Citrus Graphic MKII (ORANGE) PCB Attempt

[mydementia]

My apologies Paul - I removed your schem from my layout image (above).
Just trying to nail this one down once and for all. 

[mydementia]

Guys,
I was about to bag this one up and call it a defeat...but as a last ditch effort - I tried removing the boost pot and changing the level pot (could have been bad?) - still low output.  Then I did a search for an actual schematic for the 1974 Orange amp and found this: http://www.drtube.com/schematics/orange/grmk2mus.gif

First thing I notice is that each of the caps coming off the power rail are 0.068uF - not 0.68uF like I used.  Did I misread Paul's schematic, or is there some logic to changing this value for JFET emu?  I haven't gone through the entire thing (schem vs. schem) yet...but I'm wondering if this cap swap could be a part of my low output level problem...or is it just cutting my frequencies in the wrong place?  (I'm still trying to figure out what all these resistors and caps do in circuits).

Mike

[MartyMart]

I have two schems, one shows 0.68 and one 0.068  !!
I can't say which one I trust, but mine is built with 0.68uf's and works ...
It would only sound a little thinner with smaller drain caps, worth a try but I suspect that your
problems lie elsewhere ....

MM.  (  England out of world cup ..... again ! )

[mydementia]

MartyMart - sorry about England...maybe next year!

The only other difference I see from Nelson's schem and the one I linked to was C4 (schem = 0.022uF - Nelson's = 0.22uF).  I assume reducing this value by 10x will also thin out the overall tone, right?  Any thoughts on where to look for my volume problem? 
Here's my layout again for reference:


Thanks!
Mike

[MartyMart]

Hmm, having looked at all my other amp schems and the ones that I've converted to Jfet sims, I
would have to agree that 0.068uf drain caps seems to make sense.
All the other Fender/Marshall/Peavey/Boogie amps have between 10n and 47n caps so 68n would
fit in better than 680n !!
The C4 220n/22n confusion was sorted some time ago, definately 22n cap there !

Can't see where you are loosing all that volume, unless you have an error and lots of signal is
bleeding off to ground somewhere ?
Make sure that your "twisted" fets are not getting shorted out

Luck,

Marty.

[mydementia]

Hi All.
I just got around to rebuilding this project from the schem (in this thread) and finally have good tone and output level.  Here's my layout and .diy file for your use:

http://www.freewebs.com/mydementia/DIY%5FStompboxes/ORANGE/OrangeMKII%5FPCBrevision1.diy

My build has higher gain than I expected but is nice and full.  Decent palm muting 'chug' and reasonable sustain.  I found it much more interesting at low gain settings - nice OD amp kind of sound with a little grit.  Sounds good thru HB's and Singles...give this one a try!!

Yes, this one's getting a box!

Mike

[MartyMart]

C3/11/13/14 should all be 0.068uf's ( 68n ) not 680n's !!

These are the values used on the original 120 watt Graphic amp.



MM.

[mydementia]

Hi Marty.
From our previous discussion in this thread, you mentioned that you built yours with 0.68uF caps (as per Nelson's schematic) and that you were satisifed with the tone and that 0.068uF caps, while probably the 'right' value, would make the sound a bit thinner.  I didn't want a thinner sound - so I kept the big caps... have you changed your mind about these drain caps?  Paul, was the choice of 0.68uF drain caps 'ear driven' or just a slipped decimal place?
For anyone interested, the original Orange amp schematics can be found here: http://www.drtube.com/guitamp.htm
Mike

[nelson]

Just a simple mistake.

[MartyMart]

Just a simple mistake.

No worries, I make "lots" of them !

I did notice this a while ago and that was the reason for the "big whooly" tone.
I have since changed them all to 68n's and it's a much better amp sound. ( still quite a big thick tone BTW )
Before, it just sounded a bit like a "Big Muff" !

Marty.

[mydementia]

I finally plugged this thing into my main rig - wholly crap was it wooley!!  I replaced the drain caps with 0.068uF's and it's MUCH better.  At very low Gain pot level it drives really nice - twisting the Gain pot gets right back into BMP fuzz.  With the 0.068uF's, the tone is more open and just better all around.  Really makes me think that my little Ibanez SS practice amp isn't giving me the best DIY auditions...

I updated the image and project file replacing the drain caps...thanks for all your help.  Now all I have to do is figure out what I'm packaging it with...
Mike

[MartyMart]

GREAT
Better that way isn't it ?

MM.

[audioguy]

That link no longer works... has anyone got the PCB?

Thanks!

[jwyse]

It seems more appropriate to resurrect this dead thread than to start a new one just for one question, since the answer might help others who are doing this build based on this thread.  If I'm wrong, I apologize.

I'm just now building this based on Nelson's schematic.  Nelson mentioned a couple of times that he recommends putting the boost on a footswitch, and I'd like to do that. I'm just not sure where to insert the switch.  Should I put it between the cap and ground, leaving the 1k to ground when boost is off?  Or between the FET source and the boost pot? Or somewhere else between Q3 source and Q4 drain?

[PRR]

Switch the cap ground leg.

[Finom1]

It seems more appropriate to resurrect this dead thread than to start a new one just for one question, since the answer might help others who are doing this build based on this thread.  If I'm wrong, I apologize.

I'm just now building this based on Nelson's schematic.  Nelson mentioned a couple of times that he recommends putting the boost on a footswitch, and I'd like to do that. I'm just not sure where to insert the switch.  Should I put it between the cap and ground, leaving the 1k to ground when boost is off?  Or between the FET source and the boost pot? Or somewhere else between Q3 source and Q4 drain?

Does anyone have updated schematics of this build. It all sounds great but are there any schematics & layouts available?

Thank you, this will be my first build.