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Re: MV rect, filter tuning and sound (long)

Posted by lurcher (A) on June 18, 2005 at 11:10:42

In Reply to: MV rect, filter tuning and sound (long) posted by John Swenson on June 17, 2005 at 23:40:43:

What you say matches somrthing I have been thinking about for some time now, The Q and fr for the LC circuit can't help but have a big effect on the sound of the amp, at least if its single ended or class AB/B.

As you say, most common power supplies you meet on the net are often underdamped and have a high resonant frequency. I wonder if some of them sound good "because" of the power supply ringing, and if the ringing its not adding a certain life to the sound. But when the supply is critically damped I believe you have a more integrated sound. I wonder if some times the low frequenct resonance is used (maybe unintentially) to provide some needed bass boost when using smaller output transformers.

I can understand and work out what happens with a single LC circuit, but it gets beyond me when a second stage is added. It should be simple, two LC stages both damped should work together, but every time I try and model it, I either end up with a overdamped supply, or the fr of one stage being a lot higher, so I get ringing, or if the fr of the two stages are the same, then you seem to end up with a almost chaotic system.

I have been trying to consider the LC systems in terms of the enery transfer between the two parts, Energy is transfered from the flux in the choke to the electrostatic charge in the cap and vice versa. But adding the second stage just gives the sytem too many places for energy to go. It can move from the first choke, into the cap, then from the cap, some into the second choke, and the rest into the first choke, while thats going on the energy from the second cap is being transfered into the second choke. And so on.

What I am going to try over the next few weeks (I have a 1300v PSU thats just LC at the moment, 50H into 50u, sounds good, and is just about damped with a Q of about 0.6, but I need a bit more smoothing so I am going to add another LC stage) is a LRLC setup, the R providing a bleeder resistor to maintain the choke input supply above its critical current, but not to produce a LC circuit, Then a LC circuit to supply extra smothing, but that way I haven't got two LC stages to interact. It won't have the level of smoothing that a LCLC would have, but it may have enough for my needs.

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