Doepfer

Hello Ingo and Dieter,

The level drop in Org position is about the same as with the wasp
filters, so that would be normal.
I also think that the MN3005 would have the most level drop of all the
bbd's, since it has the most stages.

Thanks for the reply's.

By Dirk.



--- In Doepfer_a100@yahoogroups.com, <hardware@...> wrote:
>
> > hello dirk,
> >
> > well, i'm not sure, but after reading your answer
> > i think some of this could be normal behaviour.
> > the dry/wet control is a linear crossfade and not
> > an "equal power" crossfade, so you have a level drop
> > at the center position, this is normal. the bbd output
> > is not of the same loudness than the input signal
> > (or dry signal), but that is also normal. almost all
> > modules alter the loudness in some ways.
> > thats why i suggested that you compare the level of
> > your bbd module with the output of a filter (which
> > usually alters the signal loudness too).
> >
> > strange is that the lowest level on your bbd
> > is not when the mix knob is in center position,
> > and that the output is inverted.
> >
> > dieter, maybe you can chime in and help us?
> 
> OK, here is my comment.
> 
> 1. The output levels of the six different BBD circuits (128...4096
> stages/MN3xxx) are a bit different. Consequently the A-188-1 modules
with
> different stages and circuits behave a bit different. Even BBD
circuits with
> the same number of stages but different circuit types (e.g. 256
stage BBD
> circuits MN3009 and MN3209) are a bit different.
> 
> 2. The output impedance of the A-188-1 is about 5k. It's because the mix
> between the original and BBD signal is made with a linear 10k
potentiometer
> with the original signal on one terminal and the BBD signal on the other
> terminal. The center terminal is the module output. Consequently in the
> leftmost or rightmost position the signals (original or pure BBD) appear
> without additional serial resistance as the potentiometer is at one
of it's
> end positions. In the center position the two signals are mixed via
5kOhm
> each (10k/2 = 5k). This is why the level becomes a bit lower in the
center
> position. It depends upon the ouputload how much the level decreases. As
> most A-100 modules have a 50k potentiometer at the audio input the level
> drop will be about 10% (5k/50k). If the A-188-2 output is connected to a
> load less than 50k the level drop may be more. We think about an
additional
> circuit on the board that compensates the level changes. But as the
is no
> more space on the pc board a complete redesign would be necessary.
> 
> 3. The original signal appears indeed inverted at the output. But as the
> module has a polarity switch for the BBD signal an additonal
polarity switch
> for the original signal would not add new features. It would have been
> possible to plan a polarity switch for the original signal instead
for the
> BBD signal but the audible effect would be the same. I can't see any
> application where the non-inverted original signal would be necessary.
> 
> Best wishes
> Dieter Doepfer
>