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  1. Old Comment
    jan.didden's Avatar

    Superregs for your line-level projects

    Hi David,

    The answer is a few posts above this.
    Also there is an extensive thread in the forum on customizing the output voltage.
    In addition to sizing the feedback resistor values you should also adapt the output series zener so that the opamp output is around half the Vout.
    And of course make sure the electrolytics can withstand the voltages, and that you have enough input voltage for a few volts dropout reserve.
    Success!

    Jan
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    Posted 23rd July 2014 at 07:19 AM by jan.didden jan.didden is offline
  2. Old Comment

    Superregs for your line-level projects

    How do you modify this to get +/- 24v out?

    best wishes,
    david
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    Posted 23rd July 2014 at 04:06 AM by anystereo anystereo is offline
  3. Old Comment

    ESI Juli@ analog card interface details

    1audio,

    I do not read the blogs on a regular basis, so just saw this entry of yours. I believe I have the information you seek. Please contact me at my email, gstewtoo at gmail dot com so I can send you the datasheet.

    Greg in Mississippi
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    Posted 20th July 2014 at 10:48 PM by Greg Stewart Greg Stewart is offline
  4. Old Comment

    Linsley Hood amp on Taobao

    I saw the same amp on ebay with English description:
    2014 Perfect Hood 1969 Gold Seal Pure Class A Finished Amplifier 10W 110V 220V | eBay
    Even if some of the parts and assembly weren't up to scratch and needed fixing it would be a great quick way to get a very tidy JLH1969 setup.
    I just made mine so I don't need another though. This would have saved me the fun and challenge of DIYing the heatsink and chassis :-)
    permalink
    Posted 18th July 2014 at 02:47 AM by zog666 zog666 is offline
  5. Old Comment
    dimkasta's Avatar

    NwAvGuy odac 24/96 DAC review

    I recently modified one for a friend isolating the +5V from the USB cable (cutting the pcb track) and using a salas BiB for the power supply.
    Quite an improvement.
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    Posted 17th July 2014 at 10:17 AM by dimkasta dimkasta is online now
  6. Old Comment
    fas42's Avatar

    How good can the sound get?

    I was just reminded of a point worth repeating, which is an excellent marker for convincing, or 'correct' sound, as I call it - that there no optimum volume for the playback of a recording. In one sense there obviously is, being a level which would match live replay - an obvious example is solo piano, that it would correspond to a real instrument being played in your listening area. But there are many situations where you're not in the mood for that intensity of sound, or it's not socially acceptable to others in your home, at that particular moment, .

    So, if the volume has to be way down low, what then for quality? Is the best solution at that time headphones? Well, as one who has no appetite at all for the latter, luckily there is no limiting issue - the sound can be dropped to the point where it is literally a single click from being muted, and the quality can still remain! Remarkably, if everything is in place, working as it should, then the sound emerging from the speakers is fully intact, no detail is lost - even with one's ear held as closely to the speaker driver surface as possible, the sense of the musical event remains consistent with that of its reproduction, heard at a distance, at more normal gain levels. Which means, that the speakers still remain "invisible", even at very, very soft sound levels.
    permalink
    Posted 17th July 2014 at 12:28 AM by fas42 fas42 is offline
    Updated 17th July 2014 at 12:31 AM by fas42
  7. Old Comment
    abraxalito's Avatar

    The real story about closed vs open loop class D amps

    Hi miklos, no worries - your multitone results look promising. Is Phi6 a six-tone signal and Phi12, twelve tone? If so I suggest you build up more tones than 12, a minimum of 100. With 100 tones the crest factor could be up to 40dB.
    I only put up results with a six-tone signal on my blog when I was developing my hi-end chipamp but I think the noise floor was already limited by problems with the DAC in that case. We are looking for noise floor changes - 'noise modulation'. To do decent measurements I'll need an ADC which doesn't suffer from noise modulation itself, i.e. an SAR one, not S-D as 99.9% are nowadays. I do plan to develop one eventually.
    permalink
    Posted 16th July 2014 at 10:56 PM by abraxalito abraxalito is offline
  8. Old Comment
    miklos's Avatar

