Ive got a PCB im excited about building/populating, but it requires a Lundahl LL7903 and where I can find them at ALL..they're running $150-200!!
Im hoping someone here has an idea about what/where/if there are any equivalents or transformers that are close enough for government work (the specs are within a not-too-large range of the 7903)?
Ive built a good many things since I started this hobby about a year ago but I have little/no knowledge about transformers. Ive basically bought and installed..I dont really know enough to tell if one is like enough to another to use as a substitute. Im hping someone here can/does?
Thanks for any help you can provide!
or, alternately, Thanks for taking the time to read this post!
It is unlikely that you'll find anything with even close to the performance. A glance at the specs indicates that the LL is a fairly high performance device. Transformers are very much not like resistors in interchangeability. Unless there is one designed as a direct replacement, chances are very bad you'll find one that fits the same holes and is close enough but cheap. If it's designed as a replacement, it will not be much cheaper, if at all.
If we knew the PCB/circuit, it might be possible to suggest some alternatives. It is possible there is something that could be kludged into the circuit that would be a transformer that was not horrible. But it probably won't be a good physical fit.
I recall Edcor transformers having a pretty good bang for buck. Don't know if they have an exact replacement for that Lundahl, but you could try browsing their website - edcorusa.com. They've got a pretty wide selection.
~ Charlie
> Ive got a PCB im excited
To do what??
If this is a Mike Preamp, how good a preamp do you need?
The LL7903 is an exceptionally great transformer. $150 is cheap for what it is.
Do you really need +28dBu input?? (20 Volts!!)
Do you know if the PCB uses the LL7903 as 1:1, 2:1, 4:1, 8:1?
If you want a "starter" transformer, go to RadioShack and get the heavier XLR(f)-to-1/4" mike adaptor. In there is a 1:7 transformer which does not suck. Signals over 0.1V at 50hz will overload it. I worked for years in live-sound and recording and this was rarely a problem. The $20 mike-adaptor is not shielded near as much as the obsessive LL7903, so you have to keep it away from power wires and transformers.
OTOH, a "PCB" which is designed for the slick LL7903 probably has many other slick design details. Maybe 990 amp-modules? ($50-$200 each) Unicorn-hide capacitors? Platinum resistors?