Newbie question - DI box is going to be my first project

[Greg]

Just from the Bo's specs... I'm sure the 50V would be fine. And a bit of curiousity cause I couldn't find one.

 

[Bo Hansen]

Greg,

I have recomend same voltage for all electrolytic only for that is easy to remember when you buy them, but the 1 uF and 10 uF can you choose 25 volt (even 16 volt) because it is only 12 volt in this particular places, and for the 100 uF you shall use a 35 volt because there are 24 volt in this place. (fore the 0,1 and 0,047 you can use from 50 volt and up)

--Bo

 

[thomas911]

Will the Lundahl LL1538xl work as good as the LL1538?

moosapotamus: What program did you use for the PCB layout? Or what program do other people use here?

Thomas - rookie

 

[Bo Hansen]

Yes, as Kubi say, the LL-1538XL have better low end headroom because it can handle higher level with the 45% bigger core, but the normal LL-1538 are ok for this work.

For best result you shall connect the LL-1538 in 1:5 configuration:
pin 6 to the 10 uF capacitor
pin 5 and 8 to ground
pin 1 and 4 together and then to pin 2 on the XLR connector
pin 2 and 3 together and then to pin 3 on the XLR connector

--Bo

 

[moosapotamus]

Bo
Thanks for confirming the LED. Also, for the info on how you're using this and why the 10uF cap works well in your application. Maybe having a couple different value caps to switch between would make it a little more flexible to drive different loads... in different live situations, for example.

Thomas
I use ExpressPCB. It's free at their website, easy to learn, and does everything I need (for the time being, anyway). I even layed out my basement remodeling job with it. The main bug with it is that you can't print out a PCB pattern directly. You'll get a grid superimposed on top of it. So, you have to do a screen capture, crop, resize and print the image from another application. Doesn't really bug me, tho. Did I mention, it's free!

~ Charlie

 

[Guest]

Well I have bought what I think are the right parts
For Info here are the part numbers and the suppliers
Just awaiting the soldering Iron from ebay to come in the post
I tried to buy the best parts available (even overspeccing some resistors - yeah - like I know what that means)...
Unfortunately I donl;t know whther I bought the right type of Swoter transformer - I think I should have bought the PCB pin one - but this is the one I am getting... so be it..)

RS Components (www.rswww.com)
149-818 Resistor, metal film, 0.5W, 1%, 10k EACH £0.051
149-925 Resistor, metal film, 0.5W, 1%, 100k EACH £0.051
298-0071 Capacitor, polyester, metallised, 5mm, MMK5, 5%, 100Vdc, 0.047uF EACH £0.068
298-0093 Capacitor, polyester, metallised, 5mm, MMK5, 5%, 100Vdc, 0.1uF EACH £0.073
446-8769 Diode, Zener, axial, BZX79, 12V EACH £0.099
261-176 Diode, Rectifier, 1N4004 EACH £0.04
149-638 Resistor, metal film, 0.5W, 1%, 47R EACH £0.051
149-975 Resistor, metal film, 0.5W, 1%, 1M EACH £0.051
149-767 Resistor, metal film, 0.5W, 1%, 3k9 EACH £0.051
206-5526 PCB, single sided, Eurocard, prototyping, EPOXY, 100x160mm, 2.54mm pitch, DIN 41612 C-96/abc EACH £3.20
554-917 Solder, 60/40, tin/lead, 18SWG, 1.2mm, BS441, DIN 8516, 250g 250G REEL £7.99
149-795 Resistor, metal film, 0.5W, 1%, 6k8 EACH £0.051
215-5714 Capacitor, electrolytic, aluminium, audio grade, solder tag, 35Vdc, 100uF EACH £0.788
215-5685 Capacitor, electrolytic, aluminium, audio grade, solder tag, 35Vdc, 10uF EACH £0.304
221-8635 Capacitor, electrolytic, aluminium, resin coated, radial wire ended, 35Vdc, 1.0uF EACH £0.138
149-953 Resistor, metal film, 0.5W, 1%, 470k EACH £0.051

ESR Electronic Components (www.esr.co.uk)
BC109C NPN Silicon Transistor T1018 2a Unit Price 0.175
BC560B PNP Silicon Transistor T092 7a Unit Price 0.084
140 Piece Jumper Wire Kit Unit Price 3.360
Neutrix XLR Male Chassis NC3MDL Unit Price 2.100
Neutrix 6.35 mm Chassis Socket NJ3FP6C Unit Price 3.5663 (Stereo or Mono)

Canford Audio (www.canford.co.uk)
23-173 SOWTER ST3195F (Coloured Leads) Unit Price 21.31

 

[Bo Hansen]

Charlie,

A misstake, sorry for that,
of course you right, I mean pin 8 to ground and not pin 6.

Kubi,

The OEP's A262A3E connected in 6,25K to 150 ohm will fit in this circuit but I have not use this transformer in DI application when I have don a recording session so I can not tell about the sound quality.
I have only use this transformar for PA and communication applications and it is a good general purpose transformer for this very low price (under £10 in UK) and easy to get.
But the Lundahl LL-1538 (aprox. £40 in UK) is a transformer in a high quality division, and it can not be comparable with the OEP that is a semi-pro transformer.