    The real story about closed vs open loop class D amps

    Richard,
    I'm sorry to take you and Frank ,so to speak under one hat.
    Actually I tried multi tones already. A year ago I purchased a QA400 analyzer to replace my old HP one. This new one is able to dig deeper ca. -130dB, instead of -90 with the HP. In the Cool Edit I made a test CDR with a set of test tones, among three Phi6, Phi12 and Phi3x4. the frequency's I took from Jon Rich's web page. The "Phi" frequency's are chosen so that the generated harmonics would not fall under the fundamentals and not be masked by them. I measured a bunch of CD players (ca. 35-40), Bernard was doing interesting measurements on DAC's 10 years ago and presented his result on Diyaudio. Looking at CD players and playing those tones to, going from Phi 6 to 12, I could see the noise floor (distortion) increase. Also tried a noise signal with a gap in it, but I'm not sure how good it is. I imagine the best would be a gated multi tone signal and see how the transition region would look like. Any case I would like to see your results on this interesting subject.
    permalink
    Posted 16th July 2014 at 06:39 PM by miklos miklos is offline
  9. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Have mentioned volume controls, on a number of occasions, and noted that many people have a horror of digital, or software versions of these. Anyway, having got the drivers back to good shape, I had to drop the volume back to almost zero, because my wife wanted to concentrate on some paperwork matters. The PC speakers now have no analogue pot, running at full gain, so the normal XP volume mechanism is doing it all.

    Yet, with a jazz piece on at the moment with vibes, cymbals, at a setting one of two notches above dead silence, the sound, and treble, is clear, rings nicely across the room, and still is completely intact with my ear against the speaker - so, where are these "terrible digital volume control problems" ...?
    permalink
    Posted 15th July 2014 at 03:43 AM by fas42 fas42 is offline
  10. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Possibly the low bass issue, but it's filtered away below 100Hz, doesn't provoke the cone into movement. Unlike, the more ambitious looking Altec Lansing(!) unit I have here, which manfully tries to do something with lower than 100Hz signals, but just ends up sounding silly, !

    The interesting thing is that I have driven similar types of drivers to much higher SPLs over extended periods, the Philips HT speakers are very much out of the same mold, and zero issues - hard driving in fact cleans up some distortion artifacts in those ones. The difference there is that the amplifiers were more capable, had higher voltage rails, better power supplies; with the PC speakers it's easy to hear the onset of sagging of the PS, which I normally keep happening to a minimum; but, that behaviour may have played a part in the driver problem.

    Since all of this is an exploration, I'm not fussed about negative consequences, so long as understanding results ...
    permalink
    Posted 15th July 2014 at 03:22 AM by fas42 fas42 is offline
  11. Old Comment
    wintermute's Avatar

    Fix it time for PC monitor speakers

    Frank, hopefully the lesson learned is "don't crank the amp to full volume!"

    It may be voice coil damage, but it could also be damage due to excessive excursion. The particular track you played may have some high level low bass that has driven the poor little speaker past it's limits.

    Tony.
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    Posted 15th July 2014 at 02:53 AM by wintermute wintermute is offline
  12. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Okay, lesson learnt. The physical manipulation worked, and stayed working. Next morning, from cold, here was the fuzziness again; so, immediately, reasonably energetic manipulation of the suspension with the fingers, and away went the fuzziness!

    Other people have mentioned that the voice coil getting pretty hot can cause it to deform, go out round; this might be the cause of my bzzz'ng - in any case, a good massage when starting irons out the noise issues ... all's good!!
    permalink
    Posted 15th July 2014 at 01:53 AM by fas42 fas42 is offline
  13. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Veeeerrry interesting - the problems I mentioned in the last post appear, I repeat, appear, to be caused by classic Rub and Buzz issues with the speaker driver. I might be on a learning curve here - on impulse, I started prodding the speaker cone while it was working at low volumes, basically distorting its shape, and pushing it around on its suspension, in directions it normally wouldn't feel forces acting upon it. Lo and behold, the fuzziness cleared up dramatically - so, for once, , the audible problems were of a physical nature, associated with the cheap construction of the driver.

    At high volumes, these problems evaporate, the cone is moving too vigorously for the sound to be audibly affected. This is the first time I've experienced, noticed this sort of behaviour, I'm wondering whether it's an age thing, the colder temperatures at the moment or an overall effect of driving them hard - any thoughts? In any case, I'll have a look around, see if anyone has mentioned such ...
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    Posted 14th July 2014 at 03:59 AM by fas42 fas42 is offline
  14. Old Comment
    fas42's Avatar

    The real story about closed vs open loop class D amps

    If a normal volume control was close to an ideal resistive divider then I wouldn't have issues with them - but they're not, they typically also contain two poor quality sliding contacts - and that's where the damage is done.

