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  1. Old Comment
    fas42's Avatar

    Exploring laptop sound

    Things are moving very nicely at the moment, this is most pleasing! The problem with the previous disk, the Jools Holland was overcome by plugging the power adapter back in - by itself, just the raw power pack, the sound was still poor, so I used a simple approach that I often do, a basic surge buster, the MOV thing, which improved things hugely. Full spaciousness and cleanness of sound was recovered; the mains was introducing too much garbage, and a bit of filtering did the trick.

    All in all, a very good few hours fiddling, with remarkably competent sound now being extracted ...
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    Posted Today at 02:41 AM by fas42 fas42 is offline
    Updated Today at 03:00 AM by fas42
  2. Old Comment
    fas42's Avatar

    Exploring laptop sound

    Where it is still struggling is with Small World Big Band - Jools Holland | Songs, Reviews, Credits, Awards | AllMusic. This is one of my "killer" CDs, I would use this but rarely on other, audiophile systems, - very dense sound, mastered using modern studio, heavy, and clever compression methods ... forces the amplifier to be absolutely on its best behaviour, and most will fail miserably - sound will clog, and turn shouty; people will demand that the playback be stopped, .

    And this is what the laptop is doing, the power demands are too much for the circuitry to cope with, at the moment, and distortion intrudes, badly ...
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    Posted Today at 01:20 AM by fas42 fas42 is offline
  3. Old Comment
    fas42's Avatar

    Exploring laptop sound

    Very positive, just tried a classical CD, from cold the speakers have some mechanical scratchiness, and piano beautifully hightlights this - but this physical problem does steadily settle down. The good news is that full scale orchestral is doing very nicely, rings very true, has good space and depth - there seems to an issue with the CD-ROM drive and/or player output software module though, it's glitching on the end of tracks, on this CD ...

    Edit: The kicker is, that even at this relatively preliminary point in the exercise, the intrinsic quality of the sound is quite superior to the majority of ambitious hifi setups, ! Yes, it doesn't go loud, and it doesn't have walloping bass! - but everything else is in good shape ... unlike many of the clown(!), expensive audio setups one comes across ...

    "Correct" sound is just this, with the low bass filled in, and able to go to any sensible volume one wants - it's all quite simple, really ...
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    Posted Today at 12:11 AM by fas42 fas42 is offline
    Updated Today at 12:43 AM by fas42
  4. Old Comment
    fas42's Avatar

    Exploring laptop sound

    Talking of battery usage, I was getting a weird battery charging condition - both the charger and battery are no-name replacements, and I was doing a lot of experimentation with charging and not charging, and ended up with a flashing LED on the charging indicators - which didn't go away unless the m/c was on the charger, and continued even when the laptop was fully powered down, whoa ... !! Plus, the charge level number got stuck, didn't move from a setting that was almost full, no matter what! OK, pull the battery from the case, reseat it a couple of times ... that fixed the problem, a glitch somewhere must have got the logic states confused, and a full reset was necessary ...

    To backtrack a bit, what I'm looking for is that the laptop deliver the best sound that it's capable of, which hopefully will mean minimal faults, and the lowest audible level of flaws in the sound. So far, the internal speakers are doing nicely, but are indicating the worst fault, a resonance with high level, complex low frequency material - as one would expect! Solo piano is always a good test, and this material is catching it out - I might have to lift the lid and do some damping and similar stabilising to "mend" this, or it is still possible that extensive conditioning might be the only "cure".

    So far, I'm pleased with how the exploration is going - the sound reproduction is substantially correct, the main hurdle, as usual, is "unclogging" the low level detail, having all the ambient information come across cleanly - this is essential for the sense of "big" sound to happen. As an explanation for what this sounds like on a system with minimal SPL capability, this means that with the volume on maximum that putting one's head over the keyboard, almost resting on it, as close to between the speakers as possible, that it sounds like a pair of very high quality headphones - after all, that's what the speakers inside the case are in fact: headphone drivers ...
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    Posted Yesterday at 11:09 PM by fas42 fas42 is offline
    Updated Yesterday at 11:13 PM by fas42
  5. Old Comment
    rjm's Avatar

    47 Labs 0347 "Treasure" stereo amplifier

    The 47 Treasure series has moved from the 47 Laboratory web site to Sparkler Audio, but the product line has been discontinued. Just a few items remain.

