Some Possible mods for Behringer DD100 Digital delay pedal

Elektrojänis · February 19, 2007, 05:23:12 PM

After thinking some time about the ethics of buying a Behringer pedal, I decided just to go ahead and buy the DD100. Ibought it mainly as a toy for myself. So, here are some observations.

About the pedal

It works fine for basic delays. It has a plastic enclosure, so it is probably not too reliable if you think of stage use. I only play at home, so it's not an issue for me.

One thing is weird. Even the dry signal goes through AD- and DA-conversion. I tested this by feeding it some noise that has a bandwidth up to 22kHz. The pedal does not let anything over 12kHz through (sampling fequency is 24kHz). The freq response starts to fall sharply somewhere around 11kHz. For (electric) guitar use this shouldn't be a problem.

The Hold function is a bit strange... It's a looper, but the loop does not play forever. It decays about as fast as the delays when you set the feedback to full on the delay mode.

The controls seem to be a bit stepped. I noticed this on shortest delay mode when I was tuning in some comb filtering effects. Also... Changing delay time on the fly produce some clicks and pops and other artifacts.

For normal delay uses it's still just fine.

What's inside

After playing with it some time I opened it. The pot knobs have to be pulled out to get it open. I had to use conciderable amount of force to get them out. If someone tries to open one, I'd advice to pull them straight up and to try not to bend them. I have opened mine twice and it still works.

The metallic bottom plate makes up almost half of it's weight.

It's actually quite good that it's there as it stays put a lot better with that metal bottom. It's grounded too, so it helps the shielding.

Most components are surface mount. There are couple of SMT TL064 opamps and some other stuff, but the main parts seem to be Atmel ATmega8 and Coolaudio V1000.

Atmel ATmega8: http://www.atmel.com/dyn/products/product_card.asp?family_id=607&family_name=AVR+8%2DBit+RISC+&part_id=2004
Coolaudio V1000: http://www.coolaudio-semicon.com/products.html

Check out the V1000 Datasheet. It has some preset programs: reverbs, chorus, flanger, phaser...

The preset effects of the chip don't seem to have any control possibilities, so they seem to be feeding it their own program to the chip with the ATmega8. I also did some measurements with my DMM. (Yeah... quite crude for this but I dont have much else.) It seems that when I turn the pots, something happens on pins 5 and 6 of the V1000. Those are the pins that are used to feed an external program to it.

Possible mods

1. Reprogram the ATmega8
2. Make the preset programs of the V1000 available

There are some pads that lead to the ATmega8 on the corner of the PCB. Those could be for programming it, but I dont know. There are 5 pads in a row and they go to pins 15, 17, 16, 29 on the Atmega8. The last one goes to ground.

I'm not that familliar with microcontroller programming, so I'm thinking of taking the route number 2. I'm going to get an 8 dip swich bank and make ahole for it in the box. Then I will use one switch to swich between internal and external programs (pin 2 on V1000), two swiches for disconnecting the pins 5 and 6 from the ATmega8 from the V1000 and four swiches for selecting the preset (pins 5-8).

I guess the presets don't have a dry sound blended in (I'm not sure but it would seem reasonable for some other uses) so it might not be too much use with guitar. Fun to experiment anyway... Some separate dry blend box might be usefull then though...

I'm not sure if this kid of modding topic should go here or the main forum... Well... Its digital so Digital & DSP it is then.

puretube · February 19, 2007, 05:41:06 PM

worried about multi-FX ethix?

go HERE!

Elektrojänis · February 20, 2007, 02:35:13 AM

Quote from: puretube on February 19, 2007, 05:41:06 PM
worried about multi-FX ethix?

Well... I was just thinking that do I want to support behringer by buying their products. DD100 doesn't seem too bad, but some cloning they do is quite disturbing.

Quote
go HERE!

Hmmm... Looks handy. Not a lot to add to make a multi FX pedal. Any experience on what they sound like?

