[LAU] Portable Digital Recorders

[Monty Montgomery]

On Mon, Feb 1, 2010 at 4:20 PM,  <fons at kokkinizita.net> wrote:
> On Mon, Feb 01, 2010 at 01:10:03PM -0800, Kevin Cosgrove wrote:
>
>> On 1 February 2010 at 21:58, fons at kokkinizita.net wrote:
>>
>> > 99 and 106 are *very bad* - how does one design a mic preamp to
>> > be that bad ? Use a 714
>>
>> 741?
>
> !!! Indeed. Or the 'wideband' 748 IIRC. This just goes to show
> how old these things are... As a true Belgian I was of course
> thinking of the Tintin album 'Flight 714'
> <http://en.wikipedia.org/wiki/Flight_714>.

General lack of design, ground routing, lack of shielding, etc.  You
could use an OPA627 and still shoot yourself in the foot by picking up
bus noise becasue you didn't shiled low RF.  Or by 'hardening' the
inputs by using, eg, 1M input source current limiting resistors.  Any
of a million things, probably more than one of them.

Really deep S/N audio circuit design takes an awful lot effort.  Cost
cutting, deadlines and outright supersition (One transistor is better
than a whole opamp!) ruin what could have been good designs all the
time.

Monty