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  1. Old Comment
    abraxalito's Avatar

    The real story about closed vs open loop class D amps

    Ah I'm not interested in 'doing impressively well' with such a qualification. If it does impressively well unconditionally then my ears'll prick up.

    One of the reasons I like the 5756 better than the TPA3116 is they don't seem to have included the on-chip regulator for the analog signal processing. To my ears that LDO reg craps out the bass performance, it must be too noisy at LF (no surprise really, its a CMOS/DMOS process). Seems not to be a reg on the 5756 as the power pin is brought out directly.

    Your 'correct' sound in the way you've talked about it seems to have only one dimension. My sound though has dimensions even once the speakers disappear. So I still hear that for example the classD amp's bass sounds better than the classB - does this mean both create 'correct' sound? Or is classAB bass 'incorrect' and just needs a few more farads of capacitance?

    Do you have any idea what changes on a digital chip as it runs in? Any hypothesis?
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    Posted Yesterday at 11:57 PM by abraxalito abraxalito is online now
  2. Old Comment
    fas42's Avatar

    The real story about closed vs open loop class D amps

    Yes, in a closed loop, digital input unit how is the feedback actually done? Probably there is some explanation out there, but I'm being lazy at the moment ...

    Yes, the 5706 is mentioned several times on diyAudio, and generally given a thumbs up for doing impressively well, subjectively, for what it is.

    If the 5756 innards are really intelligently thought out then it may do remarkably well, there being no room for interference to creep in via sloppy, conventional implementation. Personally, as I've mentioned many times, the S-D DAC is not a problem, after switch-on conditioning always sorts that out, IME - if aiming for optimum sound in, say, 5 minutes from power up then just add extra, peripheral circuitry to keep the chip nicely simmering in the "off" times.

    Interestingly, in the my PC setup which uses a cheap Realtek onboard DAC, you can easily hear this process happening. It's configured now to run at maximum analogue volume always, the digital volume control is the gain setting. And from a cold start you can hear the DAC glitching and stumbling, the digital artifacts are obvious, as if it had only about effectively 6 bits working. Steadily, as the chip runs in, warms to its work, , these artifacts fade away and finally completely disappear, even with one's ear to the speaker.
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    Posted Yesterday at 11:44 PM by fas42 fas42 is offline
  3. Old Comment
    abraxalito's Avatar

    The real story about closed vs open loop class D amps

    You are asking if the feedback for the 5706 is digital? Meaning there is no internal ADC ? The DS doesn't give enough detail to work out how they do it. Where have you learned about the SQ? On DIYA?

    Yes I found the 5756 and mentioned it on the TPA3116 thread. No-one else has commented on it so far but I agree it could be great (even ignoring the DAC). Yes its different from the 5706 as there's an analog classD amp, not a digital-to-PWM converter. This tells me that most likely even they don't like what they've done in the 'direct-to-digital' chippery and are reverting to good old analog classD.....
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    Posted Yesterday at 01:39 PM by abraxalito abraxalito is online now
  4. Old Comment
    fas42's Avatar

    The real story about closed vs open loop class D amps

    That feedback is digital, is it not? That's a whole different ball game, how does the chip do its tricks internally is the question - I note generally positive comments about SQ, in spite of very uninspiring distortion figures ...

    And, I also just discovered the TAS5756, which I note you have also come across. This might do quite spectacular things if handled well - is this done in a different way from the TAS5706? Plenty of scope here for fine detail tweaking - everything done in one tiny box, erh, chip might just work nicely if fed with very clean power and signals.
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    Posted Yesterday at 01:07 PM by fas42 fas42 is offline
  5. Old Comment

    D/A

    I like very much the cuted Aya pcb ... and the ??? on the top of the caps .
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    Posted 9th July 2014 at 02:17 AM by Eldam Eldam is offline
  6. Old Comment
    wintermute's Avatar

    Amplifier-centric two-way XO (and system) design

    Thanks, that confirms what I was thinking. I shall scale and do some sims with a more friendly load

    Tony.
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    Posted 7th July 2014 at 08:11 AM by wintermute wintermute is offline
  7. Old Comment
    abraxalito's Avatar

    Tweeter DAC

    Accidental, thanks for the heads up! I will go investigate now.... Found an unticked box, its ticked now. Let me know if you get problems.
    permalink
    Posted 5th July 2014 at 02:53 PM by abraxalito abraxalito is online now
    Updated 5th July 2014 at 03:00 PM by abraxalito
  8. Old Comment
    fas42's Avatar

    Tweeter DAC

    Richard, you appear to have disabled comments for your latest blog, the XO-centric setup - accidental or intentional ... ?
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    Posted 5th July 2014 at 03:59 AM by fas42 fas42 is offline
  9. Old Comment
    abraxalito's Avatar

    Amplifier-centric two-way XO (and system) design

    When planet10 and I got into a conversation about PLLXOs some time ago he wasn't hungry enough (it seemed to me) to be prepared to make them work into a low enough impedance. I got the distinct impression he wanted a PLLXO that worked into 100k load. In which case, sure he'd have desperate problems with getting high enough Q. If your load is just 1ohm, then 0.1R is about 1dB droop already. I have a filter on my blog which has a 0.93ohm load and doesn't suffer droop but its made from custom ferrite bead inductors. As a general rule of thumb for not-too-demanding filters the total DCR of all the series inductors shouldn't exceed 15% of the load impedance. My AIF with 4 inductors around 1.6R each falls within this guideline for example with a 50R load. It does still exhibit about 1dB of droop but seeing as the zero-order hold of the DAC causes droop beyond this, there's already a network in place to correct for it.
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    Posted 4th July 2014 at 11:20 AM by abraxalito abraxalito is online now
  10. Old Comment
    wintermute's Avatar

    Amplifier-centric two-way XO (and system) design

    Hi Richard, I was only simming passive to get a baseline for my active implementation of the passive filter. I wound my own air cored inductors for my passive crossovers but they are speaker level not line level.

