Bo Hansen DI layout

[Ricardus]

The performances are tight and similar. If you can't get a feel for the general flavor of the traffos from this, I don't know what to tell you. I certainly can.

When I'm auditioning guitars amps in the studio for a session I don't send a re-amped signal into them. I can get a pretty good feel with a few chords which amp I'm going to prefer.

 

[radardoug]

So how do you allow for your perception bias when you play on the one you like the most, and the one you like the least? It makes for a totally unscientific test, and as such is not useful to other people.

 

[Ricardus]

I had no idea which one was being used when I performed. And the fact of the matter is. I *HAVE* no favorite. They are all useful to me in different situations.

The better question is just how the FEK are you supposed to daisy chain a high-inpedance guitar signal into all 5 DIs without wildly affecting the signal? I am sure it can be done but I don't have the gear.

Look. This is easy. I never said NASA did the test, and no one is paying money for the results, so I don't see the issue about being overly pedantic. You don't like it? Don't listen. Move on and do your own test.

 

[Whoops]

it would be great if you could do some recordings of the same instrument recorded with DIs with different transformers, that way new builders could decide what to use for a particular task.

Do you you think you can do that?

thanks

As member Ricardus built quite a few of these DI's with different transformers, I asked him in some older post in this thread if he could do some recordings. It was not directed as a test/challenge but more as "casual" listening of the different DI's.

Radardoug is totally right that as a scientific test, or even a proper test this is invalid.
The difference in performance will bias the test is a lot of different ways, the first one is that every performance is different so the timbre of the guitar reaching each DI will also be different.

We all know that it's hard to do a proper test, the signal had to be split , and to be split some circuitry at to be introduced in the chain that would also affect the interaction between the DI's and the instrument.

Personally, I think that having some recordings of the different DI's even with different performances is better than nothing and I'm already able to make some overall/general conclusions.

I would like to thank Ricardus for having the work of doing the recordings, editing it, and posting it.
and I would like to thank Radardoug for rightfully bringing to the attention that this cannot be used as a test and that is not a test

 

[Whoops]

I listened to the files, 
and overall this is what I can say:

- 1, 4 and 5 sound fine to me

- 2, 3 seem to have less high end than the other 3. The RMS level is also lower, so I don't know if I like less these 2 sound clips because the others are louder of it' because they sound actually worse to my taste.
Between two sound clips the one that is louder normal sounds better to me (and to a lot of people)

- performances are all different but between 1 and 5 they are very different.
Listening in Soundcloud doesn't help either, It would be easier to be able to listen it in a DAW so you could quickly A/B any part you want. for example I would like to compare quickly in the middle part where you play chords with more low end.

If 2 or 3 sound worse because the volume is lower, and if adjusting to the same value will make them sound closer to 1,4 and 5 then I would say any of the 5 transformers work well for me and for my work. I would choose the cheapest of the 5

If 2 and 3 have really tamed high end, or limited frequency response, then I would say any of 1, 4 and 5 would work for me (for acoustic guitar) and I would choose the cheapest of the 3

 

[Fuzz Face]

I had no idea which one was being used when I performed. And the fact of the matter is. I *HAVE* no favorite. They are all useful to me in different situations.

The better question is just how the FEK are you supposed to daisy chain a high-inpedance guitar signal into all 5 DIs without wildly affecting the signal? I am sure it can be done but I don't have the gear.

Look. This is easy. I never said NASA did the test, and no one is paying money for the results, so I don't see the issue about being overly pedantic. You don't like it? Don't listen. Move on and do your own test.

To me the solution is to record a loop using a stompbox, or record a clip and playback through “reamp” box. Then the same performance can be sent to each DI box

This is of course not intended as a critique, just a suggestion

 

[Whoops]

To me the solution is to record a loop using a stompbox, or record a clip and playback through “reamp” box. Then the same performance can be sent to each DI box

This is of course not intended as a critique, just a suggestion

Loops using a stompbox

"some circuitry had to be introduced in the chain that would also affect the interaction between the DI's and the instrument"


“reamp” box

really the worst solution, the acoustic guitar would have been already recorded through a DI, most probably also a micpreamp, then you would have 1 stage of unnecessary AD conversion, then 1 stage of unnecessary D/A conversion, then the Reamp circuit with another transformer. You could even have 3 audio transformers just in this chain.
All this circuitry and signal conversions before the actual DI you want to test?

