AW: Re: external input (again)

[Matt Haines]

>   From: Haible_Juergen
>   Date: Fri, 24 May 96 10:59:00 PDT
>
>   >Thanks Gene! If I *were* being audiophile-minded, what would I do
>   >differently?
>
>   [JH adds good stuff]
>
>And lose the gratuitous polarity inversion.  (That's considered tacky
>in both audiophile and engineering circles.)
>
>  -- Don


As in, add another op amp? Or should I be considering using the + input?
This is maybe an obvious question to most, but not to me. I thought adding
gratuitous op-amp stages was bad, and so figured the inverse polarity was
better. Opinions?


>(...Assuming of course that you don't intentionally want a polarity
>inversion.)
>
>In general, when proposing a circuit and asking for advice it's a good
>idea to give us as many specifics as possible about what you want and
>the context the circuit is going to be used in.  Input impedance,
>output impedance, gain, noise, overload issues, input/output
>protection issues, low/high end frequency reponse, that sort of thing.

Very true...assuming I know even to ask those questions! :) As far as
impedance goes, I'd assumed I would be dealing with the typical 100k high
input impedance and 1k low output impedance. Not so? I'm most likely going
to take the output of a sampler or synth and feed it into the amplifier. So
what does that make it?

Re: gain, I *think* I covered that, in that I'm trying to bring a synth's
output up to a practical modular-synth level. +/-0.5v (which is what audio
signals seem to be around, for synths anyway), up to +/-5v. Which is a gain
of 10.

Noise....uh, not too much? :)

Overload...I'd like the option to overload the amp if I *wanted* to, but
that's not something I want happening all the time.

Protection...yes, please! But seriously, I really don't know what to ask
here. I'm not going to be sticking any unusual signal sources in the thing.

Freq response...not crucial, as in not audiophile. I'm going to be running
it through horribly mind-twisting processors anyway. 20-20k not necessary,
but 200-5k in not good enough.

As far as getting a book on op-amps, yes it's something I need to do. I'm
much more likely to get answers specific to my problem here on DIY though.
I don't know enough to make the leaps of intuition necessary for designing
my own stuff. I'm learning though. Sorry if I'm being a pain.


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Matt Haines  haines at apc.net         .       .       .       .
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Moonlight, Muzak, Knick-Knack, Paddywack