
THD_10k, 10W -> -98.4dB
THD_100Hz, 10W -> -132dB
So there really is a winner in the game of optimal dimensioning.
There you go, here it is.
@m0rten
There will be no more changes unless a USER raises serious and well-founded, plausible technical concerns (which I absolutely do not expect).
MC12 has spit out heavenly data and now a practical test should be carried out.
This throw (posting #77) is so good that we can recommend Musical Fidelity a new A1 mono power block with a clear conscience (albeit only after multiple test runs).
I will be happy to do so and get in touch with Mr. Lichtenegger personally.
HBt.
There will be no more changes unless a USER raises serious and well-founded, plausible technical concerns (which I absolutely do not expect).
MC12 has spit out heavenly data and now a practical test should be carried out.
This throw (posting #77) is so good that we can recommend Musical Fidelity a new A1 mono power block with a clear conscience (albeit only after multiple test runs).
I will be happy to do so and get in touch with Mr. Lichtenegger personally.
HBt.
Hints
The power dissipation of a mono power amplifier of this type is around 70 electrical watts, which requires an effective heat sink and sufficient ventilation!
The heart of the 3/4 + 3/4 Amp is now available, but the power supply, the protection circuit, the switch-on delay and a band-limiting input circuit (I'll be happy to supply this later, perhaps balanced inputs are an issue?!), a housing for a complete device are still missing.
If there is a general interest in a genuine ++10W class A amplifier (also with the A1 seal of approval) here, this thread could be bumped soon.
If not, I will gladly release the circuit to the Asian kit faction again. A drawing of the circuit diagram may be made later, as all the necessary information and dimensions are already available.
So open fire and brave warriors one step forward.
Psst.
Otherwise I recommend the Beelzebub and the Beelzebabe ... without the 'utopian THD', of course.
The power dissipation of a mono power amplifier of this type is around 70 electrical watts, which requires an effective heat sink and sufficient ventilation!
The heart of the 3/4 + 3/4 Amp is now available, but the power supply, the protection circuit, the switch-on delay and a band-limiting input circuit (I'll be happy to supply this later, perhaps balanced inputs are an issue?!), a housing for a complete device are still missing.
If there is a general interest in a genuine ++10W class A amplifier (also with the A1 seal of approval) here, this thread could be bumped soon.
If not, I will gladly release the circuit to the Asian kit faction again. A drawing of the circuit diagram may be made later, as all the necessary information and dimensions are already available.
So open fire and brave warriors one step forward.
Psst.
Otherwise I recommend the Beelzebub and the Beelzebabe ... without the 'utopian THD', of course.
Dear fellow campaigners!
We have an exciting project ahead of us. It requires real dedication,
because:
both branches (3/4 at the top + 3/4 at the bottom) must form a fairly exact mirror image, i.e. be absolutely complementary. If there is even the slightest suspicion of asymmetry, this will have a negative effect on the 'utopian THD'.
We have to select and match carefully.
If we don't do this, or if we do it only succinctly, then no better standard than 0.03% THD will emerge for this sensitive design either. This is completely natural - and not without reason the most frequently read specification. It is up to our diligence and the PCB whether we scratch the theoretical THD beyond the -70dB mark or not.
Even renowned authors and designers, such as Mr. D. Self, make no secret of this fact.
Have fun building it yourself,
I'm looking forward to it - but most enthusiasts would probably prefer 1kW or even better 2kW than just 10 to 20 watts.
kindly,
HBt.
We have an exciting project ahead of us. It requires real dedication,
because:
both branches (3/4 at the top + 3/4 at the bottom) must form a fairly exact mirror image, i.e. be absolutely complementary. If there is even the slightest suspicion of asymmetry, this will have a negative effect on the 'utopian THD'.
We have to select and match carefully.
If we don't do this, or if we do it only succinctly, then no better standard than 0.03% THD will emerge for this sensitive design either. This is completely natural - and not without reason the most frequently read specification. It is up to our diligence and the PCB whether we scratch the theoretical THD beyond the -70dB mark or not.
Even renowned authors and designers, such as Mr. D. Self, make no secret of this fact.
Have fun building it yourself,
I'm looking forward to it - but most enthusiasts would probably prefer 1kW or even better 2kW than just 10 to 20 watts.
kindly,
HBt.