EQD Bellows

[storyboardist]

Hey guys! This might be the wrong place for this, but I figured it got the most traffic on the forum. I'm putting this up on my Perf & PCB blog today and thought I'd share it with you guys too. Anyway, I got an EQD Bellows late last year and traced it. It's fairly simple, but it sound really good (really tho, what EQD box hasn't sounded awesome?). First the guts:





A lot of what's on the board is for the relay bypass switching. Didn't trace that as it would pretty pointless without the code for the PIC, but for the actual effect circuit, here's the schematic:



I breadboarded this and built it on perf using a J201 in place of the PF5102 and it worked well.

Oh, and I whipped up a vero for you guys too:



Enjoy!

[Stymie13]

Awesome. Been curious about this one for a long time. Thank you for sharing!

[Silver Blues]

Okay that's interesting. What the heck is that JFET there for?

[storyboardist]

I had the same reaction when I traced it. Checked it like 5 times and then breadboarded it to make sure I hadn't lost my mind. I'm no EE (who I'm sure would immediately know what it's there for), but I assume it acts similarly to a diode (think Bazz Fuss), but with completely different tonal characteristics. All I know is it works. haha

[Silver Blues]

Haha yeah no kidding, Yeah I was thinking diode at first but then wouldn't the drain and gate need to be directly connected together for that? But hey yeah if it works, it works

[nocentelli]

I tried this out on the breadboard (first using a J201, then a few different 2N5457s), and whilst it does work it is quite gate-y and has a peculiar, "stepped" cut-off that is particularly noticeable at lower gain.

Maybe just my JFETs....

[Hozy31]

Built this using MPF102 for JFET and it sounds alright. Don't seem to getting any cut off or gateyness. Thanks for the vero storyboardist!

[nocentelli]

Ok, good to know, might go and try some other JFETs then. In the meantime, I stuck an LPB-1 in front of it which pretty much resolved the gateyness and turned it into a ridiculous gain beast, but a rat filter on the end helps tame the extra noise.

[Stymie13]

I'm getting the gating and splatty response too. Double checked scheme and layout. J201 DSG is opposite PF5102 but still not working correctly. Must need the PF5102 to make it work properly.

[tentomushi]

Im also getting the same gated issue using 2n5457.

[balazs.bencs]

I tried with a J113, and sounds amazing good. (I got them from here: http://www.ebay.com/itm/J113-Trans-JFET-N-CH-3-Pin-TO-92-Pack-of-100pcs-/)
 
Since I did not had MPSA13 in stock, I created a darlington from two 2n3904 on a small piece of vero. Really close to QOTSA sounds.

Edit: Also sounds good with a BF245C instead of the J113.

[nocentelli]

balazs.bencs wrote

Edit: Also sounds good with a BF245C instead of the J113.

So I tried a BF244A and it seemed better - it's hard to tell for sure because they have a different pin-out (BF244A = DGS, but J201/2N5457 =  DSG) so swapping them takes a bit of re-routing.

[Stymie13]

This circuit definitely needs a low noise, low frequency JFET like the PF5102. MPF4393 works fantastic.

[BrotherLeech]

Just built this today with a BF245B and it sounds amazing. As others have mentioned, at low gain it sounds a little gated and flat but not too badly. It's a bit like when you roll the input off on an Acapulco Gold.

It's so nice having such great results from a quick little circuit like this after the disappointment of building a superfuzz yesterday and finding it too squishy and weak. This is the perfect antidote and it slays with DAM Red Rooster in front of it, cranked.

Thanks for the layout storyboardist, you've made my day

[velouriafx]

Anyone verified this layout? I buit this and sounds like bad biasing. Are the pinouts of JFET right?

[Stymie13]

Definitely verified. I had to audition a lot of JFETs to get it to work properly. None of my 2457, 2458, or 201s would work properly but others have apparently got theirs to work. Once I used an MPF4393 and it sprang to life and sounds great.

[velouriafx]

Thanks for the answer. I used J113 and 2N5457. I will order some 4393 to test it.

[distraughtman]

Hi all, I know it might not be relevant but I don't know where else to post this : I've just done my first vero layout from storyboardist's schem (which I added here too). Tried to make it compact. Could anyone more experienced tell me if I got something wrong ?
Also, what would we need to do to get the Bellows posted to the "main" site face, since the OP's layout seems to be working ?

[Ciaran Haslett]

Nice job distraughtman.  Very tiny!

I personally would change the opacity of the 22n and 68n caps to show the cut underneath.  It may seem obvious to us but the less opportunity for someone to ask questions the better.

storyboardist left off the power filter cap on his schematic.  You can see it in the photo under the DC socket.  While it's not necessary for a working effect...I would add some filtering to any of my layouts as you've no idea what kind of power supply a potential builder may use.  Again...removing the opportunity for questions.

Other than those...great job man!

[distraughtman]

Absolutely right Ciaran, thanks for that. Looking forward to drawing more of these, it's already getting fun !