I built a test bed to evaluate different types of anode loads for my next version of the 12b4a preamp.
My current 12b4a preamp is using a 10m45s CCS as the load. It was a quicky to clean up the wiring mess I had initially, but some simple measurements of the frequency response showed it to be flat out past 30kHz.
I am now playing with Wavebourn's Gyrator. Attached is the schematic, pcb used and the response curve. I don't think a gyrator has a response like this indicating I did something wrong. The response curve is shown with a calibration run so it is the circuit response that drops off starting at 10kHz. I have switched tubes, played with bias, and moved the anode voltage up and down. The curve is taken at 140V anode, 20mA bias with 200V b+ into the gyrator.
Your help would be greatly appreciated.
My current 12b4a preamp is using a 10m45s CCS as the load. It was a quicky to clean up the wiring mess I had initially, but some simple measurements of the frequency response showed it to be flat out past 30kHz.
I am now playing with Wavebourn's Gyrator. Attached is the schematic, pcb used and the response curve. I don't think a gyrator has a response like this indicating I did something wrong. The response curve is shown with a calibration run so it is the circuit response that drops off starting at 10kHz. I have switched tubes, played with bias, and moved the anode voltage up and down. The curve is taken at 140V anode, 20mA bias with 200V b+ into the gyrator.
Your help would be greatly appreciated.
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