I had experience like this also, trying ac and dc and SMps heater and cathode referencing and no effect at all. tried replacing the signal wire with coax and ground the shield at one end to avoid loop the noise is reduced however there's still noise but tolerable to my ears but when i hold the chassis or one of the 6SQ7 GT metal base, the noise is gone when i remove my hand the noise slowly appearing.
What seems to be the other cause?
What seems to be the other cause?
You most likely have a charge building up in some capacitance or hf oscillation. Your hand, body, fingers whatever act as either a high impedance to ground (and/or chassis) discharging the charge. Or same body parts act as capacitance killing the hf oscillation.
Replace body part with high ohmic resistor such as 1meg or perhaps even 10meg. And/or with a small cap, say 100pF or maybe even 1nF depending on other impedances.
The chosen values should not interfer with audio frequency.
Your "Star ground" is not a star ground, actually. It is a bunch of wires that is connected to the real star ground through a long wire that has resistance and inductance. In order to make it a real star ground solder to it a cap that shunts B+ right on your board. Then that wires from power supply to your star ground and B+ would not matter.
Ahuh.. i will try this. my current ground is via a bus cooper wire ground directly bolted on the chassis. then the b+ cap ground is connected to the bus via wire.
So i Must lift the bus ground from direct chassis connection and solder it to cap ground then run another wire going to chassis ground.
Thanks...
Do you have an oscilloscope to see what frequency it's oscillating at? Seems like the initial complaint is and HF thing and recent comments point to grounding issues, which IMO are very different beasts. Have you tried REALLY paralleling the 6SN7 ie tie the cathodes together and deleting cathode bypass caps for now?
Try the loop breaker circuit grounding method in this article:
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
So interesting ... I re-arranged my music room and when I was done I fired the prototype up to listen to some tunes and the noise is all but gone! Not sure what changed other than physical location within the room but sounds great now! 
I'm guessing wiring was the culprit since that is the only thing that would have changed from before. Anyway ... it gets the thumbs-up now ready to start planning a chassis!
I'm guessing wiring was the culprit since that is the only thing that would have changed from before. Anyway ... it gets the thumbs-up now ready to start planning a chassis!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.