    I know planet10 has commented a number of times about pllxo's getting "droopy" when cascading more than one order, and my sims certainly confirmed that.

    I wasn't using smd so was putting in 6nH for esl for caps (which is the spec of the rifa MKP1387's I'm using. for coils even 0.1 ohms is enough to cause some serious deviation from ideal, I was quite surprised.... In my case though I was simming with 1 ohm load since that is the "normalised" filter for doing the active calculations... perhaps I should have used a more realistic load and then scaled the component values appropriately....

    Tony.
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    Posted 4th July 2014 at 08:26 AM by wintermute wintermute is offline
  11. Old Comment
    abraxalito's Avatar

    Amplifier-centric two-way XO (and system) design

    Hi Tony - yes the R is the killer of sharp corners for passive filters. Fortunately I have a supply of gapped ferrite pot cores which allow me to achieve Qs into 3 figures at 20kHz. Getting such high Qs at 3kHz is more of a challenge but can be done by going to slightly larger coils. I've not had to use Litz yet but I'm getting close....
    What kinds of inductors are you using? I've not found any commerical ones that beat hand-wound pot cores for low AC losses. ESRs are an issue with X5R and X7R ceramics - I've gone over to using NP0 for this filter to get lower ESR. ESL is never a problem for me with SMT caps in audio signal applications, it becomes a series issue in decoupling though.
    permalink
    Posted 3rd July 2014 at 01:21 PM by abraxalito abraxalito is online now
    Updated 3rd July 2014 at 01:24 PM by abraxalito
  12. Old Comment
    wintermute's Avatar

    Amplifier-centric two-way XO (and system) design

    Hi Richard, are you putting realistic parasitics into your coils and caps in spice? I found when simming passive filters that the performance degraded markedly when realistic small amounts of esr and esl were added to the caps, and dcr for the coils.

    Tony.
    permalink
    Posted 3rd July 2014 at 08:11 AM by wintermute wintermute is offline
  13. Old Comment
    fas42's Avatar

    Tweeter DAC

    Ahhh, dear - I think we're about ready for a TV cartoon series, peopled with all your critters ...

    Though, your latest "creation" reminds me of my mains DC blocker, has the same, spokes of a wagon wheel construction, .
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    Posted 26th June 2014 at 10:21 AM by fas42 fas42 is offline
  14. Old Comment
    abraxalito's Avatar

    Tweeter DAC

    They're working as DACs, connected to 51R resistors (left and right) which then lead off to the bandpass tweeter filter. All 7 are paralleled, summing their currents together.
    permalink
    Posted 24th June 2014 at 07:33 AM by abraxalito abraxalito is online now
  15. Old Comment
    fas42's Avatar

    A Better Audio Comparison Tool

    I have picked an interesting pair of tracks to use as a test run: very poor quality in the recording sense, one from a CD, the other an extract of fairly high resolution audio from a YouTube video - are they the same track ...??

    No, as mentioned above they run at different speeds, and further, the speed alters during the track - taking the CD as reference, the AAC version changes speed as it plays! The latter appears not to be vinyl, and in fact is quieter in a noise sense than the CD, looking at the waveform, at high frequencies! Even more 'laughable' - the spectrum of the YouTube version shows the intrinsic above 10kHz band is "better", there's more there! To listen to them at a casual level they sound very similar - but visually there is substantial, obvious variance between the waveforms. Which is not to say that the compressed version has "lost" information in an obvious sense - every single wriggle of the CD version is perfectly matched by a wriggle in the YouTube variant, just that the wriggles don't beautifully match, they won't "subtract" neatly.

    Interesting ...
    permalink
    Posted 24th June 2014 at 01:46 AM by fas42 fas42 is offline
  16. Old Comment
    fas42's Avatar

    Tweeter DAC

    Richard, just refresh my memory on how those multiple TDA1387s are working; IOW, what the circuit for the above is, please ...

    Thanks,
    permalink
    Posted 23rd June 2014 at 11:36 PM by fas42 fas42 is offline
  17. Old Comment
    abraxalito's Avatar

    Tweeter DAC

    Thanks Frank! Certainly I'm passionate about getting the very best sound....
    permalink
    Posted 23rd June 2014 at 12:52 AM by abraxalito abraxalito is online now
  18. Old Comment
    fas42's Avatar

    Tweeter DAC

    Richard, can't but repeat that your energy and enthusiasm is very impressive ...
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    Posted 23rd June 2014 at 12:01 AM by fas42 fas42 is offline
  19. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Duuuhh ... still haven't done the organ piece, life conspires at the moment, unfortunately ...

    Anyway, a big sigh of relief - I had an album from the library, MPD Limited, 60's Oz pop, which was a very bad transfer, or the master was in poor shape. The sound was almost impossible, and I thought I might not be able to recover listenable quality ... so today I pulled out a lot more stops, essentially making the playback electrical environment even more benign than usual - and that did the trick, high 5's!!! The recording has lots of upper midrange, and reverb was used freely in the production; combine that with poor transfer quality, and it's a recipe for an audio headache! Absolutely minimal degradation in the playback chain is essential for such recordings to bear fruit, and I needed more rounds of effort than usual to get the inherent distortion under control ...
    permalink
    Posted 22nd June 2014 at 06:23 AM by fas42 fas42 is offline
  20. Old Comment
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    Posted 21st June 2014 at 01:53 PM by SteB SteB is offline
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