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Tube OP POINTS

If you own and run EMLs, ask Jac at Jac Music, the main man , what OP Points HE likes. He will tell you !!

He will usually tell you about 10 or 11 Watts dissipation, on a Type 2A3 I THINK. Ask him.

If you run too much plate dissipation, the tube will sound thermally stressed in its music presentation, because it is thermally stressed!!

Many people who want to determine the optimum point of plate dissipation by ear, will start their explorations at the Golden Ratio, of the plate's maximum dissipation, roughly 62 percent. SO, for a 10 Watt Type 45, start at 6.2 Watts total plate dissipation. On a 250 VDC P-K differential, 25 mA. gives us 6.25 Watts.

That will be very relaxed sounding, and the tube will last for tens of thousands of hours. One can " tweak " around this point, and optimize it over time, even further, IF you are so inclined.

On a 2A3, one should NEVER run it at 250 VDC P-K and 60 mA. Golly, that is 15 Watts plate dissipation, 100 % of the tube's maximum rating. It will be stressed sounding, thermally-stressed sounding, at that point. The tube won't last long either.

However, if you have poor internal wiring, and poor out-of-time power supply energy-delivery inside the amp, " hotrodding " the op point may be necessary to your ear!! The amp may initially sound better when the op point is hotrodded, but the effect is just temporary, due to the constant thermal stress applied to the plates, in such a screwed-up conglomeration.

Build factors such as short-as-possible lead lengths, gauge and quality of internal wiring, and parts lay out, all come into play, in finding the best op point. The WHOLE amp needs to be optimized. That is why I NEVER listen to a breadboard. It isn't the real thing.

Imagine listening through crummy / long clip lead wires and clip lead terminations, versus good wire and nice Wonder Solder Signature shiny joints. All such factors, in "audio-design-by-ear", is what separates the good from the not so good.

Its NEVER easy.... to obtain high performance !!


Jeff Medwin





Edits: 10/16/16 10/16/16 10/16/16 10/16/16

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