Yes, I noticed that the highs suffered at low volumes. The frequency is definitely 60Hz. The power supply is clean, so it's not coming from there. It's probably RFI from the transformer seeping into the input cable.
A 147pF cap (from input to signal ground) does much better with the highs, but there is some noise at medium volumes (i.e. the pot is at 12 o'clock).
The noise looks like this:
_|__|__|__|
| | |
Narrow peaks, like a differentiated 60Hz square wave.
I don't live near a tower, so it's not that.
A 147pF cap (from input to signal ground) does much better with the highs, but there is some noise at medium volumes (i.e. the pot is at 12 o'clock).
The noise looks like this:
_|__|__|__|
| | |
Narrow peaks, like a differentiated 60Hz square wave.
I don't live near a tower, so it's not that.
dmitriy167 said:
Don't ground input connectors to the chassis. Isolate them from the metal, and use 2 conductor shielded cable (hint: CAT5): one inner conductor for hot, one for cold, and ground the shield ONLY ON ONE SIDE (it's better to ground it at the ground node of the cathode resistor of the first tube stage).
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.