Author Topic: Correct wiring of transformer in a passive DI box  (Read 178 times)

danfrank

Correct wiring of transformer in a passive DI box
« on: January 27, 2021, 11:36:50 AM »
Hi everyone,
I'm building a passive DI box with parts that I've acquired throughout the years. I've identified both windings for proper phasing but my question is: What is the best way to send signal to the transformer for best response? Is it best to insert signal at the begining (the wire end of winding closest to center core of transformer) of coil wind and ground the finishing end of the winding or the other way around? Does it matter?
I always thought that the dots at the winding lead denoted the beginning of the wind but it looks like they are actually there for phasing purposes.
Thanks.
« Last Edit: January 27, 2021, 11:38:23 AM by danfrank »

iainpunk

Re: Correct wiring of transformer in a passive DI box
« Reply #1 on: January 27, 2021, 03:10:06 PM »
it [basically] doesn't matter much if you start at the center or at the outside, tone wise, no difference, but having the outer windings grounded does act as a little bit of a capacitive shielding, like a Faraday cage, while the biggest type of noise you should worry about with transformers is magnetic noise, like that form fluorescent tube drivers.

you could put a phase switch on one side of the transformer so you can change the phase if needed.

cheers, Iain
half man - half snail - 6 feet to scale - Snail man's - not frail - He's been - to jail - snail man is fuccing real
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PRR

Re: Correct wiring of transformer in a passive DI box
« Reply #2 on: January 27, 2021, 03:20:01 PM »
> Does it matter?

Indeed. This sounds like over-thinking.

In fancy work (much fancier than guitar) you tend to ground the INside end of the winding because it is tight to the core and thus more groundy than the outside layer. If in fact the winding fills core to rim, which is unusual.

In short: this is above our pay-grade.
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danfrank

Re: Correct wiring of transformer in a passive DI box
« Reply #3 on: January 27, 2021, 03:47:45 PM »
Lol!
Thanks for the replies... The way I have it now, the end of the high impedance winding is grounded which will put the "shield" right between the 2 windings.
I did have a pair of NC-20 interstage transformers a long time ago, and it DID matter which way the windings were configured on those. I'm really sorry I let those go. They were nice!
Thanks again!
« Last Edit: January 27, 2021, 03:49:23 PM by danfrank »