mic pre concepts

[Laska]

[quote author="tk@halmi"][quote author="dale116dot7"]
Really, for a preamp you would ideally be able to adjust the op-amp's internal compensation against gain. A designer here is wise not to use the Av = R1/R2 formula for gain - that's the simplified version that doesn't really work if the gain is high. A nice op-amp for this is the AD797, it allows the designer to decompensate the amplifier.
[/quote]

I have been entertaining this idea for some time. Using a double pole rotary switch for gain control one circuit could adjust Ccomp and the other Av. This way at higher gains the amp would be gradually decompensated as needed.[/quote]

Douglas Self "entertained" the idea in the extreme some years ago:

http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en&DB=EPD&PN=GB2242089&ID=GB+++2242089A++I+

http://l2.espacenet.com/espacenet/bnsviewer?CY=gb&LG=en&DB=EPD&PN=GB2208053&ID=GB+++2208053A++I+

For those few that miss it :wink: just scroll thru the pages with the arrows up top or pop on the Biblio,Desc,Claims etc buttons.

Regards,
Tom

 

[Svart]

maybe we *should* investigate the possiblility of phantom without blocking caps.. could we servo after a floating input stage to keep current from flowing? or how about something along the lines of a cancelling circuit for noise.. similar to audio balancing?

 

[BradAvenson]

[quote author="Svart"]maybe we *should* investigate the possiblility of phantom without blocking caps.. could we servo after a floating input stage to keep current from flowing? or how about something along the lines of a cancelling circuit for noise.. similar to audio balancing?[/quote]

Or use a direct coupled transistor front end for something like this:
http://www.analog.com/en/prod/0,,759_777_AD629,00.html

It has a common mode rejection up to +/- 100V.

 

[Svart]

that is an interesting idea...

I'm still trying to get together a preamp featuring the ths6012 from TI.. research says that this IC should rock beyond compare.

 

[Animatic]

Evolutionary dead end here???

It looked like and interesting parallel set of ideas was coming on then pppffftttsss

The Shroom was REALLY interesting.
Wonder if I can find those tubes now...
Doubt ribbon mics would like it.

 

[Yellowguy]

What about (for transistor design) using a single ended PS in the range of 96 volts, so the input offset voltage is 48 volts?
Fully balanced circuit.... Is that what Millenia did???