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Built a power supply for my Squeezebox Touch

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Graham Slee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 2019 at 1:49pm
All active regulators are actually amplifiers used for DC purposes in controlling a series pass transistor to give the right voltage, and use negative feedback to constantly monitor for drift and loading errors. As they are able to correct for errors instantaneously and show output impedance up to 1MHz they are ac amplifiers (see page 8 first image http://www.mit.edu/~6.301/LM340.pdf).

They too have phase and gain margins and might not (do not) have the stability an old timer like me would insist on. The result is they ring, but you won't find any mention of it anywhere, save for what one EMC consultant discovered (covered in EMC Techniques for Electronic Engineers by Keith Armstrong).

I remember some Philips application notes from the 90s where a number of fixes are used on regulator outputs without stating any reasons for it. The big giveaway is when using the 79 series which will and does oscillate with the "wrong" capacitor values.

Obviously the output is swamped by the first large electrolytic it encounters but these are inductive at high frequencies allowing any oscillation or ringing to occur. In addition there is wiring or PCB trace inductance in series, so it isn't surprising that experimentation with output capacitor values and types brings different results.

That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 2019 at 8:08am
Yes I agree about burn-in. I wondered if a 'shiny' new parts sound was creating the apparent improvement in clarity so it would be short lived. My changes were intended to reduce interference and they do seem to have helped.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richardl60 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Feb 2019 at 9:20pm
The further improvement sounds a bit like burn in of the caps, cable and the connections getting bedded in Jon?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 11 Feb 2019 at 8:01pm
I am resurrecting this thread with an interesting update about the DIY power supply I built for my Squeezebox Touch. My hearing is back to its 50-something normal state after being extremely bunged up for a couple of weeks. It's taken ear syringing and worse to clear my head and chest, minor illness really but it removed some of the pleasure from listening to music.

Anyway inspired by Graham's link from the 1970's hifi thread to a very fine Dutch speaker design website's capacitor tasting notes, I pulled a 2u2 Monacor crossover capacitor from my spares box and soldered it in place of the 10uF electrolytic on the output of my 5 volt regulator. I appreciate it won't go up to radio frequencies but why not try something different for half an hour's work that can be reversed easily enough? At the same time I fitted a shielded cable (clearly inspired by the Enigma cable) in place of the bell wire I was using before.

I thought the initial improvement I heard was probably new parts but I think it has got better since then. More dynamic and more separation between instruments and keeping the bass depth from before. Perhaps it's silly that such a small change is so easily heard and I wish I had tried it before.

Apologies if this is technical gibberish to most readers and the usual accepting no responsibility if you try this at home.


Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2015 at 8:56pm
Thanks Phil, I think your review of the Majestic influenced me to save for my own and hearing the loan one sealed the deal for me. My Accession phono stage and the Michell 'Gorbe' are dominating my evening listening at the moment. The Touch/Majestic combo is enjoyed in the mornings and it compares very well to top notch vinyl.

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote msphil Quote  Post ReplyReply Direct Link To This Post Posted: 02 Dec 2015 at 4:24pm
I have to agree with you about the Majestic Jon. When I got mine it was like lifting a veil from the music! To anyone that hasn't heard digital music through it don't wait, sell the wife, sell the car and get one! It's a fantastic piece of kit that makes a big, big difference! I was told by a PMC (speakers) representative that it was better than the one they use for demonstration purposes and theirs cost over £10,000! Just to show you how much I think of it I bought two! One for my system in the lounge and one for my headphone set up in the bedroom.
'You are, through your soul not your body, a human being.'
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 29 Nov 2015 at 6:50pm
It's good to hear from you Phil. I posted this after someone else asked about my Touch PSU. Based on my experience replacing the original Logitech PSU I think you will hear an improvement although I found subsequently that plugging my Touch into the Majestic DAC improved the sound a lot.

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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