[sdiy] sync circuit woes

[Andre Majorel]

On 2008-11-21 07:34 -0600, harrybissell at wowway.com wrote:
> On Fri, 21 Nov 2008 11:22:36 +0000, Tom Wiltshire wrote
>
> > If you've got a preamp on the guitar input channel, I'd be
> > inclined  to split the gain required between the preamp and
> > the mixer. [...] Hence  I'm not entirely clear why, but
> > building gain up in this way seems to  give better results
> > than just whacking a signal through an opamp with  a massive
> > gain. I suppose you're not pushing any one stage as hard.
>
> Tom is right about multiple stages.  Each opamp has a "gain -
> bandwidth product" which in simple terms means that if you take
> a lot of gain in a single stage, the bandwidth is reduced.
> Frequency response will suffer a LOT with high gains in a single
> stage, two stages with moderate gains are MUCH better.

But isn't the GBP the consequence of the finite slew rate ? If
that's the case, it seems to me that a GBP figure is only valid
for a given input level.

Cascade two x10 amplifiers and the second one will have lower
bandwidth than the first because the excursion of its output
voltage will be 10 times greater.

Am I missing something ?

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>