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  1. Old Comment

    Richard Allan 3 Way Rebuild - So What Do They Look Like?

    Yes it is a philips AD0160 T8. Refer following article on the joys of using this.
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    Posted Yesterday at 03:04 AM by googlyone googlyone is offline
  2. Old Comment

    Richard Allan 3 Way Rebuild - So What Do They Look Like?

    The tweeter is not a Celestion HF 2000, but ye olde Philips AD 160T8 or T4. Most certainly a replacement and not necessarily an improvement.

    Eelco
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    Posted 26th January 2015 at 09:10 PM by Boden Boden is online now
  3. Old Comment
    fas42's Avatar

    Fix it time for PC monitor speakers

    Not relevant to the PC speakers, but I mentioned just lately in the Blowtorch thread about a replacement laptop I'm using at the moment, supposedly capable of decent quality sound, was sounding poorly. And I was hopeful of doing "something about it" ...

    Rather than start another blog about such, I'll just mention here that it's now looking strongly that it's not going to be worth pursing things - I was hoping that strong conditioning might throw it sufficiently into better behaviour, and in fact this does work, but it takes hours to get decent results. And, the killer punch is that the machines reverts right back to sounding awful again the next day - it's completely pointless if the whole tiresome exercise has to repeated every time ...

    So, the flaws due to age, etc, are pretty severe, and it seems that it will really require major exploration, under the hood, to improve things - and it's just not worth it ... really!! At the moment anyway, .

    The symptoms are that if there is any bass below about 200Hz or so, then the sound rasps and burbles, it sounds like bits of grit bouncing on the cone - extremely irritating symptoms. Heavy thrashing with bass signals steadily improves it, but ... see above ...
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    Posted 26th January 2015 at 06:57 AM by fas42 fas42 is offline
  4. Old Comment
    abraxalito's Avatar

    TDA1387 octal DAC looks like a good modding base

    I'll confirm when I get one, but on all the Chinese DACs I've ever seen close-up with USB they've used CM106 or something similar and then route its S/PDIF output into the S/PDIF receiver.
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    Posted 25th January 2015 at 12:13 AM by abraxalito abraxalito is offline
  5. Old Comment

    TDA1387 octal DAC looks like a good modding base

    Any idea what the usb receiver is in the unit? I can't translate the description!
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    Posted 24th January 2015 at 12:42 PM by lordearl lordearl is offline
  6. Old Comment
    abraxalito's Avatar

    TDA1387 octal DAC looks like a good modding base

    Excellent, looking forward to contributing to your mod thread I have some new Sumida 2.2mH inductors coming any day now so they could be just the ticket for an output filter for this puppy....
    Got the Sumidas - minor disappointment as they turn out to be rather lossy going much above 1kHz. Their Q is poorer than the TDKs at 20kHz (around 25-30). But for lower freqs they may turn out to be useful, for example creating a PLLXO at 3kHz or so, they're higher Q than TDKs.
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    Posted 22nd January 2015 at 01:08 AM by abraxalito abraxalito is offline
    Updated 22nd January 2015 at 01:53 PM by abraxalito
  7. Old Comment
    Malefoda's Avatar

    TDA1387 octal DAC looks like a good modding base

    And here I go, two pieces on their way to my home... I'll open a thread for this little thing, hope that will sound good and maybe we can mod it to sound just great.
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    Posted 21st January 2015 at 01:48 PM by Malefoda Malefoda is offline
  8. Old Comment
    abraxalito's Avatar

    Portable headphone amplifiers

    Yes, I wasn't meaning 20dB less noise, rather that much reduction of PSU-induced noise. PSU noise is signal dependent and I reckon its in the main introduced by the output stage. Yes partly I was inspired to try this from learning about how dynamic McIntosh amps sound with their autoformer outputs. I was shocked how dynamic my old Sony headphones (CD3000) sounded once fed via a trafo - previously I'd figured that the fatiguing sound at higher levels was due to their age. The trafo's given them a new lease of life.
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    Posted 15th January 2015 at 11:50 PM by abraxalito abraxalito is offline
  9. Old Comment
    rjm's Avatar

    Portable headphone amplifiers

    I don't think you get the benefit of 20 dB less noise since the op amp gain had to be increased 20 dB (relative to the direct-drive case).

