Phantom Power For G1176?

I was wondering if it would be any problem to feed the G1176 input trafo +48V with a pair of 6.8K's so I could plug in a condenser mic.

The G1176 sounds REALLY GOOD on kick or snare with a SM57 or D112 plugged directly into it. Plenty of gain.

I'd like to try it on overheads as well with my KM184's.

Advice/opinions? Will this particular input trafo not allow DC on the primary?

Dean

It'll be a mismatched load for your microphones.

Other than that, I don't see any problem in mounting phantom

But be ware of the fact that you may by error supply phantom to other line-level devices, which often burns their output stages

Why not simply build an external phantom adapter box? That way you'd be reasonably sure not to supply phantom by mistake...

Jakob E.

That's interesting. Which input-TX are you using ?

Thanks,

Peter

I'm using the stock Lundahl 1540 input trafo.

I like the idea of building an external phantom box, Jakob. Can you please link me to a good design/schematic?

Could the impedance mismatch be resolved with a different input transformer? (maybe more of a mod than it's worth)

Dean

Thanks Dave,

I like the idea of building an external phantom box

Click to expand...

Here's something:
http://sound.westhost.com/project96.htm

Regards,

Peter

Thanks Peter,

Yes - that looks right - figure2. For the PSU part, you could use 2x22.5V photo batteries or 5x9V PP batteries - or one of the phantom supplies described around here..

Jakob E.

My eye fell on the 2*10 Ohm resistors in fig 2. It won't matter that much in practice I guess, but it would perhaps be a pity for a pre-amp that went great lengths/uses LM394 to have low Rbb etc
FWIW...

Regards,

Peter

Thanks Peter and Jakob!

> My eye fell on the 2*10 Ohm resistors

Look at the 22uFd caps. They have much more impedance over most of the audio band.

Stuff like this matters much more in theory than in practice.

from PRR:

> My eye fell on the 2*10 Ohm resistors

Look at the 22uFd caps. They have much more impedance over most of the audio band.

Click to expand...

Thanks, I still keep getting fooled by that too many times :wink: :evil:

But I was asking myself: there where the Hertzes accumulate (so where 'sqrt(BW) really boosts the noisy-density', so @ the right side of freq-plot) the cap-impedance is low, so couldn't it be that the 10 Ohm still results in a noticable higher noisefloor ?

Well, it doesn't really since the rest will be overwhelming it, but from what I got from some toying around, for a noiseless surrounding circuit,
the integrated noise over 20kHz-BW seemed some 9 dB higher (2.6uV vs 0.9 uV).


But please don't pinpoint me on my method to arrive there; I just based it on the 10 Ohm and 1/(2*pi*capvalue) and as such, I don't know if thats a completely valid approach.

Stuff like this matters much more in theory than in practice.

Click to expand...

Fully agreed.
I have the feeling that in much of our efforts around here a lot of measures are taken just because:
* they could be done,
* would in principle be better,
* should improve things,
* was cheap to overengineer,
* was not that cheap to overengineer but might be important (if someone likes to replace the comparators in a LED-bar by 2520's, then why not ?),
* is fun to address now we understand what's potentially going to be a problem but might really never become a noticable influence etc etc.

That's at least how I feel it and it's all OK - maybe they help just a little bit,
but all those extra's will pay themselves back I think.
Whether it's economical/really noticable is another thing, but that's not really why we're into DIY.

Well, enough for now - too many words on an insignificant 10 Ohm resistor. :wink:


Regards,

Peter