This is a long debated topic in forums online, there's already thousands of discussions on this subject,
please let's leave this to other threads and concentrate on Bo's DI here.

 

[Fuzz Face]

Loops using a stompbox

"some circuitry had to be introduced in the chain that would also affect the interaction between the DI's and the instrument"


“reamp” box

really the worst solution, the acoustic guitar would have been already recorded through a DI, most probably also a micpreamp, then you would have 1 stage of unnecessary AD conversion, then 1 stage of unnecessary D/A conversion, then the Reamp circuit with another transformer. You could even have 3 audio transformers just in this chain.
All this circuitry and signal conversions before the actual DI you want to test?

This is a long debated topic in forums online, there's already thousands of discussions on this subject,
please let's leave this to other threads and concentrate on Bo's DI here.

IMO the instrument plugged into the DI is infinitely variable, so the additional circuitry is somewhat irrelevant given that it works appropriately and stays consistent across all tests. Ricardus could plug in a different instrument and the DIs would behave differently. I won’t be using his guitar (which contains active circuitry) so I’m not concerned with the difference between his guitar straight and his guitar through a looper. Same with a reamp.

 

[monkeyxx]

Finished my first one, a project I started 5 years ago!  Got the PCB from Volker.  This one has the OEP.  The next one might have the Lundahl, and I will probably add a pad switch and put it in a smaller enclosure just to make it more different.

I love the "simplicity" of this box and the fact that it "just works."  Kind of has a nice laid back sound on bass, almost in a way like a miked up bass amp to my ear.  Completely different to the Wolfboxes I usually build.  But nice!

 

[monkeyxx]

Here's "the good stuff"

Enclosure is a 1590C which is honestly a bit too roomy for this simple build.  Next I will try a  1590T.

 

[Ricardus]

Here's "the good stuff"

Enclosure is a 1590C which is honestly a bit too roomy for this simple build.  Next I will try a  1590T.

The Hammond enclosure I ended up using for most of mine is definitely bigger than it needed to be, but the extra space ended up coming in handy when I use a transformer that wasn't support on the PCB, and I had to mount it off-board.

 

[Whoops]

Finished my first one, a project I started 5 years ago!  Got the PCB from Volker. 

Nice one, congrats

 

[monkeyxx]

Has anyone ever encountered ground loop noise with the Bo Hansen DI?

I'm just wondering how effective the ground loop isolator is in real-world, demanding applications.

If it's extremely effective it seems like a possible ease of use improvement over the typical lift switch.  I get a little tired of having to flip this on and off on my Wolfboxes depending on what's turned on or not.

In a lot of the Jensen schematics there is a ground loop isolator, but there is also a direct to ground switch.  So the isolator is only in use in the "lift" position in the Jensen design.

I used the Jensen schematic for my reamp devices, and so far it's been effective.  I don't think I've ever had to fully ground the reamp with the switch.  But then again I haven't really used the reamp enough to know much over time.

I would be interested in any technical insight into the ground loop isolator circuits, and cases where they do or do not work.

 

[Potato Cakes]

Has anyone ever encountered ground loop noise with the Bo Hansen DI?

Not once on any stage in the world or in any studio with any transformer that I've tested.

If you are getting grounding noise it is before the DI or there is a problem with the build.

Thanks!

Paul

 

[Bo Hansen]

I have previously written about this "groundloop suppressor" in this enormously long thread, and now I’d like to write some more about this circuit.

We developed this in the early 1970s at the Audex amplifier factory in Gothenburg, Sweden because there were a lot of problems when musicians combined guitar amps, mixers, echo units, poweramps, etc.
Sweden started early with strict regulations that electrical equipment should have protective earthing power cable and wall outlets in public environments should also have this. Thereby there were a lot of problems with groundloops for musicians with a lot of equipment.

