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Thread: Linear vs Switched mode PSU

  1. #171
    Join Date: Mar 2017

    Location: Seaford UK

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    I'm Dennis.

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    I bet an AM radio, using the aerial as a proximity 'probe' (not connecting!) would give an idea of the noise SMPSs chuck out.

  2. #172
    Join Date: Nov 2010

    Location: Sheffield/Peak District. UK

    Posts: 574
    I'm Richard.

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    Ah, at last, an answer to my question of objective measurement of this mains injected noise. An interesting idea. Many thanks.
    Richard.

  3. #173
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    You know it's when I read a thread such as the additions today on here that I get the urge to find a new branch of electronics to make a living from....

    Much of what has been said ranges between nonsense and down right impossible!

    ALL mains power supplies are switching for a start.... SMPS can be quieter than "linear" ones (which are anything but linear unless discussing only a voltage regulator...) in terms of conducted EMI if suitable input filtration, both common mode and differential mode, is used.

    Here's the mains current in the mains lead of a typical "linear" supply (not including magnetising current and obviously not choke input)

    [IMG][/IMG]

    Not nice is it.... current going from zero to the narrow peaks every time the rectifier conducts and "switches", topping up the reservoir capacitor.
    It is also a big factor in explaining why mains leads can't make a difference. For a start the mains is only even "connected" for those brief spikes!

    Linear regulated PSU's are far better than SMPS in terms of noise etc generally but the overall PSRR of the equipment being powered will have far greater influence than whether a linear or SMPS is used. Another factor being overlooked is that a linear voltage regulator can be, and often is, used after a SMPS....

    Like virtually every other engineer I prefer linear PSU's, and for lots of reasons, lower EMI being just one of them, but, correctly used good quality SMPS can give just as good results as a linear. I reckon the bad rep of SMPS comes from when poor SMPS are used with equipment with poor PSRR. In which cases replacing the poor SMPS with a decent linear regulated PSU will indeed give a big improvement! We need to be comparing apples with apples here!

    The PSU of most power amplifiers is an unregulated linear supply and truly awful but you don't hear of people complaining about that! An oscilloscope tells a sorry tale Usually a volt-ish of 100Hz ripple is superimposed on the voltage rails and the voltage will be seen to wander up and down a volt or so as the mains powering it itself does. You can also see the voltage dipping in time with the music due to the poor-ish regulation (lack of "stiffness) of the unregulated supply. So why doesn't it sound awful I hear you ask... Why because the circuit has good PSRR of course!

    For this application a good quality SMPS can be expected to be much better than a linear supply! It hasn't seemed to have hurt Chord who famously have always used SMPS in nearly all their kit from their first product onwards!
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  4. #174
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    Quote Originally Posted by Pharos View Post
    I bet an AM radio, using the aerial as a proximity 'probe' (not connecting!) would give an idea of the noise SMPSs chuck out.
    Spot on. However, this is radiated EMI and it will often not reflect that much on conducted EMI, especially when the SMPS is some distance from the equipment. On decently designed gear there will usually be some filtration where the power enters the equipment as well. I would never use a SMPS actually inside equipment due to the radiated EMI (lots of issues can become conducted EMI if it's in the case as well!). It can be successfully done as Chord and others have shown but it needs very careful design and expensive screening etc.

    On another shoot of from the topic, class D amps are in effect SMPS's and have all the same issues of radiating noise, and potentially putting it back on the mains etc as any SMPS does!
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  5. #175
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,173
    I'm Jez.

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    And another thing... We're gonna have to get used to SMPS because linear supplies are gradually being legislated out of existence. As of about a year ago try getting a linear wallwart. Other than NOS and AC/AC ones you can't! As green legislation on efficiency etc marches on, linear PSU's are slowly being phased out by the bureaucrats... Hi Fi may well prove to be one of its last bastions.. and diy'ers the last of the few.
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

