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Regs - Shunt vs Series
Regs - Shunt vs Series
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Old 14th December 2012, 10:38 AM   #11
dahlberg is offline dahlberg  Sweden
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Quote:
Originally Posted by qusp View Post
dahlberg: it depends whether you are talking about
powering a digital section, or the analogue or clock sections of a dac, the
digital sections can easily have large, rapidly changing transients.

honestly, as i've so often posted around these threads, its the decoupling
caps that will handle the transients, there is something wrong with your
design if you are expecting the external (and often remote) regulator to do that.

why is this in the Solid State amplifier section?
So the need for a shuntregulator would be more relevant in the digital
domain, that's interesting.
When you say that the decoupling caps are responsible for the transient
response you mean quality of components and combination of different types ?
I will be replacing the XR5's for Panasonic SP polymers on the tps7a, after a few
of your comments (and reading up on specs) about them.
If that would make any real difference I don't know yet but it's fun trying

Yes, it seems to be in the wrong section.
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Old 14th December 2012, 11:44 AM   #12
qusp is offline qusp  Australia
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well its not so cut and dried. shunt regs have nice low noise too, a much more relevant attribute for the analogue sections (which includes the clock). no regulator of any type will take care of the transients at these speeds, that is what the caps are there for. the regulators are there to keep the charge up to the caps, the caps have the last word.... visualize the circuit and its really not that hard.

also with many applications the absolute voltage isnt that important because the job at hand doesnt require voltage so close to the rails, nor should it.

I never made any such recommendation, replacing XR5 with polymers would pretty likely be a bad idea; my guess is they are quite local and small in value, in which case it would be better to leave them, or replace with X7R, depends on the circuit.

it seems a very hard point to get across, so many seem to attribute high frequency transient response to something a remote regulator can help with, somehow thinking remote sensing and low output impedance makes all the effects of the distance invisible.... instead of simply making the effects of voltage drop over the resistance caused by the distance invisible

Last edited by qusp; 14th December 2012 at 11:49 AM.
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Old 14th December 2012, 11:46 AM   #13
regal is offline regal  United States
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Quote:
Originally Posted by qusp View Post
dahlberg: it depends whether you are talking about powering a digital section, or the analogue or clock sections of a dac, the digital sections can easily have large, rapidly changing transients.

honestly, as i've so often posted around these threads, its the decoupling caps that will handle the transients, there is something wrong with your design if you are expecting the external (and often remote) regulator to do that.

why is this in the Solid State amplifier section?
The issues with amps/preamps and dac's are similar enough and I think this is the only "power supply section." Really everything we deal with is an amplifier of some sort.


As far as the decoupling caps handling the transients, my problem may be unique and may not be. But my mains oscillate at a very low subsonic frequency. I calculated it at something like .01 hz, this is tough to filter. And even though it is technically AC, it appears as to DC offset drift as no one filters to such a low frequency. Probably a unique situation to my utility company but I encourage anyone to hook up a multimeter to their wall and record the voltage swing over the course of several minutes.
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Old 14th December 2012, 12:21 PM   #14
dahlberg is offline dahlberg  Sweden
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Quote:
Originally Posted by qusp View Post
well its not so cut and dried. shunt regs have nice low noise too, a much more relevant attribute for the analogue sections (which includes the clock). no regulator of any type will take care of the transients at these speeds, that is what the caps are there for. the regulators are there to keep the charge up to the caps, the caps have the last word.... visualize the circuit and its really not that hard.

also with many applications the absolute voltage isnt that important because the job at hand doesnt require voltage so close to the rails, nor should it.

I never made any such recommendation, replacing XR5 with polymers would pretty likely be a bad idea; my guess is they are quite local and small in value, in which case it would be better to leave them, or replace with X7R, depends on the circuit.

it seems a very hard point to get across, so many seem to attribute high frequency transient response to something a remote regulator can help with, somehow thinking remote sensing and low output impedance makes all the effects of the distance invisible.... instead of simply making the effects of voltage drop over the resistance caused by the distance invisible
What numbers of rms noise are we talking about for these shuntregulators? The tps7a is at 4,5uV 10-100khz.
Your'e right that you have made no such recomendation, I just read that you liked the Polymers in general
(use them wherever possible as I rembember it) and that they have very good specs.

This is the shematics of the circuit, all capasitors are X5R-10% (C1 20%).

