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Old 2nd January 2012, 03:38 AM   #121
gootee is offline gootee  United States
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Old 2nd January 2012, 10:52 AM   #122
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Quote:
Originally Posted by Duwenbleidd View Post
It's just the same as measuring in loopback. A little example follows - LM317 with Vbe multiplier. Maybe I've made a mistake somewhere, but I have calculated that it shows 5,6uV (at 50Hz)... That doesn't seem quite possible with such a simple design...
Tomáš
ok that makes sense, with no input signal (ie the 1Khz signal) it will just show what is actually there.

5.6uV does seem very low (not so much from a point of view of the circuit, but of what the soundcard can actually resolve!!) I haven't tried to do any calcs yet based on the measurements I did last night, but I see that Arta has calibration facilities, so I assume you can set it up to give absolute values.

edit: I won't probably get the measurements for a few days. It takes quite a lot of setting up to get the noise sources eliminated! possibly tomorrow evening if things aren't too busy the measurements earlier were actually done by recording 10 seconds of the PS using audacity and then analysing in RMAA.

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Last edited by wintermute; 2nd January 2012 at 10:59 AM. Reason: added comment on when I can next do measurements.
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Old 15th April 2015, 04:52 AM   #123
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Would this LM317/LM337 variant of the circuit work? The DAC I'm modding has an R-core transformer with a center-tapped secondary, hence the need for a dedicated negative reg.
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Old 15th April 2015, 12:32 PM   #124
AndrewT is offline AndrewT  Scotland
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No, it doesn't work.

The last 4 tappings to the +ve side Zero volts and the last 4 tappings to the -ve side Zero volts, must all meet at a star point.

You then need to take a single wire to the junction of the smoothing capacitor and from that junction another single wire to the Centre tap of the transformer.

Electrically this layout looks identical to what your sch shows. The difference becomes apparent when you assign values of Impedance to every wire in your sch. The performance will be very inferior and that's why I said it won't work.
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Old 15th April 2015, 01:34 PM   #125
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Thanks for pointing that out, the layout in my schematic is bad in regard to grounding. It was hastily scribbled down during breakfast... I'll hand in a proper version later.
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Old 16th April 2015, 06:58 AM   #126
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And here it is. I think I'll build a prototype over the coming weekend.
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Old 16th April 2015, 10:36 AM   #127
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YES !
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Old 28th December 2016, 06:05 AM   #128
YashN is offline YashN  Canada
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Quote:
Originally Posted by AndrewT View Post
No, it doesn't work.

The last 4 tappings to the +ve side Zero volts and the last 4 tappings to the -ve side Zero volts, must all meet at a star point.

You then need to take a single wire to the junction of the smoothing capacitor and from that junction another single wire to the Centre tap of the transformer.

Electrically this layout looks identical to what your sch shows. The difference becomes apparent when you assign values of Impedance to every wire in your sch. The performance will be very inferior and that's why I said it won't work.
How do we change this if we add a follow-up shunt circuit after it? Let's say an Active Regulator, does the Star Ground point on the right remain the new Star Ground, is there a new one or is there an additional one?
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Old 28th December 2016, 09:15 AM   #129
AndrewT is offline AndrewT  Scotland
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the post126 diagram becomes the Source of power for the next circuit/receiver.
Connect the source to the receiver using a twisted triplet.

Design the receiver circuit to minimise it's own loop areas.

Look carefully at that post126 diagram.
The transformer is connected to the rectifier with a triplet, make it a twisted triplet.
The rectifier is connected to the first smoothing bank with a twisted triplet.
The smoothing bank is connected to the regulator with a twisted triplet.
The regulator output is a twisted triplet.

All the inter module connections are twisted triplets.
That's the effective way to minimise interference.

That's why I said
Quote:
YES !
If you were to try designing a PCB layout to match the performance of the hardwired version, you must take equal care to minimise the interference effect of the loop areas. The traces between the modules must be laid out to minimise the radiation of emi.
That is achieved by placing the flow and return traces adjacent to each other, or one above the other if a multi layer board.
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Last edited by AndrewT; 28th December 2016 at 09:29 AM.
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Old 29th December 2016, 04:21 AM   #130
YashN is offline YashN  Canada
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Quote:
Originally Posted by AndrewT View Post
the post126 diagram becomes the Source of power for the next circuit/receiver.

Connect the source to the receiver using a twisted triplet.

Hey Andrew, how's it going in Scotland?

Thanks for the tips, I think I got it, makes sense.

For the 'twisted triplets', you meant the wires in a P2P build, right?

I did my current prototype with proto board and some wires, I used the components legs as much as possible underneath it.

Will take these tips into account as I was planning to do some PCB during the holidays, nothing fancy, just perhaps some etching.

Looks like the layout sure can cause large variations in the circuit's performance, I think I even read they could "make or break" the performance.

Today I tested some additional small caps on a pair of toggles. I do get more high-range output out of it, but the highs appear quite unnatural and there's a hardness to them, not quite the glare of computer noise USB, but something else.
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