Tricky? use of LL1620, vs. use of LL9202

K&K Audio / Lundahl Transformers

Welcome! Need support, you got it. Or share youe ideas and experiences.

24.107.206.179

There are more in the Lundahl data sheets than meets the eye. :-)
In trying to find a good match for an output transformer for my proposed WE 205d and/or 10/vt-62 amplifier, I've run into a snag, and have a question. The main issue is that I have 4 ohm speakers (Altec 755As in Lowther horns these days) and there aren't a lot of 10K 1 watt SE output transformers out there, let alone ones with 4 ohm taps.
At first glance, the data sheets indicate that an LL9202, used with secondary config B will give a nice 11.5K primary - perfect for the 10 or 205d. However, this nice transformer comes at a price 20mH - almost double the primary leakage inductance of the LL1620. (See below.)
Secondary connection Primary leakage inductance
for 4/8/16 W (all in series)
-/B/C B/C/D C/D/E
LL1620 11.5 k 6.0 k 3.3 k 11 mH
LL9202 23 k 11 k 6.5 k 20 mH
There seems to be no 4 ohm option for the 11.5k ohm primary on the LL1620. However, if you look at the connection option that would seem to go in that suspicious "-" blank there, option A would seem to suggest itself. Interestingly enough, option A is listed farther down in the data sheet, and is simply all secondaries in parallel, giving the highest ratio for the transformer.
Plus, who would ever need a 23k transformer, and even if they did, what madness is that, anyway :-) Single ended 26 POWER amp? Something on the order of 0.1 watt? Ok, I'm nuts, but not _that_ nuts.
Though this amp may be full range - full range isn't _full_ range really for me. 40Hz is plenty low enough. Actually, it may end up doing duty as a tweeter (Jensen RP-302) only amp, and in that case the tweeters are 16 ohms anyway. My concern there is that I want as much high-end bandwith as possible for natural highs, so lower leakage inductance is important.
So here's my (rather long winded) question - can I use the LL1620 in connection A for a 11.5K to 4 ohm OPT. And while I'm asking, do they come in 25mA or 30mA versions somewhere in the secret labs?

This post is made possible by the generous support of people like you and our sponsors:

VH Audio

Topic - Tricky? use of LL1620, vs. use of LL9202 - Tom Ronan 19:45:00 11/11/04 (0)

You can not post to an archived thread.