Hi guys,
So I've been trying to source some small single channel transformers (power). Currently I use EI core dual bobbin's and they work very well, but the hum is a problem. I wanted to try James Transformers OA core because they appear to be very high quality and sport a shield between the windings.
Anyway, if someone/s can point me in the direction where to order better EI dual bobbins, or ideally OA core toroids with a shield between windings, would be much appreciated.
Thanks!
So I've been trying to source some small single channel transformers (power). Currently I use EI core dual bobbin's and they work very well, but the hum is a problem. I wanted to try James Transformers OA core because they appear to be very high quality and sport a shield between the windings.
Anyway, if someone/s can point me in the direction where to order better EI dual bobbins, or ideally OA core toroids with a shield between windings, would be much appreciated.
Thanks!
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Output transformers on your chipamps? I'm playing with output transformers at present and have found that the leakage inductance of split bobbin EI trafos is rather too high. Meaning the HF droops too much, much more than for a NOS DAC for example. Toroids work much better their leakage inductance I've found to be at least 10X lower.
If you're getting hum maybe your OPTs are too close to a mains trafo? I had that problem with my EIs which I used for driving cans.
If you're getting hum maybe your OPTs are too close to a mains trafo? I had that problem with my EIs which I used for driving cans.
No, just 120v to 18v, that's all. 160-220va.
Leakage inductance wouldn't be my enemy in this case.
Right now I use Hammonds (they have what I need, easy to buy), they hum a little on their own and they're not constructed well enough so tiny bits of torque on them, ever, creates double the hum forever.
Leakage inductance wouldn't be my enemy in this case.
Right now I use Hammonds (they have what I need, easy to buy), they hum a little on their own and they're not constructed well enough so tiny bits of torque on them, ever, creates double the hum forever.
Oh, power transformers? I got all excited for a moment there because you said output transformers. As you were 🙂
Save
mechanical hum?
often just bad luck on the draw, buying locally you can do an even exchange for one that doesn't hum. I prefer EI split bobbin, toroids w shield may actually be worse depending on grounding and your system. Adding a new earth ground on commercial gear can be problematical in itself. YMMV
many industrial name brands come w/ varnish or potting that can increase yer chances of low acoustical noise.
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I have been very happy with the Triad "VPS series" dual bobbin power transformers that I've used. DigiKey stocks them.
Since you mention a shield to reduce hum, that strongly suggests you are concerned about electrostatic and electromagnetic coupling of (noise on the primary) into the (secondary). Then let me remind you that the DIY cost-is-not-a-constraint, Insane Overkill solution is: two transformers in series. If you get 20X attenuation from one transformer, you get (20 * 20) = 400X attenuation from two transformers. Simply by spending more money. What could be easier!
Buy this dual bobbin transformer (#1) rated 80 VA for $21, and also buy this other dual bobbin transformer (#2) rated 80VA for another $21. Connect them in series. Presto, mains VAC to 18VAC at 80 volt amperes, with tremendous attenuation between mains and 18VAC output. And you can get 2nd day air shipping from Digi-Key. It's so easy.
Since you mention a shield to reduce hum, that strongly suggests you are concerned about electrostatic and electromagnetic coupling of (noise on the primary) into the (secondary). Then let me remind you that the DIY cost-is-not-a-constraint, Insane Overkill solution is: two transformers in series. If you get 20X attenuation from one transformer, you get (20 * 20) = 400X attenuation from two transformers. Simply by spending more money. What could be easier!
Buy this dual bobbin transformer (#1) rated 80 VA for $21, and also buy this other dual bobbin transformer (#2) rated 80VA for another $21. Connect them in series. Presto, mains VAC to 18VAC at 80 volt amperes, with tremendous attenuation between mains and 18VAC output. And you can get 2nd day air shipping from Digi-Key. It's so easy.
Interesting idea to use multiple transformers.
The shield is for RF, not hum. Toroids don't block RF as well as EI dual bobbins since they have totally different leakage inductance.
Thanks.
The shield is for RF, not hum. Toroids don't block RF as well as EI dual bobbins since they have totally different leakage inductance.
Thanks.
?
it's the inter-winding capacitance that controls HF stop band attenuation
and yer right HF coupling is lower on split bobbin.
worse coupling makes higher leakage inductance
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Sure, however you want to say it. Triad looks like a nice option if they're better than Hammond.
And of course you can also install RFI filters and/or common mode chokes, at any and every location along the series chain of transformers.
This filter from EPCOS costs $8.07 at DigiKey and is good for about 140 volt-amperes. Or you could consider this beefy 350VA filter from Qualtek that has two stages of filtering and achieves 60dB of RF attenuation, for $14.73 at DigiKey.
This filter from EPCOS costs $8.07 at DigiKey and is good for about 140 volt-amperes. Or you could consider this beefy 350VA filter from Qualtek that has two stages of filtering and achieves 60dB of RF attenuation, for $14.73 at DigiKey.
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Then you can apply your self-made filters to toroidal transformers. A good filter is cheaper than a good transformer and very much cheaper than two or three transformers.
Hi, thanks, I'd rather pay 10x what a transformer is worth if it gets better performance. Thanks
For anyone actually interested in transformers, in the parts section of the website, I found these
Transformatory toroidalne - Producent transformatorów Toroidy.pl
Transformatory toroidalne - Producent transformatorów Toroidy.pl
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