Intact Audio

Just because excel says the huge resonant hump is there, doesn't mean it really will be there. I dislike the idea of any peak in the sub 20hz area, they can be excited and watch out if they are. A 1V 2hz signal (turntable rumble?) has the same flux as a 10V 20hz signal. Its not easy to measure belo...

PJ's ROT's are up there with the best... i see how the 10K tames the resonant hump (see attached images) luckily your inductance (if you have it stacked 1X1 is around 160 hy, and the Rp of the tube is 1500 ohms ot 2K at your op point. the two plots represent a 10K and a 1 meg load... try both and s...

Oh, sorry, forgot.

The calculations for the cathode bypass caps are from Morgan Jones' book "Valve Amplifiers" pages 66-67. As I understand it, of course.

I've got all this stuff on spreadsheets in case you want to look at it.


Thanks again,

Len

Maybe I have something wrong. I figured that by going to the 5ar4, I now need more resistance above the plates (plate load?). your VR tubes are setting the B+ and decoupling each stage, so any resistance "above" them shouldn't change things. by all means go for the 5AR4 then use the extra...

hey len, i shrunk the jpegs and added a full res pdf for those that want to print... hope you don't mind... the horizontal scroll is a pain and i'm on dialup at home :-( Thanks, I would have done it myself had I known how. That should get cleared up by the HT PS change shown, ie. putting a new nick...

Hi Dave and all, Finally got around to it: Here are the present and proposed preamp schematics that pertain to magnetic upgrades. All in all, the pre is working but with a few problems. Firstly, upon replacing out the last 380 uF electrolytic cap in the HT PS with a 100uF oiler, ripple rose from 0 t...