What does "transformer coupled" mean?

I've read about preamp designs that are transformer coupled (Audio Note, Supratek, others?). What's the big deal about transformer coupling?

dennis_the_menace03-30-2003 9:07pm

sean Details Discussions Posts This discussion Message User 6,231 posts 03-30-2003 at 11:47pm Copy Comment URL Report Comment Edit Delete The one advantage that i can see about transformer coupling from component to component is that the circuit of within the device tends to see a relatively stable impedance and is somewhat "buffered" from reactance that the load component may see and try to pass back further up the chain. Other than that, it too has its' disadvantages. Sean >
sattothestars Details Discussions Posts This discussion Message User 233 posts 03-31-2003 at 12:16am Copy Comment URL Report Comment Edit Delete Sean;Such as what disadvantanges?I know of none.
ghostrider45 Details Discussions Posts This discussion Message User 449 posts 03-31-2003 at 12:30am Copy Comment URL Report Comment Edit Delete Actually, the transformer reflects the load impedance to the primary side (described in another post of mine), so there's no real isolation of reactance. The real benefit of transformer coupling is that it allows one to match almost any load impedance to almost any source impedance, and it provides excellent isolation between stages to boot. This allows more freedom in selecting circuit topology. The problem is that it's hard (read expensive) to build a transformer that's truely flat across the entire audio range.