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stereo coffee

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  1. Yes its in the detail you don't mention "These measurements were taken at fairly high levels, typically corresponding to –6 dBFS on professional equipment, and will decrease rapidly with input level typically being 3 to 4 times less at 0 dBu, and virtually unmeasurable at –20 dBu. 2) The distortion products produced by an Audiohm coupler are all low order, second and third harmonics, which are much less objectionable than high order harmonics produced by crossover artifacts. 3) In the series/shunt and hybrid series/shunt attenuator configurations the worst distortion occurs at high attenuations, where the output signal level is so low that the distortion is unlikely to be very noticeable " , perhaps some equal google effort to find the distortion of potentiometers passing audio signals... hmm
  2. They were using the street lamp variety not audio type LDR's- their wording being " LDR volume controls are conceptually identical to resistive types, it's just a matter of using an optically-adjusted resistor" .Optically adjusted means they were trying to focus a external led toward the open faced element Audio purpose LDR's have ideal characteristics for audio, and are entirely different, and in a league of their own when it comes to enjoying music.
  3. The type of LDR in the forum discussion was ? ... likely a type of LDR not applicable to audio at all, like an open faced one used for turning on street lamps. Encapsulated LDR's typified by those made by Luna Inc and Elmer Perkins is what you need to discover. http://lunainc.com/product/optocouplers/
  4. The easy answer is that an LDR can be varied in resistance and is not fixed as one value. The more interesting answer requires understanding of the chemical properties of each, as LDR's are not made with the same chemistry as a metal film resistor. It may also urge you to examine opto coupling and other forms of attenuation.
  5. @eltech Yes, as a resistor or a resistive property, it is better than a metal film. Your findings are that two fixed resistors sounds good. Why- because you have removed the mechanical wiping of a potentiometer and soldered one to your input, one to your output and another from the output to ground for each channel. This same property is one of many attributes of LDR's, no mechanical wiping, but better because resistance can be varied. But there is far more with LDR's because they are an optocoupler we can place the attenuation adjustment to cause them to vary their resistance between a potential difference, that does not - and is encouraged not to include ground or signal ground.
  6. How important is a Cd player to the sound quality?

    Yes with a audio bandwidth of 80 khz ! not the miserable 20 khz we are provided, before filters come in to play https://earthworksaudio.com/wp-content/uploads/2012/07/The-world-beyond-20kHz.pdf
  7. Preamplifier Questions

    To reduce distortions, attenuation is what is needed, not in this case pre- amplification that invites unnecessary coupling and alteration - of the audio signal. Your source equipment should already have sufficient voltage and current capability. A phono stage similarly should have these attributes. This presumes your power amplifiers are reasonably sensitive. If they are, you can look at the world of passive attenuation. Hope that helps.
  8. Isolation transformers & RCD devices

    But where is the RCD located ? If it is at the isolation transformer output as an additional safety measure, you are likely to get the first RCD behaving strangely. Using one RCD in this case at the isolation transformer output protects when using that appliance, to the degree that an RCD offers protection, noting there are ratings of RCD https://en.wikipedia.org/wiki/Residual-current_device This sums it up pretty well. http://sound.whsites.net/articles/iso-xfmr.htm "Use of an isolation transformer should be limited only to equipment where it's essential. The rest of the time, equipment should always be connected to the mains in the same way as it is when being used normally. "
  9. Isolation transformers & RCD devices

    What is called Safety Earth requires the chassis metal be earthed to the IEC earth tag that then connects to your house wiring earth, which should include a copper rod driven into the actual ground. http://sound.whsites.net/earthing.htm Using isolation transformers does not remove or change the need of safety earthing.
  10. The AC/DC Appreciation Thread.

    Similarly I remember hearing the concert from 6 km away. AC/DC courteously paid for the residents of Glebe, a suburb which was right next door to the TCA ground to have alternative accommodation that evening, if they wished.
  11. Speaker cable basics required.

    From what I discern in that article, 79 Strand cable carried the best performance http://www.qed.co.uk/speaker_cables/profile/qed_classic_79_strand_cable.html however a earlier article by Cyril in Electronics and Wireless World also praised highly RG58 coax - using the inner core and having the shield floating for each cable- in so doing achieving a Faraday shield effect along the length of cable. I think Cyril at that time said RG58 was the bargain of the century. I use RG58 myself and find it very good. To clarify further you use the inner of RG58 for positive with shield floating, and a separate RG58 cables inner for negative with its shield also floating. You need to shop around for good quality RG58 as there is cheap rubbish, vs better type. Noting too RG58 has limitation with its power handling capability. I use 2x Quad 306 so 70w per channel at other times a Net Audio Mk 3 Quad 405 so about 120w per channel. In both situations the cable has not been a limiting factor. Noting also Cyril advocates a Zobel network at the speaker lead, reception end , see post Three Zobels ideally http://www.diyaudio.com/forums/multi-way/190300-zobel-network-2-print.html
  12. Speaker cable basics required.

    Essential reading: http://www.waynekirkwood.com/images/pdf/Cyril_Bateman/Bateman_Speaker_Amp_Interaction.pdf
  13. How important is a Cd player to the sound quality?

    If CD is your main source, then finding a good sounding player is a priority. The differences are due to the players DAC but more so its analogue output stage. Most CD players will have operational amplifiers to do what is called current to voltage conversion - often shortened to I to V. Some manufacturers buy in the cheapest opamp to do the task, encouraging owners of such players to try different op amps. A good thing to do is to look up the manual for your player and download its schematic Hi Fi Engine for instance is excellent, to look such information up. Occasionally a manufacturer will provide ideal opamps for their player, I think NAD make some effort in this regard. If you want to take the DIY path to swap these out, be aware there are bad sounding op amps and exceptionally good ones, and middle of the road devices as well. A good step is (- if your player uses DIP size op amps ) to install turned pin sockets, which means you are reasonably free to try one op amp vs another. Op amps come in dual packages and singles - you have to use Dual types - which can include adapters with 2x single opamps , or Single types , as your CD player is wired for one or the other. Be aware too that some players will have surface mount devices often called SOIC , which are not easy to change. For instance I use a Sony CX555ES and I recall installing LM6172 op amps - its a nice sounding player that I use every day. Whilst CD player sound is important, there are other areas where audio can and does get lost along the way. My advice is to use a dedicated attenuator, rather than an active preamp , then simply match it to a power amp with good sensitivity typically under 1 volt for full output, in so doing you usually reap reward by using shorter paths, from source components to your power amp(s) and eventually your speakers.
  14. Time for a new PC - Suggestions and advice welcome

    My advice would be not to get tied up in proprietary operating systems, as the hardware you then use becomes redundant in very little time. and has restrictions which are the exact opposite of free software, namely you are not free to run, copy,distribute, study, change and improve the software. If you want these restrictions - that is up to you. I have used Linux since 2003 and never regretted it. Linux Mint is a good place to start http://www.linuxmint.com but many flavors here http://distrowatch.com https://www.gnu.org/philosophy/free-sw.html “Free software” means software that respects users' freedom and community. Roughly, it means that the users have the freedom to run, copy, distribute, study, change and improve the software. Thus, “free software” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech,” not as in “free beer”. We sometimes call it “libre software,” borrowing the French or Spanish word for “free” as in freedom, to show we do not mean the software is gratis. "
  15. How much better

    If you require another, this might assist. Note the same website is linked to, hopefully that too is also not a problem for you. http://sound.whsites.net/valves/index.html