I am fascinated by all the permutations of wire thickness, core size interleaving paper thickness etc. around output transformers. One of the configurations that should an incredible diversity, is the push-pull transformer for the EL84 tube.
One can speculate why this is, but the EL84 is probably the most popular tube in the low power range. The 6AQ5 and ECL82/6 are all included in this expression, since their transformer demands are very similar.
Ok to continue: I noticed that if one use small cores, the results are not discouraging, except that the physical size puts people off. On the other end of the spectrum one gets the large transformers with plenty of headroom, but to keep insertion loss low, thick copper and plenty of inter leafing is necessary.
Now the question is... which one is better? Let us focus on sound quality rather than aesthetics... for the moment.
Here is two transformers with similar specifications, but different size:
EL84 OPT by Karel Mars, on Flickr
While researching this, I stumbled upon a paper that seems to put on paper everything you can know about a transformer, in this case the Mable EL84-PP OPT. Thanks to Menno van der Veen :thumbs: Maybe this can be a reference?
https://mennovanderveen.nl/nl/download/mable/MABLE-OPT-1-data.pdf
The Mable transformer is really small: EI57 laminations! It looks a bit like the Rogers Cadett III OPT's.
Notice the high primary DC resistance but still low insertion loss:
Screenshot from 2017-06-14 11-43-43 by Karel Mars, on Flickr
Maybe Ampdog can give his impressions on what aspects of an OPT would be most desirable, esp. around insertion loss and other aspects of efficiency :thinking:
One can speculate why this is, but the EL84 is probably the most popular tube in the low power range. The 6AQ5 and ECL82/6 are all included in this expression, since their transformer demands are very similar.
Ok to continue: I noticed that if one use small cores, the results are not discouraging, except that the physical size puts people off. On the other end of the spectrum one gets the large transformers with plenty of headroom, but to keep insertion loss low, thick copper and plenty of inter leafing is necessary.
Now the question is... which one is better? Let us focus on sound quality rather than aesthetics... for the moment.
Here is two transformers with similar specifications, but different size:
EL84 OPT by Karel Mars, on FlickrWhile researching this, I stumbled upon a paper that seems to put on paper everything you can know about a transformer, in this case the Mable EL84-PP OPT. Thanks to Menno van der Veen :thumbs: Maybe this can be a reference?
https://mennovanderveen.nl/nl/download/mable/MABLE-OPT-1-data.pdf
The Mable transformer is really small: EI57 laminations! It looks a bit like the Rogers Cadett III OPT's.
Notice the high primary DC resistance but still low insertion loss:
Screenshot from 2017-06-14 11-43-43 by Karel Mars, on FlickrMaybe Ampdog can give his impressions on what aspects of an OPT would be most desirable, esp. around insertion loss and other aspects of efficiency :thinking:
