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ChrisB

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  6. R.I.P Gary Moore

    in Music Discussion

    Posted

    Sure that wasn't the Scottish guitarist out of Lizzy (whose name escapes me right now)?

    Certainly he told that story in the excellent BBC 4 documentary the other week.

    And then Moore was brought in to cover for him on their US tour.

    Just remembered, it was Robbo. Robbo was saving Frankie Miller from being glassed.

    Anyhoo, here's what The Sun says, take it with a pinch of salt if you will:

    Thin Lizzy star Gary Moore found dead in hotel room | The Sun |Showbiz|Music

    It was something like that. Robbo had his hand slashed and thus couldn't play so Gary was brought in.

  20. tube grade

    in Musicians' Corner

    Posted

    I think that might be the wrong way round in part. My understanding is that higher voltage means they can run with greater volume and clarity before breaking up and lower voltage means they break up sooner.

    "Apart from this safety/valve survival issue, bias adjustment becomes a matter of taste. High current gives you power/volume, clarity, good top end. If the idle current is set too high (under bias) then the valves will run too hot and the life of the valves will be reduced significantly. Less current gives you earlier break-up, with less volume, less clarity and top end. If the current is set too low (over bias) the tone of the amp may be thin and lacking volume."

    How to bias a valve amplifier, valve amplifier biasing, biasing valves, from hifiandaudio.com, Review Hifiandaudio.com, about hifiandaudio.com

    "Don't be confused with terms like "raising the bias". This is a bit confusing because raising the bias voltage, I.E. making the bias voltage bigger by going from -40vdc to -50vdc will cause the tube dissipation to be reduced. Or it could mean to make the bias voltage more positive by going from -50vdc to -40vdc causing the tube to dissipate more power."

    Types of Tube - Valve Bias Information HTML Page

    I think you're confusing voltage and current.

    Your first example mentions "high current" which implicitly means "low voltage" (P = IV), i.e. cold biased or reducing the voltage across the valves.

  21. tube grade

    in Musicians' Corner

    Posted

    Biasing basically means altering the voltage across the valves in your amp. Each amp will have a specific biasing range, e.g. my 50W Vintage Modern likes its valves between 44 to 48 mV.

    Biasing an amp "hot" means increasing the voltage above the recommended range. I think this means that the sound will break up (distort) quicker but the side effect of this is your valves will also die quicker.

    Biasing the amp "cold" means decreasing the voltage below the recommended range. As the inverse of hot, this will smooth out your sound and make valves last longer.

    Perhaps obviously, too hot or too cold will make your amp sound like arse... Although, some [strange] people quite like this!

    I believe the grading above describes the break up of the tube. I can't remember whether A grade break up first or last but I'm pretty sure that's what the spectrum illustrates.

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