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Since its inception ten years ago, the Harbeth User Group's ambition has been to create a lasting knowledge archive. Knowledge is based on facts and observations. Knowledge is timeless. Knowledge is human independent and replicatable. However, we live in new world where thanks to social media, 'facts' have become flexible and personal. HUG operates in that real world.

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Cables the diameter of your finger? What about inside the amplifier?

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  • Cables the diameter of your finger? What about inside the amplifier?

    On this post I mentioned how extremely small the semiconductor junctions are inside your solid state power amplifier. It is those junctions of dissimilar materials where a small control signal (from your CD player) is boosted up into a big current millions of times greater, sufficient to drive your speakers. The semiconductor junctions are nothing more than a gate across a dam: the power supply is the dam or reservoir.

    So, keeping our feet firmly on the ground, do we need speaker cables that are a) exotic in their construction or will bog standard (tinned?) copper wire do the job adequately b) do the cables need to be as thick as water hose?

    Here's a picture inside a typical 50W-80W transistor amplifier (actually a Quad 306). One picture shows an overview, where I've marked the red and black output terminals: the other is a close-up where I've traced-out the signal track back from those terminals on the typical copper tin foil which is the track itself. For comparison you can see that the blue diode is about 3mm diameter.

    Is there really any point in using chunky cable when the signal is running around inside the power amp on thin tracks? You decide.
    Attached Files
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

  • #2
    Lovely pictures (and interesting to note the heat marks on the board where the leads to the banana sockets are soldered into the ends of the tracks). As a counterpoint here is an internal photo of an anti-Quad (NVA AP50):

    http://i68.servimg.com/u/f68/13/48/07/74/nva_ap13.jpg

    Mr Dunn of NVA would probably have one use the same wire from the back of the amp to the speakers as he has used from the boards to the sockets.

    Comment


    • #3
      Originally posted by A.S. View Post
      Is there really any point in using chunky cable when the signal is running around inside the power amp on thin tracks? You decide.
      No, no point at all.

      Of course the printed board tracks and internal amp wiring is very short compared to the wires from the amp to the speakers, so the external wires need to be a little more chunky, so as not to introduce a significant series resistance. This is well achieved by ordinary 79 strand speaker wire (2 square millimetre cross section). If the leads are many metres long there may be need to go up to 4 square millimetres. More is just nonsense.

      All you need is

      http://www.qed.co.uk/181/gb/product/..._79_strand.htm

      2 per metre.

      If you need to hide the wire under carpets get some ultra flat cable

      http://www.qed.co.uk/180/gb/product/...ultra-flat.htm

      That's expensive! 2.50 per metre.

      Buy the cable that does the job without any sales hype. Save your money for more music.

      Comment


      • #4
        What about the other end, the crossover? Some people find the biwire brass jumpers inadequate, and yet they are really chunky compared to any printed circuit board I have seen when it comes to area and thickness. The crossover get a lot more voltage and current and needs to be constructed thereafter I presume. We discuss cables forever , has anyone tested different materials used on the board tracks. AND how PURE is the copper in question.

        Comment


        • #5
          Exchanging the Harbeth-fitted thick heavy gold plated brass bi-wire links for another material and expecting a sonic improvement is just nuts. It is totally and utterly impossible.

          Comment


          • #6
            No, not heat marks - resin

            Originally posted by honmanm View Post
            ... interesting to note the heat marks on the board where the leads to the banana sockets are soldered into the ends of the tracks...
            No that is not heat marks at all. That is the flux lubricant that is inside all electronic solder - a brown tree-resin which is visible around most solder joints on one or other side of the circuit board when examined carefully.

            Comment


            • #7
              view as an interested non-electronic engineer

              Given the ratio between PCB track length and cable length (probably at least 1:20, more likely 1:50), imperfections in PCB tracks are going to be relatively insignificant, especially if they are nice and wide as in the crossover pic that Alan posted on the other thread.

              A "serious" issue with PCB layout (at least for amplifiers and power supplies) is the routing of ground paths, and in the subjectivist camp PCB conformal coating is seen as a Bad Thing (note the un-coated boards in the NVA amplifier linked to above).

              But the subjectivist camp don't measure, so that doesn't really answer your question, I think... however what has helped me is to identify the biggest problem, solve that, then reassess to find the next one, and so on. In my opinion making a host of small tweaks can mask the big problem that one really needs to solve...

              Comment


              • #8
                Originally posted by LarsS View Post
                AND how PURE is the copper in question.
                Is there any evidence that the purity of the conductor or its precise composition makes a difference at audio frequencies?

