Bo Hansen DI layout

[nhaudio]

Got them done today..home etched, transformers are BeyerDynamic 5:1 that match the impedance specs and transistors are bc550 C's and 560 B's.
First impression is that the sound is really punchy. Thanks to all and to Bo and Soeren in particular for this really cool project.

 

[Nele]

nice! 
how is the bass-response with the beyers?

 

[Bo Hansen]

Nice to see all building samples like version from mac and nhaudio.

nhaudi,
use isolated plastic jacks, (or metall jacks with isolated washer) to get the ground system to prevent ground loops.

You must also isolate the transformer case from the metal box, because transformer shall only be connected to the pc-board electronic ground.

Use red LED, because this colour have lowest voltage drop.

--Bo

 

[nhaudio]

@nele - bass response... I don't have any other transfo/di to compare it to but to my ears it sounds good.


@bo - Thanks for the tip.

 

[justanalogue]

Finished the 1st one...not tested yet.

Thanks to all who made this possible!

Willem.

 

[justanalogue]

Another picture...

 

[mtanttar]

Hello,

had to register to this forum because I'm currently working on two of these. I'm using Lundahls, and the rest of the parts will be the best available. I just etched the PCB's, drilled the boxes and assembled all mechanical parts. I will post pictures of finished units as soon as I have time to complete them. Lundahls are easily available here in Finland for reasonable price.

If some of you have troubles getting Lundahls I could possibly help, just PM me.

Regards,

Matti, Finland

 

[jeid]

Hello,

Got my boards home from Gustav and had a friend of mine put together the DI for me, he's way better at this kind of thing.

I've got a slight problem with my one. Every once in a while it starts making a grumbling noise, it's as if someone is adjusting a really dodgy pot. I can probably capture a sound clip of it in action. It doesn't do it the whole time, but it happens often enough for it to become an issue. I intend to use this for DI'ing guitars whilst recording, so noise is not an option, especially since I plan to re-amp the DI signals.

Has anyone had this problem.

I dunno if this makes any difference, but my jack sockets are plastic with a metal bolt. Could this be causing me issues?

Cheers for any responses

 

[Bo Hansen]

Jeid,

I will try to help you.

First, do you have a good phantom power from your console/preamp ?

What transistors and componets have you use, have they right value ?

Have put in all transistors, diodes and electrolytic in right direction ?

Have you build the box, connectors and grounding after my instructions ?

Can you post a photo on the ready pc-card.

--Bo

 

[jeid]

Hi Bo, Thanks for the quick reply.

Yep, I've got a good phantom power source. Tried it from both interfaces and still getting the same issue. I bought all of my parts from Banzai so I can't be 100% sure of the quality. I'm using a Lundahl transformer. I never built the DI, but I trust the person who made it knows what he's doing. I used the parts list for the values and put them on Gustav's board.

I got the box from Banzai also and it does seem like a tight squeeze, but nothing is touching anything it shouldn't be.

I'll get a picture up yep.

I had a Marshall amp once which made a similar noise and it was a dry solder joint. I wonder if this is the same issue?

I should say, that the clarity from the DI is amazing, makes my Pod Farm tracks so much better! Great work.

Here's the picture.

Cheers
Jeid

 

[Bo Hansen]

Jeid,

The pc-card looks good, but the first I see was the not isolated tele jacks, and also not shorted input jack when it is not plugged in.

If the buzz noise can be heard when you use the DI-box with a connected amp, it can be the not isolated jacks.

If the "ground loop suppressor" shall work ok, you must use plastic jacks (Cliff plastic or Rean brands) that have both thread and nut in isolated plastic.
Or, you can use those you have with isolated washers, that is a option fot those jacks you have.
When you use safe grounded mains operated amps or other equipments connected with the DI-box together with a mixing console or preamp, you can get ground-loops or buzz noise.

If the buzz noise can be heard when you not have anything plugget on the input jack, it can be the not shorted jack.
There are a extra solder tag on the jack, that can short the tip to ground when not anything are plugged. (see the schematic)

Mybee this can be your problem ??

BTW, if not LED are used on the box outside, you can link (short) the two holes on the pc-card.

--Bo

 

[jeid]

Hi Bo, Thanks again for replying.

I've gone and ordered a couple of isolated jacks.

Which are isolated.

So I should ground the tip of the input jack?

I've not been using an amp along with it yet, just plugging my guitar into the DI box and then going from the DI into my Pro Tools interface. I'll try these jacks out. If you can let me know about the tip, I'll be very grateful. I appreciate your help

 

[Bo Hansen]

Jeid,

Ok, you have not use any amp together with the DI-box, so it is not any ground loop problem, but change to the isolatded jacks, they are better.

No, you shall not ground the tip of the input jack, this is +/hi as normal, but the other solder tag that is the "brake switch" shall go to ground solder tag on the jack.

But you hear the buzz noise even when the guitar are jacked, so the problem is not the shorted input jack, but do this anyway, so everything conform with my schematic.

