Suggestions on reducing transformer hum?

[quad]

I have built 3 of these awesome amplifiers. All work! But they have different amounts of hum from the main input transformer, One amplifier in particular I can hear when music is not playing from a few feet away and is bothersome. Currently I am using the other two, but would like to use the problem one in another room.

All kits have the dc filament supply upgrade installed.

The hum starts up immediately upon power up if the 300b tubes have been installed. Whether or not attached to speakers. Clearly comes from the input transformer. It the same anywhere in the house I plug it into to. In my dedicated stereo area, the equipment are on their own circuit from the power fusebox.

I have tried swapping 300b tubes. I took some time and swapped the transformer from one amp to another, but I didn't detect a difference after I completed this.

Do you have any suggestions I could attempt to implement to reduce this hum? It is a grounding issue? Component issue? Just component variation?

Thank you for your time.

[bernieclub]

I have the same problem.    I can faintly hear the hum from my listening position, about 8-9 feet from amp and speakers.   I thought about a metal cover, but between heat build-up and the fact that I can't seem to quiet the hum by wrapping things around the transformer, decided it would not be effective.   I plan to put the amp in a well ventilated cabinet that is closed to the front.   I hope it works!     Great sounding amp.
Bernie   

[Paul Birkeland]

I would make sure the transformer screws are nice and tight.  Approximately when were these Kaijus purchased?

[bernieclub]

Mine was shipped August 3rd, 2018.   I had initial concerns about what appeared to be a lack of varnish, some rust, and the top few laminations pealing up.   I've cranked the screws as tight as I dare.   I can't seem to get the sound to change by leaning on the transformer, or gripping it in any direction.   The hum is internal to the trans.  A surprising amount of the hum actually comes from under the base, I guess it's exaggerated by the enclosed space.
Bernie 

[quad]

The two with more hum were purchased on July 18, 2018. Although one has a bit more than the other.

The older (my first) Kaiju amplifier with much much less hum was purchased a year or two earlier. I have to get my ear close to that input transformer to hear any hum on that one.

Carl

[Doc B.]

There was one batch of transformers in which a few had a slight noise issue that seemed to be due to the varnish not pulling completely through the core under vacuum. We will need to check if these amps were from that batch. If so, they can be exchanged for a replacement transformer from the current production run. Best bet is to email Eileen at queen at bottlehead dot com and we can start by researching what batch your transformer was from.

[bernieclub]

Thank you!!
Email sent.

Bernie

[quad]

What Bernie said, sent email.

Thank you!

Carl

[quad]

Didnt mean to confuse the matter, but I am having the problem (transformer) hum on both the amplifiers I ordered on July 2018. That is I have 2 problem transformers.

Thank you,

Carl

[bernieclub]

Just want to mention that I installed the new transformer and it is noticeably quieter than the old one, just a faint hum if you get really close, as would be expected.   Thank you B.H.!!   BTW, this amp keeps getting better and better....sounds fantastic!!
Bernie