EH BBD ECHO ISSUE A

Early Memory Man EH BBD ECHO ISSUE A Schematic 

I've only seen one of these early Memory Man units with PCB marked "EH BBD ECHO ISSUE A".

These use three SAD1024 delay ICs and a CA3094 (marked with EH number) as a noise gate.

The unit performed fine at short delay times, but the "echo" settings were very noisy compared to later models.  After taking a long look at the unit on the bench, my assessment was that the design just wasn't quite there yet. This was the first BBD based pedal at Electro Harmonix, and it seems like they were in a rush to get a portable echo effect to market. It's understandable that the engineers, without any prior experience with BBD ICs, would need multiple iterations of the design to create a really good product.

The unit I examined had cut traces and lots of jumper wires and the history of these changes were unknown.

The CA3094 based noise gate is a precursor to the "squelch" control found on the next generation of SAD1024 units.

The power supply has an asymmetrical bipolar design that is unique among the other Memory Man designs. Two of the BBD stages are biased off the ground potential (i.e. same potential as the metal box), which means the power supply for the BBD is arranged to be above and below ground. The other 4 stages are biased from a pair of trim pots. I'm not sure what inspired this arrangement as I have not seen it elsewhere; I'm chalking it up to ingenuity.