Expanding Boss DD-2 Delay Time with 256k DRAM

[aviherman5]

Thanks!

Was more wondering whether the delay control needed to be modified to have longer delay times than just changing the RAM config. Can you elaborate on whether or not I need to? How long will I get at the max settings using the RDD-10 config with SDE-3000 ram capabilities?

I actually came across 5x of the controllers, so I'm going to build the DD-2, not mod it.

Thanks for all the info and help, you've been excellent!

[Slowpoke101]

Build it? That is a much better idea. And well done on getting some of the gate array chips. You actually have some very valuable chips there.
Can't really tell you how long a delay you will get because it depends on varying factors. First set DB0 - 7 to high (+5V), build the 12 x 4164 memory bank and then experiment with the VCO and its Delay Time control (plus its high/low trim-pots). Don't forget to build the compressor and expander sections. They really help with noise reduction.

It will be interesting to see how this turns out so keep us all posted please. Always happy to help as we all are. It's a great forum.

[aviherman5]

Thanks, that was a pretty good score 
Really appreciate all the help from you and the forum, it truly is a great place!

I think when I make the test PCB I'm going to make a DD-2 with the SDE-3000 Ram config with jumpers that can leave a connection either open between a DBX pin and +5V and play with delay config times to experiment how it works.

Thank you again and will hopefully update everyone in a few weeks!

[aviherman5]

Oh, also...those diodes in the switching scheme for the RDD-10, should I use them or leave them out with the while jumper thing I'm doing?

(Picture of the jumper thing just to be specific  )

[Slowpoke101]

Use the 10K resistor bank to ground as in the RDD-10, this will pull the DB0-7 pins low. Then simply use the jumpers you wish to use to select +5V on each individual DB pin to take it high. This would allow you to select 256 combinations (00 to FF Hex or a Byte). You would not need the diodes for this arrangement.
If you chose to use the RDD-10 switching arrangement, you would be limited to as many combinations as the switches AND the diodes allowed.

[aviherman5]

Awesomeness, thanks!

Going to knock out my PCB and schematic over this week and hopefully build in 2!

[aviherman5]

Currently making the PCB for testing and was wondering about the DB pins:

They seem to set the range for delay time per the RDD-10 schematic and I noticed DB7 is connected to the muting circuit and to the expander. Why is this?

Also, DB8 and DB9 exist as well but are left unused. Per the CPU diagram in the SDE-3000 manual it seems they serve the same function as the other DB_x pins.

Could anyone shed some light one this, please?

Thank you!

[Edit]
Also, if I were to use jumpers and resistors to ground on the DB8 and 9 pins, would I connect the muting/expander node to DB9 or DB7 pin? Heck, why does that connection even do?! 

[aviherman5]

^bump