Some use a higher plate dissipation point and understand that tubes wear faster that way.but they like the sounds they get with that hotter bias. Fwiw, redplating will not occur until plate dissipation is well above the 70% ‘rule’ that many use as a target or limit. One that does not measure plate voltage is an incomplete tool, and I can do as well with only my ears and eyes.ĭo not try this eyes and ears method unless you understand it well.and one has to know what redplating is. Hence my thought that a bias probe with plate voltage measurement is a complete tool. I do not suggest that others use the shunt method, but then if one does not have a bias probe setup that reads plate voltage one is going to be measuring live circuit voltage anyway.and I do not suggest that people do that either unless they are experienced and comfortable working with live circuits. It works, and as robrob notes in his comparison of the shunt method to the method that measures OT resistance, the results are within 1 percentage point of each other. However, I did this only as an exercise and have always checked the numbers with a meter. I have used this method over the years enough to know what my results will be with my ears. A more experienced player might even be able to set the bias by ear and have it somewhere very close to some known range of plate dissipation. But.the amp will work and the sound that is created may please the player’s ears. The problem with this ‘biasing with eyes and ears’ is the same problem with biasing without knowing the plate voltage.one does not really know where the tubes are operating. My ears will put the amp somewhere in the 55-65% of max plate dissipation range, ime. The advantage of this system is that it brings the player’s ears into the equation.and that is the ultimate point, correct.sound. Within the boundaries of crossover distortion and imho redplating, one can find what they feel is a good sound for them. , long before that the amp is not sounding as I want it to sound. At some point and if the bias pot allows it, you will cause the amp to incur crossover distortion.things get harsh and imho unmusical. Lower current draw is easier on the tubes. The amp is safe to play at any setting from there on ‘down’.decreased current draw will cause the amp’s Sonics to creased harmonic content. Note: in fix3d bias, current draw increases while signal is being process as compare to current draw at idle. If redplate begins while you are playing, decrease the draw very slightly until,playing does not bring on redplate. Tube Amp Doctor Transformer 230/115V 1000VA. If the plates do not go into redplate condition while playing, This model comes with 4 octal probes, but I ordered 2 noval probes as well so that I can set up EL84s as well as 6V6s and 6L6s etc. Back away from that point and play while watching the plates. Once you know that, gradually turn the bias adjustment in that direction until the plates just begin to show some redplating. Increasing the draw will bring on a bigger, richer Sonic. Power tubes were a mismatch set of various brand el-34s (2 rubys and 2 service masters which say made in w.germ). 2) Measured 451v on all plates, -42v at bias pins. Then, turn the bias pot a small bit and play it to find out which direction one should turn the pot to increase or decrease the current draw. I wanted to would check the basics first, such as proper output tubes and biasing. All you need is the amp, a guitar and a tool to turn the bias pot. The real skill is knowing just where to set the current level, which is of course different for each and every valve type and can be slightly tweaked for your preferred sound.Okay, I’ll suggest the easiest way to bias an amp.since biasing without knowing the plate voltage is about the same thing. It's really simple and easy to use (as another reviewer has said) and you don't have any high voltage connections to make through a test meter. Four octal socket adapters For the control of the retirement At 6L6GC, 6550, E元4, 6V6 GT, 5881, KT88, KT66, KT90, KT100, 7027A. The readout on the unit is 00.0 mA to presumably 99.9 mA.Ī "Chicken head" pointer knob selects each of the 4 individual valves, or the OFF position. Then you can balance up each side of the push-pull stage. This is a good starting point, but then you need to find the valve manufacturer's specifications from their data sheets. Circuit schematic diagrams usually state a bias Voltage (e.g. The probes each contain a 1 ohm resistor in the cathode lead, so they are measuring total cathode current (anode + screen grid). You can download them from the TAD site, 2 sides of A4 folded into a leaflet. WARNING! - There are no instructions! - If you don't know what you are doing, don't try to use this unless you have a friendly tech to show you. This model comes with 4 octal probes, but I ordered 2 noval probes as well so that I can set up EL84's as well as 6V6's and 6L6's etc.
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