aramirez626
Well-Known Member
Yep, that’s it. How do you know when to change tubes? I have a tube phono stage and there is a lot of hum when I change my receiver to the “spare” channel. The tubes are lit but one is really dim.
How do you know when to change tubes?
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Lavane
Lunatic Member
Dim or bright usually is just due to the heating element sticking out of the internal structure a little further then another. Here is a picture of one of my amps. Look at the three smaller tubes front center. Notice the one on the right? It's much brighter than the two just to the left. The heater element is just sticking out the bottom more.
This isn't a problem.
This isn't a problem.
aramirez626
Well-Known Member
Okay, then my problem is a TT hum.
Lavane
Lunatic Member
Is it in both channels? Is it a stand alone phono preamp? Is the TT grounded to the preamp? Is the preamp grounded? Is the Spare input line level? I hate chasing hums myself.
aramirez626
Well-Known Member
It is a stand alone phono preamp. The TT original cables were upgraded to new RCA cables by the previous owner, and built the ground into the new cables. This hum just started, it wasn't there before. The only change is I got a new amp, and our new smart TV is right above the TT.
Tubes are probably not the cause of hum.
Try to disconnect interconnects to a minumum ( only Phone, preamp and poweramp) , does hum disappear ?
Also try to rotate non-polarised mains connectors.
If anything else fails, install shorting plugs at the phono input , if hum disappers teh problemis withing
the turntable, if not try the shorting plus into the new amps input.
aramirez626
Well-Known Member
Sorry, I am not following. What do you mean by disconnect the interconnects to a minimum, and what is meant by rotating the non polarised mains? Not sure what those are.
Your explanation is better then mine
if it's just a ground hum/buzz, it's definitely not the tubes, especially if it's both channels. properly grounding a phono setup can be a real ***** because the quietest choice can depend on the interaction of your entire system.
when the previous owner built the TT chassis ground into the signal ground of one (or both) of the TT RCAs, he limited your grounding choices a bit. in my setup, i connect the separate TT chassis ground to the 0V point of my phono stage's power supply, and this gives me the least hum/buzz/noise. do you have a multimeter and know how to use it? if so, you can check continuity between the ground plane of the RCA inputs to your phono stage and the 0V or ground plane of your phono stage power supply. if it doesn't show good continuity, you might try jumpering that just to see if it helps (if you're careful -- you don't want to accidentally put 300-400V across your TT chassis!).
does your TT just have a two-prong AC plug?
when the previous owner built the TT chassis ground into the signal ground of one (or both) of the TT RCAs, he limited your grounding choices a bit. in my setup, i connect the separate TT chassis ground to the 0V point of my phono stage's power supply, and this gives me the least hum/buzz/noise. do you have a multimeter and know how to use it? if so, you can check continuity between the ground plane of the RCA inputs to your phono stage and the 0V or ground plane of your phono stage power supply. if it doesn't show good continuity, you might try jumpering that just to see if it helps (if you're careful -- you don't want to accidentally put 300-400V across your TT chassis!).
does your TT just have a two-prong AC plug?
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Lavane
Lunatic Member
You might remove the ground incorporated in the cables and run a separate length of wire for the ground and see if that helps. Or remove the ground all together. Another thing to try is if your headshell is easily removable like what's used on an S arm, remove it and see if the hum disappears. My noise was being picked up by the cartridge. Removing the headshell or cables from the TT killed the noise.
Try adding a ground from the phono preamp to the amp ground, etc. Sometimes this helps, sometimes it just makes it worse. As cdfac started chasing phono hum can be a real pain. If the hum is gone when removing the headshell or rca cables from the tt to the phono pre you may be picking it up from your TV or something else.
Try adding a ground from the phono preamp to the amp ground, etc. Sometimes this helps, sometimes it just makes it worse. As cdfac started chasing phono hum can be a real pain. If the hum is gone when removing the headshell or rca cables from the tt to the phono pre you may be picking it up from your TV or something else.