    (I've updated the main post to remove the dead links.)
    permalink
    Posted 19th April 2015 at 11:24 PM by rjm rjm is offline
    Updated 19th April 2015 at 11:28 PM by rjm
  6. Old Comment
    fas42's Avatar

    Exploring laptop sound

    Next installment ... .

    Every time I do these exercises, I can only shake my head at those who say the differences are only imagination, or expectations - I think cloth eared is too kind a term to use for these people, . Even on these "miserable", standard, pea sized internal speakers the variations scream at one; as always the treble and low level detail, the "space" of the recording are the giveaways, make SQ adjustments obvious, .

    One thing I've noted, is that the quality does vary over time, say of a CD playing, by quite a large degree, so room for plenty of variables to be involved - I'm aiming for consistency, the worst thing is have best sound at the beginning, which slowly falls off over many minutes; far better to have a lower standard, which maintains over an extended period.

    The main movement currently is exploring alternatives to Windows Media Player, and MediaMonky has got a good rap - downloaded it, and a substantial improvement over the Windows default ... though still variable quality over a time frame. Why should another player work better? Well, looked in Task Manager at CPU usage, pretty obvious factor: Media Player running at around 9% all the time while playing, MediaMonkey, 0.2% !! Having the processor grinding continually will do quality no favours - so, Media Player gets the boot!

    Battery usage, and charge level seem to be important - a bit of detective work on that to come ...
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    Posted 19th April 2015 at 02:04 AM by fas42 fas42 is offline
  7. Old Comment
    fas42's Avatar

    What's the PSRR of an emitter follower?

    Straight off the top of my head, use Audacity to create a 20Hz square wave, the level of which is near full scale; then add a HF signal of appropriate frequency on top which causes the summed output to reach maximum amplitude, or a touch below - see what the distortion behaviour of that is ...
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    Posted 17th April 2015 at 01:37 AM by fas42 fas42 is offline
  8. Old Comment
    abraxalito's Avatar

    What's the PSRR of an emitter follower?

    I've been wondering what might be the best measurement to capture output stage PSRR issues. As you say perhaps not FFT as the average effect is going to be low but the interference is impulsive. With audio signals having high crest factors the signal isn't in the problem area (near to the rails) for very long.
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    Posted 16th April 2015 at 11:23 AM by abraxalito abraxalito is offline
  9. Old Comment
    fas42's Avatar

    What's the PSRR of an emitter follower?

    Nice detective work there, Richard! The point about PSRR being dependent on the instantaneous output level is important, I have noted that some people run tests of a low level HF signal riding on the back of a LF waveform that approaches clipping - and transient excess distortion occurs at the peak values of the LF input. In some sim's I've also noted similar behaviour - time domain glitches are where the action is, and these may easily be missed or hidden in FFT analyses.
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    Posted 16th April 2015 at 10:51 AM by fas42 fas42 is offline
  10. Old Comment
    Mark Whitney's Avatar

    Are PSRR plots all they're cracked up to be?

    Compare the supply currents with a 10kHz signal to a 10kHz plus 100Hz signal.
    Or the same test comparing a filtered and a unfiltered audio signal.

    You could also add DC to each of the outputs and force class A operation.
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    Posted 16th April 2015 at 10:15 AM by Mark Whitney Mark Whitney is offline
    Updated 16th April 2015 at 10:20 AM by Mark Whitney
  11. Old Comment
    abraxalito's Avatar

    Are PSRR plots all they're cracked up to be?

    Mark do you mean because this is an active system the HF isn't riding on the LF in the same amp, so the OPS is changing halves more frequently? If so good point that I'd not considered before, I need to reflect on it.

    Yep - bridged amps see half the impedance. When I was driving the tweeter directly that wasn't with a bridged amp though - just a normal TDA7265. Thanks to some dodgy engineering on some other speakers I tried trafos - one model is using TDA8947 (which is bridged) and fed into 4ohm units. If not for that I'd not have discovered trafos!
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    Posted 16th April 2015 at 09:17 AM by abraxalito abraxalito is offline
    Updated 16th April 2015 at 09:19 AM by abraxalito
  12. Old Comment
    Mark Whitney's Avatar

    Are PSRR plots all they're cracked up to be?

    A few things that may influence the PSRR:

    By reducing the low frequencies there is an increase of the output switching between the two rails and therefore an increase of HF rail current.

