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Rolling with my Tubes and EMI

BirdOnAWire

BirdOnAWire

Active Member
I'm going to be taking my Tube amp for a roll.

I got my 300B SET amp (Cary CAD-300SEI) in Dec - it hummed about 3dB. I took the driver tubes out, disconnected all speakers, moved it to different locations and even a friend's house. And with headphone - it still hums.
Cary replaced it. My new amp hums. They said my return was dead quiet. They made a point of making sure this was dead quiet before shipping.

Oh, I also converted power to DC, then to AC using a pure Sine wave converter. It hummed. I got a Yeti battery with pure sine wave converter - same hum. Panamax ACRegenerator - still hums.

I bought some speakers from @Rmac587 and took my amp and speakers over. It was dead quiet. Or we just couldn't hear any hum, I'm going crazy. Back at home it hums.

I'm thinking the aliens or government has a super secret magnetic source around my place. So I'm off to find out.
 
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Any fluorescent lights above or nearby hmm? :D

Something in your house has to be causing it. Maybe a light dimmer that was left on but not all the way up or something close nearby? :idea:
 
century tek said:
Any fluorescent lights above or nearby hmm? :D

Something in your house has to be causing it. Maybe a light dimmer that was left on but not all the way up or something close nearby? :idea:
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I have no florescent, no heater, no AC.
I think it is aliens, I'm going to build a tin foil hat for my amp and see if that helps.
 
What's the sensitivity on your speakers in db? Higher sensitivity speakers will allow you to hear a low level hum at idle where a lower sensitivity speaker may require a higher level of volume to hear a hum. That may account partially for the manufacturer saying the original and the replacement are dead quiet but you hear a hum. Signal to Noise ratios may be in spec, but with a higher sensitivity speaker, you may be out of that range and hear a hum.
 
larryderouin said:
What's the sensitivity on your speakers in db? Higher sensitivity speakers will allow you to hear a low level hum at idle where a lower sensitivity speaker may require a higher level of volume to hear a hum. That may account partially for the manufacturer saying the original and the replacement are dead quiet but you hear a hum. Signal to Noise ratios may be in spec, but with a higher sensitivity speaker, you may be out of that range and hear a hum.
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92dB on the Martin Logan 35XT bookshelf in video
88dB on Watkins 4 - hum comes in loud and clear
Also on the headset.
I can live with this if I am positive it is my environment, or the basic SET design. At first I thought the unit was defective, which I can't live with. Cary has a good reputation, they said it was quiet, they replaced it and the replacement sounds exactly the same.

I wanted EMI out there (I just tagged) as some may have some experience with it other than just power. And I suspect the amp design.

I did not hear any hum on my cheap MonoPrice Tube amp. Then I didn't hear near what I hear of the good stuff either.
I have a push/pull amp on order and expect by Aug (or July) so I'll see on that, but I wonder if a 300B SET is just more susceptible to EMI.

It will likely take me 10 min to test in my car which I will likely do today or tomorrow. The fantasy was hook everything up and go listen at the beach or something like that which destroys the purpose as the waves are louder.
I just need the power, amp and headset. No audio source is needed.
 
6DZ7 said:
So at your friend's it didn't hum. Did you use the same input source there? At home, are you using a TT phono pre as a source? Loose cable input's can act like an antenna and TT mag. cartridges can pick up PT magnetic radiation.
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I purchased speakers from @Rmac587 and we took the time to test my setup with my dac and my speakers and didn't hear anything. His environment was not closed, so I maybe missed it, but both of us were pretty sure the unit was silent.

With just power and cord (no ground tested and swapped on chance the wiring was bad) - no DAC, no speakers, I get a hum.

Hum is softer on warmer amp.

I'm going to turn my computer off, my monitor off and everything else and try from the battery.

Hums:
upload_2019-6-7_9-58-17.png


Going to flip headset cable again. I think the same hum.
 
Forgot this picture of power supply.


Foreground - 300W DC powersupply to 600W pure sine wave inverter - same hum.
Background - 1000W Battery with pure sine wave converter - same hum.

Going to flip headset cable again. I think the same hum
upload_2019-6-7_10-1-22.png
 
I really think it is something in your house @BirdOnAWire, perhaps maybe the way your house is wired in combination with the amp. Barring that, some kind of external EMI as you note, BUT perhaps it’s coming from offshore communications. You’re up on second floor right? I get it from the local airport at times myself.

I’d hate to have to lug beautiful beast everywhere testing it. I do have an old Adcom ACE-515 power conditioner-it maybe that a simple piece will work. Let me know if you want to borrow it.
 
Rmac587 said:
I really think it is something in your house @BirdOnAWire, perhaps maybe the way your house is wired in combination with the amp. Barring that, some kind of external EMI as you note, BUT perhaps it’s coming from offshore communications. You’re up on second floor right? I get it from the local airport at times myself.

I’d hate to have to lug beautiful beast everywhere testing it. I do have an old Adcom ACE-515 power conditioner-it maybe that a simple piece will work. Let me know if you want to borrow it.
Click to expand...
I can live with it for now. When I get my new amp I'll head up again with both and the battery power and we can check it out - again.
The thing I like about the battery is it removes a ton of variables.
 
I sat my visiting daughter down to test some things and my wife participated. Daughter heard the real crickets in a track where I could not. I guess those are typical expectations for a 24 year old vs old folks.
Everyone hears the hum. My wife says it is soothing, and reminds her of old stereos.
 
Ya check the AC panel in the house, make sure like gounds all tied together, white conductors also are on the same buss. Not sure how confident you are working on a AC panel, but if you are you could try a new breaker and run a new wire from panel to an ac receptacle in a box. You would want to be be close to the panel..just trying to isolate anything else which might be on that circuit. I just got one of those amps and mine is dead quiet..it's a few years old.
 
The OP hasn't been on AK since last Feb and the last post in this thread is 3.5 years old. May not be in the loop any more.
 
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