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01-31-2021, 12:38 PM
Hi TiCatFan
The build is past the point where you need the safety socket, so bypass it. It sounds like having the tubes biased as you think they should be is at a critical level compared to the wattage of the limiting bulbs, which brings up the point:
DO NOT set idle to the final level while power to the amp is limited by the Power Limiting Safety Socket.
The PLSS is droippong some voltage to the amp and when the limiter is bypassed all the voltages in the amp will rise. This means both screen and bias voltage will rise, but the idle current of the tubes may rise at full mains input. This is only an issue if you are aiming for close to maximum tube dissipation at idle.
Regarding the channel switching: It is okay to have the first stage of every channel receive signal at all times. Channel muting should always be positioned after the first stage regardless of whether the outputs of the channels are switched. This two-point muting is especially important for high-gain channels.
The "howl" of the active but nonselected Z channell suggests that its output wiring may be too close to its input wiring as the channel is noninverting overall - always a risk of oscillation. On the other hand, the howl can simply be the fact the channel is uncontrolled.
The build is past the point where you need the safety socket, so bypass it. It sounds like having the tubes biased as you think they should be is at a critical level compared to the wattage of the limiting bulbs, which brings up the point:
DO NOT set idle to the final level while power to the amp is limited by the Power Limiting Safety Socket.
The PLSS is droippong some voltage to the amp and when the limiter is bypassed all the voltages in the amp will rise. This means both screen and bias voltage will rise, but the idle current of the tubes may rise at full mains input. This is only an issue if you are aiming for close to maximum tube dissipation at idle.
Regarding the channel switching: It is okay to have the first stage of every channel receive signal at all times. Channel muting should always be positioned after the first stage regardless of whether the outputs of the channels are switched. This two-point muting is especially important for high-gain channels.
The "howl" of the active but nonselected Z channell suggests that its output wiring may be too close to its input wiring as the channel is noninverting overall - always a risk of oscillation. On the other hand, the howl can simply be the fact the channel is uncontrolled.