    Modded Thorens TD150, Audio Technica AT-1005 MkII, Technics EPC-300MC, Arkless Hybrid MC phono stage, Arkless passive pre, Arkless 50WPC Class A SS power amp, (or) Arkless modded Leak Stereo 20, Modded Kef Reference 105/3's
    ReVox PR99, Studer B62, Ferrograph Series 7, Tandberg TCD440, Hitachi FT-5500MkI, also FT-5500MkII
    Digital: Yamaha CDR-HD1500 (Digital Swiss army knife-CD recorder, player, hard drive, DAC and ADC in one), PC files via 24/96 sound card and SPDIF, modded Philips CD850, modded Philips CD104, modded DPA Little Bit DAC. Sennheiser HD580 cans with Arkless Headphone amp.
    Cables- free interconnects that come with CD players, mains leads from B&Q, dead kettles etc, extension leads from Tesco

  6. #176
    Join Date: Jan 2015

    Location: Leeds

    Posts: 164
    I'm Dave.

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    Quote Originally Posted by Arkless Electronics View Post
    You know it's when I read a thread such as the additions today on here that I get the urge to find a new branch of electronics to make a living from....

    [IMG][/IMG]

    Not nice is it.... current going from zero to the narrow peaks every time the rectifier conducts and "switches", topping up the reservoir capacitor.
    It is also a big factor in explaining why mains leads can't make a difference. For a start the mains is only even "connected" for those brief spikes!
    On the 1st point - go ahead, feel free

    On the second point:
    One possible benefit of the linear is that there are only 100 times a second when the PS has the opportunity to generate noise. A typical SMPS is generating noise 1000 times more often. HF conducted and radiated noise is much harder to deal with than lf noise.

  7. #177
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 110,012
    I'm AudioAl'sArbiterForPISHANTO.

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    Quote Originally Posted by Arkless Electronics View Post
    You know it's when I read a thread such as the additions today on here that I get the urge to find a new branch of electronics to make a living from....

    Much of what has been said ranges between nonsense and down right impossible!
    Well, no need to act like a grumpy old man - educate us on the 'errors of our ways', but don't necessarily expect us always to agree!

    ALL mains power supplies are switching for a start.... SMPS can be quieter than "linear" ones...
    Ah ok, the first bit I didn't know, and the second bit is interesting, however...

    Linear regulated PSU's are far better than SMPS in terms of noise etc generally...
    So, are you saying that linear PSUs are far better than SMPS, as long as they're regulated, but if they're not, they're crap, and potentially worse than SMPS? Also, in terms of your previous statement, in what circumstances can SMPS be quieter? Is it if the linear PSU in question isn't regulated?

    ..but the overall PSRR of the equipment being powered will have far greater influence than whether a linear or SMPS is used.
    I've noticed this "PSRR" term being mentioned a lot. What does it mean (how is it applied to a circuit), what are its advantages, and what relevance does it have, in terms of the 'linear vs SMPS' argument?

    Like virtually every other engineer I prefer linear PSU's, and for lots of reasons, lower EMI being just one of them, but, correctly used good quality SMPS can give just as good results as a linear.
    Yes I get that. However, say, you have two PSUs, one a regulated linear and the other SMPS, both of identical quality and technical prowess, wouldn't the former, by virtue of its lower EMI, pollute the mains less being shared by the rest of the system components?

    If so, then it makes sense for a quality regulated PSU to be used in all critical hi-fi applications. For me, when all else is equal, the lower noise/interference factor would always make a quality regulated linear PSU worth having in any piece of hi-fi equipment.

    I reckon the bad rep of SMPS comes from when poor SMPS are used with equipment with poor PSRR. In which cases replacing the poor SMPS with a decent linear regulated PSU will indeed give a big improvement! We need to be comparing apples with apples here!
    Indeed, but that doesn't seem to stop equipment with presumably good PSRR (such as the components in my system, all of which have been built by highly qualified EEs), being similarly affected, as I can clearly hear the sonically deleterious effect of plugging an SMPS-powered component into the same mains distribution block, which always deteriorates the sound - and I'm not imagining it either!

    The PSU of most power amplifiers is an unregulated linear supply and truly awful but you don't hear of people complaining about that!
    Perhaps because they hadn't thought of it before, thus done anything about it? That might change, however, now that you've mentioned it!

