Bo Hansen DI layout

Hello Guys,
I need some advice from you guys, i want to make 8x DIs for electronic music, so, as im not aware of the Xformer diferences, what do you guys would recommend for electronic music. I would like to have the most possible beat definition and punch, and great transient response would be important.
I dont even know if i'll ear a diference between jensen vs lundahl vs sowter vs whatever, but maybe you guys can share your experience with xformers.

Also, i want to make a passive summing of the lines that are feeding the 8x DIs, so i would have 4 stereo feeds to the FOH PA system, and a stereo summ of the 8 channels into monitor mixer, to make things easier in Festivals etc.
Can i make a parallel on the DI inputs and then make a passive summ onto Left XLR and Right XLR? here i wont need to drive the summ into mic pres because i would run the signal into the monitor mixer where it will be amplified.
Any advice for this?

Thank you guys in advance!

Pedro Cruz

Hello,

I'm building some Bo Hansen DI. I measured  a few transistor and found HFE to be around 250 to 520 for the BC550 and 341 to 363 for the BC560.

What HFE do you recommend ? What could append if I use one with 520 and the other with 363 ?  Is it class A design ? It looks like a darlington stage with two transistor. I am right ?  If it is not AB class, is there a risk to use different HFE ?

Best regards,
Loïc

I'm building two of these for a studio which doesn't have phantom power (disabled it on the desk, they use tube mics with their own psu.. ).
Is it possible to run these on external 24V power? And if so, should I connect it to where it says +24V on the schematic?

Thanks!
Corneel

I would think so  - probably would want to omit the two 6.8k going to the XLR out to prevent voltage going to the input of your preamp.

I have reviewed the posts and have seen the questions and answers regarding connector wiring, but am still a bit confused. Maybe I just need more coffee.

I will start with the XLR's. I purchased Neutrik DLX series connectors which feature a "duplex ground contact". I can not find documentation on what that actually means, but it says "New duplex ground contact for excellent contact integrity between chassis and cable connector".

I understand XLR 1, 2, 3, on the PCB obviously go to pins 1,2,3 on the connector. If I understand correctly, the ground tab on the connector (next to pin 1) gets soldered to pin 1.

Where I am confused is the Chasis pad on the PCB. In some of the project pictures, it looks like it is not being used at all (unless wire is soldered on the bottom). In the ones that are using it, I can't tell where it is connected on the other end.
Does it also get soldered to pin 1 on the connector, or does it go to one of the actual mounting screws that hold the connector to the chassis?

Classicaudio77 said:

Where I am confused is the Chasis pad on the PCB. In some of the project pictures, it looks like it is not being used at all (unless wire is soldered on the bottom). In the ones that are using it, I can't tell where it is connected on the other end.
Does it also get soldered to pin 1 on the connector, or does it go to one of the actual mounting screws that hold the connector to the chassis?

Click to expand...

Here's what I would do (as per Bo's instructions on his site, see page 1):

1. Connect XLR pins to board with wires
2. Solder extra wire to pin one of xlr with an eyelet at the end
3. Solder a wire to the chassis-pad with an eyelet at the end
4. Connect both eyelets to one of the fixing screws of the XLR

note: no connection from XLR pin 1 to tab on XLR

Here's what I would do (as per Bo's instructions on his site, see page 1):

1. Connect XLR pins to board with wires
2. Solder extra wire to pin one of xlr with an eyelet at the end
3. Solder a wire to the chassis-pad with an eyelet at the end
4. Connect both eyelets to one of the fixing screws of the XLR

note: no connection from XLR pin 1 to tab on XLR

Click to expand...

Okay, so two wires to the chassis/xlr screw, one from pin one of XLR, one from the PCB Chassis pad, ground tab on xlr does not get used! Thanks.

I have mounted my XLR's from the inside (I like the cleaner look). I know that usually the ground lugs should have good contact with the chassis. Any sugestions on this?

Classicaudio77 said:

I have mounted my XLR's from the inside (I like the cleaner look). I know that usually the ground lugs should have good contact with the chassis. Any sugestions on this?

Click to expand...

The XLR should be conducting and if the inside of the chassis isn't painted, the ground connection from chassis to solder-eyelets-on-screw should be fine. If in doubt you can always sand the inside of the chassis around the hole for the screws so the XLR makes a good ground-contact. You could also use two anti-shake washes between XLR and chassis for better contact.

Hey,

Just though I would post a pic of my finished units. Black model is with Lundahl, silver is with Haufe. Thanks for the awesome design.

cool!
With the schematic on top!

this is super ultra coooool

would show my units...




the black ones are with Haufe, the silver ones with Neumann BV107

I notice you did not use the the chassis ground and/or ground from pin 1 of the XLR's. Any grounding issues with your units?

i connect the XLR chassie connector to XLR pin 1. That is difficult in the picture to see. 
btw. this design works perfect in the studio and on stage, also sound excellent ! yesterday i used 3 pcs on Bass, acoustic git and cello PU.

