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norman

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About norman

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  • Birthday December 31

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    canberra
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    Australia

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  1. So, As I was away for the weekend I only got to try my first attempt linear power supply tonight. No magic smoke in evidence, so that was a good start. The hiss noise is lower than from the wall wart, however there is a hum, probably 50 Hz that isn't there with the wall wart. I can fuss about with shielding with my existing build, or jump in and just build the circuit that Stereo Coffee has provided, so I think that is the direction I will go. Incoming PM Stereo!
  2. Hi Andy. I suggested using inexpensive bits in order to try out the use of various loadings. If they font improve things then you have limited your loss. Obviously if you like the sound you then use quality parts. I personally use Neutrik Rean RCA plugs as I can source them easily where I live.
  3. Hi Andy, yes I understand I've been doing this too, works well. I liked 32k. on my Ortonon 2M Blue. If you use Jaycar bits to try it out , the 2 in 1 out gold plated RCA adapters are under $6 each, the RCA plugs are $1, and 10 resistors of each value cost under $1. A great mod for $15...
  4. I've been doing this too, works well. I liked 32k. on my Ortonon 2M Blue. If you use Jaycar bits to try it out , the 2 in 1 out gold plated RCA adapters are under $6 each, the RCA plugs are $1, and 10 resistors of each value cost under $1. A great mod for $15...
  5. Such fantastic help! Thanks for the pointer on the optional bit (U3) in the diagram, I doubt I would have worked that out! Are you located in NZ? Or in Australia? Your build offer is very kind, I will see how I go with struggling with a board layout before I take up your kind offer. Saying that, I bet that I will be asking you soon enough 🙂 If I go for 150 mA as the power demand, do I need to use a heat sink? I am assuming my existing transformer can be re-used? It provides a +12 v and 0 v taps, or would I be better replacing it with a center tapped +6.3 v / 0 v / -6.3 volt unit? I have already checked that my existing wall wart provides positive on the center of outlet. Many thanks, Norm
  6. I am in awe of the fantastic minds here that provide help and assistance, it's wonderful. I am only a beginner at this type of build, so it will take me a while to digest and draw up a board arrangement for the design that Stereo Coffee has provided. Please indulge my ignorant questions that I have. Q1) The spec for my Musical Fidelity V90 LPS pre-amp existing power supply is " 12v 500mA DC power supply" so I imagine the V90 uses somewhat less than 500mA so if I guess say 450 mA, noting the maths above the 220 ohm resistor for 57mA current needs to be varied. Q2) Which 220 ohm resistor is it that allows 57mA to be developed? Is it R2, R3, or both? And what value do I need to use to get say 12 volts, 450mA? I see that vRef/R if I use a 27 ohm resistor produces 460 mA - is this thinking correct? Q3) Also, U3 seems to have only 2 pins connected - is this correct? Pin 3 (In) appears to be not connected anywhere. I will draw up a physical layout (I am away over the weekend so it won't be until next week) and post it here for review if possible. In the meantime, I have another question regarding my existing LPS - how do I implement "adding 2 more diodes to form a bridge rectifier arrangement" using my existing transformer which is not center tapped? Or would I be better just using the existing circuit with a center tapped 12 volt trafo? All help is greatly appreciated! Many thanks, Norm
  7. Hi Stereo Coffee. Greetings from across the ditch. Yes, it is a 7812 regulator. Thanks for the link, I will read it when I get a chance. I have completed it, it delivers 12.1 volts steadily according to my Fluke 87 true RMA multimeter. Here's the circuit, noting that it is powered with a 12-18 volt (18 VA), 1 amp multitap transformer. I made a small mod - I have also used a 4,700 uF capacitor in place of the 1,000 uF shown in the circuit. Should I go back to the 1,000uf unit instead as shown in the design below?? And I am still in error - it is only half wave rectification I now see, not full wave. It would be great to have full wave instead, but I couldn't find a circuit.... I would greatly appreciate any assistance you can give me with a better circuit design. I'm trying to cut down power source noise arising from using a wall wart 🙂 Many thanks, Norm
  8. "Songs From the South" vinyl was not in stock yesterday so I went elsewhere and got it today. Looking forward to a spin tonight. I also noticed that Bowie's vinyl of "Heathen" was in stock too - is this a good listen? If so I will grab it too. Coming (already ordered) soon, a copy of Jonn Mayer's "Contiuum", on 2 x 180 gram platters, an import priced at about $45 instead of the $79 JB is asking for the exact same version. I hate being robbed....
  9. Hi all. Thanks for the advice provided. The transformer I am using is well specified for the proposed use. I have checked and I think I will be using full, not half, wave rectifcation, so my mistake. The voltage my phono pre-amp uses is 12 v DC, so it's appropriate. I will twist all internal wires, plus as I have decided to use a metal case I will use an IEC C14 input connector and I will earth the case using crimped, not soldered attachment rings. Not sure if I can shield the trafo better. Cheers, Norm
  10. I have now marked this as found as I have decided to build one instead. Thanks for the replies. Norm