Click the image to open in full size.
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Old 14th December 2012, 12:38 PM   #15
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by qusp View Post
.................... replacing XR5 with polymers would pretty likely be a bad idea;
I agree, ceramics are excellent as local decoupling. I believe they can't be bettered.
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Old 14th December 2012, 12:43 PM   #16
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by regal View Post
..................my problem may be unique and may not be. But my mains oscillate at a very low subsonic frequency. I calculated it at something like .01 hz, this is tough to filter. And even though it is technically AC, it appears as to DC offset drift as no one filters to such a low frequency. Probably a unique situation to my utility company ........
Mains frequency changes. Every mains frequency changes.
Your situation is not unique. It is NORMAL.

Changing the frequency of the mains by +-x% will not cause DC voltage drift after a properly designed PSU.

Every mains supply changes voltage. This change of +-y% will cause a DC drift in output voltage of a well designed PSU. Read the spec sheet, they will actually give a figure for Vout:Vin variation.
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Old 14th December 2012, 01:13 PM   #17
Ken Newton is offline Ken Newton  United States
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One unique advantage of shunt reg. is that it prevents the circuit being powered from dynamically loading the supply, consequently removing A.C. currents from the ground return paths.
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Old 14th December 2012, 01:30 PM   #18
qusp is offline qusp  Australia
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dahlberg:

ahh well if you are speaking of the reg above thats not local decoupling, so it really will depend on your load if you need to replace some, or all of them with polymers. leaving them ceramics will have better transient response at HF, at the cost of lower filtering ability and less storage. replacing with polymers will allow better storage and better filtering.

since afaik you are just driving another regulator with these regs, I really dont know why you are wasting so much time on it

a good shunt reg will be in the nV/Hz range, not ÁV/Hz, but the same noise performance can be given by discrete series regs also

this is one of those times where the amount of different opinions offered on the forum is a disadvantage to those starting out. These statements on many and varied applications are given or taken generally as sweeping statements. this vast information resource paralyzes those reading and researching, attempting to make ALL the right decisions off the bat, without any application.... that simply cannot ever happen, there will always be changes and even those skilled in the art with many builds under their belt realize that there comes a point you just need to make a start; that is my recommendation for you.

Last edited by qusp; 14th December 2012 at 01:57 PM.
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Old 14th December 2012, 01:45 PM   #19
Telstar is offline Telstar  Italy
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Being in solid state amps, I presume that the OP is referring to a regulated PSU to power a power amp.
It's needed to specify whether being a class A or class AB circuit and the required current and tension required. Most shunt designs have limits. See the discussion on the salas shunt and on other versions inspired by it.

Commercial more or less DIY regulators have been used, most often only for the frontend circuits (IPS and VAS), but for a low-power class A amplifier I think that a well dimensioned regulated PSU is also a better option for the output stage.
Whether series or shunt, i really dont know, usually a mix of both is required for best performance.
See for instance the excellent sigma22 that I use in all my headphone amps.
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Old 14th December 2012, 02:08 PM   #20
dahlberg is offline dahlberg  Sweden
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Quote:
Originally Posted by qusp View Post
dahlberg:

ahh well if you are speaking of the reg above thats not local decoupling, so it really will depend on your load if you need to replace some, or all of them with polymers. leaving them ceramics will have better transient response at HF, at the cost of lower filtering ability and less storage. replacing with polymers will allow better storage and better filtering, but since you are driving another regulator its really not worth spending so much effort on.

since afaik you are just driving another regulator with these regs, I really dont know why you are wasting so much time on it

a good shunt reg will be in the nV/Hz range, not ÁV/Hz

this is one of those times where the amount of different opinions offered on the forum is a disadvantage. These statements on many and varied applications are given or taken generally as sweeping statements. this vast information resource paralyzes those reading and researching, attempting to make ALL the right decisions off the bat, without any application.... that simply cannot ever happen, there will always be changes and even those skilled in the art with many builds under their belt realize that there comes a point you just need to make a start; that is my recommendation for you.
So if I'm reading this right you are saying that using a shunt closest to the load and
using a series (or another shunt?) regulator as preregulation would be the prefered solution.

I can't say that I have ever read that cheramic capasitors are superior regarding soundquality,
I have read the opposite a few times though. That's why I'm trying Polymers (Panasonic SP's).

Why I'm bothering with the preregulator ?
I'm not aiming for "good enough" in the sense that I think that a 40uf "Duelund vsf cu" is
justified in the passive filter I'm using now, "Obbligato Gold premium" sounded like crap in
comparison, nothing bad actually said about those capasitors they are actually quite good
for there pricerange (Im setting up a dsp xo, for those of you not informed).

I will of cource try different setups, just trying to save a little time sorting out what's preffered first.
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