I am familiar with one reason right off the bat why inductors are not used in SS designs. Note that tube amp PS' still use inductors for linear supplies. The current draw is so very low for tubes....low current, high voltages. SS designs low voltages, high currents. A typical 10H inductor used in a tube PS will "hold" say 800V, but only run at 300mA. This inductor is about fist sized & priced accordingly. Now, how big & expensive do you think a 10H inductor that runs at 200V & 10A would be?? Seek out PSUD from Duncan's Amp Pages for their FREE PS SIM program,...try it out.
Ayre Anyone knows its PSU?
I have an impression that I've read somewhere stating that "LC in PSU provides better regulation than only C or RC.... ", or I read it wrong, or bad memory
The current into the loudspeaker has to change or you will get no sound but it is the amplifier which should change the current into the speaker not the power supply it is quite easy to design a constant current power supply but the amplifier will be go into clipping as soon as the current reaches its design point.As to the term 'DC', I think it's not that simple. The voltage is (or should be) constant, but the current is changing.
You mean constant current from the power supply? A series pass regulator will also be constant current with these amplifiers. Shunt regulators are constant current with any load Shunt regulators are well suited to loads with minimal change in current like the ones you mentioned. Hope that makes sense.The only circuit with constant current is perfectly balanced class A PP, or SE with shunt regulator.
Bad wiring layout, even in the 30's designers knew to use twisted pair for heaters. There is no reason a properly constructed DC heater supply will inject rectification artefacts into the signal. The subject of layout is well covered in circuit design texts Check the layout and grounding yourself against good design practice rather than assuming the designer knew what they were doing or it was assembled properly . A spectrum analyser is your friend here. Even loading up the PSU and going over the wiring with a well insulated inductance loop hooked up to an amplifier can find stray fieldsOften the hum in SE tube amps comes from the heaters, not the B+ supply. Ironically rectifying a DC supply for high current heaters often makes things sound worse, partly I suspect due to the noise from the rectification process itself.
Again poor layout, as for any switching noise from the diode, The diode is looking into the filter capacitor at one end and looking into the leakage inductance of the transformer at the other end, no prizes for guessing which way any high frequency components are going to go and it is not into the filter capacitors. I have never seen any diode switching artifacts on the rails of a 50Hz capacitor input PSU but poor layout will easily put the charging current pulses into the signal path and a choke input filter might fix that but it is really covering up poor design. Also while choke input filters on single phase PSU's have good power factor they have poor load regulation until the inductor has a certain minimum current flowing, with 3 phase power they are much better but ripple is higher until a minimum current is flowing. One other problem with choke input filters is stray magnetic field, because of the large DC component in the choke the core is usually gapped to prevent saturation, the field around this gap is quite strong and capable of inducing hum in nearby circuits, again layout. Magnetic fields near valves may cause strange behaviour and anode hot spots.I think the main advantage of choke input supplies is the suppression of switching artifacts from the rectifiers. This is a big sonic problem with high current C input powersupplies in my opinion. Regulating after a high current C input supply is in some respects like shutting the stable door after the horse has bolted. Yes it will suppress hum, but the uhf noise from the rectifiers will propagate; best to suppress this at source. The current waveform from a choke input supply is very smooth compared to a C input supply.
My understanding of the resonant choke PSU is that it works a bit like the choke input PSU but uses a much smaller choke. It gains voltage stability at the cost of much higher harmonics. This is the wrong trade-off for most audio circuits.