                As long as it's DC resistance is low enough and its capacitance and inductance are not crazy, does it make any difference?

                I guess a 16A or 30A mains cable as used in house wiring would work as well as anything, though it might not look so good.

                Comment


                • #9
                  Originally posted by Labarum View Post
                  I guess a 16A or 30A mains cable as used in house wiring would work as well as anything, though it might not look so good.
                  Solid-core twin-and-earth works surprisingly well - the 3.5mm sq type is a good entry level cable. Compared to enamelled transformer wire of the same cross section, there seemed to be a loss of resolution - this was with a notoriously cable-sensitive NVA amp, and the P3ESRs. FWIW I'm presently using approx 2mm sq enamelled wire (Maplins YN80B) left over from the new amp project...

                  Comment


                  • #10
                    I'm in a quandary here, as I've used bell wire, QED 79 strand, RS 42 and 56 strand, Nordost Flatline, Chord Rumour and Odyssey silver plated PTFE insulated and mains cables of various gauges.

                    I don't care for standard 79 strand to be honest, but accept it's small in size and easily hidden. The QED Micro was popular in certain dealer chains as wives liked it, but this stuff really did have an audible effect I found in runs of 5m and over. I also found gthe twin and earth cables not to be of the finest quality and I thought that sometimes this was audible, although I'd almost certainly fail a blind test ;)

                    My favourite speaker cable for general purpose use is the 2.5 and 4mm Van Damme round blue stuff. It's cheap to buy, apparently uses good quality copper in its construction and doesn't look too intrusive. I also found the old Quad speaker cable (the thick beige round stuff with two chunky conductors within) really excellent with a wide range of equipment of varying loading.

                    I'm sure Harbeth would argue that, as their products have a benign impedance rarely dipping below 8 Ohms, that the gauge of speaker cable doesn't matter so much. I'm sure that's absolutely correct, but as my favoured cables are relatively inexpensive to buy, I'd err on the safe side and use the 4mm if possible. Anyway, the wire links inside a Quad 306 are the least of its trouble - give me a 606/707/early 909 any day - much more headroom when the music has some percussion in it.....

                    Comment


                    • #11
                      I rarely get involved in discussions about speaker wire, but the thought occured to me that there are two possibilities; it either makes a difference or it doesn't.

                      If it doesn't, then it really doesn't make any any difference what you use.

                      On the other hand if it does make a difference wouldn't you want to use what the person who designed the speaker used in its development. To use anything else would mean you were introducing a colouration not present when he voiced the crossover.

                      Comment


                      • #12
                        Why stop at the speaker cable ? Why not use exactly the same system as the designer, in an identical room, playing the same music ? Only then will you be certain of hearing what the designer hears.

                        Comment


                        • #13
                          Originally posted by hifi_dave View Post
                          Why stop at the speaker cable ? Why not use exactly the same system as the designer, in an identical room, playing the same music ? Only then will you be certain of hearing what the designer hears.
                          Good point hifi_dave.

                          In my experience, cables make a difference - but only up to a point. And for me, that point is based on price - I'm prepared to spend US$500 on cables but not more. And I have to be able to hear improvements before paying.

                          Comment


                          • #14
                            Designer's recommendations

                            Originally posted by hifi_dave View Post
                            Why stop at the speaker cable ? Why not use exactly the same system as the designer, in an identical room, playing the same music ? Only then will you be certain of hearing what the designer hears.

                            I would have but Harbeth's designer said the speakers meant to be played in an average or typical home. The designer also said any well designed amplifiers would be sufficient for Harbeth speakers. The same goes for the cables.

                            I got no problem to those who could hear the difference. I only wanted to know the reason. It is no point suggesting, say a health product which supposedly make you younger, but then with a disclaimer that it may also make you older so try it first.

                            So far, contrary to earlier assertion that cables improve sound now we have agreed they make a difference. Difference is not improvement. And no cable can improve or increase the final frequencies coming out at the amplifier's terminals.

                            ST

                            Comment


                            • #15
                              Cables - and the HUG quote of the Year 2010

                              Originally posted by STHLS5 View Post
                              ... It is no point suggesting, say a health product which supposedly make your younger, but then with a disclaimer that it may also make you older so try it first....
                              Congratulations, you are the winner of the HUG 2010 Quote of the Year.

                              It is an interesting philosophical and engineering point. How can a cable receive rave reviews by some subjectivists whilst others revile it? Perhaps the answer lies not in the cable but solely in the mind of the listener.

                              Comment

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