Hi, I'm searching for a transformer that has a ratio of 1:1 for creating a supply for two ECC83 tubes. I can't seem to find one that can be print mounted to a PCB. As an alternative I thought about cascading two normal transformers, for example 230/24V straight into 24/230V. Would this also work? I don't want a custom transformer to be made, I would prefer off the shelf components. Thanks in advance! Valentin
You can mount two small transformers back to back, but the smaller they are, the smaller is the ratio when used in reverse. E.g. a 4VA print transformer with 220V/12V will not yield 220V when fed with 12V, it wil be more in the range of 150V. Keep this in mind. The 4VA transformer will more likely give 220V on its output when supplied with 18-20V. This ratio will increase with larger transformers.
Maybe this little transformer here will do the job? It's not 1:1 but close to it. In addition you'll also get a 6.3 winding for two ECC83 tubes: https://www.tube-town.net/ttstore/tt-powertrafo-ei-230-200-6-3-7-va.html
Thanks for the answers so far. I've had another idea this morning. Would it work when I use it as I've drawn it in the photo I attached? I am needing a symmetrical +-15V anyway for my project, so I was thinking about using two transformers each with two 115V primary windings. Are there any issues I'm facing when connecting it that way? I am only guessing I have to use transformers with double the rated power because I would be only driving one of the primary windings, the other one would be used to form a secondary for the tube plate voltage (HV) -Valou
I doubt it is a good idea to abuse one half of the primary windings to get your HV supply. The transformer has a guaranteed insulation between primary and secondaries. This is not the case for the two primaries. If you get a short between the primary windings you might end up having mains voltage without galvanic insulation on your HV supply. In theory it would work though.
If you have different loads at the transformers the primary voltages/currents are not equal.
@Nils, I was suspecting the same thing already... Plus the loads not being equal is indeed a real concern here. I have to think this through again, thanks for the answers so far! -Valentin