Hi all,
I'm building a choke power supply to provide a very low impedance unregulated supply to my DAC. It has all local shunt regs on board and listening tests have shown that it really thrives on a good low impedance supply.
I've had a basic version of this thrown together in a test box for a while now, but want to put it together properly following best practice and introduce some snubbing to get rid of emi from the transformer.
Chokes are llundahl ll1694 and I'm currently using an r-core Transformer.
Here's a pic of most of the bits. Ignore the wiring here for now
The 56r resistor is a bleeder to pull enough current through the first choke to put it in its happy working zone. The load from the DAC is roughly 0.3A and I'm currently simulating load that with a 47r resistor.
The 220n caps back to back across the chokes is a suggestion from the Morgan Jones valve amps book
I'd welcome help with the physical layout of the wires and grounding as well as any pointers or recommendations on any of the other bits you see.
Here's a rough layout sketch with a first draft of star grounding (excuse the mishmash of symbols). Does that look anywhere near right?
Should I be taking my gnd to the DAC from the final cap instead?
Thanks,
James
I'm building a choke power supply to provide a very low impedance unregulated supply to my DAC. It has all local shunt regs on board and listening tests have shown that it really thrives on a good low impedance supply.
I've had a basic version of this thrown together in a test box for a while now, but want to put it together properly following best practice and introduce some snubbing to get rid of emi from the transformer.
Chokes are llundahl ll1694 and I'm currently using an r-core Transformer.
Here's a pic of most of the bits. Ignore the wiring here for now
An externally hosted image should be here but it was not working when we last tested it.
The 56r resistor is a bleeder to pull enough current through the first choke to put it in its happy working zone. The load from the DAC is roughly 0.3A and I'm currently simulating load that with a 47r resistor.
The 220n caps back to back across the chokes is a suggestion from the Morgan Jones valve amps book
An externally hosted image should be here but it was not working when we last tested it.
I'd welcome help with the physical layout of the wires and grounding as well as any pointers or recommendations on any of the other bits you see.
Here's a rough layout sketch with a first draft of star grounding (excuse the mishmash of symbols). Does that look anywhere near right?
Should I be taking my gnd to the DAC from the final cap instead?
An externally hosted image should be here but it was not working when we last tested it.
Thanks,
James
1.) Use a bridge rectifier (the one with the four diodes)! A bridge rectifier doubles the ripple frequency (100 Hz instead of 50 HZ) and the ripple filter is easier to design. 2.) Additionally to the LC, use a simple standard Regulator in front of your DAC.... this will reduce the ripple and the impedance more than a LC filter.
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Thanks, but this is already full wave with double the mains frequency. It suits me well as I already have the centre tapped transformer and less diodes to make noise is preferable for me.
Mains ripple is no problem here. It's nice and steady at the DAC and the local shunt regs take care of the accurate regulation nicely.
Cheers,
James
Don't put all the cap negatives to one star ground. Use one 'dirty' star before the second choke, and one 'clean' star after the second choke. This keeps charging pulses out of your audio ground.
I agree.
Separating the charging currents from the load currents is very important.
A common "star" defeats this necessary separation.
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