EH 1309A Memory Man

The EH 1309 matches the EH 7500 schematic (see below). I’ve seen an EH 1309B with 1978 pots on the internet.  I’ve yet to see a plain EH 1309 (no letter).

The original Memory Man uses 3x SAD1024 delay chips, a CD4047 clock and no compander (NE570/571) chip.  The special function switch is a BOOST for the input amplifier.  Outputs are DIRECT and DELAY.  3 knobs: DELAY, FEEDBACK, BLEND.

There are six trim pots.  3 of them are bias adjusts for the SAD1024 inputs.  The final delay section has a clock noise cancel trim and this is directly connected to a delay output level trim.  There is also a trim after the 3rd BBD section (right in the middle of the 6 sections) to adjust the gain of a 4558 op amp.  Couldn’t tell you why this is necessary.

Who designed it? Howard Mick Davis confirmed he did not design it in this interview: http://www.howardmickdavis.com/StonesClonesMuffs.htm. “The Stompbox” by Art Thompson includes a Mike Matthews interview that names Bob Myer as the original Memory Man designer, and Howard did the later MN3005 based boxes. EH Man’s article “How’s your memory man?” names Irwin Kornfeld as the first model designer, and the Julia Truchsess interview mentions tuning Memory Man units while working as Irwin’s assistant.

Below is a shot of the very messy/kludgy boost switch wiring that I found in the only EH 1309 specimen I have encountered so far.  I assumed that is vintage correct EH craftsmanship.

Schematic

My trace appears to match the EH 7500 schematic pretty closely: