Lundahl Mic Transformer Wiring Hookup

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

mkruger

Well-known member
Joined
Jul 25, 2004
Messages
149
Location
Southampton, New York
I'm looking at a Lundahl 1538xl mic transformer. There are four pins in on one side and three out on the other.

IN
Pin 2(+ black wire) of the XLR i would attach to pin 1 of the trafo.
Pin 3(- white wire) of the XLR would go to pin 4 of the trafo.
Pin 1 (ground/shield) of the XLR would go to pin 2 and 3 of the trafo.

OUT
Pin 6 is signal
Pin 7 & 8 are ground.

http://www.lundahl.se/pdfs/datash/1538_8xl.pdf

Do I have this correct for the 1 + 1:5 ratio?
thanks for your help!

-mike
 
15388xl25.gif


15388xl.gif
 
so if i wanted to use this, or the Lundahl 1577, for an output trafo to the XLR out... then would i connect the trafo in reverse? with the XLR on pins 5, 6, & 8...
 
Specifically the Lundahl 1577 with the 1:14 ratio. It notes at the bottom of the spec sheet that

"...these transformers are often used in reverse for line out..."

so i'm just making sure i understand what reversed means. They are talking about the signal flow being reversed, not the actual transformer.

http://www.lundahl.se/pdfs/datash/1576_77.pdf
 
OK, even without the schematic, what are you building? It really does make a difference. Transformers can be used in many ways but all transformers don't work in all circuits. Posting the schematic helps others to help you better, but just describing the circuit may also help. Just saying can I hook an XLR up like this wont get you a good answer.
 
WHAT! you give up! i thought i had mentioned it was for a tube mic pre.... but after reading the posts i see i have not. anyway i undersatnd it now. sorry to give you the runaround... your help is and has always been appreciated!!
 
OK, now were gettin somewhere.
You need more iron than a 1538xl in reverse for an output.
65 grams isn't gonna cut it.
mic inputs usually are designed to handle the delicate input signal from a mic.
this means they want low core loss and insertion loss, capacitance and leakage. therefore they are sized accordingly.
i mean you could use it backwards, and i am sure that people here have done it, but for a really high bass signal, you will distort.
get something in the 150 to 200 gram range.
cj
 
The 1577 is an EXELLENT trannie for ribbon mics, but surely you can you use it in reverse for a line output :shock:

I think Lundahl means for DI use or maybe a tubemic. They can't take much level.
 
sismofyt - so did you just say it can, or did you mean it should not be used for line out?

I have two 1577's i'd like to use for somthing and i'm wondering if it's worth it to make the circuit boards for their pin-outs or is that a waist of time. will they just distort horribly?

here are the schems. i labeled the RCA output and the trafos.
Schematics2.gif
 
That will not work!

Take a look at the max levels for the 1577... -4dBU gives +19dBU out. So if you wanna drive a +4dB input you'll get 148% distortion or something like that. Also notice that you need a cap and resistor across the trannine to get a good high end response. They're only really good for mics, imo.
 
yes that is the slow blow pre! there were a few typos with the origional schems and some other things iv'e changed...

but i wanted to do this project because i happen to have some of those parts and particularly those trafos on hand.
 
Ok, I've seen several re-written schematics of that slowblow pre. The original one I did, did _not_ have any typos :cool:

Check you PM :wink:
 

Latest posts

Back
Top