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  1. Old Comment
    fas42's Avatar

    How good can the sound get?

    Obviously, I am a little bit inspired, ...

    I was just doing a bit of forum surfing, and found references to the dartZeel 458 power amplifier, which is viciously expensive for the levels of THD it produces, the latter can easily be beaten by a cheap chip amp in PC speakers, . However, it does pump out a lot of power, which helps things .

    Anyway, the Stereophile review of the unit mentions the playing of an LP of Paul Simon's Graceland, which reminded me of what I heard years ago when I was fiddling, and used this album on CD quite a bit for assessment:

    Quote:
    In "Diamonds on the Soles of Her Shoes," Ladysmith Black Mambazo's opening chant, split between the channels, attained a hair-raising level of transparency and three-dimensionality, while the drum thwack that introduces the melody exploded from the left channel with alarming power and textural suppleness. As the "ta-na-nas" faded out at the end, everyone who sat and listened, from manufacturers to friends to John Atkinson, and without exception, exclaimed, "Wow!"
    Now, that is a good description of how that track should come across - and if it doesn't, then the system is not up to scratch. The recorded content is there, in the recording to produce the subjective experiences described ... it's up to the playback system to do its job properly, to reveal all that is in the recording.
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    Posted 12th April 2014 at 05:18 AM by fas42 fas42 is online now
  2. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    A thought - the chip amp powering these is a nothing thing, on just a rectangle of aluminium as a heat sink, only capable of a few watts per channel at reasonable distortion spec's, yet the subjective impact is far, far more than this would imply. Yesterday, running highly compressed, dense modern rock you could easily hear the limitations of the miniscule power supply doing its best, yet really only the major problem was that the sparkle of the cymbals, etc, was steadily lost and squashed as the volume was pushed - it was capable otherwise of clean, "deafening" volumes, that would start my ears ringing if I sat too close for a decent period.

    It also has that telling property of not changing its character as the volume drops - going from a reasonable max - some obvious soft clipping - down to the lowest that the digital volume would do, in its coarse decrements - the tonality of the sound doesn't significantly alter - the same intrinsic 'bite' of the recorded sound comes through ...
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    Posted 11th April 2014 at 10:44 PM by fas42 fas42 is online now
  3. Old Comment

    Rebuilding a Hafler DH200 Part 1

    This was helpful,I have a very stock board (other than recap,and repair(no mods)and it was great to see a original pc 6 to compare to.
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    Posted 10th April 2014 at 04:13 PM by KTnC KTnC is offline
  4. Old Comment

    Best source for TX2575 Naked Z-Foil Resistor

    Texas Components

    Yes, I agree, Arbie Lopez from Texas Components I S the best adress worldwide to buy world class resistors. And, what also counts: If you have special wishes, they can make things possible you wouldn´t think about... and thank you for the trim pot hint...
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    Posted 8th April 2014 at 04:38 PM by Scheff Scheff is offline
  5. Old Comment

    Sapphire Headphone Amplifier rev. 2.0

    Hi RJM,

    Just wanted to point out that using these ltspice models from Cordell you can simulate your Sapphire buffers with BD139/BD140. The distorsions are a bit higher by the way and quite different with the third order becoming dominant. Here's a look:
    Click the image to open in full size.
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    Posted 8th April 2014 at 08:46 AM by SunRa SunRa is offline
  6. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Some interesting behaviour occurring, timing is everything ...

    In the course of trying something, I fed near full level 15kHz sine waves into the speakers - the correct tone was certainly there, but very obvious were some pretty loud artifacts, way down in the midrange. Even more interesting, a particular "note" would appear at precisely a certain volume, above and below that setting that artifact disappeared.

    So, was this the speakers/amplifier, or the DAC/source misbehaving? Easy to test, pull the power on the speaker setup, and leave the player running at full volume - previous experience demonstrating that warm-up solved many things ...

    And, somewhat later, try powering up the speakers again - immediately, quite a bit better, and that peculiar level dependent artifact was gone. This demonstrates quite clearly that electronic misbehaviour in areas directly relating to the DAC can very much be part of poor sound ...
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    Posted 8th April 2014 at 06:01 AM by fas42 fas42 is online now
    Updated 8th April 2014 at 06:04 AM by fas42
  7. Old Comment
    fas42's Avatar

    One Farad capacitor array

    Yes, once in the single digit or so milliohm range, everything starts to matter - how much copper, for what distance, is being used to pass current really starts to be relevant ...
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    Posted 8th April 2014 at 01:48 AM by fas42 fas42 is online now
  8. Old Comment
    rjm's Avatar

    Voltage Regulators for Line Level Audio. Part IX : Two Transistor Series Regulator

    Thanks for the tip.

    To plot V(vout)/I(I1), click "add traces" on the plot menu, and type the expression in the blank line at the bottom of the dialog box. Then change the axis to linear as Calvin says above.

    Since the small signal current I(I1) is set to "1" in the example files, however, dividing though by the current does not change the numerical answer. I agree its more comforting to see it displayed in the right units though.
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    Posted 7th April 2014 at 07:55 AM by rjm rjm is offline
  9. Old Comment
    abraxalito's Avatar

    One Farad capacitor array

    Good point - but still charging time is an issue if I wanted to turn this into a reproducable design. My customers aren't going to want to wait hours for sound to come out, powering from cold.

