Reversing it made no difference. Unfortunately I do not have any capacitors anywhere near .01uf......Replacements will be here in four days. I'll report back....
They are 0.1 µF and you can use anything between 47 nF and 1 µf for testing. Measure voltage over them to be sure and even an electrolytic cap may do for testing. In fact any cap can be used when the voltage is about right. Even a ceramic disc cap from an old SMPS could be used.
Since I get no answers on basic questions and suggestions I wish you good luck. My bet is that the new cap will hum just as much but I do hope I am wrong on that.
Since I get no answers on basic questions and suggestions I wish you good luck. My bet is that the new cap will hum just as much but I do hope I am wrong on that.
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A devilish problem. It's not a capacitor. Tapping the board is just the tube microphonics. It's almost surely a grounding issue on that channel.
I wonder if the cap has gone high resistance. If the input impedance on the grid is very high then the audio would still get through but the grid and cap would be sensitive to pickup.
But if I tap the tubes there is ZERO noise. If I tap the board, there is ZERO noise....If I lightly tap the cap, it makes noise.....Swapping the caps move the noise to the other channel. I'm far from a technician, but sounds to me something is up with that cap.
Valve amps are sensitive to noise as they are high impedance on the inputs.
1/ Input signal should be screened.
2/ Keep input signal away from heater voltages and mains transformer.
3/ Use star grounding where possible.
4/ Sometimes a valve can suffer from pick up worse than others.
5/ Check electrolytic smoothing caps for ESR in case old and worn out.
1/ Input signal should be screened.
2/ Keep input signal away from heater voltages and mains transformer.
3/ Use star grounding where possible.
4/ Sometimes a valve can suffer from pick up worse than others.
5/ Check electrolytic smoothing caps for ESR in case old and worn out.
My replacement caps came in from DigiKey. Couldn't wait to install them........Replaced both and there is absolutely zero hum now! Dead quiet! My be wishful thinking, but I think it sounds better........Maybe they were both bad or going bad. I'm a VERY happy camper. Thanks for all your help!
Top picture is the old Cap...Bottom is what DigiKey sent me.
Top picture is the old Cap...Bottom is what DigiKey sent me.
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Glad we could help dude 🙂 Happy listening.
It might indeed sound better - the old caps were old polyester ones and one of them was bad enough to cause a hum... The other might not have been in great shape either.
Now, you have metalized polypropylene from a current stock 🙂
It might indeed sound better - the old caps were old polyester ones and one of them was bad enough to cause a hum... The other might not have been in great shape either.
Now, you have metalized polypropylene from a current stock 🙂
I had it out in my shop. Running through the "Main In" on a NAD C320BEE integrated amplifier and Sony SSCS5 speakers that I have on my electronics bench....Sounded great! Brough it inside and connected to First Watt F5v2, KEF LS50 Metas and using Node2i through Gustard DAC......No question, the sound quality has improved......MUCH better bass and mids.....I was using the Gustard directly into the First Watt as it sounded better than going through the Zero Zone preamp. Not now. The preamp adds that "tube" thing that the Gustard wasn't delivering......NICE!
