laney in a pedal - schematic inside

[boratto]

Hi guys,

finally a Laney Supergroup schematic (link to pdf):

http://www.4shared.com/office/iSlBha9Wba/SGBv2.html

[Travis]

Sick! I wonder how this would sound if we paired it with a treble booster like that Catalinbread Black Sabbath pedal

[Silver Blues]

Well that's interesting.

[Frank_NH]

Very cool.  Looks like another Dr. Boogie style high gainer.  The stage after the tone stack looks interesting.  

Q: How many J201 gain stages do you need before your signal becomes a square wave??  

[rocket88]

I agree this looks neat and would be fun. We all did think that the sabbath pedal from catlinbread was basically this with a treble boost infront of it. Soooo, the question is whose going to make the layout for this.

[boratto]

Naga Viper! People who build it reports it is not all that hi gainer...that are excelent results with a naga viper before the SG.

[Frank_NH]

"People who build it reports it is not all that hi gainer..."

Hmmm.  I may be up for this one then.

I suppose you could start with a straight vero layout without a boost, then add a boost stage if desired.  I have an ROG Omega booster pedal that sounds great (provides a very nice treble boost), and I could experiment with that on something like this.

[boratto]

yeahh, it is supposed to sound like the ´69 beast
https://www.youtube.com/watch?v=zc52Yon-YPQ

[Frank_NH]

That sounds pretty good!  I'm sure it's loud...

[Chris60601]

Could I ask some kind soul to actually post this PDF please? I really dont want to register to another site and wait some stupid 900 second pause.

Cheers
Chris

[boratto]

SuperGroup.pdf

[Chris60601]

Thank you, sir!

[Travis]

mmmm. I want this to happen! I'm already daydreaming of sitting at home playing Sabbath riffs at high volumes

[Frank_NH]

OK.  Here's my attempt at a layout.  I'll post it here since it's not verified yet (let me know if there are any errors).  Will try to build it this weekend (peer pressure ).

[glasspak73]

Im getting ready to start building this,has anyone else tried this yet?

[Frank_NH]

Hi,

I finished my build the other night and I would hold off for now.  I'm getting some low end "motorboating" at the second stage JFET and I'm not sure why.  I'm in the debugging mode right now and will report back when I get it working.  The circuit design is similar to The Dr. Boogie, JCM 800 emulator, and other amp sims, so I'm looking at those circuits for clues.  One thing I did notice were the bias voltages reported on the original schematic document with the pcb layout.  For the second stage JFET the recommended drain voltage was reported as 0.7 to 1.0 V.  hmmm.  Not sure about that but...

[Frank_NH]

Well, I tried yesterday but couldn't figure out the problem.  I can get the first JFET stage to work correctly, but when I add the second JFET, I get squealing/motorboating noise from it's output when I max the gain pot (I'm using an audio probe with a 100 nF cap for debugging).  I notice that when I do that, there is a small DC voltage (-.2 V) appearing at the output of the 22 nF cap (which may certainly cause noise).  Is this an effect of the second JFET?  I just don't know right now.  I'm tempted to start adding some blocking caps to see if that makes the noise go away.  I am biasing the JFETs appropriately, but nothing seems to get rid of the noise at max gain.  Very baffling.  I'll eventually figure it out...

[Travis]

Hey Frank. I've gotta get ready for work so don't have much time to double check pinouts etc

But one thing jumping out at me is that it kinda looks like the source resistors are connected to the gate instead

Ie the 820Ω on Q2 looks to be on the gate

Sorry if this is dumb cause like I said I didn't have time to take a very careful look

[Frank_NH]

Remember the pin out for J201s and similar FETS are D-S-G so the source is the middle leg...

[glasspak73]

Should Q4 and Q5 be faceing each other on the vero layout?I'm only asking cause it looks that wayto me on the schematic?hope this isn't a dumb question.