Bo Hansen DI layout

[3nity]

Bo.
Great explanation
I realized my idea was confusing me.
Its all clear now.
Thanks for clear it by this great explanation.
Thank you.

 

[goldfish]

I am new to the forum and a rookie when it comes to electrics, but I am determined to build two of these boxes  .  I want to build two boxes to be used by my daughters  who are learning guitar/bass (and go to music school) and myself.

I have a few questions:

1) I'm about to order 2 x Lundahl Audio Transformers (LL1538XL). I understand these are better for bass guitar. But I assume they work just as good for electric guitar. Can anyone confirm that this is correct?

2)  I looked at the "shopping list" who someone posted earlier in this thread, but some of the components are no longer available (for example BC560CTA) and some components are not in stock. Would anyone have some time to guide me  to replacement components that are of good quality and that fit on the PCBs from Volker? I would like to order the components so that I can start the project
Here's the component list I am referring to: https://www.mouser.se/ProjectManager/ProjectDetail.aspx?State=EDIT&ProjectGUID=df6dbfb1-93de-4770-82fe-d02c158a06c0

Thanks!

 

[monkeyxx]

If you go to Bo Hansen's official website, his pages will answer a lot of your questions.  For example, he gives a long list of suitable transistor options.

I'm sure the Lundahl will be excellent for guitar.  I don't have one yet though, that will be my second "Bo."  The OEP in the first one I made kind of surprised me, I like it.  You see OEP now in BAE and Telefunken direct boxes, so they must be pretty good, by that measure.  I'd like to try the VTX transformer to see if there's any difference between it and the OEP.

 

[Ricardus]

I've built 8 of these and I don't think there is a bad transformer choice for these of the 3 transformers the PCB is set up for. I used the 1538XLs for my Lundahl builds and they're fantastic. Hard to go wrong.

 

[Whoops]

2)  I looked at the "shopping list" who someone posted earlier in this thread, but some of the components are no longer available (for example BC560CTA)

Welcome to the Forum,
Bo has written extensive Transistor replacement info in his website and thats the first link that appears in first post of this thread.

Also on the first post there's even a direct link called "Help: TRANSISTOR CHOICE"


You're new to the forum, it's your first post but please remember the Forum Rules:

You will find that the members of this community are incredibly courteous and respectful of each other, but no one likes to keep replying to the same questions over and over. Please Read the Threads before posting. Please do a search before posting.

___________________________________________________________________________________________________________________________________________

If you do have any difficulties with other components, let us know where you are located and what store you want to use and we can help.
As far as sizes, generally, Diodes with the same reference will have the same size, resistors stick with the same value and watts rating (size will be similar), Electrolytic capacitors stick with the same value and volts rating (size will be similar), Film Capacitors size might vary a little bit depending on the dielectric used, but you stick to the same value and voltage and use Polyester or Polypropylene chances are they will fit the board.

 

[Whoops]

I want to build two boxes to be used by my daughters  who are learning guitar/bass (and go to music school) and myself.

I have a few questions:

1) I'm about to order 2 x Lundahl Audio Transformers (LL1538XL). I understand these are better for bass guitar. But I assume they work just as good for electric guitar. Can anyone confirm that this is correct?

The LL1538XL it's not better for Bass guitar than any other transformer suggested, what Lundhal docs says is that in the really really low end (50HZ) it has a little little small less distortion than other transformers. That doesn't mean much in terms of sound.

First that difference is marginal you will not be able to hear it (although is measurable with measurement equipment) and second who says that less  THD on a transformer at 50hz sounds better than higher THD on a Bass?

The LL1538XL is extremely expensive, for the uses you suggested "I want to build two boxes to be used by my daughters  who are learning guitar/bass" you will have no benefit of the Extra cost, even in a Professional studio I doubt the benefits of the LL1538XL.

The Haufe ST8456 and the OEP A262A3E sound great on this DI. They sound tremendously well on Bass guitar and on Electric Guitar,
for your uses I recommend you those you will not regret it.

 

[Bo Hansen]

gouldfish,

If you are going to buy transistors from Mouser then you can choose one of these according to Mouser article number.

As BC550C use:
512-BC550CBU or 512-BC550CTA

As BC560C use:
512-BC557BTA or 512-BC557BTF

Regarding Lundahl transformer LL1538 and LL1538XL, these sound the same, the difference is that XL can withstand a little more level in the lowest frequency end.
The XL version is only necessary if, for example, you have a bass with an extremely high output level and a microphone input that can withstand this.

—Bo

 

[EvLoutonian]

Hello guys,
I've got this DI that I made years ago with OEP connected 6.45:1, it's sound really good I like it.

Hi, I know this is an old post from ten years ago now, but I've been trying to confirm exactly which windings are utilised on the OEP (or Vigortronix version) transformer with this board.  (I got the Vigortronix ones, but looks to be essentially identical to OEP).

on the Spec sheet it says this transformer is 1 + 1 : 6.45 + 6.45.

