modifications roadblock named HUMMMMMMM

[errnst]

Been modifying a Conrad Johnson pv3 preamp. I put in new line capacitors, stepper volume control, star ground, grid chokes, power supply regulator. Everything was going wonderfully till i put in the new regulator. At first there was a hum, i managed to add a ground wire and fix it, then it came back, and i did something else that stopped it for a while, then it came back and nothing i could do stopped it. Now it is much louder than any music signal. It hums like crazy with the volume down, inputs connected or not.

anybody have any ideas about what can be done to save this preamp?

 

[Sceadwian]

It's a ground loop obviously, where it's coming from there's no way to tell as you've posted no schematics. Basically you wired something wrong and unless we know exactly how everything is wired there's no way to help.
A ground loop means that the ground you're using for your pre-amp is sharing some kind of power ground that's producing enough voltage after amplification to drown out the signal. Improper grounding of a pre-amp will do this, it has to go straight to the power supply all by itself with low impedance to the total system ground, you can't just tack it on to existing circuits.

 

[Nigel Goodwin]

Put the old regulator back - why did you change it?.

 

[errnst]

When i changed the regulator, and when i could stop the hum, it sounded better, tighter bass, more defined highs, that is what i was hoping for.
Here is the schematic of the original amp **broken link removed**
I removed the old rectifier and regulator and caps and installed this **broken link removed**

this thing worked for brief periods of time but any ground loop solutions did not last, that is confusing

 

[errnst]

the preamp is conrad johnson pv3, if you google it you can get the schematic easily, i removed the power supply portion except for the last capacitor in the high voltage circuit, this is where i attached the high voltage from the new regulator, the 12 volts is attached to the heater circuit, i have tried various grounding schemes, they have not made any difference, i have a tech guy who can fix most things without a schematic, he could not figure it out, so...

the regulator was changed because i wanted to try something