DirtBag Delay ~ Deluxe Memory Man

culturejam · Post by **culturejam** » 12 Oct 2010, 12:48

madbean wrote: I'm also thinking of a conversion to PT2399 with 2 chips of them in series to get around 800ms of usable delay. It won't be a DMM, obviously, but maybe it could get reasonably close. And, that would require no calibration at all

I'm so in on this. Let me know if I can help out on that front.

coldcraft · Post by **coldcraft** » 12 Oct 2010, 13:33

from the schematic, it looks like D4 might be backwards? It's early, I could be seeing things...

coldcraft · Post by **coldcraft** » 12 Oct 2010, 13:35

coldcraft wrote:from the schematic, it looks like D4 might be backwards? It's early, I could be seeing things...

Sorry, I just realized the hole thing is run off -15... my bad.

madbean · Post by **madbean** » 12 Oct 2010, 16:14

Yeah, the power scheme is a little new to me. The 7915 converts it to a negative regulated version. I actually discovered that I had the pinout wrong on my board after I started putting it together. Since I don't have a 24v PS, I think I'm going to include a daughter board with the project that uses a charge pump and the 7915 to supply the main.

roseblood11 · Post by **roseblood11** » 12 Oct 2010, 20:08

-Can a charge pump IC deliver enough current for that circuit?

-Does the 7915 really need a 24V power supply? Wouldn´t 18V be enough?

madbean · Post by **madbean** » 12 Oct 2010, 21:02

roseblood11 wrote:-Can a charge pump IC deliver enough current for that circuit?

-Does the 7915 really need a 24V power supply? Wouldn´t 18V be enough?

My thoughts exactly. I think 18v would suffice, and yes it should be fine, current-wise. The official EHX replacement is only 100ma, which is probably over spec. A manual will probably list the actual current draw.

madbean · Post by **madbean** » 12 Oct 2010, 22:37

You know, I just realized something kinda of interesting. The Aquaboy layout was set up to use either MN3005 or the v3205 by setting two jumpers. These jumpers switch ground and Vdd to match with the particular BBD used. But, this was only because both were being supplied by the same +9v supply. In the DMM, the MN3005 is using -15v supplied to Vdd already. This means the pin configuration is the same but the voltage requirement is different. This also means that by simply changing the supply voltage, you could use the same layout. The one caveat being that in the DMM, the supply is fed into pin4 of the other opamps and ground into pin8, which is opposite of what you would do in a normal +9v setup. So, I think by adding two jumpers at the power stage to flip those two, it would solve all the necessary voltage requirements for either version. And, by further changing some of the electrolytic caps to there non-polar equivalents, then the only changes to make are in how you put together the power supply and how you set those jumpers. So, if I'm correct in my thought process here, the only thing to do is design one power supply board that can be built two ways depending on what BBD is used. And, by using a charge pump to blow everything up to 18v before conversion, you can keep the higher voltage supplied to all the op-amps (except the v3205 which needs 5v).

coldcraft · Post by **coldcraft** » 13 Oct 2010, 13:39

sounds pretty feasible! The build notes would have to very clear. I know I don't bother to buy non-polar caps and I wouldn't mind flipping polarities as long as the directions are clear!

quaternotetriplet · Post by **quaternotetriplet** » 14 Oct 2010, 07:42

madbean wrote:Thanks for the nice words, atreidesheir.

Here's a pic of the board for size reference. As you can see, there is still some wiggle room. I think the jacks should fit okay up top, but it will be a little close.

OMG this is a monster build..

madbean · Post by **madbean** » 01 Nov 2010, 10:54

Board is populated and almost ready to test. Silly me, I didn't realize until tonight that the EH power supply is positive tip, not negative. Fortunately, I tested out the power scheme before attaching my board, so it's all good. More in another day or so.

WhiteKeyHole · Post by **WhiteKeyHole** » 02 Nov 2010, 12:20

Maybe you could add some pads so R55 can be replaced by a VR and limiting resistor.

Shrug.

MullisMan · Post by **MullisMan** » 04 Nov 2010, 06:15

Brian, you're a genius.

madbean · Post by **madbean** » 14 Nov 2010, 18:23

I've been on vacation the last week, but I've used some of that time to get a design done on a dual v3205 delay in the spirit of the DMM. I've changed some things to lower the part count, but the basic design is input, level control, compressor, filter, delay with DMM modulation, filter, expandor, output. The BBDs and clock run off regulated 5v and everything else off regulated 15v. For the filters, I'm going to try some double pole active filters which I came across in one of the TI application notes (simple, but I have not used them before). The input/output and filters are all on a single TL074 to further simplify.

Anyway, I'll have some more on this as time allows. The vintage DMM has been built, but I have not had time to calibrate it. Right now it isn't passing delay, but I hope to fix that up soon.

gilmour_pugliese · Post by **gilmour_pugliese** » 14 Nov 2010, 18:51

great work, Brian...

just a question: what sonic differences do you think that will be between the dirtbag and the aquaboy with dual v3205 and modulation board?

madbean · Post by **madbean** » 14 Nov 2010, 21:21

I don't expect a dramatic difference, but it would be nice to get some DMM tones. The main differences are in filtering and the higher voltages. I'd like to evolve the Aquaboy since I will need to decide soon whether or not to re-order them. Regardless, there will be a single sided design for home etching.

SoundPerf · Post by **SoundPerf** » 15 Nov 2010, 02:26

I'm new around here, but I'm very interested in this project. I will definitely want to build this. (very likely more that one) I have a Tek 2246 O-scope, so any I'm open for early debugging help.

gilmour_pugliese · Post by **gilmour_pugliese** » 15 Nov 2010, 09:15

madbean wrote:I don't expect a dramatic difference, but it would be nice to get some DMM tones. The main differences are in filtering and the higher voltages. I'd like to evolve the Aquaboy since I will need to decide soon whether or not to re-order them. Regardless, there will be a single sided design for home etching.

I've already built an aquaboy with your board plus abfackeln's LFO and dual BBD boards:

and sounds awesome... but I wanna build the DMM

Post by **jstbrowsin** » 08 Dec 2010, 02:46

bump. Any news anyone? I have been watching and waiting with baited breath. . I soooo want this one.

plugzzzz · Post by **plugzzzz** » 16 Dec 2010, 00:02

this project is very interesting up for this

andersom · Post by **andersom** » 26 Dec 2010, 18:53

Hi maddbean, did you have any time for the DMM with v3205? Really interesting.