radial j48 Di box transformer?

[12afael]

I was reading this article and I notice the small transformer on that di box.

http://www.radialeng.com/di-j48-features.htm

someone have an idea of how the transformer is being used? zero field transformer??? or maybe it is part of the switching supply?

a better picture could clarify everything.

Rafael

 

[Cainester]

Go to this page
and download the user manual. Judging from the block diagram, it looks like it is for the psu.

 

[12afael]

14. Power supply transformer
The transformer in the power supply helps eliminate ground loops by isolating the power coming in from the XLR’s 48V phantom feed.

how the h*ll they do that??? on DC???? common mode choke??

 

[12afael]

The Magic is in the supply!
The Radial J48 uses phantom power but steps up the internal rail voltage by
combining a timing chip and a British-made switching transformer to create it's
own power-house. This brings the rail voltage high enough to allow one to hit
the J48 with as much as 10 volts without distortion! The result is smooth, natural
sound even when the guitar player has his volume ‘cranked'!

:roll:

 

[owel]

That transformer is probably used for the DC-DC boost converter.

The transformer in the power supply helps eliminate ground loops by isolating the power coming in from the XLR’s 48V phantom feed.

I think a marketing person wrote this.

 

[CJ]

same deal as the "country hick" DI, remember?

 

[PRR]

"deploy the limited energy resources of phantom power to the audio signal path.... steps up the internal rail voltage to an impressive 10 volts." (also "internal rail voltage to 9-Volts.")

10V (or 9V) is impressive? My 440 mikes did that 20 years ago. Whatever you fed them, P52 to P12, ended up as 9V internally.

And 48V to 10V sounds like step-down to me.

The old 440 is, IIRC, passive regulation, so its long-term current supply is just the 2mA of older Phantom specs. The switcher could give 8mA to load with 2mA from Phantom. But the 440 will deliver HUGE music voltage to mike inputs. The fact that it may not sustain a clean 140dB SPL steady-state into an actual 150 ohms is not something I care about. I know it does 131dB SPL drum-peaks better than I do.

"single-digit inter-modulation distortion"

And what is that digit? "9%IMD"? (This HAS to be a marketing misunderstanding.)

 

[12afael]

is fair to compare a traformerless DI box with a transformer di box????

 

[mobyd]

[quote author="12afael"]I was reading this article and I notice the small transformer on that di box.

http://www.radialeng.com/di-j48-features.htm

someone have an idea of how the transformer is being used? zero field transformer??? or maybe it is part of the switching supply?

a better picture could clarify everything.

Rafael[/quote]

Looks a lot like the OEP PT4 pulse transformer that BSS uses in their AR133 DI box. BSS drive them with a CMOS 555 and that forms the DC/DC converter to isolate the phantom power from the input amp.
Those little transformers are designed for thyristor gate driving etc but
they work just fine in this application (and they're readily available and
cheap).
M

 

[12afael]

Mobyd, thanks for the info.
so they just make a different voltage, other value and other filter, the ground is the same. they are not isolating grounds.

here is a high resolution picture if someone is interested.
http://www.radialeng.com/J48-34view-inside-hirez.zip

not enought for route it... :evil:

lm833
5458???
mpsa12