    For this application a good quality SMPS can be expected to be much better than a linear supply! It hasn't seemed to have hurt Chord who famously have always used SMPS in nearly all their kit from their first product onwards!
    Lol.. Well, maybe that's why I've always found Chord amps to sound rather bland and sterile!

    I think given what you've said, I'm more of a mind ever now that, if you really want the best in critical applications, then use a top-notch regulated linear PSU. Anything else is really a compromise

    Marco.
    Main System

    Turntable: Heavily-modified Technics SL-1210MK5G [Mike New bearing/ETP platter/Paul Hynes SR7 PSU & reg mods]. Funk Firm APM Achromat/Nagaoka GL-601 Crystal Record Weight/Isonoe feet & boots/Ortofon RS-212D/Denon DL-103GL in Denon PCL-300 headshell with Funk Firm Houdini/Kondo SL-115 pure-silver cartridge leads.

    Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.

    Other Cartridges: Nippon Columbia (NOS 1987) Denon DL-103. USA-made Shure SC35C with NOS stylus. Goldring G820 with NOS stylus. Shure M55E with NOS stylus.

    CD Player: Audiocom-modified Sony X-777ES/DAS-R1 DAC.

    Tape Deck: Tandberg TCD 310, fully restored and recalibrated as new, by RDE, plus upgraded with heads from the TCD-420a. Also with matching TM4 Norway microphones.

    Preamps: Heavily-modified Croft Charisma-X. LDR Stereo Coffee. Power Amps: Tube Distinctions Copper Amp fitted with Tungsol KT-150s. Quad 306.

    Cables & Sundries: Mark Grant HDX1 interconnects and digital coaxial cable, plus Mark Grant 6mm UP-LCOFC Van Damme speaker cable. MCRU 'Ultimate' mains leads. Lehmann clone headphone amp with vintage Koss PRO-4AAA headphones.

    Tube Distinctions digital noise filter. VPI HW16.5 record cleaning machine.

    Speakers: Tannoy 15MGs in Lockwood cabinets with modified crossovers. 1967 Celestion Ditton 15.


    Protect your HUMAN RIGHTS and REFUSE ANY *MANDATORY* VACCINE FOR COVID-19!

    Also **SAY NO** to unjust 'vaccine passports' or certificates, which are totally incompatible with a FREE society!!!


  8. #178
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 110,012
    I'm AudioAl'sArbiterForPISHANTO.

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    Quote Originally Posted by Arkless Electronics View Post
    And another thing... We're gonna have to get used to SMPS because linear supplies are gradually being legislated out of existence.
    That may apply if you buy brand new commercially produced equipment from mainstream manufacturers, but not for those of us who don't... Somehow, I can't see the 'Linear Police' coming to arrest me, if one of my many DIY friends, who builds equipment from home, makes a 'non-compliant' PSU for my hi-fi!

    Marco.
    Main System

    Turntable: Heavily-modified Technics SL-1210MK5G [Mike New bearing/ETP platter/Paul Hynes SR7 PSU & reg mods]. Funk Firm APM Achromat/Nagaoka GL-601 Crystal Record Weight/Isonoe feet & boots/Ortofon RS-212D/Denon DL-103GL in Denon PCL-300 headshell with Funk Firm Houdini/Kondo SL-115 pure-silver cartridge leads.

    Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.

    Other Cartridges: Nippon Columbia (NOS 1987) Denon DL-103. USA-made Shure SC35C with NOS stylus. Goldring G820 with NOS stylus. Shure M55E with NOS stylus.

    CD Player: Audiocom-modified Sony X-777ES/DAS-R1 DAC.

    Tape Deck: Tandberg TCD 310, fully restored and recalibrated as new, by RDE, plus upgraded with heads from the TCD-420a. Also with matching TM4 Norway microphones.

    Preamps: Heavily-modified Croft Charisma-X. LDR Stereo Coffee. Power Amps: Tube Distinctions Copper Amp fitted with Tungsol KT-150s. Quad 306.

    Cables & Sundries: Mark Grant HDX1 interconnects and digital coaxial cable, plus Mark Grant 6mm UP-LCOFC Van Damme speaker cable. MCRU 'Ultimate' mains leads. Lehmann clone headphone amp with vintage Koss PRO-4AAA headphones.

