Doepfer A-188-2 Handleiding

Doepfer Niet gecategoriseerd A-188-2

Lees hieronder de 📖 handleiding in het Nederlandse voor Doepfer A-188-2 (16 pagina's) in de categorie Niet gecategoriseerd. Deze handleiding was nuttig voor 31 personen en werd door 2 gebruikers gemiddeld met 4.5 sterren beoordeeld

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System A-100 BBD Module A-188-2

Fig. 1: A-188-2 Controls and In/Outputs

1. Introduction

Module A-188-2 based on a so-called Bucket Brigade

Device (abbr. BBD). In contrast to the A-188-1 the A-188-

2 uses a tapped BBD circuit, i.e. the circuit has available

six different outputs at the BBD stages 396, 662, 1194,

1726, 2790 and 3328. Each of the taps is available as a

single output but the module features also two mixing

sub-units. For both mixers the levels and polarities of

each BBD output can be adjusted to obtain two different

mixtures. Each mixer has a wet/dry control that allows

choosing between the original signal, the BBD mix or

anything in between. The outputs can be treated as

stereo outputs but that's not . Due to the six taps even six

different feedback types are possible. The feedback input

socket is normalled to the "396" output. But by patching

the feedback socket to any of the single output sockets

another BBD tap can be used for positive or negative

feedback to obtain different sounds. Even external

feedback processing is possible. The A-188-2 uses a

high speed VCO to generate the BBD clock. The clock

and consequently the delay time can be controlled

manually and by the two control voltage inputs CV1 and

CV2. CV2 is equipped with a polarizer. The module has a

clock output available that is normalled to the clock input

socket. These sockets can be used to link different BBD

modules and to run them with the same clock. A voltage

composed of the manual delay control, CV1 and CV2 is

available at the CV out socket, e.g. to control an external

clock suppression filter as the A-188-2 is not equipped

with such a filter.

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System A-100 BBD Module A-188-2

2. Basic Principles

A BBD circuit can be regarded as a chain of Sample &

Hold units (S&H) which pass on their voltages to the next

S&H in the chain at each clock pulse. From this also the

name Bucket Brigade Device is derived as each stage of

the BBD can be treated as a bucket. At each clock pulse

the content of each bucket is forwarded to the next bucket

in the chain and the current bucket is filled with the

contents of the preceeding bucket.

Fig.2: Bucket Brigade

Remark: In reality two "buckets" are required for each

stage as the content of a bucket has to be stored

temporarily in a "slave bucket" before it can be filled with

the contents of the preceeding bucket, in contrast to a

"real" bucket brigade not the buckets are passed on but

only the contents.

In the BBD the water is replaced by analog voltages

which again represent audio signals. The first bucket (1)

is the audio input, the last bucket (n) is the output of the

BBD. As in reality there are losses while the water (resp.

voltage) is passed on, because some drops of water go

wrong and at the end of the chain not the same amount of

water (resp. not exactly the same voltage) appears. In a

BBD the buckets are replaced by capacitors and analog

switches. As the capacitors of a BBD are very small

(some pF only) even the time required to pass on the

input to the output is crucial as the capacitors loose their

charges if it takes too long. This is why a minimum clock

frequency is specified for each BBC circuit. Below this

frequency the flawless operation of a BBD is not

guaranteed. In the A-188-2 intentionally frequencies can

be used that go below this value to obtain special "dirty"

and "crunchy" effects.

Standard BBD circuits as described above are available

(or rather have been available) with different numbers of

stages. Usual numbers are 128, 256, 512, 1024, 2048 or

4096 stages. In the A-188-2 a very special BBD circuit

with 3328 stages is used (MN3011) that is equipped with

additional outputs (taps) at the stages 396, 662, 1194,

1726 and 2790.

The number of stages defines the delay time that

corresponds to a certain clock frequency. The higher the

number of stages, the longer is the delay. The higher the

clock frequency, the shorter is the delay.

Example: At 100kHz clock frequency the delay time is

10.24 ms for a BBD with 1024 stages and 20.48 ms for a

BBD with 2048 stages.

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System A-100 BBD Module A-188-2

The following table shows the relation between clock frequency, used output stage (tap) and delay time for the BBD circuit

used in the A-188-2 (MN3011).

Table 1: Relation between clock frequency [kHz], used output (tap) and delay time [ms]

clock frequency

(clock input socket)

BBD clock frequency

(= 1/2 clock input)

MN3011

tap/stage output

[kHz] [kHz] 396 662 1194 1726 2790 3328

1 0,5 396,00 662,00 1194,00 1726,00 2790,00 3328,00

2 1 198,00 331,00 597,00 863,00 1395,00 1664,00

5 2,5 79,20 132,40 238,80 345,20 558,00 665,60

10 5 39,60 66,20 119,40 172,60 279,00 332,80

20 10 19,80 33,10 59,70 86,30 139,50 166,40

50 25 7,92 13,24 23,88 34,52 55,80 66,56

100 50 3,96 6,62 11,94 17,26 27,90 33,28

200 100 1,98 3,31 5,97 8,63 13,95 16,64

300 150 1,32 2,21 3,98 5,75 9,30 11,09

400 200 0,99 1,66 2,99 4,32 6,98 8,32

500 250 0,79 1,32 2,39 3,45 5,58 6,66

Remarks:

The grey italic characters indicate parameters out of the data sheet specifications as the MN3011 circuit is specified only for

clock frequencies between 10kHz and 100kHz. But the A-188-2 is able to generate even clock frequencies below 10kHz

and above 100kHz. From our experience the MN3011 cannot be damaged if it is operated with frequencies out of spec. This

is why we decided to include out-of-spec frequencies to obtain special audio effects – especially for clock frequencies below

10kHz. But the regular circuit behaviour is no longer guaranteed (especially increasing voltage losses at lower frequencies).

As the clock frequency falls below ~ 15 khz the clock signal itself will become audible. This clock noise can be used as

unusual audio source or it can be ltered out with an external low pass filter.

Product specificaties

Merk:	Doepfer
Categorie:	Niet gecategoriseerd
Model:	A-188-2

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