[quote author="dharma one"]how would you characterize sounds of different transformers? what do they actually do to the signal (apart from their textbook electrical properties)? i understand some people prefer the sound of some over others but why is this - how do they sound different?[/quote]
I cant tell you what they actually do which would lead to an understanding of how they sound different, but I have spent great deal of time auditioning transformers and can tell you that some transformers will make your circuit sound different the way blue, red or green paint will make your house look different.
A good test of extremity is the comparison between lundahl and beyer transformers. The beyer transformers I have played with have a VERY up front midrange with kind of a gravely top and a somewhat rolled off bottom. The lundahl transformers I have played with all pretty much do exactly the opposite in all respects, they have a sparkly top end, a scooped midrange and an extended big low end. On a graph, I bet the midrange is probably flat but appears "scooped" because of the high and low end characteristics. If you take the beyer, it fits exactly inside the lundahl, if that makes any sense.
I built a rev e 1176 earlier this year and wasnt happy with the 0-12 input and tried a lot of different stuff. Wound up using a 31267. The difference there was sorta light and airy vs led weight authority.
On the bench, differences may seem subtle, perhaps too subtle to bother paying attention to. The real test, which of course is where the time comittment gets crazy, is mixing with the stuff. The tiny bit of rise that one transformer did over the other on the bench is probably not the biggest deal and you may laugh at someone like me for insisting there is a difference between the two, but when you mix you may find that that tiny bit of rise at 5K made a vocal work without EQ where the transformer without the slight rise needed EQ lift to work. If you dont have any continuously variable EQs and only stepped gain eqs where your option is flat or +2 dB of boost, that tiny bit of rise all of a sudden is a HUGE difference between transformers...
Transformers make things sit in totally different places in a mix and thats where the real difference between this and that becomes really apparent and really really relevant. Unfortunately you really need to put in the time and listen to lots of stuff, Ive changed transformers in and out of some boxes dozens of times. If you have a patch bay you can save some time by wiring output transformers directly to patch points on the bay and then leaving your box transformerless and listening to the different outputs as you go, picking one and then going installing your pick into the box, I do that quite a bit. Save up some dough and wire in 5 or 6 common types that you like, saves lots of time with testing alternatives.
One other general thing, the cheaper steel lam transformers tend to be the ones that sound like a chunk of metal more often in comparison to the ultra high end expensive transformers which tend to have the "bulk" without the sound of a hunk of metal if that makes any sense. More expensive in my experience has translated to generally more transparent, good or bad depending upon what you like.
dave