Does this mean the DI circuit uses only one of each winding (primary and sec)?

or is the ratio relationship the same whether one or both windings are used at each side?

Just trying to get my head around which configuration is used, also as a way to clarify in my mind about audio transformer possibilities, such as variations on which transformers could be used, depending on whether we connect one or both pri +/or both secondary windings, series or parallel...  I got myself a bit confused, so thought it best to just ask here about this example in particular, as that's what I'm currently working on.

(I'm building my first Bo H. DI using the Vigortronix (like OEP option), but I also plan to build another using some other transformer that I can find here, just to try something different)

 

[Bo Hansen]

EvLoutonisn,

This copy of the OEP transformer has as the original two identical primary and two identical secondary, and to get the correct ratio 1: 6.45, the two primary must be connected in parallel and also the two secondary in parallel.

I ordered a Vigortronix 10 years ago but I never heard anything from them, so I do not know the quality of this copy is.
But according to the rumor, should the Vigirtronix factory be started by someone who comes from the OEP factory ?

The pin-out on OEP and Vigortronix is ​​probably identical, so it must be connected according to the circuit board layout that you find on my help page for my DI-box design: www.hansenaudio.se/techpage.htm

If you are going to try other brands and types of transformers, this DI-box design only supports a microphone transformer type with a ratio of 1: 5 (usually stated as 200 ohms to 5 Kohm) which must be connected backwards in this DI-box and gives a level  loss at about -15 dB and which is suitable for an active DI box like this.
The OEP and Vigirtronix have a couple more dB’s loss, but it's perfectly ok in this case.

On my help page www.hansenaudio.se/techpage.htm I have listed a lot of possibly useful alternative transformers, I have also done some previous posts here regarding this.

—Bo

 

[Jazzyjerk]

Hi,
i work on Bo's di with lundahl 1538xl and second with oep, i finished it and both have the same issue, sound coming out is like "fuzz pedal with dying battery(i hope you know what i mean) kind of gated fuzz/distortion.
i use (BC547B TRANSISTOR, NPN, TO-92)
please help, i have no idea what's wrong.

 

[monkeyxx]

That soldering on the XLR doesn't look very good at all.  I would re-heat all the joints until they flow properly, and then go from there.  Check the soldering on the PCB as well.  Look for bad solder joints and any bridged connections that shouldn't be bridged from sloppy soldering.

 

[[silent:arts]]

i use (BC547B TRANSISTOR, NPN, TO-92)

Only one transistor is NPN (BC550 on the PCB),
the other one needs to be PNP (BC560 on the PCB).

 

[TillM]

Hi,
i work on Bo's di with lundahl 1538xl and second with oep, i finished it and both have the same issue, sound coming out is like "fuzz pedal with dying battery(i hope you know what i mean) kind of gated fuzz/distortion.
i use (BC547B TRANSISTOR, NPN, TO-92)
please help, i have no idea what's wrong.

On the picture I don’t see a cable for chassis on PCB which goes do ground.
Your DI is definitely not grounded.
That’s why you have fuzzy sound.

 

[Bo Hansen]

Jazzyjerk,

As silent:arts said here earlier, both transistors can not be a NPN BC547B, the one located at the bottom of the card next to the 3.9k resistor must be a PNP for example BC557B or C or BC560B or C.

Here are some important things you need to check ....

1. Have you carefully checked that all resistors, capacitors and diodes have the right value and are mounted correctly.

2. Have you put all the cables in the right place, both on the card and connectors, I see in your picture that you have not connected the chassis cable from the card to the metal box cover, it must be connected for the box to be grounded / shielded.

3. Do you have a 48 volt phantom voltage feed from the balanced microphone input you connect the DI-box to.

4. Have control measured the test voltages I describe on my help page: www.hansenaudio.se/techpage.htm

5. Have you turned the LED correctly, and that you have chosen a small red LED and not some other strange type.

—Bo

 

[Whoops]

both have the same issue, sound coming out is like "fuzz pedal with dying battery(i hope you know what i mean) kind of gated fuzz/distortion.

That's good because at least you know you made exactly the same mistake on both units.
So easier to troubleshoot

 

[Jazzyjerk]

Thank you Bo for project and troubleshooting help, other guys big thanks to you too .
The issue was wrong transistor npn instead pnp
sounds superb!!! and quiet ass hell.

 

[Bo Hansen]

Jazzyjerk,

Nice to hear that you found the error, and that you liked the character of my DI-box design.
Hope you will enjoy it a lot in the future.

—Bo

 

[FarisElek]

Built two. One works perfect. The other works when I shut off phantom power. But otherwise doesn't work when phantom is on. Strange.

Edit: NVM. I was plugged into the Amp out instead of the input HAHA.

Ryan

 

[FarisElek]

This is the 4th I built. Experimented with different cases and lights but I really like this steel case. Used the OEP transformer, Dale CMF55 metal film resistors + WIMA MKP poly prop caps. Love it.

 

[[silent:arts]]

Inspiring  8)

THE HOT BO HANSÉN IRON
by Markus Krippner