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  1. Old Comment
    abraxalito's Avatar


    I have given that some thought - I've only had capacitors go short when overvoltaged though, they overheat and then explode. The total energy storage is about 2.2kJ but very high peak currents are possible so yes its entirely possible that one cap would have vapourized lead-outs.
    Posted Today at 12:58 PM by abraxalito abraxalito is online now
  2. Old Comment
    miklos's Avatar


    Excellent looking job, gratulations.
    I guess if one would get shorted, the rest would burn the short off.
    Posted Today at 10:48 AM by miklos miklos is offline
  3. Old Comment
    fas42's Avatar

    Doing interesting things with electronic keyboards

    A quick note just to emphasise that when the Yamaha is in the "zone" - like just now - that it passes the Listening In Another Room test. I've got it running its auto Rock accompaniment with solos sequence, and from the other end of the house it's got the bite and kick of something close to being taken seriously. So, how can a miserable 10W amplifier do that? Well, because it's been engineered to work well, and because I've taken some steps to ensure that its full potential is actually realised in the now ...
    Posted Today at 01:08 AM by fas42 fas42 is offline
  4. Old Comment
    fas42's Avatar

    Doing interesting things with electronic keyboards

    I've been inspired to use this particular exercise as a way of showing how I go about dealing with issues, and Yet Again, the no. 1 lesson is - LEARN HOW TO USE YOUR BLOODY EARS !!!

    There now, was that loud enough for everyone, ? It's a simple thing, but I note that so many run off to their oscilloscopes, and other assorted instruments, or DBX exercises, so that they "know what's going on" - and I suspect their chances of picking up anything of real significance are so close to zero that way ... why bother??

    This is a lead-in to remarking that a fancy keyboard makes the job of learning how the sounds change by doing little things, when the objectivists most likely will insist that they don't and can't, so very easy ... it's trivial to make the electronics repeat a sound pattern over and over again, and for that pattern to be as complex as you care to make it - it's a signal generator, all nicely bundled up in a single, solid box, producing acoustic output. Set up a musical pattern, and then hit the beast - not literally, - with bits of electrical nastiness, and see how it responds. Since it's a "black box" it's somewhat hard to probe various bits - so, fall back to using your ears!

    Right, this all came about because our fridge is on the same circuit as the keyboard - and, it disturbs the audible sound. Not by causing audible glitches, the usual obvious stuff people mention - but the quality of the sound is degraded. As something people can relate to, it's like the difference between using a really 'musical' amplifier, and a so-so one, in a normal audio system.

    So, this post is not about "how to fix this problem" - there are obviously a myriad ways of going about that; it's that one should learn to recognise that this type of thing is going on, and therefore something has to be fixed!! Not, "I don't like the sound of my system - I guess I'd better design and build a better amp" - talk about doing it the hard way, !

    Anyway, enough bluster for the moment ...
    Posted Today at 12:03 AM by fas42 fas42 is offline
    Updated Today at 12:57 AM by fas42
  5. Old Comment
    fas42's Avatar

    Doing interesting things with electronic keyboards

    Okay, just looked up YouTube, a few people demonstrating the unit, the best one to get an idea, so far, of what it can do is this - Yamaha PSR-6700 Keyboard 2 Demonstration Songs - YouTube. Note the range of sounds and effects - and, that what you are hearing is a straight capture of the analogue signal, NOT what is coming from the speakers - you can pick this because the camcorder switches back on with noise at the end.

    Imagine an infinite combining and selecting of everything you can hear in that video, plus much more, to give one an idea.

    Now as regards SQ, how it comes across from the inbuilt speakers almost perfectly matches how the video sounds, on my PC speakers. But, now imagine that running at serious high end speaker levels, near maximum volume, and still sounding as crystal clear - won't do it from cold, needs serious running in to make it happen ...

    For a complete contrast, Kris Nicholson Demos His New YAMAHA PSR 6700 Arranger Workstation Video 1 - YouTube and the following videos show what it can do, but the sound quality is appalling!! Just listen to the first voice the chap plays, a grand piano - a million miles from anything worth listening to! So, why is it so bad? Firstly, the camcorder is picking up the sound from the speakers, there's no fudge involved, two losses of quality right there; but mostly the instrument has likely just been switched on, and no effort has been made to improve the quality of the internal sound system.

    That grand piano sound ends up pretty damn good when the instrument is fully wound up to optimum tune; it won't fool anyone, but it doesn't sound like the tinny nonsense in that video ... and that's where the tweaking becomes very important ...
    Posted 30th July 2014 at 04:59 AM by fas42 fas42 is offline
    Updated 30th July 2014 at 05:29 AM by fas42
  6. Old Comment
    fas42's Avatar

    Doing interesting things with electronic keyboards

    Very pleased at the moment ... without doing anything too specific to mitigate interference so far it's finally broken through the quality barrier - the essential trick was constantly running it, over many days, most of the time as loudly as was reasonable, allowing all the capacitors and circuitry to stabilise. Hence the quick follow-on update, this only just came about in the last hour or so ...

    Basically this now allows the unit to run at full volume, and still sound extremely clean - the cymbals and drum strikes sound pretty authentic - remember, these are just sampled sounds - and all the layering of the instruments nicely separates, subjectively. Rock styles are very punchy and full, good clarity - even the boring, me-too rhythms work; meaning interesting to listen to - good signs ...
    Posted 30th July 2014 at 03:23 AM by fas42 fas42 is offline
  7. 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.

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

    Superregs for your line-level projects

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

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

    ESI Juli@ analog card interface details


    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
    Posted 20th July 2014 at 10:48 PM by Greg Stewart Greg Stewart is offline
  10. 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 :-)
    Posted 18th July 2014 at 02:47 AM by zog666 zog666 is offline
  11. 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.
    Posted 17th July 2014 at 10:17 AM by dimkasta dimkasta is online now
  12. 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.
    Posted 17th July 2014 at 12:28 AM by fas42 fas42 is offline
    Updated 17th July 2014 at 12:31 AM by fas42
  13. 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.
    Posted 16th July 2014 at 10:56 PM by abraxalito abraxalito is online now
  14. Old Comment
    miklos's Avatar

    The real story about closed vs open loop class D amps

    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.
    Posted 16th July 2014 at 06:39 PM by miklos miklos is offline
  15. 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" ...?
    Posted 15th July 2014 at 03:43 AM by fas42 fas42 is offline
  16. 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 ...
    Posted 15th July 2014 at 03:22 AM by fas42 fas42 is offline
  17. 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.

    Posted 15th July 2014 at 02:53 AM by wintermute wintermute is offline
  18. 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!!
    Posted 15th July 2014 at 01:53 AM by fas42 fas42 is offline
  19. 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 ...
    Posted 14th July 2014 at 03:59 AM by fas42 fas42 is offline
  20. 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 ...
    Posted 14th July 2014 at 12:22 AM by fas42 fas42 is offline
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