Right, but it's perfectly silent in operation.
OTOH, some shielded transformers were noisy...
The volume (~1200 cm3) suggests a 700VA, efficiency of 94% isn't that great.
Lots of core, less copper.
I have not noticed much correlation between mechanical and electrical
noisiness. I have a decent pile of transformers whose shields buzz, and
another pile where they are mechanically quiet, but have strong field lobes
that are picked up by the circuit. (In the latter case it often helps to rotate
them, so I leave the leads long enough for some adjustment)
Hmm .. informative.
My Annoying Tx doesn't buzz it's shield.
Yet infects the nearby circuits with a distinct Hummmm, clearly audible through my speakers. Now I know it's not unique.
Seeing as no one considers or deigns to answer my "relocate it ?" query.
Did once try the rotate trick, small to no effect unfortunately
I'll have try locating it at some distance
My Annoying Tx doesn't buzz it's shield.
Yet infects the nearby circuits with a distinct Hummmm, clearly audible through my speakers. Now I know it's not unique.
Seeing as no one considers or deigns to answer my "relocate it ?" query.
Did once try the rotate trick, small to no effect unfortunately
I'll have try locating it at some distance
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Exactly. When I started using toroidals in mid-eighties, they all were good, but in that time there were not a lot of companies that manufactured them and they were more expensive than they are today. Nineties brought market/production expansion and with it the junk prevailed.I have not noticed much correlation between mechanical and electrical noisiness....
All of the old toroidals had the cast core but now all cores are made of spiral iron ribbon that is prone to mechanical oscillations (when done quick and cheap). Quality of winding is often bad (uneven distribution of wire) which brings unpredictable dispersion of EM field (lobes with spatial peaks) which causes hum in surrounding circuitry.
Although all modern companies brag with IS9000 standard certificates a majority of them can't/won't always keep the same level of production quality (except the really bad ones - they are reliably bad)...
William, I have some toroids and transformers that have been wound with the secondaries in pairs: that means that both secondaries have the same length and same coupling to the iron.
This means that the rectified voltages are same and similar. No third harmonics (?) that will saturate or make noise. (also easy to filter off any residual commutation peaks as they have the same form and timing).
Secondly, if you do not exactly balance the current in the two halves (such as: you also have a relais that you tap from the plus to earth) then that will also give noise from unbalanced loading of the windings..
You have toroids. You could try a DC-blocking configuration that isolated the transformers from the mains [or from each other]. If the 50/60Hz is not stable (not a sine) then the toroid can easily saturate, sound like you describe. A DC blocker is a bridge, maybe with an extra diode, and a bipolar capacitor.
my 2¢
This means that the rectified voltages are same and similar. No third harmonics (?) that will saturate or make noise. (also easy to filter off any residual commutation peaks as they have the same form and timing).
Secondly, if you do not exactly balance the current in the two halves (such as: you also have a relais that you tap from the plus to earth) then that will also give noise from unbalanced loading of the windings..
You have toroids. You could try a DC-blocking configuration that isolated the transformers from the mains [or from each other]. If the 50/60Hz is not stable (not a sine) then the toroid can easily saturate, sound like you describe. A DC blocker is a bridge, maybe with an extra diode, and a bipolar capacitor.
my 2¢
Hi,
DC blocker has been tried (and still installed), doesn´t help in this case.
Exactly balancing does help but is not so simple in an Aleph-X unless I use a servo to keep the absolute DC at exactly 0V. I tried this but the amp still hummed.
I got my toroidys and will try them in the near future. Let´s wait and see (hear)
William
Are you still referring to a mechanical hum from the transformer/s?
Is there any measurable hum/buzz/noise at the amp output?
Hi Patrick,
I already have. See pic a few pages back. Since absolute DC is directly dependent on the mains voltage it varies as does the humm.
William
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