Re: Copying Op Amps to Make Mic Amps

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Trade offs....
I'm aware of:
noise
gain
PSRR
CMRR
distortion
dynamic range
stability (DC bias and feedback)
power efficiency
PCB size
cost

How much more can there be?
D from BC

Re: Copying Op Amps to Make Mic Amps



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I think this is a point that Graham has been trying to make. For a musician
or sound engineer, there is a certain sound to micpres, etc., and maybe
that's why his design was successful. In technical terms, I suppose it's
probably some lack of quality (I'm not saying this about Graham's design
BTW) in the design that imparts a difference in tone to whatever's being
recorded. This explains why you see Neve channel strips going for a couple
grand on eBay, even though Rupert himself admits that today's designs are
far better. This may also help explain why the high end boutique micpres can
fetch a similar price, even though there couldn't possibly be enough spent
on actual components or R+D or whatever to justify the cost. Maybe Phil's
right and the engineer types are deluded, but they seem convinced that there
is a difference, and maybe there is - this mysterious tonal quality that
certain designs impart. Whether it is better for the sound or not is a
matter of opinion and personal taste. I'm a musician myself, and what I
record is largely classical guitar, which requires a very low noise micpre,
which the SSM2017 is able to deliver. The noise contributed by the micpre
itself, with whatever resistors or other noisy passives I have in there is
miniscule, and for all intents inaudible, so this one works great for me.
I've not had the fortune to A/B it with a Focusrite to see if the latter has
a better 'sound', although a local studio owner has invited me to bring my
micpre and go head-to-head with his Focusrite. Maybe I'll take him up on it
some day, but I figure that my playing itself needs more work than my
recorded sound anyway. ....





Re: Copying Op Amps to Make Mic Amps



"tempus fugit"

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** You're not using a condenser mic -   then?




......  Phil






Re: Copying Op Amps to Make Mic Amps


On Sat, 17 Mar 2007 23:02:55 -0500, "tempus fugit"

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Welll...I have some audiophoolery for yah... :)
The mic amp difference is... the distortion.
(Here comes the tomatoes... :) )
Some distortion sounds nice.
But it's gotta be the right flavour of distortion..
Something to do with even harmonic content sounding better than odd
harmonic content..
(A gross example is the Tony Iommi (Black Sabbath) guitar sound. But
much more subtle in a mic amp.)

I keep showering but the audiophoolery doesn't wash off....  :)

More scientifically I'd get an Audio Analyzer from:
http://ap.com /
And test the mic amps for a difference.
It's rentable....
D from BC

Re: Copying Op Amps to Make Mic Amps



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I'm using 2 actually. Why, does that make a difference for noise level in
the way it interacts with the preamp?




Re: Copying Op Amps to Make Mic Amps



"tempus fugit"
 "Phil Allison"
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** Have I got news for  YOU  !!!!

Condenser mics have * pre-amps*  inside them   !!!!!!!!!

Almost always, the noise level coming OUT of these internal per-amps is way
MORE than the input noise level of typical mic-pres in mixing consoles and
elsewhere.

There is no noise benefit in using a low noise pre-amp  UNLESS  it is being
used with a dynamic mic.

This is what the EIN figures always refer to a 150 ohm or 200 ohm source
impedance   -  ie a DYNAMIC  mic !!

It all goes  RIGHT  OUT  THE  WINDOW  when a condenser mic is used.




.......   Phil






Re: Copying Op Amps to Make Mic Amps


On Mar 17, 9:02 pm, "tempus fugit"
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I think that the mic preamp has reached its state of the art, and
further improvements are probably found in reducing the cost while
keeping the performance.  It's not all that difficult to build a mic
preamp that measures flat from single-digit hertz to 200 kHz over a
reasonable gain range.

Anyways, I think the most obvious reason for differences in the sound
of mic preamps is simply the input loading.  Change the input
impedance and how it reacts with a dynamic mic changes.

-a


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