Synthbox

[jdub]

I've breadboarded both incarnations, and while both sound quite cool, to my ears the discrete version sounds noticeably more "synthy" and seems to track better than the opamp version.  Anyone else notice this?

[isildur100]

Ok here is a soundclip of the opamp version I have on the breadboard.

http://www.upload-mp3.com/files/153980_htl9t/synthbox2soundclip.mp3

I added a bit of stereo reverb to the mix but nothing else. This circuit sounds really good when putting a chorus or flanger after it. It really becomes synthy.

I was playing with my fingers (like a bass player) on a strat, neck pickup noise canceling single coil. That's the way I obtained the best tracking, with the fingers.

Enjoy! 

John

[jdub]

Wow, that sounds pretty sweet...I'll have to poke around my boarded opamp version and see if i messed something up somewhere- sounds more like a fuzz octave...good, but not like yours.  Thanks fer the clip!

[jdub]

Hey all-

Not sure if anyone's done a perf layout for the opamp version (Synthbox 2), but for those interested, mine is here:
http://www.aronnelson.com/gallery/main.php/v/jdub/synthbox+2+project.png.html

Not the best layout, but works well. The trickiest parts were the jumpers (green wires) feeding the -9v to opamps 1&2- they run partially under the IC sockets on the component side of the board. I used a MAX1044 for the bipolar supply (onboard), but didn't find the need for R.G.'s transistor jack switching (but this could be added if desired using a little daughter board).  I also included a function for same-octave sound by switching the caps in the oscillator section (.22 to .047)- it's a little glitchy tracking-wise, but sounds pretty cool when normal guitar sound is blended in via the attack pot.  The caps are mounted on the switch- I used a footswitch, but a toggle could be used.  Also, the .047s could be varied (.01 for example)- these just worked best for me.  The only other thing I noticed is that the treble and bass pots tend to crap out a bit at the very extremes, but most of the range works fine. I used TL072s for opamps 1-3 and an LF353 for the active filter section. 

This is built and verified- fits comfortably in a 1590BB, but the layout could probably be condensed even further if resistors were mounted upright. Sounds great, with a nice variety of tones. If anyone would like the .diy file to fiddle with, PM me and I'll be glad to send it. 

Props to Liquids & Isildur100 for all the work on this fine box, and of course to Joe D for the Shocktave.  Enjoy!

[kdowqo]

some questions about synthbox2 perf layout
there is some E B C spots in there, is it suppose to be transistors there? if so, should it be MPSA18s or something else?
c14 is a 10uF non polarized cap, right? but is there any alternative here as i having trouble finding a big non polarized cap like that?

sorry if those are stupid questions 

[jdub]

Not stupid at all- actually, it's my bad  . I use sockets for all the trannies, and DIYLC doesn't have an image for sockets, so I fudged it a bit- and forgot that the transistor types won't show up in the BOM when doing that.  So I forgot to list them  . Anyway, all trannies are 2N5089s except for the one for the attack pot, for which I used an MPSA18.  I should also mention that the 5089s for the oscillator (right side of board) should be matched as closely as possible.  I'll fix the layout when I get a chance. 

As for the 10uF nonpolar, I used a monolithic multilayer ceramic from Mouser- they're very compact.  Here's the link: http://www.mouser.com/ProductDetail/TDK/FK22X7R1E106M/?qs=sGAEpiMZZMuAYrNc52CMZNINJMxZfzHjfBZIDGnSImg%3d.  A 10uF mylar would be huge, so you kinda hafta use a ceramic.

Sorry for the omissions- hope this helps. 

[Ben N]

Liquids, your Google page is keeping me out. 

[isildur100]

The 10uf cap can be a normal electrolytic polarized cap (that's what I used). No need to try to find a non polarized 10uf cap, I think it was an omission. The + side should be connected to the op amp output.

The transistors can all be 2n5089 except for the mosfets which are bs170.

John

[jdub]

Oooops, forgot to mention the BS170s.  Boy, I'm really batting a thousand here, ain't I...

[jdub]

OK, perf layout is now revised: http://www.aronnelson.com/gallery/main.php/v/jdub/synthbox+2+project.png.html

Without thinking, I had notated bipolar leads (EBC) where the MOSFETs should be in the gain section. These are now corrected & I added some notes regarding the trannies, etc.  Lemme know if I forgot anything...  

[isildur100]

Hi jdub,

I think you forgot to connect the 2.2uf caps. The one from the mosfets and the other for the tone section. I don't see the 1k resistor going from the mosfet to the 2.2uf.

John

[jdub]

Hey man-
Actually, the 2.2uF cap for the tone section is there, mounted on the bass pot (C17).  As for the MOSFET 2.2uF & 1k: aw, crap  . I was working from a rough layout and the schem when I built the box, so those components are in my build, but I did the DIYLC layout after the fact & forgot 'em.  Thanks fer the heads-up; looks like another revision for me...  Apologies- I'll try to get a(nother) fixed one up after work...

[DougH]

Where's the schematic for this? Google pages are gone.

[liquids]

I took the site down.  But minus the values in the Baxandall (tweak that as you like), I've loaded the schem as I last had it and put it on Aron's gallery. 

http://www.aronnelson.com/gallery/main.php/v/liquids/Synthbox+Op+Amp.JPG.html

[Ben N]

thx!

[DougH]

What kind of op amps and MOSFETs are you using? The sound clips sound pretty cool.

[isildur100]

I made mine with TL072's and BS170's. I guess any of the popular opamps can do the job.

Trannies were 2N5089.

cheers

[~arph]

This box is still on my to do list..  especially trying to improve the tracking on those first frets on the low E.

[kdowqo]

ordered the parts needed for this now. I hope I manage to build this, haven't built anything this complex before but I love the sound of it so I just have to give it a go
thanx for the help btw 

[jdub]

OK, I think I got it now... the new final revised updated  perf layout for the Synthbox 2:
http://www.aronnelson.com/gallery/main.php/v/jdub/synthbox+2+project.png.html?g2_imageViewsIndex=1.  Hopefully I remembered everything this time...

Enjoy!