# Dunwich DA-120 on a breadboard



## Dan M (Sep 19, 2022)

Well, this is my most ambitious breadboard.

For new breadboard bakers:  Don’t get discouraged when your board doesn’t work.  This is a monster with 7 pots, 3 different voltages, 2 IC’s, and 4 transistors.  And it was crippled by a missing jumper and an out of place resistor leg.  Just walk away, and come back later with a clear head and trace it out.

I saw the strip board layout over at dirtboxlayouts and had the idea to translate it onto a breadboard before committing to build it.

I worked out the schematic from the dirtboxlayout.  I picked away at it in the evenings while watching tv.  Once I had the schematic figured out, I built the breadboard and of course it didn’t work.  
Then it collected dust for 2 months until tonight.  I had 1 resistor leg out of place and 1 power wire missing.

So after 4 months, here it is.  It’s a big ole beast and it sounds awesome!  One of the pots is standing in as the internal trimmer, just because it was easier to place.  And the FAC rotary is missing (I just swapped the caps by hand to test them out).

I’m definitely going to build and box it.  I’m fiddling with ways to board mount some or all of the pots. Or maybe move the schematic to perfboard, if that provides a nicer layout.


----------



## lrgaraujo (Sep 19, 2022)

That's incredible! Would you be willing to share your schematic? I'm very curious to see what is going on with the power amp emulation


----------



## Harry Klippton (Sep 19, 2022)

lrgaraujo said:


> That's incredible! Would you be willing to share your schematic? I'm very curious to see what is going on with the power amp emulation


+1 please


----------



## Dan M (Sep 20, 2022)

Here it is.  I just noticed I don't have the pot values labeled, but they are the same as shown on dirtbox layouts.


----------



## lrgaraujo (Sep 20, 2022)

Awesome! Thanks a lot!


----------



## temol (Sep 20, 2022)

I've seen a bit different version. With J201 instead of the BS170, with clean blend. Without FAC switch. From what I remember there are different revisions of the circuit.


----------



## lrgaraujo (Sep 20, 2022)

temol said:


> I've seen a bit different version. With J201 instead of the BS170, with clean blend. Without FAC switch. From what I remember there are different revisions of the circuit.


According to the person that runs Dirtbox Layouts, this is the newer version


----------



## fig (Sep 21, 2022)

Dan M said:


> Just walk away, and come back later with a clear head and trace it out.


Excellent advice, and a great BB circuit!


----------



## Dan M (Sep 25, 2022)

I decided against the available strip board layout because I don’t enjoy off board wiring and wanted board mounted pots.  

So I worked out a perfboard layout in DIYLC.  Once it’s done and confirmed, I’ll post the layout.  It’ll fit in a 1590XX. 

I triple checked the layout against the schematic.  Then I moved the components one at a time from the breadboard to the perfboard, checking along the way and talking out loud to myself.  “Input, 10 meg to ground and 100nF.  100nF to Q1-2 and..and…, etc”

All of the components are placed.  Tomorrow I’ll cover it in blue tacky, flip it over and start soldering.


----------



## steviejr92 (Sep 25, 2022)

Dan M said:


> I decided against the available strip board layout because I don’t enjoy off board wiring and wanted board mounted pots.
> 
> So I worked out a perfboard layout in DIYLC.  Once it’s done and confirmed, I’ll post the layout.  It’ll fit in a 1590XX.
> 
> ...


I really want to see how this turns out!


----------



## fig (Sep 27, 2022)

IC1-4,5 & IC2-4 required expansion I see


----------



## Dan M (Sep 27, 2022)

fig said:


> IC1-4,5 & IC2-4 required expansion I see


It interesting:  When I was working in diylc, it was a challenge to pack everything in.  But looking at the picture, the board appears to have a bunch of wasted space.

Ultimately, I didn’t see how to fit it into a 1590BB.  When I moved the footprint up to 1590XX, I had enough room for a symmetric layout with 5 knobs in the top row, then Volume and Boost on the bottom row.

The board is soldered.  Later today, I’ll test it, see that it doesn’t work, and drink a beer.


----------



## fig (Sep 27, 2022)

I have the utmost confidence in its success, but a beer probably wouldn't hurt either way 👍


----------



## cdwillis (Sep 27, 2022)

Awesome so far. Looks like some kind of vintage Orange amp in a box?


----------



## lrgaraujo (Sep 27, 2022)

cdwillis said:


> Awesome so far. Looks like some kind of vintage Orange amp in a box?


It is supposed to emulate a Matamp GT120 being hit by a boost

Edit: oops GT120, not DA120


----------



## Feral Feline (Sep 28, 2022)

R12 to C9...


----------



## Dan M (Sep 29, 2022)

Dan M said:


> Later today, I’ll test it, see that it doesn’t work, and drink a beer.


Well, I am right on track!  
It does nothing until I aggressively twist the volume knob.  Then it goes “scritch scratch scritch scratch, WHEEEEEE”

Debug time.


----------



## Fuzzonaut (Sep 29, 2022)

Good luck!


----------



## Dan M (Oct 2, 2022)

It’s alive.  I missed 4 solder points.  Once I found those, it fired up.  Laying out the drill template next.


----------



## Dan M (Oct 2, 2022)

Done except for labels.  I like this thing A LOT!

Top row:  treble, bass, drive, gain, depth
Bottom row:  volume, boost
1590XX in “portrait” orientation.

The layout wouldn’t work with top mounted I/O jacks.  It would have pushed the knobs down too close to the foot switch.  I was too focused on packing all 7 knobs and the depth rotary into a tight space and didn’t plan ahead for the jacks.

This is my first vertical, portrait 1590XX.  I kind of like how it looks, even though it won’t live in a nice, neat row with 125B’s and others.


----------



## Feral Feline (Oct 7, 2022)

Thanks for sharing this Dan.


Would love to know if this is a worthwhile build for Bass...


----------



## Dan M (Oct 8, 2022)

Feral Feline said:


> Would love to know if this is a worthwhile build for Bass...



I know there are bass demos on youtube.  For guitar, it works as expected.  It sounds good on its own and it definitely stacks well.  So far I've tried a Rat and a Muff in front of it with great results.  I think I'm going to build a mini doom pedalboard with a compressor, parentheses, big muff, and this pedal.  ("mini" pedal board with only 4 pedals, but 3 of them are 1590XX. . . )  Plug that into any power amp and it should shake the house down.


----------



## Feral Feline (Oct 9, 2022)

That would be an awesome board: just a few, but BIG, pedals!

PS: Definitely worthy of a build for bass, but then ... most Dunwich stuff is.


----------



## Chuck D. Bones (Oct 11, 2022)

Looks good.  How noisy is it?  That's a whole lotta MOSFETs and they are noisier than JFETs.


----------



## Dan M (Oct 12, 2022)

Chuck D. Bones said:


> Looks good.  How noisy is it?  That's a whole lotta MOSFETs and they are noisier than JFETs.



It gets noisy.  I did a check today.  The Drive and Gain behave similarly, with the gain causing a bit more noise.  

For some perspective, my Mojito is very quiet.  

With drive and gain below 10 o’clock this DA120 is quiet.  
At noon it’s noticeable but acceptable (similar to a maxed Mojito). 
Maxed out it’s pretty noisy.  

There’s a lot of fidelity in the gain and drive sweep.  In the 9-12 o’clock range, there’s quite a bit of drive available while still being quiet.  North of 12 o’clock, it’s well outside of “subtle overdrive tones”.  At that point, the noise doesn’t bother me if I’m trying to vibrate the paint off the walls.


----------

