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RE: not sure what you mean by outside of the chokes

64.13.14.96

In Reply to: RE: not sure what you mean by outside of the chokes posted by Slider on September 21, 2008 at 10:18:52

Sorry for the confusion. I was just thinking that it should be desirable to have a choke isolated common to reduce the power system as a source of crosstalk noise.

Actually I'm now more interested in the differential output capacitors. I can see that they reduce rail to rail noise, but it seems to me that you end up with a rather high supply impedance when trying to drive an unbalanced load. Say you want to deliver some positive current to a load, it looks to me that the energy is going to end up coming from the input capacitor, C5 through the choke and that the output capacitors won't help very much as they go through another choke and have half the value the effective value and ESR that they would have if they were connected to ground. Why do you connect them differentially? For that matter, why use half-wave rectification?

I'm probably missing the point (old age and dry rot?). Are you trying to increase the dynamic impedance to allow more effective local bypassing or something of that nature?

Rick

Follow Ups:

It is a full wave rectifier - Slider 21:36:50 09/21/08 (2)
Standard bridge, just with discrete diodes. You must've not noticed the connections. The supply impedance is mostly determined by the shunt voltage regulators (not shown), but I use the differential connection because it gives me 4x the charge storage for the same amount of capacitance and as I said before, I think it sounds better. Bipolar audio circuits typically flow current between the supplies, not through the ground, which is mostly for the signal. Best to keep the AC currents out of the ground, where possible. Of course, as I mentioned a power amp has to be designed a little different for best results since it is typically supplying power to a ground referenced load, but I was mostly referring to lower power devices like DACs and preamps, which is where the pictured supply is from.
- RE: It is a full wave rectifier - rick_m 08:16:16 09/22/08 (1)
  I did indeed miss the connection... It's an interesting design, something to chew on. Do you shunt regulate each rail to ground?
  
  Rick
  - shunt regulators - Slider 08:36:34 09/22/08 (0)
    Yes, they are ground referenced and do use the ground path for current, which does go against what I just said about AC currents in the ground, but most good sounding audio designs do become a hodgepodge of compromises in the end :)
    
    The regulators are a simple design using an isolated voltage reference, the high voltage I/V and output stage reg using the chokes for the series element, with the 5V D/A convertor reg using an additional series resistor, and also supplies power to the control chip.

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