"...No I'm just joking. BUT the valve (tube) tester will tell most of the story..."
In high gain pre-amps good tubes can be noisy and they have to be specially selected for low noise. Good shops like Upscale will use special equipment just for this.
Upscale Says: " After this test, the tube is listened to with high-quality Sennheiser headphones in a circuit that simulates a phonostage. In other words, real-world voltages and high amounts of gain. This lets us hear any noise that might be present in a tube, as well as grading the level of microphonics present. For a deeper discussion on the ins and outs of microphony..."
In high gain pre-amps good tubes can be noisy and they have to be specially selected for low noise. Good shops like Upscale will use special equipment just for this.
Upscale Says: " After this test, the tube is listened to with high-quality Sennheiser headphones in a circuit that simulates a phonostage. In other words, real-world voltages and high amounts of gain. This lets us hear any noise that might be present in a tube, as well as grading the level of microphonics present. For a deeper discussion on the ins and outs of microphony..."