Replacement for the Unobtainium - SAD1024

[RahmschnitzelStudio]

Hello everyone,

for a 'simple' pin compatible replacement of the SAD1024, a friend asked me for a layout based on the work of Thomeeque.
9V Electric Mistress retrofit with MN3007

The goal was to make do with the space available around a SAD1024 in a normal stompbox. The test object was a FL303 from a friend who kindly lent it to us.


Ibanez FL-303

The result fits, at least in the FL-303.


Klick for more details

Klick for more details

The circuit diagram is basically a copy of Thomeeque's great preliminary work. R7 & R8 are only for flexibility. Depending on the external circuit of the stompbox, R3 is optional. If not available, the ferrite beads FB1 and FB2 can also be replaced by resistors. It is only important that the total resistance does not increase. So R2 becomes 4R7, FB1 becomes 4R7, R4 becomes 47Ohm, FB2 becomes 47Ohm.


Schematic


Klick for more details

Klick for more details

The terminals of the MN3007 must be bent or cut off for assembly to turn it into an SMD component. There are two resistors and the output transistor under the MN3007. You can currently get the MN3007 here:
https://aionfx.com/component/mn3007/

Anyone can order the PCB here:
https://aisler.net/p/GXZFJWDF

Have fun with it and best regards from germany
Matthias

[mzy12]

This is pretty incredible... do you have any measurements comparing the replacement to the original?

[DrAlx]

The schematic for the FL-303 shows it uses both 512 bucket delay lines in series, so it's not surprising a 1024 bucket MN3007 can be wired up as a replacement in this particular case.
But the PCB is not going to provide a general pin compatible replacement for the SAD1024.
For example, a pedal might use only one of the 512 bucket delay lines, or both lines in parallel, or both lines in series but in different order to how the FL-303 uses them.

[DrAlx]

The schematic for the FL-303 shows it uses both 512 bucket delay lines in series, so it's not surprising a 1024 bucket MN3007 can be wired up as a replacement in that particular case.
But the PCB is not going to provide a general pin compatible replacement for the SAD1024.
For example, a pedal might use only one of the 512 bucket delay lines, or both lines in parallel, or both lines in series but in different order to how the FL-303 uses them.

[DrAlx]

Oops repost

[RahmschnitzelStudio]

Hello mzy12,

no unfortunately I didn't, I was just trying out whether the replacement works in principle or sounds different. In my opinion, it didn't. It should also be mentioned in this context that we had to adjust the bias.

As I wrote above, I was mainly interested in doing my friend a favour by casting Thomeeque's work in a smaller form factor, as he has to repair pedals from time to time.
Normally, a flanger has no place on my pedalboard. The FL-303 showed me again why

Best regards
Matthias

[RahmschnitzelStudio]

Hello DrAlx,

good that you mentioned that, you are absolutely right!
That's why I'm currently working on making a circuit board that adapts two TDA1022 to one SAD1024. Unfortunately, the TDA is also rather hard to get, although easier than the SAD. But this is also mainly a favour for my friend, who still has a lot of TDAs.

I just think that such work should be made available to everyone. Hence the publication of the boards and provision of the layout data.

Best regards
Matthias

[RahmschnitzelStudio]

Hello everyone,

That's why I'm currently working on making a circuit board that adapts two TDA1022 to one SAD1024. Unfortunately, the TDA is also rather hard to get, although easier than the SAD. But this is also mainly a favour for my friend, who still has a lot of TDAs.

I have just completed and ordered the PCB. It adapts two TDA1022s to one SAD1024. As with the first PCB with the MN3007, I generate the voltage, called Tetrode Gate for the TDA, myself using a voltage divider. Otherwise, it is purely an adaptation board. This makes it more universal than the first one with the MN3007, as it can also be used for circuits that do not connect both 512 blocks from the SAD in series.

The only disadvantage is that the TDA is not as cheap as the MN3007.

Best regards
Matthias