You also probably won't find a practical resistor small enough to act as a fuse, so whatever's cheapest should work fine. You'd probably prefer that resistor burned open before your output tubes melted.
So any size resistor will work, the smaller the better. Let's say you figure you'll never idle the tubes as high as 100mA. Decide on a maximum safe sustained current for your output tubes. One form of the Equation for Power is Power = Current 2 * Resistance. I don't know why people get carried away with thinking they need a high-wattage 1Ω resistor. Unless the amp is cathode biased, in which case you have the bias resistor to ground (but in this case you still only measure across the 1Ω resistor and nothing else). So don't add any additional resistors between the 1Ω resistor and ground.
I adjusted both and its stabilized at just over 49mV on each channel.
#Left channel only bias amp 2 manual#
I took the liberty of checking bias and DC offset the bias was quite low at under 15mV on each channel (service manual says 50mV +/-5mV). No specialized equipment required, and no high voltage to probe. I just acquired a used Adcom GFA-5500 two channel amplifier. So the value of the 1Ω resistor is that you're replacing "Resistance" in the Ohm's Law equation with "1" so that milliamps of current through the resistor directly translate to millivolts measured across the resistor. Or you need a specialized current clamp to place around a wire carrying the current to be measured. Or you have to use the transformer shunt method, requiring power off/power on with clip-on meter leads, or risk arcing as you probe the highest voltage in the chassis. You want to know the tube's cathode current, but measuring current directly requires you to break the circuit and use an ammeter's leads to complete the circuit so that circuit current flows through the meter. Now at 35mvs across R88 the heatsinks are to hot to touch. In those 2 small mvs of a difference, I could honestly feel that the right heatsink was hotter. My left channel was 21mv and right was 23mv. Ohm's Law: Voltage = Current * Resistance. My Adcom service manual page on bias and DC offset lists 23-43mv across R88.
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