SergeAuckland

Super Wammer Plus
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About SergeAuckland

  • Rank
    Certified Measurist

Personal Info

  • Location
    Bury St Edmunds, UK
  • Real Name
    Serge

Wigwam Info

  • Turn Table
    EMT948, TRS9000, BD1
  • Tone Arm & Cartridge
    TSD15,V15VSAS,MC15S
  • SUT / Phono Stage
    In turntables
  • Digital Source 1
    SBT
  • Digital Source 2
    Meridian 206
  • DAC
    DEQ & DCX
  • Pre-Amp
    Meridian 501
  • Power Amp/s
    3 x Behringer A500
  • My Speakers
    Active B&W 801F
  • Headphones
    AKG K270 KOSS Pro4AA
  • Trade Status
    I am not in the Hi-Fi trade
  1. cartridge loading

    That makes sense, thanks. I also remember one with little spring clips that went round the pins, maybe that one was for Shure cartridges, possibly made by SME, maybe Shure itslef, it's a looooong time ago now, and my HiFi YearBooks don't show them. S.
  2. cartridge loading

    That's the one! I thought it was Ortofon, but couldn't work out why they would make something for a rival cartridge manufacturer. Or maybe those were only for Ortofon cartridges and I imagined they were for Shure...... S.
  3. cartridge loading

    The V15s did need a lot of capacitance, around 550pF, so with the capacitance of the cable, which, whilst not ultra low, was still nicely low, and the capacitance of the phono input, 200pF additional seems about right. There was one manufacturer that made little chip capacitors that fitted directly on the pins of the V15 series to add something like 200pF. Can't remember who that was, but a clever idea. S.
  4. cartridge loading

    Indeed. The V15 series all needed additional capacitance to flatten the HF peak. There's one web site I looked at that did a lot of adjustment of R and C on the V15V, and the flattest response was with a 33k resistive loading and 550pF capacitance, if I remember the numbers. Arm lead capacitance was something of an issue in the early 1970s as CD-4 quadraphonic required very low capacitative loading to maintain the HF carrier, so all arm manufacturers reduced the capacitance of their cables. Several people offered special low capacitance cables for arms with a socket at that time. That of course made things worse for the majority who weren't interested in CD-4 quadraphonics, as capacitance was even lower with the new arm cables. S.
  5. cartridge loading

    Low output MC cartridges are pretty insensitive to loading once the resistance is more than 5x the coil resistance, and definitely once it gets to 10x the coil resistance. They are totally insensitive to capacitance unless it's enormous. The 150-1000pF range of typical input capacitances (including cable) have no effect on a low output MC. MM cartridges are very sensitive to capacitance, and the ideal capacitance varies between cartridges, so it's not sufficient for it just to be low. Some cartridges work best with about 200pF, others need 500pF or more. All MMs are designed for a nominal 47k ohm input impedance, but there's evidence that the flattest response can be best achieved with a different resistive loading as well as capacitative loading. A MM stage that allows the adjustment of both would be ideal. High Output MCs are closer to low output MCs than MMs as far as Capacitative loading goes. They have a higher coil resistance and hence inductance, so are more sensitive to capacitance than LOMCs, but the inductance is still much lower than an MM, so the sensitivity to capacitance is much less pronounced. Having a higher coil resistance means they need higher resistive loading, and it's normal to run a HOMC into the standard 47kohm MM input, with whatever capacitance that input provides. It should be noted that the capacitance the cartridge sees is the total capacitance of the arm wiring, the arm-phono stage cables and the phono stage's input capacitance. That's why it's pretty much impossible to get the capacitance down to 100pF or below, a figure of around 150-200pF is the practical minimum. Fortunately, most MMs need that or more, so it's rarely a problem. S.
  6. Do all power amps buzz?

    I got the design from here http://sound.whsites.net/articles/xfmr-dc.htm I used a Bridge rectifier rather than 4 individual diodes, and I put the blocker in the neutral line rather than live. S.
  7. Do all power amps buzz?