Since then, I have used this ”groundloop suppressor” in all equipment I have designed for musicians and the recording/broadcast industry. It has been found that equipment with this supressor inside is not so sensitive or causes any ground problems.

It should be added that a resistor of some 10 ohms has been used between earth in audio equipment-systems since the 1940s-50s. The "groundloop suppressor" is a is a further development to become more efficient and more durable.

In addition to the usual resistor the main task of the components are:  the capacitor is for reducing buzz and also as a decouple for RF interference/unwanted demodulation of the many high frequencys today from switched power supplies, mobile telephones and a lot more.  The two opposite diodes allows a max. 0.6 volts of potential difference between units where the DI box is included and thus protect the resistor from burning in the event of a temporary electrical short-circuit or a live device.

When it comes to passive DI-boxes, it may be ok with just only a ground lift switch.
But in active DI-boxes that use XLR pin-1 as negative for the phantom power, in my opinion, that is not a good solution to have this switch.

If a ground lift switch breaks the XLR pin-1 which is the most common, then the DI-box will not get any phantom power.
In some cases the negative will find its way through mixing console protective ground and maybe via an connected guitar/bass amplifier to the DI-box.
This long way is not recommended.

—Bo

 

[monkeyxx]

Thanks!  Sorry if this came up before it is a very long thread indeed.

I might test the ground loop supressor in a passive DI to "see how it does" in a known noisy configuration (guitar amps connected as well as recording equipment.)

This is a wonderful DI I'm really growing to like the sound of it.

 

[Bo Hansen]

Sure, works perfectly even for passive DI boxes, you never have to think about groundloops or in what position switch is.

—Bo

 

[Whoops]

thank you so much for taking your time and explaining Bo

 

[3nity]

I have a pair of those that im gonna feed with 48v straight to the 6k8 resistors. My question is where should i feed the 0v reference? Pin 1 is not grounding the rest of the board so im thinking gng from either the input di or amp out gnd?
Any thoughts?

 

[Bo Hansen]

3nity,

First answer to your question about phantom ground.
XLR pin-1 is the only and proper ground for phantom power and is also the main ground from the mixing console / preamp.
Maybe I misunderstood you for applying phantom power directly on 6.8k resistors.
You might mean to apply external voltage direct to 6.8k resistors inside the DI-box, if that is the case you should come back and I will explain this to you.

But I'll write a bit about external phantom powering (in my long-winded way) if there are more of you thinking about this.

If you are going to apply phantom power externally without having a microphone input with phantom power.
Here are some suggestions for doing this.

The first thing to check is if the input you are going to use the DI-box to is a transformer balanced and that it can withstand 48 volts applied from the outside.

If it is not transformer balanced or can withstand +48 volts you must mounting 2 pieces 47 uF/63 volt electrolytic capacitors in series with the mixer/preamp XLR input connetor pin-2 and 3 with positive side against the DI-box  input.
Instead of electrolytic cspacitors, you can use a 1: 1 isolation transformer before the mixer XLR input, for example Lundahl LL1527.

If the above does need to be done or not, then  simply apply 48 volts phantom power to the DI-box by mounting 2 pieces.  6.8k 1% resistors in one of the microphone cord’s XLR connectors, one to pin-2 and the other to pin-3.
The other end of these resistors are connected together and connected to the positive on your 48 volt power supply and minus to the XLR pin-1, then everything is ready.

But you have to observe some important things:

If you install this in one end of the XLR cable then you must isolate resistor and incoming 48 volts carefully in the XLR plug so that there is no risk of short-circuiting, as this can damage the transformer in the DI-box or in the mixer/preamp.

The 48 volt power supply MUST be of DC type and well stabilized and have a clean snd stable output voltage.
The current capacity need not be high, 100 mA is ok, this is enough for several DI-boxes.

There is an easier way to avoid having to do the above procedure, you can buy small pre-built external phontom adapter in the form of a small box with two XLR connectors that connect between your DI-box and mixer/preamp.

—Bo