  11. I decided to bite the bullet and build, not buy, a transformer-fed 12 volt DC regulated linear power supply with half wave rectification for my phono stage to drop the noise floor as far as I can, and get away from the wall wart that came with it. The design is from the "Short Circuits 3" book. I decided to try a kit for the solid state regulator component, and a nice multi-tapped transformer as the AC source. The trafo provides AC +12 V positive, and the rectifier needs at least 2.5 volts more than this to work. How do we get the extra volts out of a 12 volt transformer? The answer it seems is that the AC voltage from the "12 volt" transformer is of course RMS, not peak voltage, which is actually 1.414 x the RMS voltage, so around 17 volts AC at its peak. I have bought a biggish case to fit it all into - plenty of air space and ventilation, and lots of room to keep the high voltage and I presume noisy transformer away from the regulator board. I have already drilled out and fitted stand-offs, and fitting bolt holes, and supply and output fitting openings. Tonight I will start soldering the board and components in place. The regulator only has a few components including a rectifier, 2 diodes, 2 capacitors, and a resistor. I do have a question - the supplied smoothing capacitor is a 1000 uF 25 volt polarised electrolytic in the design. Would I be better to substitute a bigger capacitance but same 25 volt value smoothing capacitor?- I can get a 2200 uF 25 volt low ESR cap or a 4000 uF ordinary cap that will fit right in? I understand that regulator circuits like low ESR components best, so is the 2200 uF part better? Or should I stick to 1000 uF and get a low ESR cap? The lower the ESR, the lower the ripple and therefore noise. I have seen similar pre-made regulator boards\ with 4000 uF caps, hence my question. Another question - is it OK to twist wires pairs together? For example the wires that will lead from the regulator board to the output connection? Would this have any impact on noise? Thanks in advance.
  12. I decided to bite the bullet and build, not buy, a transformer-fed 12 volt DC regulated linear power supply with half wave rectification for my phono stage to drop the noise floor as far as I can, and get away from the wall wart that came with it. The design is from the "Short Circuits 3" book. I decided to try a kit for the solid state regulator component, and a nice multi-tapped transformer as the AC source. The trafo provides AC +12 V positive, and the rectifier needs at least 2.5 volts more than this to work. How do we get the extra volts out of a 12 volt transformer? The answer it seems is that the AC voltage from the "12 volt" transformer is of course RMS, not peak voltage, which is actually 1.414 x the RMS voltage, so around 17 volts AC at its peak. I have bought a biggish case to fit it all into - plenty of air space and ventilation, and lots of room to keep the high voltage and I presume noisy transformer away from the regulator board. I have already drilled out and fitted stand-offs, and fitting bolt holes, and supply and output fitting openings. Tonight I will start soldering the board and components in place. The regulator only has a few components including a rectifier, 2 diodes, 2 capacitors, and a resistor. I do have a question - the supplied smoothing capacitor is a 1000 uF 25 volt polarised electrolytic in the design. Would I be better to substitute a bigger capacitance but same 25 volt value smoothing capacitor?- I can get a 2200 uF 25 volt low ESR cap or a 4000 uF ordinary cap that will fit right in? I understand that regulator circuits like low ESR components best, so is the 2200 uF part better? Or should I stick to 1000 uF and get a low ESR cap? The lower the ESR, the lower the ripple and therefore noise. I have seen similar pre-made regulator boards\ with 4000 uF caps, hence my question. Another question - is it OK to twist wires pairs together? For example the wires that will lead from the regulator board to the output connection? Would this have any impact on noise? Thanks in advance.
  13. Today's new vinyl - David Bowie, "Black Star". Haven't played it yet (but I will). Looking forward to hearing it.... It has the start cutout in the cover so you cab see the vinyl inside, which is in a touch, hard acrylic sleeve that won't be a long-term home for the record, it will go into a more forgiving inner. EDIT - Listening now. Nice and quiet vinyl, great dynamics, solid bass drum sound. Excellent! Also just noticed that the double opening sleeve will fit the disc in the rear pocket in a new inner. In there I found a beautiful glossy booklet, a surprise! And the design of the package is immaculate - the inside of the cardboard is also black instead of the usual beige unfinished card surface.
  14. Hi Alan. It is for a Musical Fidelity V90 LPS phono preamp. It needs 12 volts DC. The power draw is stated as 500 mA so 1 to 2 amps current capability is all that I need max.. I am hoping to get a transformer based linear power supply with low ripple to replace the noisy wall wart. Cheers, Norm
  15. Item: 12 volt 500 mA Linear Power Supply Price Range: up to about $100? Don't really know... Item Condition: New or Used Extra Info: Looking for a 12 volt Linear Power Supply to use with a phono pre-amp. A Musical Fidelity V-PSUII would be ideal, but a nice DIY or other kit is fine. The connector plug doesn't matter as I will fit what I need. Not looking for a switched wall wart unit.... I'm Canberra-based, but I will be in Sydney (both Cronulla and Waringah) next weekend. EDIT - I have marked it as found as I have decided to build one instead. Thanks for the replies. Norm
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