Di Box Transformer specs

[llamma]

Hi Guys,

what specs does the transformer in a di box meant to be

i read the schematic for the rolls db25 and it had a 50k/600 unit, the jensens are 200k/1.5k

the unit in the behringer di 100 appears to be 1:1

is there any way to test the actual value of the units? just sticking my meter on it only gave me about 22ohms each side

cheers
Blair

[Gilles C]

What you are reading with your meter is the dc resistance of the primary/secondary

For example, the Jensen xmtr has 4.6K and 63 dc ohms for impedances of 200K and 1.5K, and that is disconnected from any circuit.

When connected to a circuit, it is kind of in parallel with some other parts, which gives another reading on your meter.

Check these specs.

http://www.jensen-transformers.com/datashts/dbe.pdf

The specs of your xmtr will depend on the reflected impedance from the secondary that you want your electronic circuit to see.

For example, if you use a 1:1 xmtr, your circuit should see "roughly" the same impedance than is connected to the secondary of the xmtr.

But you also have to match the output of your circuit to the primary of the xmtr, and the secondary to the impedance of what will be connected to it.

Lots of formulas to calculate that.   :roll:  :shock:

Gilles

[martinbertrand]

Hi, here is a picture I took from a rolls DI. hope this helps
//www.cjonquiere.qc.ca/martin.bertrand/DI.jpg

[Mike Burgundy]

is it me or does that really look like a mouser tranny?

[llamma]

that would be a rolls db25 matchbox

basically just a transformer,

the one i have sitting next to me has no part number on top of the transformer

that code on top includes the specs 50k/600 as per the schematic,

rolls are really good and have included the schematics for their products in the manuals, including the adi6 which is an active di using 2 2n5087 trannys, and thats about it, (few resistors and caps),

this should make the di building nice and easy, even works off phantom power

[Gilles C]

On their site, they talk about "shielded transformer balancing."

Well, it doesn't look like a shielded xtmr.

It looks exactly like the Mouser xmtr I once bought, except the part number is printed in black, not engraved.

Btw, it's not to say the Rolls DI box is not good, but for the same price, the Berhinger GI100 freq response is 10-160Khz, and the Rolls is 50-15K, so maybe the xmtr has something to do with that.

Gilles

Added: ok, i checked Jensen XMTRs and this shielded one looks like the Mouser XMTR I have.  :oops:

http://www.jensen-transformers.com/datashts/dbeu.pdf

[Paul Marossy]

My DI box has a 10K:10K transformer in it. It appears to be a Mouser transformer from what I can tell...

[llamma]

hey Paul,

any buffer circuit in that di box?

the behringer di100 seems to be a 1:1 transformer but has a jrc4559 based buffer circuit before it.

if anyone is interested i can trace this circuit out.

regards
Blair

[Paul Marossy]

Nope, it's just an audio transformer and that's it. When I saw how simple it was, I said, "I paid $40 for that?!" That was before I was a DIY guitarist.

A buffer circuit, huh? That would be interesting to see how that is implemented...