Bad hum in Tweedle Dee

[galtjunk]

I built a Tweedle Dee Deluxe with a VVR.
Everything works and it sounds great, but it has a bad hum.
I used Classic Tone transformers.
The PT has center taps for the HV and the heaters.
I used Dumble style grounding.
It hums with or without anything plugged into any of the input jacks.
I bypassed the VVR by disconnecting the wire from the rectifier to the VVR board and connecting a jumper to the first PS cap. No help.
The VVR is reconnected.

See the attached drawing of the amp for the layout.

The AC ground is to a transformer bolt.
The cathode resistor is to another transformer bolt.
The center taps and the VVR ground to another transformer bolt.
Are there too many ground points?
Should I try to elevate the heaters by connecting the heater center tap to
the cathode of a power tube?

[martin manning]

I'd ground the first two filter caps on the left with the VVR's output ground. Also, you should place the VVR between the first filter and the OT, and ground the first filter directly to the CT's.

[Stevem]

If the ground swap does not help then which preamp tube do you need to yank to kill or change the hum?

[galtjunk]

I changed the ground point 0f the first two caps to the CT lug.

Now I can't hear any noise at all.

It's working great now.

Thanks.

[martin manning]

Ok cool. Still have the first filter after the VVR? Not saying that won't work, but it's not the way it has been done. The FET will have to deal with the high ripple, but that might not be a problem.

[galtjunk]

I just changed the ground point for the first 2 caps.
Everything got nice and quiet after that.

Are you saying I should feed the first cap from the rectifer then feed the vvr input from the first cap and then attach the vvr output to the second cap?
Wouldn't that bypass the dropping resistor?

Maybe add another cap?

[Synchu]

Just go from the VVR out to the first dropping resistor.
Niki

[martin manning]

Usually the sequence is Rectifier > cap > VVR > (OT, cap, dropping R) > cap, but your layout isn't set up for that. It's working and it's quiet, so maybe try it as it is for a while.

[galtjunk]

It's working as it is so I will leave it alone for now.


Thanks again.