Last mont projects I: Brett's Hidrosis (PCB, layout, pictures)

[yeeshkul]

I built Brett's modified Maestro MFZ called Hidrosis. It sounds really cool!
I used LM358 chip and some modifications:
25kB drive
220n output cap
10k trim in the feetback of the first OA
120p fettback cap

PCB and layout

http://www.hoho.cz/osobni/hidrosis/hidrosis-nanet4.gif
http://www.hoho.cz/osobni/hidrosis/hidrosis-nanet5.jpg

the PCB is designed to be fixed straight on the pots (with 4.5 cm distance of the pots)

My build in Hammond BB

http://www.hoho.cz/osobni/hidrosis/hidrosis-nanet1.jpg
http://www.hoho.cz/osobni/hidrosis/hidrosis-nanet2.jpg
http://www.hoho.cz/osobni/hidrosis/hidrosis-nanet3.jpg

Soundsample (VOXAC15+LP Standard, clean sound)
http://www.hoho.cz/osobni/hidrosis.mp3

[John Lyons]

Look and sound nice!
Good work.

john

[brett]

Man, That's excellent.  Great idea to mount the pots straight onto the PCB.
Too cool.   

[Cliff Schecht]

Holy curved traces, Batman!

[brett]

Hi
can I suggest a few minor changes?
1. Make the 10k trimpot a fixed 10k resistor.
2. Change the 1M feedback resistor to a 47k resistor in series with a 1M trimpot (for a given amount of drive, this sets the gain and therefore the amount of clipping).
3. Use the full name "Hidrosis" on the PCB so that in the future people know what it is.

The reasons for 1 and 2 are (1) so that noise is kept low and (2) that there is still control over the available range of clipping.

Another idea is to use 3 diodes for asymetric clipping.  I am in two minds about this because asymetric clipping is sweet, but the Hidrosis is intended to be dirty.
cheers

[yeeshkul]

Hi Brett, thanks for the ideas, i didn't put the whole name on the PCB because this is the smallest font that comes out fine when the PCB is etched and the name is a bit too long hahah. I'll revise it. By the way i used the trim, because i wanted to optionally move the sound closer to MFZ (buffered) - am i right when i say that if i turn the 10k down to 0 the first IC becomes a buffer (A=1+Rfeed/2k2)? However the 10k setting sounds better to my ears now. I have to check out the suggested "TS" style changes though, it sounds interesting and as i can see it may fit the PCB fine.

EDIT: i managed to squeeze the full name in 

[rnfr]

those noise mods are probably a good idea.  i have the original, and man, does that thing hissssss...

[brett]

Hi

However the 10k setting sounds better to my ears now.

Yes.  I'm a bit of a fan of high gain/low noise, too.  I should also mention that my current version of the Hidrosis uses a 47pF cap in the second feedback loop.  This lets some more (sharp) highs through.  A 100pF cap is probably a better starting value for most people than 120pF.
cheers

[yeeshkul]

I was building this for a buddy who has an original MFZ and he wanted another unit, just maybe less hissy . That's why the values are kept close to the MFZ and the trim, that can turn the first stage into a buffer. 

[tiges_ tendres]

Sorry to bump an old thread, but what size should the board be printed at for making a PCB?

[yeeshkul]

1:1, it's a 300dpi picture.

[tiges_ tendres]

1:1, it's a 300dpi picture.

Do you mean the thumbnail image or the link to the larger image?

[yeeshkul]

i mean the larger image.

[tiges_ tendres]

i mean the larger image.

Thanks for the help!  When I print the larger image it's massive!  I scaled it back to 25% and that was just the right size. However, after etching, drilling and getting set up I realized I didnt flip the layout before hand!  Doh

I got it working though, I had to solder my IC to the other side of the board and my pots work backwards.  My fault! 

I love the sound of this pedal on open chords and lead lines, but on Barre chords you can really hear the clean tone in the back ground. 

Also I noticed on your layout that you oriented your clipping diodes differently from Both the original Hidrosis and the MFZ1.  Is this your personal clipping preference?

Digging the curvy traces too!