modelling PSU for Aikido

[Sheldon]

Originally posted by cbutterworth
I replaced the 10 ohm ground lift with a 20 ohm and now I actually have to put my ear to the speaker in order to hear a faint hum. I'll get a 30 ohm 5W and see if that totally diminishes it, although I am not going to rush out and do that as I need to redo the signal wiring first.

5W is serious overkill for the lift resistor. There should be no current through that resistor. If you're are worried about it failing open in a fault condition, parallel it with a pair of antiparallel diodes (diodes with enough current capacity to blow your fuse before they do).

I built a RIAA phono preamp using an Aikido topology on the output. It has no hum. So any audible hum from your lower gain preamp is something that can definitely be fixed. On thing you might check is the resistor divider the supplies the lower grid on the output tube (the noise cancelling input). You could plug a pot in here and adjust for lowest noise to see if that improves matters. This is probably not the cause, but it's easy to check.

Sheldon

[kianbach]

I'm in the process of either converting my srpp 6sn7 pre to aikido or scratch building it with 6n1p/6SN7 and was wondering if I could
A- build this psu with a valve rectifier and
B-have a variable voltage on the output say 225 to 325v?

[kianbach]

Sorry forgot to mention the 380-0-380@240Ma HT tranny sat in the shed!!

[kianbach]

One more thing.....Does anyone have a schematic for a regulated 6.3v dc supply?And what does it mean on lm350 datasheet output connected to case?

[Bruce Anderson]

Charlie

As others have pointed out (meaning me) Your current power supply is good but not best. I told you in great detail how to make it much closer to the very best for cheap. Your lack of faith is painful : )
My Aikido phono is dead quiet at full gain. With your identical supply my line amp was dead quiet. Your looking for love in all the wrong places! Neither increasing the first cap nor the choke(s) is going to get you where you ultimately want to go. OK, I'm done now. Best of luck whichever way you go.

[JoshK]

Hey Bruce,
Would you share with the rest of the class?

[Renron]

Originally posted by JoshK
Hey Bruce,
Would you share with the rest of the class?

In case someone else (like me) is trying to build a PS for the Aikido PCB, here is a link to the other post refered to above.
Related Post from Bruce

Ron