DI from DIY Factory

[Nikolay]

Thanks Samuel!
I forgot to remove R12.

About BC550 there is no PCB modificatoin. Only is need to rotate BC550 - pin 3 will be pin 1.

Here is a new pcb and sch without R12:
http://www.mediafire.com/?bza3zyb3pfk
Mirror:
http://naudio.hit.bg/di/di.pdf

 

[bigswole]

i thought this was a transformerless design?

 

[AudioJohn]

I've always thought that using a parallel reverse diode was a horrible way of protecting against the accidental reverse polarity connection of an external PSU - as it usually results in destruction of the diode (which will fail short circuit due to excess current draw).

It might blow the fuse in the PSU (if there is one) - or destroy that as well.

Use a series connected diode - and tolerate the small (0.7 volt) drop across it - and nothing will break if the supply is wrongly connected.

Who would use an external supply with a DI Box anyway?!!

All active DI's should be capable of being Phantom powered surely?

 

[BYacey]

[quote author="AudioJohn"]I've always thought that using a parallel reverse diode was a horrible way of protecting against the accidental reverse polarity connection of an external PSU - as it usually results in destruction of the diode (which will fail short circuit due to excess current draw).

It might blow the fuse in the PSU (if there is one) - or destroy that as well.

Use a series connected diode - and tolerate the small (0.7 volt) drop across it - and nothing will break if the supply is wrongly connected.

Who would use an external supply with a DI Box anyway?!!

All active DI's should be capable of being Phantom powered surely?[/quote]

It's the smoke indicator that alerts you to power supply incompatability.

 

[BYacey]

[quote author="bigswole"]i thought this was a transformerless design?[/quote]
This design has many desirable characteristics, A much higher input impedance than is possible with just a transformer, and full floating balanced output with excellent galvanic isolation for when ground lift is required.

 

[SonsOfThunder]

>>>Who would use an external supply with a DI Box anyway?!!
>>>All active DI's should be capable of being Phantom powered surely?

These seem like contradicting statements...wouldn't Phantom qualify as "external power"? If you used 48V for this ckt, you have to throw away 30V somehow as it does like 18V (two 9V batts in series.).

Bill is right, it is a very nice sounding ckt, especially when connected to a large transformer for more headroom with bass gtr.

The JLM Simple DI can be built transformerless, I believe.

HTH!

 

[Nikolay]

I make my first PCB
Here I use 47nF input cap, BC550 and 2SK246 transistors.
Here is a picture how it looks:
http://www.picvalley.net/u/153/38032_529.JPG

And here some test with spectralab via my emu0404 soundcard:
http://www.picvalley.net/u/153/38033_533.GIF

 

[kato]

Cool! How does it sound?

Is 2M2 a viable substitution for R5 and R6, or do they have to be 2M5?

 

[Nikolay]

R5 and R6 are voltage dividier to make half of V+. Any resistor with the same values are suitable.
At my opinion this di box with oep transformer sounds good.

 

[kato]

[quote author="Nikolay"]
At my opinion this di box with oep transformer sounds good.[/quote]

Cool, I will build one! Thanks for the project!

What's the ideal voltage to use? Should I just use 9v battery?
Or will it sound better at higher voltage / 18v? Can it run on phantom power?

Sorry if these are dumb questions, I'm not familiar with what this circuit is based on. Kato

 

[kato]

found the link here:

http://www.diyfactory.com/projects/countryhick/countryhick.htm

 

[Nikolay]

At this time I try only with 9v power supply. I don't have enough time to try with 18v.

 

[SonsOfThunder]

Nikolay,

Which OEP are you using?

Thanks, nice job on this!!

 

[kato]

[quote author="SonsOfThunder"]
Which OEP are you using?
[/quote]

The schematic lists: OEP A262A2E

 

[SonsOfThunder]

Doh! Thanks Kato. :grin:

 

[AMZ-FX]

The value of R3 is shown as 1000k (1M) in the parts list and on the second schematic. It should be 10M (or 10000k).

regards, Jack

 

[clintrubber]

[quote author="SonsOfThunder"]>>>Who would use an external supply with a DI Box anyway?!!
>>>All active DI's should be capable of being Phantom powered surely?[/quote]
While at it why not make phantom power possible as well ?
Doesn't look too elaborate here, but I haven't looked at the numbers yet.