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Old 24th May 2002, 06:12 PM   #11
tiroth is offline tiroth  United States
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The "many regulator" approach is exactly what I am using in my DAC design. Not going nearly as all-out as Hpotter though.

To answer your question, Hpotter, I'm still at the drawing board so I can't really comment on a sonic differences between the regs. Certainly seems like a nice reg though...I'll let you know in a couple of months.
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Old 24th May 2002, 06:28 PM   #12
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Default "Goudreau triplet",

I urge everyone to read this link and try the decoupling stratagy outlined by Pete Goudreau. The guy is super sharp and a have a paper he wrote on digtal decoupling that is one one my references on the subject. While the regulators are important, the bypass caps are doing all the work above a few hundred KHz
The OSCON caps are great for electrolytics with COG ceramic bypass caps for the real high frequency stuff. We are talking currents in 10s of MHz here and a film cap is not going to cut it.

H.H.
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Old 24th May 2002, 07:26 PM   #13
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Quote:
Originally posted by ftorres
WOW!!! Monster design !

Did you use the 1000uF HFQ in input or output of the regs ? Both ? Any ferrite/inductance ?

And did you use toroids for yout transformers? I was told they are too wideband for digital (Noise can pass through, back and forth between xformers)...
I used 1000u HFQ both before and after reg., ferrite beads everywhere. No toroids, split bobbin transformers.

Jocko, I have no idea about those parameters, I thought you might know better.
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Old 24th May 2002, 07:40 PM   #14
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This is how I managed to mount separate reg. for digital part of the DACs. Analog part reg. are on the other side. Did it this way because the board (David Broadhurst DAC) didn't have provision for separate regulators. But the trouble was worth it.
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Old 24th May 2002, 07:56 PM   #15
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Harry makes a good point. All the regulator does is to keep the output voltage at a fixed point. It does so with lots of feedback, which means the impedance goes to pot at around 100 kHz or so.

At frequencies above this, the caps do all the work. Film caps work OK in non-critical applications. But if there is lots of switching transients, you need to switch to SM ceramics. Get those tweezers out.

HPotter:

You are the one who needs to decide how tight the regulation needs to be. With low current draw, and some leeway in regulation, you can use a simple discrete circuit. But you will still need caps. And lots of them.

Jocko
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Old 24th May 2002, 08:34 PM   #16
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That's what I'm talking about. What's better: using IC with tight regulation and maybe 5000u before and 1000u after reg., or using series transistor with zener and 80,000uF around it, somthing like that (check the DAC without oversampling schematic and power supply): http://www.homestead.com/whaan/files/index.html
Again my only concern is the sound and I can only check it in the circuit, but maybe someone already made those comparisons and can share his findings. After all that what this Forum is all about.
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Old 24th May 2002, 08:47 PM   #17
UrSv is offline UrSv  Sweden
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I am a bit unaquainted with ceramics. Why C0G?

/UrSv
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Old 24th May 2002, 10:18 PM   #18
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Talking This is how I managed to mount separate reg

Is that vectorboard in an HPotter construction? You don't have to have C0G caps, X7R will do. SM (surface mount) caps have very low inductance. More digital decoupling data later.

H.H.
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Old 24th May 2002, 10:41 PM   #19
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Default Re: This is how I managed to mount separate reg

[QUOTE]Originally posted by HarryHaller
[B]Is that vectorboard in an HPotter construction?

Yes. This was installed 1 month after listening to DAC. I'm not making PCBs anymore.
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Old 24th May 2002, 11:52 PM   #20
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You can build a simple follower that will have <10 ohms impedance without trouble. Might sound high, but how many times have you seen a circuit with a 10 ohm series resistor to isolate the stages? And what follows it: several caps. The follower should have better reverse isolation.

1000 uF sounds like overkill, especially when you look at the frequency it starts to become inductive. How high of an impedance the design can tolerate is your call.

Have designed commercial digital audio products, and they all had lots of 3-terminal regulators, popular film bypass caps (you know, the ones that make rotten coupling caps.......), all for "oooooo......aaahh!" effect. If anyone was smart enough to look on the underside of the board, there were axial-leaded moulded ceramic caps.

Jocko
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