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"Noise" on all Inputs of PrimaLuna EVO 400 Integrated Amp / Recording Provided...


JeffLebowski
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Hi again Jeff,

You mentioned that, " I am not sure what was going on with it but I think it is fine now."  I can understand that, and can also offer a couple of things I've also had to learn:

 

Performance interruptions like this (just referring to the conditions you encountered....scratchiness, occasional crackles, pops, etc., a veritable bowl of crisped rice breakfast cereal!) is not uncommon with tube equipment, particularly when tubes and associated sockets are exposed (rather than enclosed within the chassis) to the same surface-hunting dust particles that land and take up residence everywhere else in the house.   Add to that the exposure to air, humidity, and so on, and one begins to realize how important it is to keep components that are more vulnerable in this respect clean and as free of dust and oxidation as possible.

 

Just as dirty records sound scratchy as the stylus literally grinds it way through that long groove, similar things happen with male tube pins and sockets.  Sometimes noises like those you brought up start happening after the filaments have been on for awhile and tubes get hot.  The expansion and contraction that takes place during heating and cooling can worsen those conditions -- or at least make them more audible and problematic.  Even if a component is turned on and warm (but generally quiet), and one gently moves a tube around within its socket,  it's possible to find a position, such as the tube leaning more to one side or the other, where those noises start happening.

 

But I would like to say here, too, that others who offered advice on this were most certainly not 'wrong.'  Arcing; poor or cold solder connections, and so forth, can also cause similar problems.  I just happened to perceive the symptoms you presented a l little differently.  Noisy tube sockets do not sound unlike a loudspeaker driver's speech or voice coil that has become off-center in its magnetic gap, and subsequently begins to rub and cause distortion.  When dust finds its way into the proceedings; and, depending on the amount of space that exists in that magnetic gap, the presence of dust and other similar contaminants and pollutants can get so bad that the driver seizes up completely and stops working.  THIS HAPPENS TO OUR EXTREMELY HIGH EFFICIENCY LOWTHER DRIVERS FAR MORE FREQUENTLY THAN I WOULD LIKE -- EVEN WHEN LEAVING THE CABINET GRILLES IN PLACE!  ugh.   I'm generally A reasonably patient person, but this problem really gets to be a pain in the assparagus!  :) 

 

so.  Happy listening!

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Thanks for your reply Erik!

I am new to this all and am slowly gathering information from this forum and others.

The people on this site have been so helpful and friendly to me and I just wish I could give back somehow but I 

am a noob. 

The amp is simply beautiful. I can't state that enough. I am covering it now when not in use to avoid any sort of dust accumulation and will try to clean as required.

 

Anyway,

Merry Christmas to you and all others on this thread and elsewhere who have helped me.


And of course, have a Happy and Healthy New Year.

 

Cheers

 

 

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On 12/3/2021 at 8:19 AM, erik2A3 said:

Captainbeefheart 

"they use a 1/5 watt resistor"

 

They do?  or maybe 1.5 watt?

 

 

Good catch! Thank you!!

 

It was a typo, I meant to write 1/2 watt not 1/5 watt. My book 400mW with a 1/2 watt resistor is yes within limit but not good engineering practice. I will go back and edit the original post.

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"It was a typo, I meant to write 1/2 watt not 1/5 watt. My book 400mW with a 1/2 watt resistor is yes within limit but not good engineering practice. I will go back and edit the original post."  The period and back slash are neighbors on the keyboard -- easy mistake!

 

I thought that was likely the case -- you've been at this a long time!  Totally agree on the power issue.  Being conservative is SMART!

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8 hours ago, erik2A3 said:

 

"It was a typo, I meant to write 1/2 watt not 1/5 watt. My book 400mW with a 1/2 watt resistor is yes within limit but not good engineering practice. I will go back and edit the original post."  The period and back slash are neighbors on the keyboard -- easy mistake!

 

I thought that was likely the case -- you've been at this a long time!  Totally agree on the power issue.  Being conservative is SMART!

You should have the same DB headroom in your resistor as you do in your amp!

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On 11/10/2021 at 2:56 PM, captainbeefheart said:

Sounds to me like arcing, that crackle and pop, bacon in frying pan sound when a resistor starts to internally arc. Could also be just a bad solder connection arcing or even a tube/tube socket.

 

This often happens to plate load resistors especially if chosen near it's limits. Many engineers feel it is ok to run a resistor near it's dissipation limit, I will say depends on application but for a high quality amplifier a good engineer will choose plenty of headroom, I like at least 5x preferably 10x. For example you have a plate load resistor dissipating 100mW, I personally would use a 1 watt plate load resistor (1 watt) but 1/2 watt (5x) would be ok. I have seen way too often 2mA of current on a 100k plate load resistor, this dissipates 400mW and they use a 1/2 watt resistor. Yes technically it is within the maximum limits but depending on the temperature coefficient it could change values drastically and also fail sooner. 

 

If you are careful around high voltage open her up and poke around with chopsticks until you hear the arcing noise become worse. Wiggle everything you can and keep one hand behind your back or in pocket while doing this.

 

I got shocked (on my one hand - palm to fore finger) by 1kVDC poking around. My other hand was in my pocket. It burned more than hurt and will definitely wake you up. 

 

I use a chicken stick now, no more fingers. 

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