Where should I connect ground reference for heater supply?

[mevang]

I ended up with connecting the heater supply center tap to local grounds. The local grounds of the two gain stage boards are both star grounded to the ground of the power supply board. This star ground is then connected to the chassis through a 100 nF capacitor.
All works well and the system is dead quiet.
Thanks to you all.

Paul

 

[Soundude]

Great, glad to hear it...sit back look at your creation and enjoy the music....

 

[Soundude]

Sandor
How about some pics of your new creation??

 

[riccoryder]

The ground location shouldn't be critical since it isn't carrying current. You may get less noise in the input stage with some positive bias on the filament. If wanting to bias it with no added parts, tapping the d.c. from a output cathode resistor usually works better than ground.

 

[speakerfritz]

My suggestion would be to take the heater CT for each triode (if it is a separate heater winding just for the one triode) to the star ground of that triode's channel board. The heater is electrically isolated, but parasitic hum/noise current can flow, and so should be confined to that local cathode circuit loop.

Ciao, Tim

I recently did a mod using this approach and a background hum/buzz was eliminated.

 

[trobbins]

In many amps there is likely to be negligible 'noise and/or hum' voltage between ground points around an amp chassis - but distributed star grounding is the preferred method to 'not get caught'.

If there is noise between grounds, then connecting a heater CT or humdinger to a noisy point relative to the input stage 0V point may cause the ground noise to become part of the input stage heater-to-cathode (or grid) leakage circuit. In general though, the relative signal level of ground noise would be much less than half heater AC voltage (mains and rectifier distortion frequencies), so its usually a mute concern.

 

[fluckscapacitor]

i have a similar question and found this thread

im building an amplifier which has a separate power supply chassis, connected to the amplifier with a 6 foot cable

if i need to elevate the filament supply (which is AC) with a resistor divider on the B+, should i add the resistors in the power supply chassis, at the filament transformer/B+ supply, or in the amplifier chassis at the tubes, which are indirectly heated triodes/pentodes?

 

[12E1]

The location of the resistor network used to elevate the heaters should not that make any noticeable difference. The elevated voltage is large compared to any small variation caused by the location differences. When I did this I did it in the amplifier, simply because I had more space in that chassis than in the power supply.