So I’ve realised that these little flimsy piezo disks are just not going to cut it. They practically disintegrate very quickly when driving the flask. I guess they just aren’t meant to be driven by these kind of frequencies… Remember this is just the disk that is epoxied onto the side of the flask to pick up the vibration, this has not been fried electrically – it has been fried acoustically!
A different method of acoustic monitoring could be employed – involving a 25khz ultrasonic transducer that is positioned close to the flask. This way we’ll be picking up the amplitude of the flask indirectly, and not destroying things. The fact that it is not attached to the flask shouldn’t be an issue since the thing is radiating ultrasound which can be picked up some distance away… let’s try it out anyway.
The other thing that turned up was a dead cheap 30W PA amplifier – this cost me a tenner, it’s billed as frequency response up to 18khz, which is some way under what we need, but actually these amps are capable of handling frequencies way outside their spec.
The idea is to drive the amp with 1V signal from the generator and boost the signal for driving the transformer and transducer combination. 30W gives us a lot of headroom – even if we’re talking higher impedances into the transformer, we should get enough power.