RaceDriver205 · February 20, 2007, 03:34:08 AM

Quote1. Reprogram the ATmega8
2. Make the preset programs of the V1000 available

There are some pads that lead to the ATmega8 on the corner of the PCB. Those could be for programming it, but I dont know. There are 5 pads in a row and they go to pins 15, 17, 16, 29 on the Atmega8. The last one goes to ground.

I'm not that familliar with microcontroller programming,

Forgive me, but are you MAD? Why would you want to do any of these things?

TELEFUNKON · February 20, 2007, 04:08:26 AM

Steve at Ampage has tried it

Elektrojänis · February 20, 2007, 05:35:29 AM

Quote from: RaceDriver205 on February 20, 2007, 03:34:08 AM
Forgive me, but are you MAD?

Probably...

Quote
Why would you want to do any of these things?

For fun... The same reason that I build/mod other stuff like fuzzes or amps or mics. I have even built some stuf just to see if I can.

I just want to see if I get it to work and what it sounds like.

RaceDriver205 · February 20, 2007, 06:05:36 AM

Its not that. Its the complexity thats involved, and the lack of any info about the circuit and the program in the Atmega8.

Elektrojänis · February 20, 2007, 06:53:08 AM

Quote from: RaceDriver205 on February 20, 2007, 06:05:36 AM
Its not that. Its the complexity thats involved, and the lack of any info about the circuit and the program in the Atmega8.

Well I was aiming at the number 2 on my list... (making the presets on V1000 available). The presets should not need the Atmega8 for anything. Atmega8 uses only two lines (and ground ofcource) to feed the program to the V1000. Disconnect those and disconnect the pin 2 on V1000 from ground (int/ext) and the preset can be selected by selectively connecting the pins 5-8 to ground.

If I'm ever going to try reprogram the Atmega8 I will first try to extract the original program from it if possible. If I'd learn to program the Atmega8 it shouldn't be too difficult to make a program that reads the pots and feeds a delay program to the V1000. The V1000 datasheet seems to have enough info, and delay is basically simplest digital effect there is. I haven't programmed microcontrollers before, but this might be something that gets me started. It might take a while though.

Meanwhile, I will try to get the presets on V1000 running.

RaceDriver205 · February 20, 2007, 07:45:05 AM

QuoteI haven't programmed microcontrollers before, but this might be something that gets me started. It might take a while though.

Take it from someone who does a lot of micro programming, this is not where you want to start. You seem to be thinking its quick and easy.

As for the pedal:
The V1000 is digital in-digital out. It does not take analog. According to the schematics in the V1000 data sheet, there is a second IC which does the D-A and A-D converting. If the pedal does not have this IC, then the Atmega IC is somehow being used integrally with the V1000. So if there is no second IC, getting the presets running is unlikely to be so simple.
Thats how I see it anyway.

Elektrojänis · February 20, 2007, 08:12:16 AM

Quote from: RaceDriver205 on February 20, 2007, 07:45:05 AM
Take it from someone who does a lot of micro programming, this is not where you want to start. You seem to be thinking its quick and easy.

Ok... I was not really thinking that reprogramming Atmega8 would be easy. I was thinking that once I learned to program Atmega8 (which is probably not easy) it would be easy to make a program that sends an apropriate program to the V1000.

At some point I'm going to try some micro controller stuff, but I haven't done any research on that yet. If the Atmega8 is too complex for a beginger, I will check out something else.

Quote
As for the pedal:
The V1000 is digital in-digital out. It does not take analog.

Yes. I noticed it.

[/quote]
According to the schematics in the V1000 data sheet, there is a second IC which does the D-A and A-D converting. If the pedal does not have this IC, then the Atmega IC is somehow being used integrally with the V1000. So if there is no second IC, getting the presets running is unlikely to be so simple.
Thats how I see it anyway.
[/quote]

I failed to mention that there are ofcource a bunch of other stuff in on the DD100 board, including AD and DA converters. So... As I see it the V1000 is permanently stuck on ext. mode and the Atmega8 is used to read the controls and based on those, send an apropriate program to the V1000. So, if I lift the pin 2 from ground, it should be possible to use the program select pins to select the presets.

