driver plates voltages??

[swt]

Can someone tell me how critical is, and best values??. Is this as critical as V1 and V2?. Thanks a lot!

[llemtt]

No it isn't critical because this amps aren't supposed to be run with full power amp overdrive. However 400V of power supply to the PI should be considered to give it enough headroom and gain.

It's more important to AC balance the entire power amp via the PI trimmer.

teo

['67_Plexi]

Around 300V on the plates seems to work for me. Did you mean 400V at the PI B+ node because 400V at the plates would be pushing it.

[swt]

I'm having around 285volts. should i go a little higher?.

[llemtt]

Around 300V on the plates seems to work for me. Did you mean 400V at the PI B+ node because 400V at the plates would be pushing it.

Yes I mean 400V at the PI B+ node, it should give you something around 280V at the plates.

teo

[Smitty]

s3988009 shows B+3 at 433V and plates at 303 ad 317V with regard to ground. The effective plate voltage is 243 and 257 because the cathode is at 60V.

Bias is about 1ma. Happy clean land for a 12ax7.