hi tim,
thanks for your reply. that's useful info. maybe what i'm hearing is premature
slew limiting (or something!) because i notice a loss of detail w pretty much
any gain setting, especially hi ones, like you say. i scrapped using the
symmetrical early on due to noise and started using a high quality impedence
transformer (reamp box) in front of the assym input instead, so the +4db signal
from the console gets knocked down to instrument level. that helps alot.

i'll pose the opamp upgrade question to the synth DIY group and see what
they say..

also, seems that by the time i amplify the signal enough to get a healthy
envelope signal from the a119 the audio on output is really dull. maybe
there's an adjustment for making the envelope follower more sensitive..( )
thanks!
-psm



--- In Doepfer_a100@yahoogroups.com , "Tim Stinchcombe" <timothy@t...>
wrote:

> Hi psm,
>
> Not much experience in this area, but a quick look at the 'audio'
> chapter in Jung's 'IC Op-Amp Cookbook' (1st edition *only*!) suggests
> that a key factor is 'gain bandwidth product' (you need large one),
> but also slew rate comes into play as well. Basically the more gain
> you want, the less bandwidth you get. Thus the gain stage on the 119
> acts as a low-pass filter, and as you crank the gain up, the lower
> the cut-off frequency gets. I probably won't have time to try any
> real measurements, but I did a quick simulation of the gain stage of
> the 119, and the results (very, very roughly) suggest that there
> shouldn't be much of a problem with the asymmetric input unless the
> gain is nearly max (8-9 perhaps), but with the symmetric input
> problems are likely to be noticed at much lower gain settings,
> perhaps around 4 or 5. (This is because the overall gain requirement
> for the symmetrical input is much greater.) Does this tie in with
> your use
>
> The book also shows how to improve standard op-amp set-ups for audio
> use (gets non-trivial very quickly - external compensation, extra
> bits 'n bobs everywhere!). As for a recommended chip, you could try
> searching the Synth DIY archives (www.buchi.de/sdiy) as I bet the
> question comes up there from time to time, or you could of course
> pose the question directly to that list (there's a link at the bottom
> of the archive page).
>
> Tim
>
>
> --- In Doepfer_a100@yahoogroups.com , "ps_minor" <pscottm@h...> wrote:
> > lately i've been using my system for processing external signals
> quite often
> > and i've come to notice that my a119 degrades the sound more than
> i'd like.
> > the studio environment i'm usually in is of a high standard, neve
> console, etc...
> > unfortunately i'm sometimes limited to what i can send to the a119
> due to
> > lessened sound quality of the results. especially w vocals and
> drums. i'm
> > very careful w gain-staging so i don't think it's me.
> >
> > out of curiousity just patched the a119 from a send and back to
> the desk, the
> > quality drops considerably w vocals and drums, but the narrowed
> bandwidth
> > is usually pleasing on synth and guitars.
> >
> > was looking at the opamps inside the a119, i believe the one that
> handles
> > audio duties is a TI tl064c, pretty run of the mill chip w low
> power draw and
> > pretty low slew rate according to info i found on TI's site.
> >
> > i imagine a chip upgrade would make a big difference here as long
> as it
> > doesn't draw too much current. not looking for anything fancy but
> an
> > improvement in bandwidth and slew rate would be nice. anyone have
> any
> > knowledge of opamps enough to recommend a suitable upgrade
> >
> > anyone else feel this way about the a119
> >
> > thanks!
> > -psm