    I made my own, a Bridge rectifier and two capacitors, in a box. £10 in parts, plus box. Don't understand why they need to be so expensive. S.
  8. Speaker sensitivity

    The reason for asking the question, was that he used an AT cartridge, and I wasn't aware that AT ever sold ceramic or crystal cartridges. I agree sound quality would have been iffy indeed. My first introduction to Cream was Fresh Cream being played through a Vox amp at a party, but at least from the 'tape' output of a record player (couldn't call it a HiFi). That was loud! S.
  9. Do all power amps buzz?

    There's a difference in the mechanism causing hum and buzz. Buzz is caused by the sawtooth waveform of the full-wave rectified mains breaks through into the output. This in part can be due to inadequate filtering and/or the design not having sufficient immunity to HT variations. Mechanical hum is caused by the transformer core physically moving due to the changing magnetic field (magnetostriction). This can be made a lot worse by even small amounts of DC on the mains, especially with large toroidal transformers that have very low resistance primary windings. Here, even small amounts of DC can result in large currents which saturate the core, cause the primary inductance to collapse and the transformer to get hot and hum. Hum in the loudspeakers is caused by the 50Hz induction into sensitive parts of the circuit, and is rare in SS amplifiers, more common in valve amplifiers where the 50Hz heater supply modulates the valve current. In output stages, this modulation is small, but small-signal valves as used in preamps can suffer from this quite badly, which is why well-designed preamps and power amp front-ends often have DC heaters. Hum-bucking is a cheaper solution, which in effects injects a hum of opposite polarity, cancelling the induced hum. A further source of hum can be earth loops, where the inevitable mains transformer fields induce into the screens of coax cables and set up loop currents. These currents create voltages in the small but finite resistance of the screens and which appear in series with the signal voltage. Balanced inputs are used in effect to cancel these induced voltages so although the earth loop is still there, it has a much reduced effect. S
  10. Do all power amps buzz?

    Exactly that. It's totally a matter of degree. And yes, buzzing raises the noise floor, both the electronic and ambient noise. Whether it matters is again only one of degree. If you can't hear it, it won't, if you can, it might. S
  11. Do all power amps buzz?

    Therefore 'wammers contain mains transformers. Spot the logical flaw. S
  12. Speaker sensitivity

    How did you do the RIAA equalisation with that rig? S
  13. Do all power amps buzz?

    Yes, all amplifiers will have a small amount of buzz through the 'speakers the issue is the extent. Any half-decent amp will have buzz that's inaudible at the listening position, unless you're using very sensitive loudspeakers with an excessively powerful amp in a quiet environment. In most cases, the buzz is only audible very close to the 'speakers. Also every amplifier will have a small amount of mechanical hum from the transformer, and again the issue is whether it's audible and intrusive. It may depend on whether you have any DC on the mains, but even with a DC blocker, you'll still get the mechanical hum from the transformer. The important thing is that it should be so low as to be inaudible, and this depends on how quiet your room is, how resonant your location is, how the amplifier case is made, and of course, the quality of the mains transformer itself and its mounting. It's not just amplifiers that can hum mechanically, anything with a mains transformer in will do so to some extent. S
  14. bi-amp vs pre/power vs pre/2-monoblocks

    ^ Agree with the pointlessness of bi-amping whilst retaining the passive crossovers. If you want to make a genuine improvement, bypass the passive crossover and go active. S.
  15. radio 2 sounds better

    Actually, even the digital platforms go through an Optimod, albeit a different model. Main network FM uses (used) the 8500, digital the 6200. The latest Optimod which the BBC may have changed to has separate processing for analogue and digital platforms in one box. On-line delivery may have used the 6200 or the PC1100, but as far as I know, all BBC output goes through an Optimod, even if it's used only for protection as a final limiter which should never be activated. BBC Local Radio used an Omnia processor at one time, but I think they changed to the Optimod 8300 some years ago. S