All OpAmp mic design (no FET at first stage)

[kingkorg]

Just to reiterate. This was just a exercise of mine to get the most out of the opamp already used without using internal pad. Also, since we use dedicated tube mic PSUs, why not one for fet/opamp mics?

Second was i have a Neumann sdc capsule that can take 150db spl by specification from Neumann and i want to stick it on top of a snare without thinking what could happen under recording and if internal circuit will cause non-linearities i might not be able to catch immediately.

This kind of thing is not necessity by any means.

Also well worth knowing your typical mics can easily put this kind of voltage at your fet gate (tube grid) on plosives if pop-filter is not used.

 

[Paul W]

It's funny because vintage circuits change performance on high transient sources like drums a lot and for a long time I saw people on here being like "vintage circuits can't affect sound that much because they only affect much higher levels than a capsule would output" and then Kingkorg proved that capsules are actually really hot in terms of voltage. Of course tube and transformer microphones sound different on drums. The transients are huge! They're distorting!

Can somebody explain how transformers distort transients? Is it saturation, or slew rate limiting, or both, or what? And how does it differ from amplifier saturation and/or slew rate limiting (or whatever else matters).

Should we think a classic circuit does a particularly good job of shaping transients? Or should we engineer some distortion pedal-like saturation circuit into microphones, or what?

 

[rogs]

Most AD converters in audio interfaces these days run on 3.3, 2.5 or most recently on 1.8 volts. And convert nicely slightly less.

No point in bringing 26dB snare into the DAW either. We are long past tape days when we had to fight high noise floor.

I think setting gain and trims to suit your source is still often required even with 24 bit A/Ds, to ensure optimum performance?

That's not something you need to worry about at all with 32 bit float recording.
Not really a standard format as yet, but I can see it growing in popularity?

As I mentioned above, I use a Zoom F3 which only records as 32 bit float.
I find it very useful to record bat ultrasound, which has a notoriously unpredictable dynamic range.... No more worries about accurate gain setting in the dark with 32 bit float!

The Zoom utlises the AK53888 A/D converter, with 2 x 24 bit converters per channel, configured for 32 float recording.

I use an ancient version of Adobe Audition as my DAW, and that is happy to accept 32 bit float files.
Once they're inputted into the DAW, its's simple enough to adjust the gain and carry out any processing on the 32 bit files, which can then be converted to 24 or 16 bit files, for onward use.

With my cheap Behringer UMC404 audio interface capable of handling 24 bit 192 KHz sample rate formats, it's astonising the quality that can be obtained from really not very expensive kit these days.

Doesn't help at all with rubbish source material though!

 

[rogs]

Further to my earlier comments in THIS POST I've built a transformer coupled version of the OPIC.45 mic.
That's a multipattern OPIC mic, built into a U87 style body, and fitted with one of Ari's 'flat 47' capsules.

Some notes here: https://www.jp137.com/lts/OPIC.45TX.pdf

Initial tests are very encouraging .... still need to check things like the values of the resistors in series with the transformer windings (intended to minimise any reactive loading 'nasties' ).

And I've yet to discover how the transformer will react to high level transients.... They will presumably saturate the core in some way?
How that 'distortion' will actually sound, I've yet to find out?.....

I think I maybe entering the snake oil filled world of finding 'trendy' words to describe distortion!