    Tube Distinctions digital noise filter. VPI HW16.5 record cleaning machine.

    Speakers: Tannoy 15MGs in Lockwood cabinets with modified crossovers. 1967 Celestion Ditton 15.


    Protect your HUMAN RIGHTS and REFUSE ANY *MANDATORY* VACCINE FOR COVID-19!

    Also **SAY NO** to unjust 'vaccine passports' or certificates, which are totally incompatible with a FREE society!!!


  9. #179
    Join Date: Mar 2017

    Location: Seaford UK

    Posts: 1,861
    I'm Dennis.

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    A few points.

    I have not studied electronics formally since '79 and so SMPSs are a more recent development and I have had no tuition on them.

    My impression is that they were developed for economic reasons, the cost of transformers, big capacitors, and a very long time ago even series inductors becoming high, and also making large the size of the PS.

    If this is the case then that philosophical stance may also be taken to the extreme and cheap design and components used.

    Instinctually I dislike the idea of RF being generated as a by product of any design, unless it is intended, and this is to me very undesirable.

    I was concerned about my speakers, using ICEpower suffering as a result of this design, but B&O has a very good reputation.

  10. #180
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 110,012
    I'm AudioAl'sArbiterForPISHANTO.

    Default

    Quote Originally Posted by Pharos View Post
    My impression is that they were developed for economic reasons, the cost of transformers, big capacitors, and a very long time ago even series inductors becoming high, and also making large the size of the PS.
    That's my impression, too: they're a compromise, created for convenience and economic reasons, unfortunately like so many other things in today's cost-first, quality second, society.

    I also get the impression that some EEs/audio designers know full well that's the case, but because they also know that they have to comply with regulations and all legal requirements, pertaining to the designing and building of audio equipment, they feel that they have to 'talk up' SMPS and try and deflect attention from its negatives, so as not to lose sales!

    Furthermore, for me, the PSRR argument smacks somewhat of 'locking the stable door after the horse has bolted'. Surely it's better not to create a problem (EMI/RF noise generation) in the first place, than trying to address it later in the design of equipment?

    I've never been one for applying a bandage, to try and cure a problem - far better not to create the problem in the first place!!

    Marco.
    Main System

    Turntable: Heavily-modified Technics SL-1210MK5G [Mike New bearing/ETP platter/Paul Hynes SR7 PSU & reg mods]. Funk Firm APM Achromat/Nagaoka GL-601 Crystal Record Weight/Isonoe feet & boots/Ortofon RS-212D/Denon DL-103GL in Denon PCL-300 headshell with Funk Firm Houdini/Kondo SL-115 pure-silver cartridge leads.

    Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.

    Other Cartridges: Nippon Columbia (NOS 1987) Denon DL-103. USA-made Shure SC35C with NOS stylus. Goldring G820 with NOS stylus. Shure M55E with NOS stylus.

    CD Player: Audiocom-modified Sony X-777ES/DAS-R1 DAC.

    Tape Deck: Tandberg TCD 310, fully restored and recalibrated as new, by RDE, plus upgraded with heads from the TCD-420a. Also with matching TM4 Norway microphones.

    Preamps: Heavily-modified Croft Charisma-X. LDR Stereo Coffee. Power Amps: Tube Distinctions Copper Amp fitted with Tungsol KT-150s. Quad 306.

    Cables & Sundries: Mark Grant HDX1 interconnects and digital coaxial cable, plus Mark Grant 6mm UP-LCOFC Van Damme speaker cable. MCRU 'Ultimate' mains leads. Lehmann clone headphone amp with vintage Koss PRO-4AAA headphones.

    Tube Distinctions digital noise filter. VPI HW16.5 record cleaning machine.

    Speakers: Tannoy 15MGs in Lockwood cabinets with modified crossovers. 1967 Celestion Ditton 15.


    Protect your HUMAN RIGHTS and REFUSE ANY *MANDATORY* VACCINE FOR COVID-19!

    Also **SAY NO** to unjust 'vaccine passports' or certificates, which are totally incompatible with a FREE society!!!


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