    Add to that the low impedance (2ohm) seen by each of the bridged IC. The bypass caps and IC are working harder than with a normal 8 ohm load and full audio signal.
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    Posted 16th April 2015 at 09:08 AM by Mark Whitney Mark Whitney is offline
  13. Old Comment
    abraxalito's Avatar

    47 Labs 0347 "Treasure" stereo amplifier

    Links to 47 Labs site no longer point to anything.
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    Posted 16th April 2015 at 04:56 AM by abraxalito abraxalito is offline
  14. Old Comment
    abraxalito's Avatar

    Are PSRR plots all they're cracked up to be?

    Thanks for the question. The reason that the roughness on HF is related to the PSRR is because it reduces with more capacitance on the rails. More caps means lower supply ripple. No other changes were made than adding more low ESR caps close to the chip. I have no other explanation but that its related to power supply noise and the chipamp's ability to reject that. I got a similar effect with my TDA8566 - HF roughness went down from adding a lot (30 or so) of 10uF ceramic caps across its supply pins.

    On your second point perhaps you could turn up KSTR's work in a similar vein - he convinced me that this is a reasonable method to eliminate the negative rail supply issues. He also reported improved SQ when he implemented his idea. So what about my explanation is lacking for you?
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    Posted 16th April 2015 at 12:13 AM by abraxalito abraxalito is offline
  15. Old Comment
    rjm's Avatar

    Are PSRR plots all they're cracked up to be?

    A couple of quick comments.

    1. What makes you think that the roughness you hear (HF distortion?) should be related to the power supply ripple rejection figures? Sorry I don't follow the logic.

    2. Your last reply "...no signal-related current is flowing between local 0V and VEE meaning there can be no ripple." sets off alarm bells. I'm not saying you are wrong, just that your explanation does not convince.
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    Posted 15th April 2015 at 11:39 PM by rjm rjm is offline
  16. Old Comment
    rjm's Avatar

    I've been cloned!

    Thanks for the suggestion. To be honest I'm not out to stop the sale of the module. All I would ideally ask for is attribution.

    I think I will contact the seller, though I doubt it will come to anything.
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    Posted 15th April 2015 at 11:28 PM by rjm rjm is offline
  17. Old Comment
    abraxalito's Avatar

    Are PSRR plots all they're cracked up to be?

    Its important if your circuit configuration is the usual balanced one around ground yep. I've bypassed this issue though by creating a local 0V from a couple of TL431s in series (because the max per device is 30V and I want 31-37V depending on my power supply) and referencing that local 0V directly to pin4 (VEE) of the LM4766. So no signal-related current is flowing between local 0V and VEE meaning there can be no ripple. Therefore only the positive PSRR matters in my configuration.
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    Posted 15th April 2015 at 02:21 PM by abraxalito abraxalito is offline
  18. Old Comment

    Are PSRR plots all they're cracked up to be?

    Forgive me if this is an obvious question, but isn't the -PSSR just as important as +PSSR in a split supply device? Particularly because it's only 50% of what +PSSR is at 20K?
    permalink
    Posted 15th April 2015 at 01:16 PM by MrSlim MrSlim is offline
  19. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Things have moved on - I have yet another laptop to use as my main m/c, and this is looking promising in terms of the internal sound - the built in speakers don't obviously misbehave, it will be worthwhile exploring a bit.

    I'll start another blog entry detailing what I find ...
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    Posted 15th April 2015 at 07:37 AM by fas42 fas42 is offline
  20. Old Comment
    abraxalito's Avatar

    Are PSRR plots all they're cracked up to be?

    Good questions Frank.

    I'm working on part 2 right now and went back to first principles - that is the PSRR of a single transistor operating as an emitter follower. At least that's a common feature of all the opamp and chipamp output stages which aren't rail-to-rail types.

    Yes to your question - PSRR in a closed loop (feedback) circuit is going to vary according to gain - more gain means poorer PSRR. Tom's ultra-high loop gain amp has proven that - but his poor results in THD for the 'bare' LM3886 on a non-bench PSU is one of the things which prompted me to look into this rather deeper. A quick finger in the air shows Tom's THD+N (0.003%) with naked LM3886 is more than 10dB worse than would be expected from the PSRR plot of the chip.
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    Posted 15th April 2015 at 06:18 AM by abraxalito abraxalito is offline
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