Yes.
The first image is with bells on. This is how I tested it.
The second image is with nothing on. I'm making much better finishes in my last two trannies. The buzzing is much loader (obvious)
The third image is with a new hardware I'm testing. Similar buzz noise level than with bells. The idea is to place bells on top, which lack the "L" shaped on the bottom to bolt to the chassis.
Something strange (to me) is this: when I hold the transformer in the air with one hand (I use an insulated+leather globe), the buzzing noise almost fades away completely.
Any idea why?
I also tried to press hard over the filament winding, but the buzz doesn't change. If those thick wires were producing the buzz, this should have alleviated it, shouldn't it?
The first image is with bells on. This is how I tested it.
The second image is with nothing on. I'm making much better finishes in my last two trannies. The buzzing is much loader (obvious)
The third image is with a new hardware I'm testing. Similar buzz noise level than with bells. The idea is to place bells on top, which lack the "L" shaped on the bottom to bolt to the chassis.
Something strange (to me) is this: when I hold the transformer in the air with one hand (I use an insulated+leather globe), the buzzing noise almost fades away completely.
Any idea why?
I also tried to press hard over the filament winding, but the buzz doesn't change. If those thick wires were producing the buzz, this should have alleviated it, shouldn't it?
Attachments
100Hz vibrations are not loud from a transformer that size. Placing it on a table or other large area increases the sound because the heavy transformer manages to get the whole surface to vibrate. So more sound from the big area. Holding it ur hand the only surface area to emit sound is relatively small and that produces less sound. Think big speaker vs small vibrating so lttle u cant feel it with ur fingers. Only the big speaker will be audible.
I think...
I think...
OK now I am beyond my knowledge limit so I finding this interesting. I thought u needed some current thru the windings for magnetostriction to become active enough so as to become a problem.
What is the primary inductance? Is the magnitization (primary idle) current pretty high?
Are all the inductances as expected? Could a winding be the wrong way as to work against some of the other?
1T is high enough, the RDH4 computations are just 0.9T
that 1.3T could be the cause of buzzing, not enough turns in the primary...
like so....
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I don't think any windings is working against other.
B+ supply, bias supply and filament supply are all perfect, in terms of voltage. I use this PT in a real SEUL/SET amplifier, and it sounds great (probably my best sounding amp).
I measured the inductances (primary and also leakage) when I built it, and it seemed ok to me.
I'll measure it again today and post the exact value.
The idle current is something close to 90 mA (the amplifier is a monoblock). But, as already mentioned, the buzz is still there even when no loading at all.
There's some window height available (probably around 2 mm), and I'm using a split bobbin [primary/shield/bias] on one side, and [HV sec/filament sec] on the other.
I could unwind the top windings, and add some more turns to all, to lower the magnetization... but I probably won't get below 1.1T.
Of course this is quite a bit of work, so I was trying to avoid that if possible.
So, enough talk. This required work 
I unwinded and added 76 more primary turns.
Magnetization should have drop to 1.2T.
I've put everything together again, and after some hours of careful work , I just tested it, and...
Partial success.
It's still buzzing, but it seems to be a bit more quiet.
Perhaps 5 dB less (according to a crude sound meter app run on my phone, just next to the core, with the same exact mounting and on the same surface).
Now I need to be close to it to be able to hear it clearly.
I even have some winding window left,... maybe I could get down to 1.15T, but unwinding it again is something I just can't think about right now
As a curiosity, I measure the magnetic field before and after the modification.
At 30 cm, it was above 2mT from the front, and about 1.2mT from one side.
Now, it is lower. 1.6mT from the front, and 0.85mT from one side.
I suppose this makes sense.
I'm still using the same stiff 1.4mm wire for filament winding. I wanted to play with a single variable at a time. I could try to replace it with bifiliar 1mm. But many hours seem to be required to get a perfect result (at least two more times taking aways the laminations, and putting them back together
)
I unwinded and added 76 more primary turns.
Magnetization should have drop to 1.2T.
I've put everything together again, and after some hours of careful work , I just tested it, and...
Partial success.
It's still buzzing, but it seems to be a bit more quiet.
Perhaps 5 dB less (according to a crude sound meter app run on my phone, just next to the core, with the same exact mounting and on the same surface).
Now I need to be close to it to be able to hear it clearly.
I even have some winding window left,... maybe I could get down to 1.15T, but unwinding it again is something I just can't think about right now
As a curiosity, I measure the magnetic field before and after the modification.
At 30 cm, it was above 2mT from the front, and about 1.2mT from one side.
Now, it is lower. 1.6mT from the front, and 0.85mT from one side.
I suppose this makes sense.
I'm still using the same stiff 1.4mm wire for filament winding. I wanted to play with a single variable at a time. I could try to replace it with bifiliar 1mm. But many hours seem to be required to get a perfect result (at least two more times taking aways the laminations, and putting them back together
)
Before this one, I made a small PT for a preamplifier, with regular non-GOSS laminations, at 1 Tesla. It is quiet. So for this bigger one, being GOSS, I felt confident, so I targeted to 1.4 T.
Even at two meters distance, in complete silence, I can hear the buzz clearly.
It is not very annoying, but it is there, so I'm going to try to improve this further.
I'm testing the transformer like shown in the picture. No bells, no wedge, no pads. Just four bolts and those metal pieces (which I don't know their names in English) to make pressure along the short laminations sides.
Could a bad electrostatic shield or not perfectly insulated bolts make the transformer buzz? I think I've done it right, but just to know.
Even at two meters distance, in complete silence, I can hear the buzz clearly.
It is not very annoying, but it is there, so I'm going to try to improve this further.
I'm testing the transformer like shown in the picture. No bells, no wedge, no pads. Just four bolts and those metal pieces (which I don't know their names in English) to make pressure along the short laminations sides.
Could a bad electrostatic shield or not perfectly insulated bolts make the transformer buzz? I think I've done it right, but just to know.
Attachments
@TonyTecson, what a HUGE beast!
What EI size is that? EI-171?
I can get EI-150 and EI-180, and I think EI-174 (5,8 cm center length, which is a little bit bigger) but that one I need to ask. Is this one OK for you?
For EI-180 there're bobbins for up to 12 cm stacking height, so probably there will be bobbins the height you need. Just tell me if EI-174 is good for you, or not, let me ask, and I'll come back with some news in several days time.
What EI size is that? EI-171?
I can get EI-150 and EI-180, and I think EI-174 (5,8 cm center length, which is a little bit bigger) but that one I need to ask. Is this one OK for you?
For EI-180 there're bobbins for up to 12 cm stacking height, so probably there will be bobbins the height you need. Just tell me if EI-174 is good for you, or not, let me ask, and I'll come back with some news in several days time.
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