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In Reply to: RE: God made these for a reason posted by Chip647 on November 18, 2015 at 17:00:44
And it made NOOOOOOOOOOOOOOOOOO difference!
And I'm using a Genalex 12ax7LPS with "Spiral Filiment" - NOOOOO difference.
cheap crappy zenith with no shield - quiet as a church mouse.
Follow Ups:
The crappy Zenith was made for Zenith. You're likely using a vintage tube by RCA, Sylvania, Tung-Sol, etc. that is better than your new production tube(s).
"I can't compete with the dead". (Buck W. 2010)
"You're likely using a vintage tube by RCA, Sylvania, Tung-Sol, etc. that is better than your new production tube(s)."
That's pure speculation at best. The old stock tube may be different, but better? What criteria is better in such a way to not hum?
As Chip posted in this thread, it could be the old tubes are tired while the new tubes are fresh ("better"?) - the exact opposite of what you said. The reissue Genalex has a spiral wound hum-rejecting heater winding, the reissue Tung-Sol does not. So the Genalex is equivalent in construction to the old tubes' heaters - but is humming just like the Tung-Sol without the spiral wound heater.
The tubes can't hum on their own - the hum is either induced by an external hum field that exists either above OR below the chassis deck - or there is hum coming in on one of the connections to the rest of the circuitry. We simply have not been able to track down the source so corrective action could be taken.
It has nothing to do (with the possible exception of what Chip posted) with "betterness".
I try to avoid using better in here. That was an error. Most of what people say in here are only opinions. Saying better, best, greatest....which we hear all to often in this forum, is just a descriptor in an opinion.
"I can't compete with the dead". (Buck W. 2010)
and a new tube has higher output/sensitivity. I do not think you are dealing with magic or evil spirits.
To really understand, you will have to look at the voltages on the tube: Heater Voltage, Plate Voltage, Plate Current. My guess is that one or more of those is making your new tubes unhappy.
Hmm. So much for my spiral filament theory. Was the Sherwood rebuilt to stock specs? I think that V5 is for the tone controls. I'm really curious to what it can be.I experienced something kinda of like this that ended up being a bad solder joint but it did it with any tube.
Edits: 11/18/15
I would like to check Chips theory out. But I really don't want to invest in a NOS/NIB tube just to try it out.
The Sherwood was restored to what I believe was stock or near stock by Mike Samra. So I trust his expertise in this matter.
The ONLY thing I could try is testing the voltages in V,4,5. Because there is NO hum using new tubes in positions V3 and V4. Only with a new tube in V5.
If I test the voltages what pin/pins would be the culprit voltage?
I'm sure that Mike does fantastic work but i'd double check under the socket to be sure something didn't fall through the cracks. Did you try any other new tubes besides the New Sensor made ones? Maybe a JJ or Chinese 12ax7 would do better.
Just the Genelex LPS and the TungSOl.
Oddly enough the Genelex with the spiral filament hums louder/harder (hard to actually describe being isn't a unique hum) than the TungSol.
One more thing to look for, and it's a super long shot, is that the heater wires are tightly twisted going to V5. I hope that you figure this out. I know how frustrating it can be. I have a Citation V with some hum that I can never figure out and I'm too lazy to send it to someone that can.
Does the hum change at all when you move your hand near the tube - or when you install or remove the shield?Does the hum change when you adjust the tone controls?
Do the new tubes hum in any other socket?
Note: edited to add content
Edits: 11/19/15
No change with hands near the tubes.No change with or without the shields or steel case shield.
The new tubes do NOT hum in any other socket. ONLY the V5 socket. The new tubes work very well in sockets V3 and V4.
If the tube is quite it is quiet WITH or WITHOUT the shield.
So for some reason the shielding has nothing to do with it????
Edits: 11/19/15
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