512 stage bbd ?

[lowstar]

hi all,

is there any affordable bbd chip out there that has 512 stages ?
i want to build a bf-2b clone, and the mn3204 is hard to get. i have one, but they are practically non-existent out there, and expensive.
so, i thought, with a little working on the circuit, other 512-stagers could be used, but i could not come up with any candidates.
there is the sad512, which is even harder to find than the mn3204 i think.
there are the mn3010 and mn3004, which are just as scarce as the reticon.
to my knowledge, there are no coolaudio chips with 512 stages out yet ?
clocking the normal 3207 into the regions of the 3204 would produce some probs, i think ?
the difference between the two is big, i own the bf-2b (an original) and had a bf-2 to a/b, and it is not only the higher x-over freq of the bass version, the stages play an important role (in having a more subtle flanging effect).

cheers,
lowstar

[Lurco]

TDA1022

[lowstar]

oh yeah, that´s right. but the tda1022 seems to be just as elusive as the other ones.
smallbear, banzai, musikding don´t carry them. wasn´t there some project recently that used tda1022 that "emptied" all the stock of those bbd´s ?

cheers,
lowstar

[oldschoolanalog]

http://www.vintageplanet.nl/semiconductors.html

[Mark Hammer]

is there any affordable bbd chip out there that has 512 stages ?
i want to build a bf-2b clone, and the mn3204 is hard to get. i have one, but they are practically non-existent out there, and expensive.
so, i thought, with a little working on the circuit, other 512-stagers could be used, but i could not come up with any candidates.
there is the sad512, which is even harder to find than the mn3204 i think.
there are the mn3010 and mn3004, which are just as scarce as the reticon.
to my knowledge, there are no coolaudio chips with 512 stages out yet ?
clocking the normal 3207 into the regions of the 3204 would produce some probs, i think ?
the difference between the two is big, i own the bf-2b (an original) and had a bf-2 to a/b, and it is not only the higher x-over freq of the bass version, the stages play an important role (in having a more subtle flanging effect).

The BF-2b seems to be, from a casual look-through, identical to the BF-2, except that the delay range is shifted downward via means of a 512-stage delay chip instead of 1024.  What that means is that none of the capacitor filter values needs to be changed for anti-aliasing or clock noise reduction purposes.  It also means that the lowest-produced notch will be one octave higher than that introduced by the BF-2.

The stock BF-2 is limited in terms of how fast it can clock and the shortest attainable delay (1msec).  This is a product of the MN3102 clocking chip, however, rather than the MN3207 itself, which is why the BF-2b opts for simply swapping chips rather than monkeying around with the clocking.  HOWEVER, as many others here can attest with their A/DA Flanger builds, some surprisingly short delays can be obtained from the MN3X07 series, IF you clock them right.  "Right" means inserting a buffer between the clock generator and the BBD so that there is enough current delivered in that clock pulse to overcome the input capacitance of the chip.

In theory, at least, you should be able to double the clock frequency of the BF-2 by adopting similar buffering (quite often a simple 4049 hex invertor with three paralleled invertors buffering each clock line), and attaining the shorter delay times of the BF-2b.

Although there is a nuisance of layout and extra parts involved, note that the "fidelity" at the slowest rates should be better than the BF-2 or 2b in some respects, because of the faster sampling rate.

The other alternative is to score yourself an MN3209 (256 stages) and halve the clock frequency of the basic BF-2 to achieve the delay times of the 2b.

Finally, note that the metallic resonantqualities of the basic BF-2 that can irritate some people can be softened considerably by limiting the bass content in both the feedback path and the final delay output sent ot the mixer stage.  In many schematics of the BF-2, you'll see a .047uf cap in the feedback path labelled C7.  Every halving of that value raises the bass rolloff point by an octave.  You'll also see a .22uf cap labelled C20 just before the switching JFET.  Again, every halving of that value raises the bass rolloff point by an octave.  Chopping C20 down to .047 or even .022uf will help remove the boxiness/tankiness of the flanger sound that sends many folks running for cover to a BF-2b.  Similarly, chopping C7 down to .01 or thereabouts will help too.  Many people who have done similar mods have told me how pleased they were with the improved usability of their BF-2 units