Why not implement plate choke? I have ordered from AlieX 1380H (up to 30mA) choke. It has 5.4K ohm. For 3A5, good operating point is 100V/10mA with about ~-2.5V bias.
So, with B+ of 150V on one side of plate choke and the other on plate, you will have about 100V on plate. I recommend fixed bias.
P.S. I ordered these chokes, but have not tested them yet. I think they will do a great job.
Double C amorphous iron core 30mA 1380H 5450Ω choke coil for European tube amplifier Choke coil Eliminate hum|Transformers| - AliExpress
So, with B+ of 150V on one side of plate choke and the other on plate, you will have about 100V on plate. I recommend fixed bias.
P.S. I ordered these chokes, but have not tested them yet. I think they will do a great job.
Double C amorphous iron core 30mA 1380H 5450Ω choke coil for European tube amplifier Choke coil Eliminate hum|Transformers| - AliExpress
I'll probably go for Ale's boards I'd imagine.
In the meantime, I didn't factor in the parallel halves, so yes, the CCS is now set for 4mA. But it is not a big job to bring that up to 8mA. Its at a friends house just at the moment, but should have it back in a week or so. When I get it back, I'll adjust and report back.
Great to read the recommendations here - thanks!
In the meantime, I didn't factor in the parallel halves, so yes, the CCS is now set for 4mA. But it is not a big job to bring that up to 8mA. Its at a friends house just at the moment, but should have it back in a week or so. When I get it back, I'll adjust and report back.
Great to read the recommendations here - thanks!
I just thought I'd come back here to update this thread.
I eventually got around to building the Ale Moglia gyrator boards, and fitting them to the output stage. I also rejigged things around a bit so that the whole setup uses filament bias exactly as per the schematic on Ales website
After a few hiccups getting it all setup, primarily just due to having to rearrange how things were placed, everything sang along together beautifully. There was a lot more gain, which I treated as Ale suggests using a resistor divider at the output. I think I will add his source follower in time. For now though, there is a sizeable improvement in sound, and that was on top of it sounding excellent before with a 10m45s simple CCS.
Once all was setup and running right, it has proven to be extremely stable in use. Those kits from Ale and Rod make it sooo much easier to bring out the excellent sound available from these valves.
I have all the parts gathered now to put together an 01a preamp in the future.... and a lot of the parts to build a 211 amp in time to come, but thats a lot more ambitious!!
I eventually got around to building the Ale Moglia gyrator boards, and fitting them to the output stage. I also rejigged things around a bit so that the whole setup uses filament bias exactly as per the schematic on Ales website
After a few hiccups getting it all setup, primarily just due to having to rearrange how things were placed, everything sang along together beautifully. There was a lot more gain, which I treated as Ale suggests using a resistor divider at the output. I think I will add his source follower in time. For now though, there is a sizeable improvement in sound, and that was on top of it sounding excellent before with a 10m45s simple CCS.
Once all was setup and running right, it has proven to be extremely stable in use. Those kits from Ale and Rod make it sooo much easier to bring out the excellent sound available from these valves.
I have all the parts gathered now to put together an 01a preamp in the future.... and a lot of the parts to build a 211 amp in time to come, but thats a lot more ambitious!!