Sorry guys, I have not been on the forum the last time, I've had too much to do at my company, But will now try to answer your questions.

First of all, please always read my DI-box DIY instructions available here: www.hansenaudio.se/techpage.htm
There is lots of build information,  circuit explanation, different choices of transformers, transistors and other components and much more, that can provide answers to your questions and problems.

Loicm
In this simple dual emitter follower circuit, is not Hfe so important, but to secure the high impedance and working point/bias on the first transistor base, it is good to have a transistor with at least medium Hfe.
But avoid using the "A" graded transitors due to some unknown brand that may have poor Specifications.
Use BC550/BC560 B or C, in better brands as Philips, Motorola, Fairchild, National, SGS/Ates.

Nele
You can apply regulated +24 volt on the positive side of 100 uF electrolytic capacitor.
But take away the two 6.8 k resistors.
Note that the ground/- 24 volts must be connected to pin 1 on the XLR connector, so the ground loop suppression circuit work correctly.

Classicaudio77
The extra connection/ground-lug you can find on a Neutrik or other XLR connectors is designed to properly ground the housing/frame on the connectors.
This additional ground-lug is used such as a chassis connectors shall be mounted in a box or panel made ​​of plastic or wood. where the box or panel is not automatically connect the connectors housing/frame to ground.
If you wish, you can connect this additional ground-lug to XLR pin 1, it will be a further ground to the DI-box case, the same way as in the original, so it does not matter.
Can be an extra precaution if there is painting and anodizing to insulate between the connector and box/case.

As I describe on my web page, the ground connection between the PC card, connector and DI box case, to be made ​​as follows:

XLR pin 1 shall be connected to the PC card connecting point labeled "XLR out 1" and the PC card connecting point labeled "chassis" be connected to the DI-box case on a separate screwed solder lug or a solder lug attached to one of the XLR  mounting screws.

If you are not using our specially designed PC cards, and instead build the electronics on your own way, please carefully follow the "metal box / case ground" instruction, which you can find on my web page.

Lars78
Sure, it is also possible to use the extra XLR ground-lug connected to XLR pin 1 without PC card connecting point "chassis" is connected, but then you have to trust that the painting/anodizing on the XLR housing and DI box case does not make any insulation.

--Bo

Bo Hansen said:

Nele
You can apply regulated +24 volt on the positive side of 100 uF electrolytic capacitor.
But take away the two 6.8 k resistors.
Note that the ground/- 24 volts must be connected to pin 1 on the XLR connector, so the ground loop suppression circuit work correctly.

Click to expand...

Thanks for the reply! I also had to connect the red LED differently because if I connected it as it is on the pcb it kept blowing up.

Cheers and thanks for your design!

@Bo
i know the "painting problem", and i measured from Pin 1 to the chassis... no problem (-:

what do you think about the neumann BV-107 transformer in your design ? it´s from the neumann KM84.
it´s approximately 3db less gain at the output with the BV107 than with the Haufe


Lars

Lars78,

Neumann "09107" is a good transformer, maybe a bit small for high level in the low end.
As you say, it have a bit more loss compare with Lundahl and Haufe, but approx. same loss as OEP.

--Bo

I mostly use it for acoustic guitar, rhodes, bass guitar or other instruments with PU.
I think that should work well...

Lars

Thank you for your input Bo.
I have a couple of these built with the OEP and they sound great.

I have a couple of questions on component selection.

1) I have access to some high quality Mil Spec resistors (0.1% 25ppm), but they are 1/8 watt instead of 1/4 watt. Will these be okay in this circuit, or must they be 1/4 watt and above?

2) Will the quality of the electrolytics make a difference in sound quality in this circuit? I built mine with Panasonic FC series, but was wondering if using some of the speacialty "audio" caps like Nichicon Muse (KZ) or Elna Silmic will make any difference.
Also, any audible difference between Polyester and Polypropolene for the .01uF's?
I know there are often debates on whether or not capacitors can make an audible difference. These DI's sound great as they are, just wondering if anyone has experimented with the caps.

3) I understand using an LED other than red will have a higher voltage drop. What does a higher voltage drop do in terms of the circuit? Will it affect audio quality, output etc..?

4) I did a search from the place I bought my OEP transformers from (Newark Electronics) and I notice that now another transformer comes up when I search the OEP part number. Looks exactly the same as the OEP but manufacturer is VIGORTRONIX. Anyone ever hear of them?