Dummy load for bench testing tube pre.

[wanders]

I just finished building a line level, unbalanced, stereo preamp which performs well for about 10 minutes then begins to develop hum and noise as it warms up.

I want to bench test without hooking up to an amp & speakers. How would I assemble and hook up a dummy load to handle the output?

Thanks

 

[SY]

A 10k resistor will be sufficient.

 

[wanders]

A 10k resistor will be sufficient.

Thanks,

Any concern about wattage?

 

[SY]

No, you're unlikely to dissipate much. For 2V out, 10k, P =V^2/R = .0004 watt.

 

[DF96]

Problems after 10 minutes suggests a heat related issue. Are you running any valves near their dissipation limit, or near their grid leak resistance limit?