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RE: that's a good photo

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john635@earthlink.net

In Reply to: RE: that's a good photo posted by Palustris on October 24, 2024 at 14:32:46

Good afternoon Palustris!
The only wire that I disconnected, was an earth ground wire that was attached to one of the output transformers, via a bolt and nut.
The wire is turminated by an O-lug.
And that wire is coming in from the IAC power inlet.
But on the primary side of the output transformers, they each have two wires.
One is going to the plate of each one of the output tubes, and the other wires are going to the B-plus power supply.
I mean B-plus voltage.
But on the secondary of the output transformers, there are three wires each.
One is ground, the other two are 4ohms, and 8ohms per channel.
But wouldn't that choke get rid of hum too?
I have a much larger amp then this one, that also has a choke in it too.
it is equally the same age as this one.
But it's push-pull.
Two KT77 tubes per channel in that one.
And after 16 long years of service, I've never once heard that amp hum.
But that one, is my Eastern Electric M-520 amp.
But the one that I uploaded a picture of, is the inside of my Musical Paradise MP-401 amp.
This is the one that I'm trying to figure out.
I also read somewhere on the net that, "heavy filtering, can make single ended tube amps stop humming."
But it didn't say how.
I guess you have to use more caps?

Follow Ups:

RE: that's a good photo - Palustris 15:06:22 10/24/24 (1)
The problem is not the wire that grounds the amp by the power cord. That should be connected or the amp won't be grounded.

You never answered my question: is anything connected to the amp such as a CD player?

Has this amp ever worked without hum? Is this a new problem? How old is this amp?

The problem is probably not insufficient power supply filtering; there are plenty of capacitors unless the amp is old and the caps have dried out. The problem appears to be a ground loop.
- RE: that's a good photo - john635@earthlink.net 01:42:48 10/30/24 (0)
  Good morning Palustris!
  I don't know if you saw my last few posts, but I did tell Cougar about all of this.
  But sense you asked, no.
  The amp hummed, as soon as I unboxed it, and hooked it up.
  The amp was made in 2008.
  So there for, this amp is 16 years old.
  I drove the amp via my iPad, and Earman Angel portable headphone amp/DAC.
  I wanted to see what this amp sounded like, when fed DSD files.
  Aside from that, my Presonus Quantom ES 4 audio interface, with the computer providing the digital audio signal.
  And later on, my digital talking book player, with NLS cartrages that have 16bit, 44.1KHZ wave files.
  But either way, I couldn't make the humming noise go away.
  I did call and spoke to mark about it yesterday afternoon.
  When I told him about the part where and when I removed the tubes, and still heard the humming noise, it stumpped him.
  But I told him about that problem, sense he was the one that sold it to me.
  I think he's gonna make arangements for me to send it back to him, so that, he can check it out.
  But I also thought about something.
  If the primary side of the output transformers are wired up wrong, wouldn't that be causing the humming noise problem too?
  Thanks in advance!
  - https://www.soundsclassic.com (Open in New Window)

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