Babo Tries New Voltage Regulator for F5

[audiorob]

It looks like I was mistaken and assumed the bias was 2.6A.
If the F5 is biased to 1.3A then the maximum ClassA current is ~2.5Apk not ~5Apk.

The maximum transient current is very much music and speaker dependent. It can approach [Vpk / Speaker nominal impedance / factor].
A moderate speaker load can have a factor of 0.4 to 0.3
A severe speaker load can have a factor 0.3 to 0.2

This indicates that the worst case (music) transient peak currents can be up to 5times higher than what the nominal impedance would predict.
25Vpk / 8ohm / 0.32 predicts ~ <=10Apk for short term transients.
The F5 will deliver this by going into ClassAB mode.

With a 4ohm or 2ohm speaker connected, many of the high SPL transients will make the F5 go into the AB mode. The 8ohm ohm load will do this much less often.

I dunno Andrew. This might be where we (respectfully) disagree. Or maybe I
have misunderstood what you are trying to say.

What is the source of energy for your "factor" term?

I would agree that the impedance curve for some speakers can take dramatic
dips at certain frequencies. The low resistance at these frequencies would
cause peaks in current when the F5 tries to reproduce that frequency. This is
all consistent with Ohm's law. Aside from some negligible reactant components,
I have some trouble understanding something beyond that.

Bringing this back to the regulated vs unregulated topic, I can see that for an
unregulated supply, powering something like a class B amplifier, that there
could be some peak voltage (and current) due to differences in the transformer
secondary voltage when unloaded vs loaded (ie: the amplifier is on, but working
at low voltage levels, then it gets a relatively big signal for a short term, driving
output voltages higher than they can normally sustain). But I think this affect is
minimized in high current class A amplifiers because the transformer is always
under a load. This is my guess, I could be very wrong.

But the last paragraph, including wall voltage fluctuations, are all supporting
arguments _for_ regulated power supplies, as these voltage fluctuations do
wierd things to the bias, dc offset, heat, and so on. I would tihnk that a regulated
supply should minimize those fluctuations.

These are just my opinions. I can't prove any of it. I hope they made sense.

thanks,
Robert

 

[Luke]

Andrew,

are you arguing that the cost of extra power dissipation is not worth any possible gains made by regulating supplies?

 

[Babowana]

Andrew has said: "a voltage regulator feeding a Class A power amplifier is a waste of resources.""--post#63
And, "Yes, there are probably some benefts, but . . ."--post#77

Then, I'm totally lost myself . . . He is trying to prove "the benefits or not" or something only based on his complicated calculations . . .

Meanwhile, he is very eager to get a good shunt regulator, which is the worst efficient regulator, for his Class A pre amplifer. In our schools, we call this a "contradiction".

I'm not blaming Andrew . . . I just feel strange . . .

I look forward to his response to your question, Luke.

 

[AndrewT]

he is very eager to get a good shunt regulator, which is the worst efficient regulator, for his Class A pre amplifer.

regulated power for ClassA and ClassAB power amps is a completely different argument from regulated power for pre-amps voltage stages inside a power amp, opamps and all the other low current stages that show significant benefits from excluding the artefacts that a power amp imposes on the supply rails.

The calculation was to explain why <5% was erroneous.
The calculations have nothing to do with whether you think they are a complicated way to prove "something"

 

[AndrewT]

are you arguing that the cost of extra power dissipation is not worth any possible gains made by regulating supplies?

Indeed not.

I am very much a value for money spendthrift.
What can be achieved for a budget?

Regulating the power supply of a ClassA power amplifier is a waste of resources.

I am convinced that those who want and have the wherewithall to spend on that type of solution will do so whether I am on their side or not.

I think the money could be spent in other ways to improve the system or your lifestyle or support all the underprivileged kids on the block. You choose, as I can't choose for you.

 

[Babowana]

regulated power for ClassA and ClassAB power amps is a completely different argument from regulated power for pre-amps voltage stages inside a power amp, opamps and all the other low current stages that show significant benefits from excluding the artefacts that a power amp imposes on the supply rails.

So, what kind of benefits you gain by using the worst efficient shunt regulator for your Class A pre amplifier? What kind of value makes you feel not waste your money? I'd like to learn from you.

 

[AndrewT]

I'd like to learn from you.

I don't believe you mean what you have written.

 

[Babowana]

Andrew,

Believe me and give me your advice on my questions in post86.
I will not return you any talk on your advice at all . . . Will just listen . . .

Now I have to go to Queen's bed . . .