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Guys,

Just a quick follow up on this topic.

I finished a new MN3005 Dirtbag and did find it very dark on the repeats.
Lucky the chips I bought worked first time, and even repeated without a bias when I fired it up.
Way darker than an old DMM I could compare it to.
It still sounded fantastic, just dark repeats. Very strong repeats as well.
And a lot darker than the MN3205 version I built earlier.

So I checked all my components and found nothing wrong component value wise.
I had a good look at posts here and info from other sources.
I swapped all the TL072P chips out for old school 4558's and that actually thinned it out a bit,
and did not make it appreciably noisier or worse sounding.  Just a bit less hi fi.

I also checked a couple of schematics and found that the values for C32 and C4 near the output were different on a couple.
Nearly every other component was the same or equivalent value. Great job done by Mad bean on
his schematic.
So I swapped those, and voila, old school charm. Brighter and clearer.
C32 became 10uf (not 22) and C4 became 22uf (not 47).
These could be switched in and out I suppose.
I lost some delay time so I  changed C41 to about 270pf and that was enough extra.
No obvious weirdness in the longer delays either.

Maybe someone more techie than me can explain the changes/interactions caused by the swap.

Basically this now sounds really, really close to a DMM.


There is some great info others have provided that show how to thin repeats by adding a tone control to
the feedback area.
Swap C5 for about 3300pf and put the 22nf off one leg of a 500k pot to allow fatter or thinner repeats.
I have not tried this, but some seem to like it for variations on a theme.
Sounds like a great add on though.
Link below.

http://www.diystompboxes.com/smfforum/index.php?topic=46822.0

Eventually I will do a proper audio or YouTube comparison between:

Dirtbag MN3205, Dirtbag MN3005, DMM and BOSS DM2(has MN3005 chips).

Cheers,

DjK

Guys,

There are a couple of resistor values I have a question about in the Dirtbag schematic.
R56 and R57 are 27k, in the original DMM these values appear as 27k and 2.7k.
Is this just an original typo or does this difference affect anything?

Also, there are a few posts in the forum about getting a little more treble in the Dirtbag delays.
This seems to be the only area where comparisons to the original DMM fall a bit short.

Which are the best areas to play with (cap and resistor changes)for some extra treble, or maybe bass cuts.

Any tweaking advice greatly appreciated.

DjK

Thanks,

Tight fit in there. I think I'll use a bigger box for the next one.
Any better enclosure size suggestions from other Dirt bag builders?
Maybe just a deeper version of this one.

I am about to build an MN3005 Version, and once done I can compare all 3 at once.
Looking forward to that.
The Chips have just arrived and look OK. I'll soon find out if they are legit.

Interestingly, I thought I had a clock noise issue on the longest setting with this, but when I used another 9v wall wart it went away completely.
I think that has also happened to a few other DBD builders.

Cheers,

DjK

To all interested,

Pics of the final boxed Dirt Bag in Psycho Vein Green paint:



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Sounds great, hopefully some clips soon.
I compared it to a vintage DMM and this Dirt Bag was a bit darker, had longer repeats, but was good in different ways..
Just a little funkier/dirtier sounding ,which is to be expected I suppose with the lower voltage on these chips.

Thanks all,

Cheers DjK

Guys,

Mods were as per the latest in the build info.
I can say the trim adjustments were critical.
One tweek too far in the wrong direction and you are out of the zone.
We are talking millimetres on the trimpots.
I had a number of attempts to get a feel for it with each set of chips.
But when it is right, the repeats are strong and undistorted.
Plus some of the trim pots I have are the old fashioned stand ups, and are harder to adjust.

Cheers,


DjK

Hi All,

The first build of two planned is up and running.
Photos and stuff later on.
Not boxed but all working like the real deal.
I got some MN3205 chips to compare to the v3205 for the 9v build.
Had lots of extra clock noise on the v3205 and none on the MN3205.
I had to re-bias when I changed chips, but not that much variation in trim position.
The repeats were stronger and clearer with the MN3205, easier to dial in and just punchier.
The MN3205 just sound better overall. Chorus and vibrato sound fantastic, and it's really
easy to get those feedback builds and Edge type sounds.

I have some utsource PAN MN3005 chips on the way, I hope they are not duds, otherwise it's a double up
board I suppose.

Thanks to all for previous posts and info. Fantastic resource for this challenging build.
I went close a few times to pulling up solder pads from too much heat. Very close components as well.
Thanks Brian for the boards.

Cheers to all,

DjK

Thanks for responding.

Burkey 6 looks like a good unit.
I just remembered that Gig Rig do a 9V to 15V thing called the El Paso. Size of a battery.
I have the Gig Rig power supply/generator system already, so that seems an easy way to do it. Plenty of grunt.
Similar idea to the Burkey voltage change, but outside the box solution for the other voltages.

Just a bit more mess on the board.

http://www.thegigrig.com/acatalog/PS_High_Current_Adapters.html

cheers,

DjK

Hi Guys,

1st time post on this site. Thanks to Brian for locating some Dirt Bag boards for me.
Dirt Bag Deluxe builds coming up, and I have a couple of questions regarding power for the MN3005 option.
Everyone seems to use a Road Rage to get the juice required, is this simply because no one wants an odd voltage wall wart on their board, or due to other technical reasons?
Is anyone successfully using an external supply that meets requirements ala more recent DMM reissues?
15V regulated with the right current available I assume for the Dirt bag.
The DMM was 24v down to 15v originally by the looks of things.

I intend to try both chip types if I can get some real 3005s, the first build will be v3205.
If the Road Rage is the only way to go for MN3005 chips, then so be it.

Any help appreciated.

DjK