[quote:d2aecddf1f="hpn"]I'm confused. From the schematics, the two tubes should be either 12AX7 or 5751. But why we are using one 12AX7 and one 12AT7?[/quote]
I simply pick one schematic to show the measured voltage. I am using 12AX7EH for the 1st stage and 12AT7EH for the 2nd stage to build the PV3
Any reason for not following the original PV3 design, i.e. use two 12AX7 or two 5751?[/quote]
I think the schematic that I picked up is not correct. The 2nd stage should be 12AT7 because based on the schematic diagram to calculate the idle cathode current is 2ma and bias is -2V that match with the specification of 12AT7.
Probably it is not you who picked the incorrect schematic diagram. In fact, I've seen in various other ocassions that the same 12AX7/5751 schematic was stated for PV3. So, just wonder whether the PV3 DIY course conducted by HiFi Fever was the original design/circuitry.
Probably it is not you who picked the incorrect schematic diagram. In fact, I've seen in various other ocassions that the same 12AX7/5751 schematic was stated for PV3. So, just wonder whether the PV3 DIY course conducted by HiFi Fever was the original design/circuitry.[/quote]
The DIY course of HiFi Fever is using 12AX7 and 12AT7.