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 Forum index » DIY Hardware and Software » Circuit Bending
How to add CV for delay time on Boss DD5 digital delay ?
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rogerlatur



Joined: Dec 22, 2012
Posts: 118
Location: france

PostPosted: Tue Jun 18, 2013 7:38 am    Post subject: How to add CV for delay time on Boss DD5 digital delay ? Reply with quote  Mark this post and the followings unread

Please has anybody an idea how to add control voltage functionality for delay time on the Boss DD5 digital delay pedal ?
Or even a good circuit picture (I only found a DD2 circuit online here) so other friends could help me here ?
I asked here too generally and would like to ask now here more precisely.
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Cynosure
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Joined: Dec 11, 2010
Posts: 709
Location: Toronto, Ontario - Canada
Audio files: 42

PostPosted: Tue Jun 18, 2013 9:09 am    Post subject: Reply with quote  Mark this post and the followings unread

http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossdd2.png

It looks like the delay time is controlled by the VR-1 pot, which is wired up as a voltage divider. You should be able to replace the pot with a vactrol and send your cv into the vactrol.
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rogerlatur



Joined: Dec 22, 2012
Posts: 118
Location: france

PostPosted: Tue Jun 18, 2013 11:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Cynosure wrote:
http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossdd2.png

It looks like the delay time is controlled by the VR-1 pot, which is wired up as a voltage divider. You should be able to replace the pot with a vactrol and send your cv into the vactrol.

The link (which I was not able to open, but I see that on this site there is only a DD2 circuit picture) goes to a DD2 schematic, so I guess you mean it is the same with the DD5 ?

Maybe someone did it already and can give a more concrete example on how to achieve on the board. But I will verify on the board itself, will also compare to the schematic and try to understand. I will ask for help here if I cannot go further as this sounds quite advanced.
Thank you !
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Cynosure
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PostPosted: Tue Jun 18, 2013 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

That is so weird. I saw it just this morning, but now it is gone.

Anyway, here is another link:

http://www.hobby-hour.com/electronics/s/schematics/dd2-digital-delay-schematic.gif
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gdavis



Joined: Feb 27, 2013
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PostPosted: Tue Jun 18, 2013 2:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

The fact that it's a digital delay probably makes this a little easier. As mentioned, the delay pot is basically just providing a control voltage. If it was an analog delay the pot likely would be in the timing path which would be more difficult to control with a voltage.

I found one incomplete schematic of the DD5 (supposedly) and it looks significantly different than the DD2/3, but simpler.

I can't be 100% certain since it's not complete, but it looks like the delay pot simply sends a control voltage to an analog input of a microcontroller. I would measure the voltage on each of the outer lugs of the pot (I'd guess something like 0 to 5V) and generate a control voltage in that range applied to where the center lug of the delay pot is connected (remove the pot).

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rogerlatur



Joined: Dec 22, 2012
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PostPosted: Wed Jun 19, 2013 9:43 am    Post subject: Reply with quote  Mark this post and the followings unread

gdavis wrote:
The fact that it's a digital delay probably makes this a little easier. As mentioned, the delay pot is basically just providing a control voltage. If it was an analog delay the pot likely would be in the timing path which would be more difficult to control with a voltage.

I found one incomplete schematic of the DD5 (supposedly) and it looks significantly different than the DD2/3, but simpler.

I can't be 100% certain since it's not complete, but it looks like the delay pot simply sends a control voltage to an analog input of a microcontroller. I would measure the voltage on each of the outer lugs of the pot (I'd guess something like 0 to 5V) and generate a control voltage in that range applied to where the center lug of the delay pot is connected (remove the pot).

Thank you ! Posted Image, might have been reduced in size. Click Image to view fullscreen.
I will check this.
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rogerlatur



Joined: Dec 22, 2012
Posts: 118
Location: france

PostPosted: Thu Jun 20, 2013 10:18 am    Post subject: Reply with quote  Mark this post and the followings unread

gdavis wrote:
I can't be 100% certain since it's not complete, but it looks like the delay pot simply sends a control voltage to an analog input of a microcontroller. I would measure the voltage on each of the outer lugs of the pot (I'd guess something like 0 to 5V) and generate a control voltage in that range applied to where the center lug of the delay pot is connected (remove the pot).

Pardon me if it is not possible to answer without having the circuit in front:
do you have any suggestion how I could do, supposing it works like mentionned before, if I want to keep the pot and do not want to loose its functionality (adding the CV control input as option I mean, without loosing pot).
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gdavis



Joined: Feb 27, 2013
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PostPosted: Thu Jun 20, 2013 10:40 am    Post subject: Reply with quote  Mark this post and the followings unread

rogerlatur wrote:
gdavis wrote:
I can't be 100% certain since it's not complete, but it looks like the delay pot simply sends a control voltage to an analog input of a microcontroller. I would measure the voltage on each of the outer lugs of the pot (I'd guess something like 0 to 5V) and generate a control voltage in that range applied to where the center lug of the delay pot is connected (remove the pot).

Pardon me if it is not possible to answer without having the circuit in front:
do you have any suggestion how I could do, supposing it works like mentionned before, if I want to keep the pot and do not want to loose its functionality (adding the CV control input as option I mean, without loosing pot).


If you want to have it as an option as in "either pot or CV input but not both at the same time" you could just use a switching jack for the CV input. Wire the wiper of the pot to the switch so that when nothing is plugged in the jack the switch is closed connecting the pot to the microcontroller, and when you plug in a source the switch is opened disconnecting the pot and sending the CV source to the microcontroller.

Another option would be a voltage summer or averager which would allow you to modulate the pot setting with the CV input. Just be careful that the total doesn't exceed 5V (or whatever the stock max value is). You could probably do that with a clamp diode or by setting the gain of an opamp appropriately.

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rogerlatur



Joined: Dec 22, 2012
Posts: 118
Location: france

PostPosted: Fri Jun 21, 2013 1:13 am    Post subject: Reply with quote  Mark this post and the followings unread

gdavis wrote:
If you want to have it as an option as in "either pot or CV input but not both at the same time" you could just use a switching jack for the CV input. Wire the wiper of the pot to the switch so that when nothing is plugged in the jack the switch is closed connecting the pot to the microcontroller, and when you plug in a source the switch is opened disconnecting the pot and sending the CV source to the microcontroller.

Another option would be a voltage summer or averager which would allow you to modulate the pot setting with the CV input. Just be careful that the total doesn't exceed 5V (or whatever the stock max value is). You could probably do that with a clamp diode or by setting the gain of an opamp appropriately.

These are very good ideas. Thank you very much !


Just in case... Thanks to yogi who mentionned this page when I did more generally ask how to control voltage, here are some very interesting infos about vactrols :
http://www.perkinelmer.com/CMSResources/Images/44-3429APP_AnalogOpticalIsolatorsAudioApps.pdf
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