DI box or simple preamp?

[l0calh05t]

Hey, I'm planning to do a small DIY audio project (I have done a few digital projects, not much analog yet though). I'm thinking either an active DI box, or a simple preamp (solid state... also have a tube project in mind but that's for later).

I've been looking at the Bo Hansén DI, or the Country Hick. Now For the first, I can get pretty much all the parts without any problems, the second... not so much. Would these substitutions work:
2N5457->BF245A
2N4401->BC639

Anyways, they should both work with the LL1538, so I could breadboard+test both first before finally deciding.

Or would you go with a preamp instead (would have to be with a instrument in though) or some other DI box? (application will be electric bass for the time being)

 

[wolfgang]

Hello!

I breadboarded the Bo Hansen DI a little Time ago and must say it sounds fantastic!!!!!! especially on bass!

Thanks to Bo very much for this nice circiut!

But you also need a little gain after this DI. It has relative Low Output compared to comercal DI´s!

regards,
Wolfgang

 

[chrispbass]

This thread may be useful if you're thinking of building Bo's DI?

http://www.groupdiy.com/index.php?topic=36569.0

Also, I believe that alot of people really like the fetboy pre for bass. I can't personally vouch for this but it's on the 'to build' list 

http://www.groupdiy.com/index.php?topic=16907

Kit available here.

http://diypartssupply.com/index.php?main_page=product_info&cPath=2&products_id=7&zenid=h4c4rc5353dsqevs0331m8o930


Chris

 

[l0calh05t]

This thread may be useful if you're thinking of building Bo's DI?

http://www.groupdiy.com/index.php?topic=36569.0

Also, I believe that alot of people really like the fetboy pre for bass. I can't personally vouch for this but it's on the 'to build' list 

http://www.groupdiy.com/index.php?topic=16907

Kit available here.

http://diypartssupply.com/index.php?main_page=product_info&cPath=2&products_id=7&zenid=h4c4rc5353dsqevs0331m8o930


Chris

Any sources for interesting PCBs/Kits in europe?

 

[Ptownkid]

Shipping from North America is only $8-$10...

 

[Ptownkid]

On a sidenote, that is most likely the LAST fetboy kit ever. Scott Hampton requested that we no longer carry it, and we are respectfully complying.

 

[3nity]

BF245 can be found at Newark.ca and the other one can be substituted by a BC550? or 560? depending the type!

 

[l0calh05t]

BF245 can be found at Newark.ca and the other one can be substituted by a BC550? or 560? depending the type!

I wasn't looking for a replacement for the BF245, I can get those (btw. I'm in Europe, so Newark would be a bad choice). I was asking if a BF245(A) is a good replacement for the 2N5457 and if a BC639 is a good replacement for the 2N4401 (although after a little more browsing, I think the BC337-16 might be a better match)

 

[l0calh05t]

Shipping from North America is only $8-$10...

It's not really the shipping I'm worried about. More about our customs office.

 

[Davo]

+1 on the Bo Hansen DI.... best sounding DI I've used

 

[l0calh05t]

Actually about the Hansen DI...

Could I easily add a Pad to it? (Maybe exactly as it is done by the Country Hick?) Also, having a High-Z loop out might be useful, but from a first look at the schematic, the input impedance would seem a little low for that (which is probably the reason for that monitor out)

 

[Ptownkid]

Shipping from North America is only $8-$10...

It's not really the shipping I'm worried about. More about our customs office.

You should add your location to your profile.

 

[l0calh05t]

done

 

[Bo Hansen]

l0calh05t

Regarding the JFET, you can use a lot of "general purpose" N-channel JFET you find on the market, it is not so important in a source follower, so long you not must play with things like current limiting/Idss, gain/gm, or noise/nf.

You can use JFET's as 2N3818, 2N5457, 2N4401, BF244, BF245, 2SK30, 2SK68, 2SK170, 2SK246 and many others.
Note: regarding Idss selecting, choose some mA and up.

The "Country Hick" PAD are for speaker level, and gives a input Ri of 10 Kohm.

