Newbie question - DI box is going to be my first project

[strahl]

Hi!
I'm trying to build one of these but I got a problem. It seems I only get aprox 12 v where it sholud be 24 and when i plug my bass in its like I've built myself a distortion box instead of e clean DI box. I'm kind of new at this, any suggestions?
I'm using Lundahl LL1538XL by the way.

EDIT: problem solved.... I'm stupid

 

[rotation]

I'm just soldering Bo's DI and am not sure how to connect OEP A262A3E transformer.
I know it is connected backwards, but those start and finish markings are confusing me.
I'm also not sure what to do with 9th pin. Is this shield?

 

[Bo Hansen]

"rotation"

You shall connect the OEP A262A3E in paralell both on primary and secondary to get 150 ohm to 6,25 kohm, and use it backwards to get a ratio of 6.45:1.

pin connecting as following:

use as primary, feed from the DI electronic
5+6 as high
7+8 as low

use as secondary, output to the XLR connector
1+2 as high
3+4 as low

Transformer core ground is pin 9

BTW, I find one of my earlier posting, about this OEP transformer.

Prodigy pro lab, 2004-07-08

Kubi,

The OEP's A262A3E connected in 6,25K to 150 ohm will fit in this circuit but I have not use this transformer in DI application when I have don a recording session so I can not tell about the sound quality.
I have only use this transformar for PA and communication applications and it is a good general purpose transformer for this very low price (under £10 in UK) and easy to get.
But the Lundahl LL-1538 (aprox. £40 in UK) is a transformer in a high quality division, and it can not be comparable with the OEP that is a semi-pro transformer.

A good middle alternative are the transformer that I use in my orginal version around 1975 the Sowter 3678 in 1:5 configuration (under £30 in UK)

Or maybe try the old famous Neve microphone input transformer
10468 / VT-22670 / T-1454, configurated in 300 ohm to 4,8 K
To day manufacture by Carnhill, type: VTB-9045
or Sowter type: 9145

--Bo

 

[rotation]

Thanks for your kind response. I have one more question

What means 5+6 high and 7+8 low? Does it mean i have to connect pins 5+6 to upper side of schematic where 10uF capacytor is and connect 7+8 to the ground?

 

[Bo Hansen]

"rotation"

Ok, I understand why you are confused, I refer to a other OEP product paper with different pin out numbers, but you can find it here and compare with the pin placement you have:
http://www.canford.co.uk/commerce/resources/catdetails/2739.pdf

High and low explanation:

use as primary, feed from the DI electronic
5+6 as high= from the 10 uF capacitor
7+8 as low= to electronics ground rail

use as secondary, output to the XLR connector
1+2 as high= to XLR pin 2
3+4 as low= to XLR pin 3

Transformer core ground is pin 9= to electronics ground rail (same as 7+8)


--Bo

 

[datape]

this DI is fat with a cinmemag 75101aPC in there. thanks!!!

 

[Bo Hansen]

"Datatape"

Nice to here that you like my DI-box.

Yes, I think Cinemag CM-75101 is a good transformer, but in 15 k to 150 ohm, 10:1 ratio configuration, it have to much loss, so in 15 k to 600 ohm, 5:1 ratio config. it will work better.

--Bo