Bottlehead Forum

Bottlehead Kits => Kaiju Stereo 300B amp => Topic started by: Yme on September 21, 2018, 08:00:21 AM

Title: 50 Hz hum of the PT-9 power transformer [resolved]
Post by: Yme on September 21, 2018, 08:00:21 AM

This week I completed my Kaiju 300B Stereo Amplifier. All in one time okay and the sound is really better than the previously built Smash - Seductor combination. During the assembly and during the first volt measurements the PT-9 power transformer showed a big hum.
Now that the Kaiju is ready and connected, this annoying hum is still present. The hum comes above low music passages and can then be heard well.
I have completely checked the mounting of the transformer and all lockwashers, screws, shoulder washers and locknuts are properly mounted.
All measured voltage levels corresponded to the specified levels.
And again, the sound is great.

What can I do to get this hum (more mechanically) out of the transfomator?

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Deke609 on October 05, 2018, 10:35:04 AM

I haven't used it, but this gadget is supposed to remove "DC offset" from AC lines.  Apparently, DC over AC lines can cause mechanical buzzing of transformers.  From what I've read, the DC can be pumped into your lines by all manner of electrical devices including dimmer switches and microwave ovens.

https://emotiva.com/collections/accessories/products/cmx-2 (https://emotiva.com/collections/accessories/products/cmx-2)

Might be worth a try.  A quick search suggests it gets pretty good reviews.

Good luck,

Derek

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Sp33ls on October 22, 2018, 02:27:41 PM

Hey Yme,

Any luck?

I'm going to pick up that Emotiva device now actually and see if it makes a difference.


I've had the same issue -- DC Filament Supply didn't address it (tho, I wouldn't expect it to either). I've since moved to a different apartment and it hums the same in my new apartment as well. It sometimes seems that it's just slightly less audible after it warms up (tho, a subtle difference).

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Yme on October 29, 2018, 08:16:45 AM

Hey Sp33ls,

To exclude possible DC pollution, I installed a filter between the main power supply and the Kaiju. Design and manufacture by LC Audio Technology Denmark and specifically for filtering out unbalanced loads on the grid. I mounted the v3.1 but unfortunately ... no result. It remains a mechanical thing and Bottlehead does not get any further than an advice of "put something heavy on it ..." I have now applied thicker studs and nuts, which has decreased the humming a bit. Unfortunately it is still audible from the position where I listen to the music. Distance between Kaiju and the listening position is 3.30 meters. (about 10 Feet)

At this moment I have no more options and consider putting the Kaiju in a closet with a door that I can close.

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Felice on October 29, 2018, 12:43:04 PM

Good to know.
return shipment, exchange?

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Doc B. on October 29, 2018, 12:50:14 PM

We are looking into this, but it is pretty much impossible for us to analyze the problem without the amp in front of us, or at least the power transformer. The sound level reading that has been posted so far seems to be below the ambient noise level of a quiet room, which is rather confusing. We have a transformer coming back from a customer which we will put into one of our Kaijus and see how it works. Once we have some more understanding of the situation we will let everyone know.

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Yme on October 30, 2018, 09:01:29 AM

Hey Felice,
Fortunately, the cost of the filter was limited to about $ 70 including shipping. Decided not to return the filter. Who knows, maybe it comes in handy again.

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Doug on December 19, 2018, 07:51:37 AM

Was the mechanical hum of the power transformer resolved? I still have the hum in my Kaiju are is this normal?
Doug

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Dallas on December 21, 2018, 06:09:49 AM

Does this only affect people who are on 60Hz systems too?
I am just starting to build my Kaiju and would appreciate any advice on mitigating this hum during the build rather than getting it all put together and backtracking.
Thank you!!

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Doc B. on December 21, 2018, 06:24:17 AM

Yes the problem has been resolved. Before everyone who has a Kaiju starts to worry, it was limited to a small percentage of one production run of transformers. If you have a transformer from that batch that mechanically hums, you can send it in to us and we will evaluate it and send a replacement the transformer if necessary. Josh would be the one who might be able to identify whether your kit might have a transformer from that batch. We all take the week of Christmas off, so it may be the most effective to wait until the first of the year to pursue this. 

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: bernieclub on December 30, 2018, 03:56:58 AM

I finally got a chance to unpack my kit.   Shipped August 23, I think I got one of the suspect power transformers.   It seems to have not been varnished very well...some rust on laminations on one corner, and the top lam is peeling up from the stack.  Should I attempt to use this transformer?
Thanks, Bernie

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Paul Birkeland on December 30, 2018, 05:42:56 AM

Yes, you need to use the transformer.  There is no way to look at the transformer and know one way or the other.

Title: Re: 50 Hz hum of the PT-9 power transformer
Post by: Doug on January 28, 2019, 02:48:52 PM

New transformer in and mechanical noise is resolved!!!
Doug