Boss DM-3 project

[MetalGuy]

Hi,

Recently I got some V3102s and V3205s and used couple of them for the AD3208 project but I couldn't find any ready to go projects like the DM-3 for example. That's why I decided to transform the DM-2 PCB into a DM-3 PCB.

The DM-2 board:

http://www.diystompboxes.com/smfforum/index.php?topic=57928.0

Few notes:

1/ The board is made to accept E-B-C transistors not E-C-B. This is made because of egoistic reasons - I'm using mostly BCxxx type of transistors.
2/ 1uF NP capacitors where possible.
3/ You can use MN3205 or MN3208 for this project.
4/ You can use MN3102 or BL3102 or V3102 for the clock chip.
5/ The regulated 7V5 as found in the original DM-3 schematic is replaced with a 7V5 zener diode.
6/ Part values can be read directly from the layout not from a different place. Please don't do it because it's VERY ANNOYING!

I haven't built an actual device using this layout yet. Although I checked the layout many times please check it one more time before using it and let me know if you find anything wrong with it so I can fix it.

Both pictures below are at 300dpi.

Boss DM-3 schematic:

http://www.freeinfosociety.com/electronics/schemview.php?id=2291

DM-3 layout and parts:



DM-3 board:



Happy New Year!

[miqbal]

It would be really helpful if anyone can also post his/her top & bottom view of DM-3 pcb.
Btw, great job metalguy!!

[MetalGuy]

Hi,

Just to confirm that the layout is OK. I built the unit and it worked from the first time.
All trimpots were set to the middle. Tweak them until you get clean signal/repeats.
Parts that I used: V3102, V3205, uPC1571, TL072, transistors - BC550C.

Good luck!

[gaussmarkov]

very nice!  thanks for putting this together.  i have some 3205s myself and this would be a nice home for a few.  i may end up changing the the transistor pinouts. 

you do very nice work!

[MetalGuy]

i may end up changing the the transistor pinouts.

I can change them for you. Just let me know how you want them - C-E-B or E-C-B

[gaussmarkov]

thanks very much for the offer!  on second thought, i am good to go.  i will use 2N508x transistors and they are the opposite pinout to the BCxxx family.

cheers, gm

[Ry]

I got a batch of the 3205's as well and am itching to use them.  I had been eyeing the DM-2 (and maybe modding it to accept more 3205 chips). 

What's the difference between the DM-2 and the DM-3?

[jbgron]

I built this today using the new CoolAudio IC's, works great.  Thanks for the project.

[Mark Hammer]

I put one together last year as well.  Decent unit.

A recommendation...

There is a 22k resistor in the Feedback (Echo) path.  Convert that into a 12k + 10K in series, with the 12k end connected to the .1uf cap coming from the Echo pot.  From the 12k/10k junction, run a wire to a toggle.  Use the toggle to connect one (if its a SPST) or two (if you have a SPDT centre-off) caps to ground to form a shallow lowpass filter dedicated to the repeats.  The result will be to trim progressively more treble from successive repeats, mimicking what happens in the real physical world when sound bounces off imperfectly reflecting surfaces.

What values to use?  A .015uf cap is probably a good starting point, and a reasonable contender for using a SPST toggle and single alternate tone.  It will roll off starting around 880hz.  Larger values will roll off lower, smaller values higher.  Try it, you'll like it.  I might note that it does double duty by cleaning up the grunge that normally accumulates over multiple repeats at longest delay. 

Note that you will not be able to get "runaway repeats" with this...which is why I suggest using a toggle to disable it, instead of merely hardwiring it.

[jbgron]

Thanks Mark, that sounds great.  I'll give it a go before I box it up.  I tried the v3205 in a DM-2 circuit with the recommended mods but I could never get it to sound right, I always got slight distortion on the repeats.  This thing sounded great even before I got the oscilloscope out to fine tune it.

Does anyone know of any other uses for a CoolAudio v3205 BBD?

Cheers

Mike

[jbgron]

I get a slight volume drop when engaging this delay.  Can anyone point me in the right direction on how to increase the volume slightly?

Many thanks.

[guitar413]

Sorry for my ignorance, is this a true bypass or a exact copy of the original DM-3?

[guitar413]

Can I substitute a 1v4148 for the 1s2473's?

[guitar413]

Can I substitute a 1v4148 for the 1s2473's?

sorry 1n4148

[Mark Hammer]

Yes to all your questions.  No FET-switching used, and modern non-Japanese diodes are fine.

[guitar413]

Thank you

[Peeping tom]

It would be really helpful if anyone can also post his/her top & bottom view of DM-3 pcb.
Btw, great job metalguy!!

I realize that this is very old topic but still....
I've tried to build this one using the layout and
mv3102,3105,sa571,jrc4558,bc550b
but the repeat sound comes very week and muddy.Any suggestion?
Should I try another chips, transistors or tweaks?I\m also using 1uF tantal caps, 7v6, 5V6 zeners and 3x 50kB pots
Thank you very much, Metalguy!

[Peeping tom]

Hi,

Recently I got some V3102s and V3205s and used couple of them for the AD3208 project but I couldn't find any ready to go projects like the DM-3 for example. That's why I decided to transform the DM-2 PCB into a DM-3 PCB.

The DM-2 board:

http://www.diystompboxes.com/smfforum/index.php?topic=57928.0

Few notes:

1/ The board is made to accept E-B-C transistors not E-C-B. This is made because of egoistic reasons - I'm using mostly BCxxx type of transistors.
2/ 1uF NP capacitors where possible.
3/ You can use MN3205 or MN3208 for this project.
4/ You can use MN3102 or BL3102 or V3102 for the clock chip.
5/ The regulated 7V5 as found in the original DM-3 schematic is replaced with a 7V5 zener diode.
6/ Part values can be read directly from the layout not from a different place. Please don't do it because it's VERY ANNOYING!

I haven't built an actual device using this layout yet. Although I checked the layout many times please check it one more time before using it and let me know if you find anything wrong with it so I can fix it.

Both pictures below are at 300dpi.

Boss DM-3 schematic:

http://www.freeinfosociety.com/electronics/schemview.php?id=2291

DM-3 layout and parts:



DM-3 board:



Happy New Year!

I realize that this is very old topic but still....
I've tried to build this one using the layout and
mv3102,3105,sa571,jrc4558,bc550b
but the repeat sound comes very week and muddy.Any suggestion?
Should I try another chips, transistors or tweaks?I\m also using 1uF tantal caps, 7v6, 5V6 zeners and 3x 50kB pots
Thank you very much, Metalguy!
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