Input transformer as injection transformer suggestion

[Darko ObretanParticipant]

Hi Michael,

Do you maybe know which audio input transformer goes lowest in frequency response? I've been playing with some ideas and need one that I can use as injection transformer for some measurements and I need it to go down to 1Hz and also up to few tens of kHz or so. (Ratio can be from 1:1 to preferably 10:1)

Regards, Darko

[Michael StuckerParticipant]

Darko,
Wow, that's an interesting question. I do not know of any transformers that would have a reasonable response that low. I would suggest contacting David at Cinemag. If one can be made, or exists, he would know. My first thought is that an active input circuit would be the best option for 1Hz, but it is hard to know without knowing more about your use case.
http://cinemag.biz/

• This reply was modified 4 years ago by Michael Stucker.

[Darko ObretanParticipant]

Hi Michael,

Thank you, I was searching a bit more and find few transformer sources, but such transformers are really expensive and don't go that low either.

I mainly need it for galvanic isolation between measurement equipment and different electronic devices. I intended to use one as injection transformer for switching power supply feedback loop response measurement (I would inject error signal over this transformer and measure how long does power supply take to react and stabilize after that).

The other use would be to hook it up between function generator and various circuits (audio or other) to avoid ground loops.

I was thinking about your suggestion and active circuit would also suit my needs if I power it from battery and isolate its input with optocoupler and linearize it. The only downside I see is some additional noise (which could be really low with certain OPAMPs) and some small DC offset which could be also removed.

I think I can build really good active circuit for the price I would need to pay for transformer that goes down to ~10Hz (which is around 300USD here http://www.trafco.rs/tubeaudio.php).

Thank you for suggestion! Do you have any specific active circuit in mind?

Regards, Darko

• This reply was modified 4 years ago by Darko Obretan.
• This reply was modified 4 years ago by Darko Obretan.
• This reply was modified 4 years ago by Darko Obretan.
• This reply was modified 4 years ago by Darko Obretan.
• This reply was modified 4 years ago by Darko Obretan.
• This reply was modified 4 years ago by Darko Obretan.
• This reply was modified 4 years ago by Darko Obretan.

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