** He's baaaaaaak .......

Here's some news, noise is accumulative. Stop testing at 60 db gain and
go back and test EIN at 20 db gain.
The TLO7X is noisy.


** Not in this case.


Do FFT and see
and see all the harmonics riding up to the 11th order residing at about
-105 db.


** Yawn.

Reality holds no interest for this dude.



Use smaller
resistors around that opamp, more thermal noise is added. Most folks
don't use 60 db gain, testing at 20 and 40 db offers more real world
results. Take that 60 db of EIN gain out and you sit at a 68/69 db S/N.


** Remember this ??

" The noise floor is at -95 dB rel 1 volt output - unweighted.

Using a 5534 drops it by less than 1 dB. "



How does it do with a 50 ohm source?


** The noise figure is 3 dB for a 50ohm source.

EIN = - 132.5 dBu



Not so good if you are recording
quiet sources.


** Bull**** - room noise will dominate.


Here's some more news, a 50 ohm ribbon mic has lower noise than any
active condensor mic preamp, like around -132 db EIN.


** Only when placed in a bloody vacuum - you pathetic ****** !!!!


How does your 30 year old design do with that?


** With rare ribbon mics in a vacuum ??

Go ask an astronaut.



This is the type of circuit that drove up
the prices for used discrete English consoles after the masses rejected
the sonics of the TLO7x opamps.


** The loony bin is missing an inmate.




............. Phil

"Scott Dorsey" wrote in message
...
In article , Geoff Wood
wrote:
"Buster Mudd" wrote in message

Maybe we should take a hint from vinyl-philes and their phono
headamps...er, I mean "pre-preamps". Or, wait, if they're using a low
output moving-coil cartridge I guess it'd be a "pre-pre-preamp", no?

Mine's a transformer.

Yeah, but do you get gain from it? Or is that another horrible thread?

Voltage gain, yes.

geoff

Pooh Bear wrote:

snip

Plural of dB is indeed dB - so you can say the level is 1dB down or it's 3dB
down for example.

That should be "1 dB" or "3 dB". (Note spaces between the quantities and
units.)

--
================================================== ======================
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
mrkesti at comcast dot net | - The Who, Bargain

Phil Allison wrote:

in my quest for a better sounding close snare mic, i'm gonna give a
josephson c42 a try. a 57 is not giving me what i want. i emailed
josephson asking if i should get the c42H high level version instead of
the standard one, and they suggested trying the standard first, as the
high level version is a lot noisier, thus reducing it's usefulness on
quieter sources. how high do snare drum peaks get, worst case SPL with
the mic within 3-5 inches? say a 300 pound drummer with 2B sticks
hammering a loud brass shell snare, hitting a rimshot. the standard
c42 clips at 135 dB SPL. the c42H can do 155! thanks.

First of all, I don't think you'll exceed 135 dB SPL. Also you should
note
that this is a spec _across the band_. It's worst case... midrange
frequencies can probably go well above that before the mike clips.

snip

Since when does the pre-amp in a condenser mic have a clipping level that
varies with at an audio frequency ????

Never.

Not never. Seldom (principally in microphones with equalization in the
electronics, not with the C42) but not never. But, since you're not
connecting to the preamp but rather putting sound into the capsule, it's
irrelevant -- the clipping level of the entire microphone is the
specification of interest.

The C42 is speced at 8.5mV / uBar and the C42 H is 0.8mV/ uBar - so, 135
dB SPL corresponds to an output of 0.95 volts from the C42 and 0.095 volts
from the C42H.

Your numbers are right but the units aren't. The C42 free field
sensitivity is 8.5 mV/Pascal. 1 Pascal (not 1 microbar) is 94 dB SPL. 1
microbar, or 1 dyne per square centimeter, is 0.1 Pa or 74 dB SPL. 135
dB SPL is 41 dB more than 1 Pascal, or 112 times the voltage. 8.5 mV
times 112 is 0.95 volts. The electronics of the C42 exceed 1% harmonic
distortion at about this level (about 2.8 volts peak-to-peak, open
circuit, with real IEC spec P48 phantom power). Actual clipping level is
somewhat higher, typically 8 to 10 dB for impulse waveforms like drum hits.

Frankly the concern about mics clipping at high SPLs isn't really
warranted. Most modern condenser microphone capsules such as those in
our C42 are undamaged to at least 160 dB SPL. It is very seldom that
even the loudest snare reaches 130 dB. As we responded to the original
inquiry mentioned in this thread, try a regular mic first. If you really
think you need a higher SPL ratings, we have the C42H and the e22S,
which is specifically designed for close-up drum and other pickups.

--
David Josephson * Josephson Engineering, Inc. * www.josephson.com

Ignoring the rude noises being passed here, there is a basic and
commonly made error here that needs a comment.

Since when does the pre-amp in a condenser mic have a clipping level that
varies with at an audio frequency ????

Since they started putting preamps inside of condenser mics.

snip

See above, most microphone electronics have a relatively flat clipping
level with frequency. We don't call them preamps. Some German-speaking
and other manufacturers do, although the German term is the more
accurate "Impedanzwandler" or impedance converter, which is their real
function.

Quiz: What's the function of the electronics inside a condenser mic?


** To " pre amplify " the tiny power level coming from the capsule.

The power gain is about 10,000,000 times or 70 dB.

Sorry, no. This was stated once in an old audio textbook and is simply
wrong. The power gain is irrelevant. The electronics in a condenser
microphone typically have less than unity gain. Many have substantial
voltage loss. The capsule of our e22S, for instance, has an output
around 10 mV/Pa. The output of the microphone is around 5 mV/Pa, or
about a 6 dB loss. A few mics have a few dB of gain but not more than 6
or 8 dB.

--
David Josephson