I will try to explain,
In the top end on the jack you have two solder tags, one is the tongue that will lift when you put in the tele-plug, and this is the normal +/hi tip connection. the other lug is the brake switch solder tag, and shall go to ground, the rear "tongue solder tag", the ground connection to the card.

If you use the new plastic jacks, don´t forget to ground the metal box to the pc-card "chassis" connection point.
Use a solder tag on one of the mounting screws for the XLR connector, for safe box connection. (or a separate screw, solder tag and nut)

Try also to change the input transistor BC550C, because even a new transistor can have a fault like noise or other thing.
If not this will help, try the other transistor BC560C, or the two zenerdiods on the input.

--Bo

 

[mtanttar]

One unit with Lundahl 1538 completed:

I used only the best parts I could find. Metal film resistors, polypropylene capacitors etc. Switchcraft jacks are insulated from the chassis with insulating washers. I self-etched the boards.

Thanks Bo and Soeren for this great design.

Btw. In the original schematic all electros are marked 35 volts. Is this enough? Just thinking because my 100u/100V electros just run out and I have some marked 50V.

 

[gemini]

Bo, how about using cinemag trafo? Anyone has try it?

 

[Bo Hansen]

mtanttar,

The internal voltage is only 24 volt, so everything from 35 volts an up is ok to use.

gemini,

You can use all brands and types of a good 1:5 mike-transformer, and Cinemag have some nice types that can work very well in this DI-box circuit.

We have talk before about transformers, see this link:
http://www.groupdiy.com/index.php?topic=36569.msg482959#msg482959

Note, if you mount a transformer outside the pc-cart, you must isolate the transformer case from the metal box, because the transformer case/ground shall only be connected to the pc-card electroninc ground.

A other thing,

Some of you use different colour on the LED, but use only red colored LED´s, because this have lowest voltage drop, and gives the highest internal voltage.

--Bo

 

[jeid]

Jeid,

Ok, you have not use any amp together with the DI-box, so it is not any ground loop problem, but change to the isolatded jacks, they are better.

No, you shall not ground the tip of the input jack, this is +/hi as normal, but the other solder tag that is the "brake switch" shall go to ground solder tag on the jack.

But you hear the buzz noise even when the guitar are jacked, so the problem is not the shorted input jack, but do this anyway, so everything conform with my schematic.

I will try to explain,
In the top end on the jack you have two solder tags, one is the tongue that will lift when you put in the tele-plug, and this is the normal +/hi tip connection. the other lug is the brake switch solder tag, and shall go to ground, the rear "tongue solder tag", the ground connection to the card.

If you use the new plastic jacks, don´t forget to ground the metal box to the pc-card "chassis" connection point.
Use a solder tag on one of the mounting screws for the XLR connector, for safe box connection. (or a separate screw, solder tag and nut)

Try also to change the input transistor BC550C to a, because even a new transistor can have a fault like noise or other thing.
If not this will help, try the other transistor BC560C, or the two zenerdiods on the input.

--Bo

Hi Bo, Thanks again for your reply. I'm struggling a little with your English, but I think I get what you're saying. I'll wait for the new jacks to come home this week and see if they make any difference.

I've managed to record the noise that the DI has been making and attached a link to the file. Get a pair of headphones or some loud speakers to hear it. It's visibly and audibly creating noise on the track.

https://dl.dropbox.com/u/3526809/Audio%201_01.wav

When I unplug the guitar the noise disappears and when it's plugged back in, it stays away for a little while then comes back. I've tried this with a few guitars now as a trouble shooting exercise and it's not the guitar I'm using.

 

[Bo Hansen]

Jeid,

Yes, I know that I write extremely bad and funny English, especially when I shall explain difficult things.
But I think it has become my signature on various forums around the world.
I am sure that with a little imagination and patience, you will understand what I mean.

Yes, I have listened to your audio clips, and I think it can be one of the transistors, so as I wrote in my last replay to you

Try also to change the input transistor BC550C, because even a new transistor can have a fault like noise or other thing.
If not this will help, try the other transistor BC560C, or the two zenerdiods on the input.

On the picture I can not see what type of 0,1 uF capacitors you have use,
it is non-polarised polyester types, and not some kind of electrolytic with higher value ??

--Bo

 

[jeid]

Hi Bo, thanks for replying again. Haha, your English is indeed funny. You should hear me speak it though. Being from Scotland, it can be rather amusing!

I've decided to scrap the parts in the project and replace them with the ones listed in the parts list on the first post of this thread. I bought all of these parts about three months ago before I saw that list. I don't think I got the right type of parts before.

I'm planning on using the other PCB I have to make another DI. For the extra money, it's worth it. I'd never use two at the same time, but there's nothing wrong with having one spare.

How do you find the Lundahl compared to the Haufe transformer? I'm sorry if you've been asked that before.

 

[Bo Hansen]

Jeid,

Haufe ST-8456 is a very nice transformer, but Lundahl LL-1538 is a bit better, and LL-1538XL (extra lardge) have a bit more headroom in the low end.

--Bo