A good middle alternative are the transformer that I use in my orginal version around 1975 the Sowter 3678 in 1:5 configuration (under £30 in UK)

Or maybe try the old famous Neve microphone input transformer
10468 / VT-22670 / T-1454, configurated in 300 ohm to 4,8 K
To day manufacture by Carnhill, type: VTB-9045
or Sowter type: 9145


uk03878,

Use BC-550C instead for the BC-109, it is a better transistor and it is in same case as the BC-560.
The BC-109 and BC-177 are the orginal transistors I use in 1975, but it is better to use the BC-550C and BC-560BC that you can get to day, and I prefer them from Philips, markt PH.
(what is in side the BC-109 or BC-177 types to day, you newer know)

--Bo

 

[Greg]

Has anyone sourced a chassis for this (or any) DI, or are you buying a DI and then hacking it up and reusing connectors and just replacing the guts?

 

[Greg]

[quote author="kubi"]A simple 1HE 19" chassis should be big enough for 4 DI channels plus PSU. Perfect for studio usage.
If you want to use the DI on stage, you should probably get hold of an old fuzzbox plug the guts out and insert the DI box, just for stability.

kubi[/quote]

This would be for studio use only. Would the Lundahl mounted to perfboard (or some PCB) on say 1/4" standoffs be too tall for a 1 space chassis. I don't know how tall the Lundahls are, so I just want to make sure before I buy a chassis. I'd probably put 2 DIs, possibly each with a different tranny.

 

[Guest]

This is a very embarissing question but I can;t find the info at all ont he web
Looking at Bo's schematic
The two transistors Q1 and Q2 (NPN and PNP)
I am sorry but I can't understand the symbol used.
On Q1 NPN
Is North the base
Is South the emitter
Is West the collector
Is east a red herring?

On Q2 PNP
Is North the Emitter
Is South the base
Is West the Collector
Is east a red herring?

many thanks ...

 

[Mark Burnley]

uk,

They're a different symbol for transistors- I think they're European (I know I've got schems with that symbol somewhere). Here's the pinout:

Mark

 

[Bo Hansen]

Hi uk03878,

This is my way to draw transistors sinze 40 years ago, I know some people think it is misleading, but it is easy to draw this symbol on a 5 m.m. square drawing block, and I´m used to do that when I draw schematics and even when i draw a pc-layout.

I have PC CAD drawing program, but I work faster in the old way, yes I know, I´m a reactionary but I´m a old-fashioned analog electronic designer.

Here is some hints for you:

As the usal transistor symbol the pointer on a bipolar transistor are always the emitter and the lead on the opposite side are the collector and the lead that goes in side of the symbole are the base.

So in your language:

Q1 NPN
North is the collector
South is the emitter
West is the base

Q2 PNP
North is the emitter
South is the collector
West is the base

(in normal simple amplifier circuits are the collector on a NPN transistor connectet towards the positive voltage rail and the PNP transistors emitter connected towards the positive voltage rail)

--Bo

 

[Bo Hansen]

Hi Mark,

I also print slow on my computer, in the time I wrote this post, you have all ready explain the thing fast and easy with a picture.
I think I will use square drawing block when I write my forum posts, so I can speed up my replay posts.

--Bo

 

[Guest]

Guys you have been most helpful and most of all patient
one more question - if I am allowed (well today at least)
i bought a sowter 3195f (the one with the coloured leads) 1:7 for this...

Stupid question - but it has 5 outputs and the schematic has 4 joins...

The transformer I have has the following leads:

1 Green 4 yellow

2 Pink

3 Brown 5 Orange


I assume that the 1,3,4,5 are soldered as is on the board
What do I do with the pink one? (stop sniggering at the back!)

 

[Bo Hansen]

uk03878,

Here is the connetions for Sowter 3195:

Yellow to the 10uF cap. and 10k resistor
Orange to ground
Green to XLR pin 2
Brown to XLR pin 3
Pink not used (isolate the end)
Be sure that the transformer metall case is connected to ground.

--Bo

 

[Guest]

Bo many thanks
Should it be Brown to XLR pin 3 ?

I take it I just put a solder a jumper wire from the transformer casing to ground

many thanks ....

 

[BYacey]

Hammond makes a nice enclosure for DI boxes, it is an extruded aluminum case. Have a look:
http://www.hammondmfg.com/1455.htm

 

[Bo Hansen]

uk03878,

Sorry, a misstake again, typical me.

Yes of course, it shall be BROWN led to XLR pin 3.

--Bo

 

[moosapotamus]

I had the pin spacing for the LL1538 wrong in the layout that I posted earlier in theis thread.

Here's the corrected image...
http://www.moosapotamus.com/boDIBOXpcb.gif

~ Charlie

 

[Greg]

moosapotamus - Where you planning to get some boards made for this? Or do you plan to etch yourself?