Vintage Flanger Effects Pedal - SAD alternatives

[terjewinther]

I am interested in the Vintage Flanger Effects Pedal, but on the web site it says that "The original BF-1 used a SAD1024 and this is the preferred part for this project if you intend to use your pedal as a flanger and not just a test circuit for BBDs"

I don´t have any SAD1024s in my parts bin, but I do have several SAD512. Would the pedal project be of interest at all using SAD512, or would it become such a weak sound effect that it is of no use?

If there are any comparasing sound files between SAD1024 and SAD512 for this pedal effect, that would of course be of interest.

[Synthbuilder]

Would the pedal project be of interest at all using SAD512, or would it become such a weak sound effect that it is of no use?

It still sounds lovely with a SAD512D. But note the D suffix at the end. The SAD512 is a different chip and I haven't tested it with these.

The SAD1024 is effectively two SAD512 (or SAD512D) so gives twice the amount of delay time. In flanger terms this allows a greater depth of sweep at the bottom end and a better chorus effect. But plenty of really good flangers used the SAD512D including the brilliant Bel BF20.

That said I regard the BF-1 with the SAD1024 as the gold standard of Flangers and it's the one I tried to get close to with the Oakley Flanger/Chorus module.

[KSS]

Two 512's can be chained on a daughterboard.

[Synthbuilder]

Two 512's can be chained on a daughterboard.

If you have two SAD512D then it may be worthwhile selling them*. They are getting really rare.



And buying a single SAD1024A. Which are also expensive but less rare.

Or even buying a flanger pedal with a SAD1024.

* Unless you have an older VP-330, RS-09, BF20 et al.

[terjewinther]

Thanks. I need to check if I have 512 or 512D. I mostly keep these ICs because I do have lots of old string machines with these in them, like the VP-330 Mk I and RS-09 Mk I. Thought they could do some good while I still have them. Or will they get "used up" if I put them in a pedal?

[terjewinther]

Two 512's can be chained on a daughterboard.

That is of course a solution. Any pointers to how this is done, or is it all in the data sheets?

[Synthbuilder]

I mostly keep these ICs because I do have lots of old string machines with these in them, like the VP-330 Mk I and RS-09 Mk I.

Both of those use the SAD521D. It's a 8 pin DIL chip.

The older SAD512 is actually just a SAD1024 with only half the silicon die wired to the outside world. I think this is because the other half of the die didn't work properly when tested but still allowed the manufacturer to make a saleable product with it.

Or will they get "used up" if I put them in a pedal?

Quite possibly. Over time the materials that make up the specific patterns in the silicon die migrate to other parts of the silicon causing the the performance to degrade and eventually failure. Modern chips are way better in this respect. Heat speeds up this process and using a chip will warm it up and speed the ageing process.

Any pointers to how this is done, or is it all in the data sheets?

Check the data sheets on the SAD1024 and SAD512D. Note that the SAD512D has a very different clock requirement as it has the biphase clock drivers on the chip.

[KSS]

Over time the materials that make up the specific patterns in the silicon die migrate to other parts of the silicon causing the the performance to degrade and eventually failure. Modern chips are way better in this respect. Heat speeds up this process and using a chip will warm it up and speed the ageing process.

This -the italicized- is surprising to me. My experience does not bear this out, with unused 512's and 1024's going bad while those in actively used gear still work fine since the 70s. I realize this is anecdotal, rather than strong fact. But it is empirical rather than theoretical.

I'm not disputing the statement because I think there are enough variables involved -from the mfg. to the storage, to the use- that will easily support different results and conclusions. So it seems a bit like tin whiskers. They're real, but their appearance and poor result is not a given in all situations.

I do know that it is super easy to blow these chips with wrong bias current and it's reasonable to assume that some circuits will be less stressful to their chips.

[Synthbuilder]

My experience does not bear this out, with unused 512's and 1024's going bad while those in actively used gear still work fine since the 70s.

You may be right. I think the SAD chips were very sensitive to static damage. And perhaps it's all too easy to zap them when they are stored somewhere. In my past life as a synth repair man, I used to buy a lot of my old delay chips as tested pulls from Organ spares places, and several of those arrived dead, or half dead in the case of the SAD1024A.

That said, the reason I had to buy SAD delay chips would be that all too often they would die in various bits of gear.

[terjewinther]

I checked my parts bin, and I have 4 of these ICs, and they are all SAD 512D. They are reserve parts for my old strings ensembles, so I need to keep them.

Since I have four of them, I thought I could temporarily use one of them for the flanger pedal, but if that means that it will degrade, I am not sure. Maybe I should build the flanger pedal to use as a IC checker, and sometimes flanger? Hmmm..... I need to think about that.

[umma gumma]

Someone needs to make an SAD1024 replacement!

I may build this flanger to test the ones I have, great idea

[ropesalesman]

When it is a design where the sad1024 sections are used in series it can be done with modern parts with a bit of a headache.... some modern BBDs CAN be clocked to the speeds SAD1024s reached with the right driving circuitry.

However when the sections were paralled up for some of the trickier applications it gets much more difficult. I don’t think any reasonably priced 512 stage BBD is currently out there?

[thetwlo]

If I recall, it was the SAD4096 that was the fragile one, ESD etc... most died.
I have many things with 1024's and spares, so far all seem good. Even dead gear with SAD1024s, the 1024s are good, just my experience of course.