    The increase in load impedance seen by the op amp is the more persuasive argument. A McIntosh amp for headphones!
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    Posted 15th January 2015 at 11:23 PM by rjm rjm is offline
  10. Old Comment
    abraxalito's Avatar

    Portable headphone amplifiers

    Having the trafo improves the dynamics, considerably. With IEMs the swing is perhaps 1V peak, with the 10:1 trafo a 10V peak swing is downconverted to 1V, the PSU noise goes down 20dB. Or put another way, the IEMs look like 1600ohms.
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    Posted 15th January 2015 at 03:34 PM by abraxalito abraxalito is offline
  11. Old Comment
    rjm's Avatar

    Portable headphone amplifiers

    Oh, I imagined MOSFETs running at 100-200 V. If you are just using regular op amps and normal voltages why do you even need an output transformer? Whatever you gain by the step down ratio you lose by having to increase the voltage gain of the op amp proportionately.
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    Posted 15th January 2015 at 06:34 AM by rjm rjm is offline
  12. Old Comment
    abraxalito's Avatar

    Portable headphone amplifiers

    I guess mine are parafeed, I just put them between the driver (normally a CFB high-drive opamp like AD8017) and the transducer, fed through an LC low-pass filter and a 'lytic to block DC. I like to run the driver IC as close to its max supply as possible, so around 10V for the AD8017. I reckon though that higher voltages will probably sound better, because that necessitates a bigger step-down ratio and hence attenuates PSU noise more. Forgot to mention - given the AD8017 is a dual, I run them anti-phase, i.e. the trafo is driven as BTL, doubling the swing.
    permalink
    Posted 15th January 2015 at 02:01 AM by abraxalito abraxalito is offline
    Updated 15th January 2015 at 02:15 AM by abraxalito
  13. Old Comment
    rjm's Avatar

    Portable headphone amplifiers

    It depends if your output transformers are cut for single ended use. If not you are going to have to go push pull or parafeed.

    What kind of voltages are you looking at?
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    Posted 15th January 2015 at 12:31 AM by rjm rjm is offline
  14. Old Comment
    abraxalito's Avatar

    Portable headphone amplifiers

    I have some reasonably compact ferrite trafos in my transportable Ozone DAC. For driving low impedances from opamps they're invaluable but they're at least 20mm tall so wouldn't fit into a low profile case. However I still need a much bigger volume of caps to get the best dynamics, so caps are the primary problem. Perhaps pure classA is a better solution though. When I said 'insufficient' I meant insufficiently low impedance - i.e. too saggy.
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    Posted 15th January 2015 at 12:23 AM by abraxalito abraxalito is offline
  15. Old Comment

    Voltage Regulators for Line Level Audio. Part 10 : Simple Shunts

    is it the best result from all regulator on simulation ?
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    Posted 14th January 2015 at 12:52 PM by oxoxbyx oxoxbyx is offline
  16. Old Comment
    rjm's Avatar

    Portable headphone amplifiers

    Well, there's insufficient in power, which is a rather subjective point, and there's insufficient in voltage, which since I imagine most of these units are regenerating voltage rails using DC-DC converters should not be an insurmountable problem.

    As you know, output transformers solve problems and create them. For a push-pull design they wouldn't have to be all that large, but perhaps "portable" is still a bit of a stretch.
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    Posted 14th January 2015 at 11:53 AM by rjm rjm is offline
  17. Old Comment
    abraxalito's Avatar

    Portable headphone amplifiers

    I can't help thinking that portable amps are going to be hamstrung by insufficient power supplies - as you say the size constraint is severe. Have any portable amps taken up using output transformers yet? I have an idea that with a small enough transformer, an amp could use photoflash caps which have the highest energy density of any high voltage caps (excluding supercaps). I rather suspect the trafo won't be particularly portable though.....
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    Posted 14th January 2015 at 10:14 AM by abraxalito abraxalito is offline
  18. Old Comment
    abraxalito's Avatar

    Revisiting mods to the Lite DAC-AH

    I replied by email. I've also found these - Magnetically shielded inductor 16 * 16MM (472) 4.7MH-in Diodes from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

    a bit risky but they might work well. There's no technical data there, no idea of manufacturer. The size though is promising - bigger means more thick wire
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    Posted 13th January 2015 at 01:07 PM by abraxalito abraxalito is offline
  19. Old Comment

    Revisiting mods to the Lite DAC-AH

    I send you by pm because I don't want kind of advertise online shop
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    Posted 13th January 2015 at 11:57 AM by oxoxbyx oxoxbyx is offline
  20. Old Comment
    abraxalito's Avatar

    Revisiting mods to the Lite DAC-AH

    If you're limited by inductors, what's the biggest inductor you can get easily? Can you get the 1mH SLF7045s from TDK? Can you get the next size up (12mm) from TDK? They go up to 1.5mH. The bigger the inductor (in mH) the more voltage swing you can get out of the filter.
    If you can only get the 1mH SLF7045s I can design you a filter which uses them in series (say 5 in series for each element) and that'll give more output volts.

    I got your PM with the webshop links, will check them out and get back to you on here.
    permalink
    Posted 13th January 2015 at 08:38 AM by abraxalito abraxalito is offline
    Updated 13th January 2015 at 11:58 AM by abraxalito
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