Thats how I see it... I could be wrong, but well see. I'll try it when I have time to do some shopping (I need some unleaded solder and a new tip for my iron... The DD100 has a sticker that says ROHS on it. Leaded and unleaded solder shouldnt be mixed or so I have heard...)

big bustle · February 20, 2007, 11:47:46 AM

great thread so far!

i'd love to see some pics of any changes made to the pedal.

RaceDriver205 · February 20, 2007, 11:52:03 PM

QuoteIf the Atmega8 is too complex for a beginger, I will check out something else.

My favourite is the ATTiny13.

Look for a good practical introductory book on programming AVRs. AVRs are very cool as far as electronics go.

QuoteI failed to mention that there are ofcource a bunch of other stuff in on the DD100 board, including AD and DA converters. So... As I see it the V1000 is permanently stuck on ext. mode and the Atmega8 is used to read the controls and based on those, send an apropriate program to the V1000. So, if I lift the pin 2 from ground, it should be possible to use the program select pins to select the presets.

Well in that case it may be possible.

The Tone God · February 22, 2007, 01:36:10 AM

I will add that it is HIGHLY unlikely that you could extract the program from the uC or reprogram the Mega8 as it is probably locked.

Andrew

RaceDriver205 · February 22, 2007, 03:38:27 AM

+1

The Tone God · February 22, 2007, 02:25:56 PM

I did a quick look at the V1000 and it looks like a compatible IC to the AL3201 that the FEMTOVERB / Wavefrontsemi project is based on. So maybe you can take a look at that to get some ideas.

Andrew

puretube · February 22, 2007, 02:50:35 PM

http://www.diystompboxes.com/smfforum/index.php?topic=48982.0

Elektrojänis · February 22, 2007, 04:24:25 PM

Quote from: The Tone God on February 22, 2007, 01:36:10 AM
I will add that it is HIGHLY unlikely that you could extract the program from the uC or reprogram the Mega8 as it is probably locked.

Ah... That kind of thing did not cross my mind. Those pads on the edge of the PCB just looked so tempting.

Quote from: The Tone God on February 22, 2007, 02:25:56 PM
I did a quick look at the V1000 and it looks like a compatible IC to the AL3201 that the FEMTOVERB / Wavefrontsemi project is based on. So maybe you can take a look at that to get some ideas.

I actually stumbled on that stuff by following the links on this thread... It took me a while to realize the compatibility.

Quote from: puretube on February 22, 2007, 02:50:35 PM
http://www.diystompboxes.com/smfforum/index.php?topic=48982.0

Cool! Thanks! I tried searching the forum before I started this thread, but did not see that one. It confirms what I suspected... They use the same board/chips for a bunch of pedals.

It seem that the DD100 has one difference though... The crystal is 6.144MHz. Well... As advertized on the box... Sampling frequency is 24kHz... Thats how they get 1.3 second delay out of it.

I bought some unleaded solder and some tips for my iron today... I hope that I have some time on weekend to test this stuff.

The Tone God · February 22, 2007, 05:04:04 PM

I think part of what Puretube is suggesting with that thread is that Behringer sells a multi-fx unit cheap that probably accesses everything that IC can do. Why waste your time with hacking the delay when you can buy the a unit with everything done for you cheap ?

On the other hand if you just want to experiment then by all means have fun but its a tough road you are choosing.

Andrew

puretube · February 22, 2007, 05:36:57 PM

it served both purposes:
showing e-j more info about that chip,
and
what you, T.T.G. correctly interpreted as the quintessence
of the reason for my reply #9 in that thread...

Elektrojänis · February 23, 2007, 08:41:19 AM

Yes... I'm not trying to get more and cheaper. It' more experimenting for fun. In any other case I would have probably bought the damn things allready... Or maybe something else with the same functionality.

I just want to see if ti works. It's a hobby.

And thanks again for all the info.

News:

Some Possible mods for Behringer DD100 Digital delay pedal