    I'll go step by step and see what supercaps bring to the party, if anything. I don't yet know for example how low in frequency the low impedance needs to go. For sure supercaps are major overkill in terms of going several octaves below 50Hz with their impedance.
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    Posted 4th April 2014 at 11:31 PM by abraxalito abraxalito is offline
  10. Old Comment
    fas42's Avatar

    One Farad capacitor array

    Just to check things out, no need to go to 5.4V charge - at the worst the actual values may be say 2F and 3F, just charge up to 4V, hence a safety margin ...
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    Posted 4th April 2014 at 10:25 PM by fas42 fas42 is online now
    Updated 4th April 2014 at 11:48 PM by fas42
  11. Old Comment
    abraxalito's Avatar

    One Farad capacitor array

    Yeah except charge balancing is a bit of a pig with two in series. LT makes a nice chip to do it, but its easier to begin with to go for a single one and see how it pans out. I know there are major sized ones available, but charging time becomes an issue and those hell-for-leather ones have terminals at opposite ends, not well suited to DAC chips...
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    Posted 4th April 2014 at 12:05 AM by abraxalito abraxalito is offline
  12. Old Comment
    fas42's Avatar

    One Farad capacitor array

    Why not just do 2 in series, for 50F/5.4V?

    Edit: man, why not go for broke - Illinois Capacitor DCN Series: 3,500F; 2.7V; 2,300amps; ESR - 0.24mR; 0.6Kg ...
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    Posted 3rd April 2014 at 11:03 PM by fas42 fas42 is online now
    Updated 3rd April 2014 at 11:18 PM by fas42
  13. Old Comment
    abraxalito's Avatar

    One Farad capacitor array

    I'm wondering for my next level up of insanity, an array of 19 of these caps, seeing as they say the max ESR is 15mohm. 1900F would take 1.5hrs @ 1A charge current to reach 2.7V, this voltage is just enough to get a TDA1545 to fire up. Not a bad price either at 4RMB a piece.
    Click the image to open in full size.
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    Posted 3rd April 2014 at 03:18 PM by abraxalito abraxalito is offline
  14. Old Comment
    abraxalito's Avatar

    One Farad capacitor array

    Yes the DAC chip could, except I'm also using a pair of output buffers (AD815) which are quite a bit more power hungry. They will have their own caps but not as large a value as the DAC chip. Battery poiwer could always be applied from an SLA if the purpose is just to test for isolation-related issues. Alternatively (and more compact) a handful of supercaps (3F and up) could be used as power source. I don't use these directly because their ESR sucks, but they could easily feed the cap array.
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    Posted 3rd April 2014 at 10:31 AM by abraxalito abraxalito is offline
    Updated 3rd April 2014 at 10:33 AM by abraxalito
  15. Old Comment
    fas42's Avatar

    One Farad capacitor array

    Now, this is getting interesting ... quick sim, an isolated 10F charged up to 5.5V, feeding 4mA supply current to the DAC chip, will last 100 minutes before dropping to 3V, lowest spec'ed V for the chip. So, you could easily do a whole album on 'pure battery power' - would be a fascinating exercise ...
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    Posted 3rd April 2014 at 07:00 AM by fas42 fas42 is online now
  16. Old Comment
    abraxalito's Avatar

    One Farad capacitor array

    Thanks Frank - I was discussing with my friends here how to get some of these made as it took me a few hours to wire up. Labour should be fairly cheap locally to get a dozen or so built up so I could have a 10F cap array on the rails of my TDA1545......
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    Posted 3rd April 2014 at 03:27 AM by abraxalito abraxalito is offline
  17. Old Comment
    fas42's Avatar

    One Farad capacitor array

    ... and very artistically photographed, too, ...
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    Posted 3rd April 2014 at 03:19 AM by fas42 fas42 is online now
  18. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Well, I'm rather pleased - by dint of enough fiddling, and general fooling around I've worked out a pretty reasonable combination of temporary tweaks, fixes to lift these speakers to the point of decent disappearing - no actual further tweaking on the insides, just trying to create as electrically benign environment around everything as possible ...

    As usual, that old bugbear, static induced interference was a major offender - will have to work out some better arrangements to keep this at bay.

    Have got on now one of my fav' torture albums - Southern R&B, tons of very busy, upper midrange EQ - and it's going very nicely ...

    Edit: what I always look for, unconsciously mostly, is for a system to give me a good endorphin hit - and it's especially satisfying when it's not really expected, it comes as a bit of a surprise. This is what I got today, so quite chuffed at the moment ...
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    Posted 3rd April 2014 at 02:28 AM by fas42 fas42 is online now
    Updated 3rd April 2014 at 04:36 AM by fas42
  19. Old Comment
    jean-paul's Avatar

    Modification of the S.M.S.L. sAp VI headphone amplifier

    Wima MKS2 XL 4.7 µF would be a better choice for input caps.
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    Posted 2nd April 2014 at 10:17 AM by jean-paul jean-paul is offline
  20. Old Comment
    merlin2069er's Avatar

    My Ref Music Server - Lampizator meets Red Baron

    Hey Walter, did you get your red baron up and running?
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    Posted 31st March 2014 at 08:53 PM by merlin2069er merlin2069er is offline
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