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In Reply to: RE: what do you look for in the graphs? posted by Tre' on May 28, 2017 at 19:29:14
A single L-C filter when handed a step-change in current draw is going to ring a bit. I think that the OP was looking for a realistic means to model the amplifier circuit. Not that the step change in current is not useful, but it has limitations. For example, when run w/o a turn on delay, the difference between a resistive load and a constant current one is about 100V on the initial peak.
I am fairly confident in saying that an L-C filter, when given enough capacitance will work quite well. I'd further the Class A bit, with the addition that a PP Class A is going to vary its draw from the PS hardly at all compared to an SE one. The SE being roughly constant when averaged over a complete cycle vs. nearly constant at any given part of it.
When adding a second L-C stage, the step change in current test can be quite useful. I recall a linestage PS I built( and then Sim'd ) that rang at about a half a Hz...nearly no ripple though...LOL
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
"I am fairly confident in saying that an L-C filter, when given enough capacitance will work quite well."
That's absolutely true. But then there are the designers who claim too much capacitance ruins the sound. Other designers prefer oil caps or other non-electrolytic types, often not available in larger values. Given all these variables and self-imposed limitations, there's no substitute for analyzing potential PS filters with SPICE.
--------------------------
Buy Chinese. Bury freedom.
"But then there are the designers who claim too much capacitance ruins the sound."
Presumably such designers are finding that they prefer the sound they get when they effectively introduce a tone control by means of limiting the low-frequency response of the amplifier, achieved by causing the power-supply impedance to become non-negligible at low frequencies. That is fine, if that is the sound colouration that they like. But there must surely be better ways of introducing a tone control for the amplifier than this.
I have nothing against tone controls, but I would think it is better to use a well-designed device with convenient adjustments available for personal taste, rather than a fixed low-frequency fall-off whose slope might, or might not, be to the individual listener's liking.
Chris
"there's no substitute for analyzing potential PS filters with SPICE."Agreed. I've never used PSUD2, but from what I've gleaned, it doesn't sound to be particularly appropriate for trying to optimise the performance of a power supply for an amplifier. As Tre says, the kind of time dependent load that a class A amplifier imposes on a power supply is not the kind that can be particularly well analysed if the only time-dependent thing one can model in the power supply software is the effect of a stepped load. LTSpice is really much more versatile for the kind of modelling that will realistically show the behaviour of the power supply when the amplifier is playing music. I don't see the point of trying to use PSUD2 for this kind of application.
Chris
Edits: 05/30/17
It is fairly easy and since i am usually using second hand transformers, i can run lots of different values of the different trans i have on hand and get close to the circuit specs.
When one ov those 'designers' can point to something sound as to why, I may just pay some attention. I suppose if the PS is playing with the rest of the SE tone machine, it may be possible...:)
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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