Thanks @euro21 I actually did start with that schematic and changed it a bit and added the output stage to it. Thanks again for the details, I can now do proper simulations with this software.
I did find that the Log is showing almost 16% distortion which seems very high. And the Anode mA on the 300B is is only showing 30mA which is stage since it should be pulling almost 80mA at the bias/B+ I set. I set that meter on Ix(U2😛) yet still 30 which is strange. The 16% at the 3.82V input is my concern really. I attached the screenshot to this post.
I did find that the Log is showing almost 16% distortion which seems very high. And the Anode mA on the 300B is is only showing 30mA which is stage since it should be pulling almost 80mA at the bias/B+ I set. I set that meter on Ix(U2😛) yet still 30 which is strange. The 16% at the 3.82V input is my concern really. I attached the screenshot to this post.
Attachments
If you can see the 300B grid voltage swing (IT secondary), it's in the A2 region.
IT driving grid current hungry tube (spice model) gives high/er/ distortion (IT can't produce enough current) in A2.
In these cases I test the schematic only up to A1 border (also measuring grid PP).
If you use these tubes in A2, CF or SF absolutely necessary.
BTW about 5% THD with 3k:8 OPT is believable.
I usually use 300B with 4-5k OPT and higher Uak (usually near 400V).
IT driving grid current hungry tube (spice model) gives high/er/ distortion (IT can't produce enough current) in A2.
In these cases I test the schematic only up to A1 border (also measuring grid PP).
If you use these tubes in A2, CF or SF absolutely necessary.
BTW about 5% THD with 3k:8 OPT is believable.
I usually use 300B with 4-5k OPT and higher Uak (usually near 400V).
Thanks @euro21. Will let you know how it measures when its turned on and I get some real works measurements. Will send some pics of the build as well.
Switching gears a bit, has anyone ever tried building a 300B driving a 300B, obviously the gain of a 300B isn't huge and usually isn't used as a driver except for a middle stage in a 3 stage amp driving a bit transmitter tube.
But....
For fun as I learn LTsprice I put one in place of the 46 and adjusted to bias as needed to see what would happen. at 4V in with the 1:4 LL7903 it produced only 3.9%THD with the output only 4V less (24Vpp to 20Vpp)...
I saw this method in a GM70-GM70 which I never built but it employs the "Sakuma" Method:
https://www.jacmusic.com/kits/amp/gm70/GM70-index.html
Switching gears a bit, has anyone ever tried building a 300B driving a 300B, obviously the gain of a 300B isn't huge and usually isn't used as a driver except for a middle stage in a 3 stage amp driving a bit transmitter tube.
But....
For fun as I learn LTsprice I put one in place of the 46 and adjusted to bias as needed to see what would happen. at 4V in with the 1:4 LL7903 it produced only 3.9%THD with the output only 4V less (24Vpp to 20Vpp)...
I saw this method in a GM70-GM70 which I never built but it employs the "Sakuma" Method:
https://www.jacmusic.com/kits/amp/gm70/GM70-index.html
