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In Reply to: RE: How do you represent your tubes in PSUD2? posted by DAK on May 28, 2017 at 12:24:13
What I look at most is once I have the proper voltage and ripple within what I set as targets, I use the stepped load option. I always set my load as a CCS, as that is what I usually use as a load, (that is of course optional). Then with the stepped load, I can see how fast my power supply can respond to variations of current demand. Remember CCSs aren't perfect and there is always some variation in demand, even more so with other loads, so chose your stepped demand carefully. To me, the response to variations of time/current are key.
I can use various values of caps, chokes, resistance, number of sections, as well as choke or cap input, to effect the speed of power delivery (while of course keeping voltage and ripple requirements within limits). I try and get the quickest response from my supply, while staying within the voltage/ripple criteria that I want.
twystd
Follow Ups:
"I try and get the quickest response from my supply"Why?
The quickest response means the quickest voltage change due to current draw change.
Wouldn't the slowest voltage change due to current draw change represent better voltage regulation?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/29/17
The amount of voltage sag remains the same, so regulation is the same. The power supply is just quicker to stabilize to changing demands of current.
twystd
"The amount of voltage sag remains the same, so regulation is the same."We might be talking about two different things but I don't think the above is true. I am talking about a supply that Dennis Fraker would use.
A supply filter built to take longer to "stabilize" after a current draw change will be less regulated if the current draw increase (or decrease) is sustained. The chokes will be bigger with more DCR and the caps would be bigger.
If the supply is operating a Class A circuit then the only thing that will cause the current to increase or decrease from the idle current is the music.
BTW the current will never increase (or decrease) instantaneously as it does with the "stepped response" feature in PSUD2. It will, instead, follow the music and it will take time for the current to increase and decrease.
The longest duration the current will increase (or decrease) due to the music is 12.5ms ( 1/4 of a 20Hz wave cycle) before it heads the other way.
If you look real close to a supply designed to stabilize quickly vs a traditional power supply I think you will find that in the first 12.5ms the traditional (slow) supply dips (or soars) less.
Looking a sims of each, the "fast" supply dips 2 volts in the first 12.5ms and the traditional (slow) supply dips only .27 volts in the first 12.5ms
(I admit the two supplies are different, one is a 464 volt supply and the other is 530 volts but I think my conclusion is valid)
Now if the current increase were sustained the traditional supply dips 4.5 volts and the fast supply dips only 2.75 volts for a current increase from 60ma to 70ma. but Class A amplifiers playing music don't do that.
As I said, we might be talking about two different things.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/30/17
No, I'm definitely not talking about a supply Dennis Fraker would use. I usually use choke input critical inductance filters. I'm too tired to model and show you what I'm talking about. Maybe later....
twystd
I re-model my critical inductance choke input supply and just by lowering the last cap to 50uf the voltage dip in the first 12.5ms is 2 volts (and of course the ripple is up) and the total drop is still 4.5 volts because the DCR didn't change.
I believe that's in keeping with what you said.
So I conclude it's all about storage. The bigger the last cap the more voltage is stored and the longer it takes for that voltage to drop due to a change is current draw. The supply has a lower impedance.
When the current draw increase is sustained long enough then the voltage eventually drops in accordance with the DCR of the rest of the supply.
The DCR of the supply vs. the impedance of the supply.
I conclude that designing for a fast settling time is designing for a high impedance supply.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I tried a few PSUD runs, and the more capacitance there is on the south end of a northbound LC supply the smaller the drop, the smaller the rise and lower is the ripple.
For PP, Class A, I have yet to see where this sounds worse than a liddle capacitor, ripply supply.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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