    Simple way to test it. Set a pot to give the right resistive division, measure that setting out of circuit - then swap in and out either the pot, or pure resistors that match the pot setting. I did the equivalent decades ago, and the quality compromise was too great ...

    miklos, what I'm after is that the heard quality doesn't depend on the recording 'quality' and media - the goal is that 100% of everything I put on hits the spot. Led Zeppelin I is an amazing recording, it has a massive acoustic which is immensely deep, that makes normal, "audiophile" recordings sound pretty pathetic - it would be a huge shock to many people to hear it reproduced properly, at realistic volumes ...
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    Posted 14th July 2014 at 12:22 AM by fas42 fas42 is offline
  15. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Bit concerned at the moment - I may have overcooked the poor little amp in the speakers ... or it may be the colder weather we're having at the moment, causing longer times for the electronics to condition themselves. The sound at low volumes is very "fuzzy", the noise modulation I mentioned elsewhere is very bad, on both channels - is the DAC "wearing out"? High level sound is fine, I'm listening to a harpsichord at the moment, at max. volume, and there are no problems, earlier on I had high energy rock running also at close to max, and didn't pick any issues. But, with normal classical, say solo piano, with plenty of "space" between the notes the fuzziness was quite bad on softly played notes ... hmmmm, will see how it goes with more playing ...
    permalink
    Posted 14th July 2014 at 12:02 AM by fas42 fas42 is offline
  16. Old Comment
    wintermute's Avatar

    Multi Channel Amplifier with DSP Crossover - Retro styling

    looking forward to the finished pics googlyone

    Tony.
    permalink
    Posted 13th July 2014 at 09:50 PM by wintermute wintermute is offline
  17. Old Comment
    abraxalito's Avatar

    The real story about closed vs open loop class D amps

    Perhaps you are assuming that because Frank shares something here that I find the same as he does? No, I've yet to experience the 'degradation' of a resistive divider and I use them to set the right levels between my DAC and amp when I'm too lazy to wind a new trafo with the right turns ratio.

    No, I don't so much mean the decays of bass (organ) notes rather the whole LF 'bloom' or ambience which sets apart holographic soundstaging from the merely decent.

    As for how low, no there's no number as I've yet to decide a measurement. I'm sure its measurable though, just requires some ingenuity. Playing back a single tone - no, that wouldn't be a worthwhile exercise as its so unlike music. The test stimulus really does need to be as music-like as possible, if you've not come across such a stimulus I suggest you search on 'MTPR'.
    permalink
    Posted 13th July 2014 at 01:00 PM by abraxalito abraxalito is offline
  18. Old Comment
    miklos's Avatar

    The real story about closed vs open loop class D amps

    Maybe you two have way to sensitive ears (and I thought I have to) and very high demand on your electronics.
    It is much easier for me, once i have a pair of relative good speakers ,the sound quality is depending on the recording and a media carrying it. For example I don't understand how a simple, or a set of resistive dividers can degrade the sound so much at this would bother me. Not sure of the LF ambiance either, you mean like a bass pipe decaying in a church? The "dynamic noise (noise modulation) as low as possible" How low, is there a value, a number here? How would one measure if a DAC can retrieve the low level information, or not. Is playing back a -70dBFS tone and analyzing it would be good enough, or would one need a digital storage scope to see the decreased S/N on a dynamic signal? It's a surprise to me that the Led Zeppelin I would be any good for testing audio, other than maybe amplifier power output, no acoustic instruments in it, other than the drums.
    permalink
    Posted 13th July 2014 at 11:03 AM by miklos miklos is offline
  19. Old Comment
    abraxalito's Avatar

    The real story about closed vs open loop class D amps

    Thanks for that Frank, looks like there's more to the story than indicated in the initial paper so another update is in order. Before I write that though I'll need to study more in-depth the different OPS modulation styles as these seem to impact the PSRR....
    permalink
    Posted 13th July 2014 at 05:09 AM by abraxalito abraxalito is offline
  20. Old Comment
    fas42's Avatar

    The real story about closed vs open loop class D amps

    Richard, that paper you mention in your update has a powerpoint style summary of the paper here, http://wenku.baidu.com/view/cf49390b763231126edb118f, 2/3 of the way down. Might be enough to give you the gist of it ...
    permalink
    Posted 13th July 2014 at 03:23 AM by fas42 fas42 is offline
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