Well, you were definitely on the right track.
Heater noise.
from my very first post in the thread:
Sooner would have been better than later ! I went about elevating the heaters for kicks, and found everything cleaned up perfectly. Interestingly, tho, when I played around with the magnitude of the elevating voltage, there was no effect. Turned off the voltage supply but left it connected, problem still solved. Connected to common through a mica cap, problem solved. Tied directly to common, problem solved.
So I didn't have the heater referenced properly; in the rats nest I was referenced to the cathode instead of common. Noob mistake to be certain.
Still curious that the FFT looked similar to your phono stage, but perhaps you took those measurements in a similar condition as mine, pre-build.
Attached noise floors of AC and DC heating (DC was non-regulated, with 0.4V of ripple, but still much improved). So far no further improvements with AC heating, so I might pursue DC if I can't get further.
Sorry if I took you on a wild goose chase, SY. At least we now know a potential characteristic of heater noise beyond hum.
Heater noise.
from my very first post in the thread:
Sooner would have been better than later ! I went about elevating the heaters for kicks, and found everything cleaned up perfectly. Interestingly, tho, when I played around with the magnitude of the elevating voltage, there was no effect. Turned off the voltage supply but left it connected, problem still solved. Connected to common through a mica cap, problem solved. Tied directly to common, problem solved.
So I didn't have the heater referenced properly; in the rats nest I was referenced to the cathode instead of common. Noob mistake to be certain.
Still curious that the FFT looked similar to your phono stage, but perhaps you took those measurements in a similar condition as mine, pre-build.
Attached noise floors of AC and DC heating (DC was non-regulated, with 0.4V of ripple, but still much improved). So far no further improvements with AC heating, so I might pursue DC if I can't get further.
Sorry if I took you on a wild goose chase, SY. At least we now know a potential characteristic of heater noise beyond hum.
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No, that's cool, delighted you tracked it down! It's also a testament to the usefulness and versatility of sound card measurement systems.
I may still hook up my phono stage and remeasure the noise using my current gear- that spectrum was with my old sound card in a noisy environment (two moves ago).
I may still hook up my phono stage and remeasure the noise using my current gear- that spectrum was with my old sound card in a noisy environment (two moves ago).
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