[sdiy] phantom power: how to avoid electrolytics?

[Czech Martin]

Oh, sorry, 
I should have said: no iron, please.

Yes transformers block DC perfectly, but I just wanted
to know if I could avoid them. Good transformers
(Jensen) can be difficult to obtain (overseas etc.).

The impedance transformation can also be done
with multiple input transistors, like in the old MAT02
app notes (or was it SSM20xx dual transistor?).
Multiple differential input stages give lower base 
resistance, thus noise and since the individual 
transistor noises do not correlate, the gain outweights
the additional noise. The app notes desribe 3 pairs,
but I can not see why 8 pairs shoulnd't be done.

Of course, I do it with BC549C, not selected,
the DC offset is no matter here, the distortion should be also no
problem.

I think the SSM2017 is basically the same thing, on a monolitic
chip.

m.c.


-----Original Message-----
From: René Schmitz [mailto:uzs159 at uni-bonn.de]
Sent: Donnerstag, 3. Juli 2003 12:38
To: Czech Martin; Synth DIY
Subject: Re: [sdiy] phantom power: how to avoid electrolytics?


Hi Martin and List,

> Or are there better solutions arround?

Transformers. Advantage is that you also can step up from the 200 ohms 
line, and gain some voltage "amplification". Resulting in an improved 
signal to noise range.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159