If you want a -10 dB pad on input, that still have same Hi-z as un-paded, use the circuit from my API 312 card DI-modification, for 1 Mohm input Ri (impedance), if you want it for 10 Mohm Ri, scale upp all resistors 10 times, and the capasitor down 10 times.
http://web.telia.com/~u31617586

Wolfgang

Glad to hear that you like my old DI-1975 design.

Regarding the output level.

Because you use a microphone transformer backwards you get "loss" negative gain, and a 1:5 ratio transformer have approx. 15 dB step-up gain, or loss used backwards.

You want loss in a DI-box, because the level from a guitar or bass, (after a 1:1 impedance converting) are to high to match a console microphone input.
(with a Hi-z input and high output pickups, you can get a volt or so)

I will guess that mostly of active DI-boxes on the market have approx. 5-15 dB loss, and passive have approx. 20-30 dB loss.
But there are some active designs thay have a electronical balanced output amp, like a transformerless condenser microphone (Schopes style) that have no loss, or 6 dB higher) but this is to high to match a guitar/bass to a microphone input.

But if you after all need more gain, use the 2,5:1 configuaration instead for the 5:1 configuraton on the Lundahl LL-1538 transformer and you get only appr. 10 dB loss instead for 15 dB in normal case.
(but the best transformer match in this circuit are the 5:1 configuration)

--Bo

 

[l0calh05t]

l0calh05t

Regarding the JFET, you can use a lot of "general purpose" N-channel JFET you find on the market, it is not so important in a source follower, so long you not must play with things like current limiting/Idss, gain/gm, or noise/nf.

You can use JFET's as 2N3818, 2N5457, 2N4401, BF244, BF245, 2SK30, 2SK68, 2SK170, 2SK246 and many others.
Note: regarding Idss selecting, choose some mA and up.

The "Country Hick" PAD are for speaker level, and gives a input Ri of 10 Kohm.

If you want a -10 dB pad on input, that still have same Hi-z as un-paded, use the circuit from my API 312 card DI-modification, for 1 Mohm input Ri (impedance), if you want it for 10 Mohm Ri, scale upp all resistors 10 times, and the capasitor down 10 times.
http://web.telia.com/~u31617586

Ok, I expected most JFETs would work but I wasn't entirely sure.
I know the CH pad is a speaker level pad. Which can also be useful though... maybe I'll add both methods on a 3-way switch.

Would it be possible to use a higher input impedance (~5M) on your DI as well? I'm thinking a parallel Hi-Z output might be useful, but not if the input impedance is too low.

 

[Bo Hansen]

l0calh05t,

Because it not have a JFET as input transistor, and the base on a normal transistor draw some current, you can not have to high resistance "bias divider" or in this case a bias serial resistor on the base input.

I´m sure you can double (or more) the 1 Mohm serial resistor with a good transistor, but 1 Mohm is very safe bias point for both transistors, so I would not change this input Ri/impedance.

The 1 Mohm impedance are also a good reference for all passive guitar and bass instruments, because near all guitar amps have just 1 Mohm as a input impedance, so you recognize the load behavior on your guitar or bass.

Of course, you can use a JFET as input transistor and scale up the serial bias resistor 10 time or more, but you gett a other DI-box character.

My DI-boxes I build to day, are a bit more high-tech, and are a "all JFET design" with cascode and constant current source topology, but this old "1975 design" sounds more charming from time to time.

--Bo

 

[mitsos]

hey Bo,

I saw a few references here to a tube DI of yours... There was even some talk of you redoing the layout a while back.. I wondered where this had left off? Is it still upcoming? I am considering building a New yorkdave 1bottle pre as DI only for use with nylon guitars, but I figured I'd ask before in case you were still planning on releasing info on that design?

thanks!

 

[Bo Hansen]

Mitsos,

Yes, I remember that, but I have to little spare time in this day,s for this type of projects.

For the moment the support on my "DI-Box 1975" plus some other interesting forum talk, take all time, but I will do a nice DIY Tube DI-Box posting in the future when the time allow that.

--Bo

 

[mitsos]

no worries, I am looking forward to the 1975 DI as well. Just thought I'd ask since I recently found some threads talking about your tube DI.. Thanks for putting in the time!