Me too. They can be designed such a way so thanks to parasitics they form additionally very good band pass filters!
Repurposing makes it enormously more affordable!
1. ADSL,
2. Current sensors
I mean line level transformers.
Sure, thanks to them lot of studio recordings are saved on different media, from LPs to files...
Lifesavers, then!
I really do use hundreds of transformers each year for my projects. I just came back from a high school football field where a six foot unbalanced cable would pick up a buzz from the wye power transformer feeding the field lights and press box.
Hum, buzz, EMI etc. are worse than the reduced frequency range and increase in distortion in real professional applications.
In those cases such as home reproduction systems where the gear can be connected with unbalanced cables and not have issues then of course a transformer is a disadvantage.
These days I am using an offshore made transformer that costs in quantity about $6! Used to spend closer to $80.
Just ran into an interesting problem. I have two of the same model passive full range loudspeakers in parallel. Output drops like a rock above 3,000 hertz. Sweeping each individually both work properly. Time to get two replacements, check them in the shop as a pair, then rent a lift and replace the other ones. Going to be an interesting warranty claim.
Hum, buzz, EMI etc. are worse than the reduced frequency range and increase in distortion in real professional applications.
In those cases such as home reproduction systems where the gear can be connected with unbalanced cables and not have issues then of course a transformer is a disadvantage.
These days I am using an offshore made transformer that costs in quantity about $6! Used to spend closer to $80.
Just ran into an interesting problem. I have two of the same model passive full range loudspeakers in parallel. Output drops like a rock above 3,000 hertz. Sweeping each individually both work properly. Time to get two replacements, check them in the shop as a pair, then rent a lift and replace the other ones. Going to be an interesting warranty claim.
I have been struggling with noisy transformers from many differnt vendors.
Who can make a really quiet transformer? Right now I am loking at Plitrons low noise series.
Which ADSL transformers are worth looking at. When I had a precursory scan the LF rolled up way too early on the ones I looked at, but must admit I never measured them.
There is one sure fire way to get a very quiet (mechanically) power transformer. If you need a 500VA, for instance, ask them to wind it on an 800VA core. Dead-silent. But it'll cost you.
Jan
Most often hum cause is saturation of cores. They save copper winding less number of turns than needed.
And secondary rectification with big caps causing high current peaks may increase hum as well.
Exactly. Having them put those windings on a larger core fixes it. It's a spec they understand.
Jan
Doubt it as they are 100' apart. Should be interesting when they get to the bench. Sweeping in the field, each sweeps alone, but in parallel just above 3K amp-speaker combination chirps and above that no output. When driven by system amplifier the feed line is a few ohms. The result is no output above 3ish.
Don't have AC power at the best test location. So my guy did the frequency impedance sweep at the amplifier end.
I used a battery powered amplifier based on auto sound chip that can drive 18 watts into 4 ohms. Test signal fed from my cell phone.
What I have seen that causes the problem (and it’s a spec they understand) is volt/turn for the primary side.
They use high volt/turn in their calculations mostly for to increase the voltage regulation spec of the transformer and secondary to reduce the amount of copper.
Ask them to reduce vol/turn for the primary (about 10%).
This means more copper (so tell them you are willing to pay more), less core flux (so no saturation) and inevitably worse voltage regulation.
Increasing the iron volume alone without reducing the primary volt/turn, will increase the cost further and will most probably reduce the voltage regulation further.
George
IIRC, increasing the core volume decreases the Volt/Turn. Volt/Turn=Fi-max/t where the maximum magnetic flux Fi-max=Bmax/A A is the core area and of course it increases with the core volume. A practical rule of thumb is Volt/Turn~50/A and A~SQRT(Pmax) (good for iron with Bmax=1.2T, again IIRC).
Building 'low noise' power transformers is as much a 'commercial art' as it is engineering design. DC (often created by significant 2'nd harmonic on the power line) can be a cause that is hard to fix. Cheap core materials seems to be important, and may vary from batch to batch, and of course core size and number of windings also makes a difference. It is often experience, or 'cut and try' that gets results.
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