Orange Graphic MKII "Stompbox Adaptation" Schematic Inside. Happy Kwanzaa!

[nelson]

This is perhaps one of the last of the classic amps to be turned into a Jfet based stompbox.

So here it is, the Citrus Graphic MKII.












Any errors, suggestions most welcome.

[petemoore]

  Looks Sweet and Juicy !!

[nelson]

  Looks Sweet and Juicy !!

Yeah, I am really tempted to take a bite soon.

Will make a PCB for it.

[chokeyou]

good luck.
I've got this project sitting on perfboard. had it for a while now and havent got it working.
I'd love to see any results you have with it though.

[nelson]

good luck.
I've got this project sitting on perfboard. had it for a while now and havent got it working.
I'd love to see any results you have with it though.

Dont see any reason for it not to work.

[Bob N]

Based upon my previous successes with jfet emulations of classic amps, I look VERY forward to doing this one as well.... Are you going to post the PCB when ready? Happy Holidays! and Thank You!

[nelson]

Based upon my previous successes with jfet emulations of classic amps, I look VERY forward to doing this one as well.... Are you going to post the PCB when ready? Happy Holidays! and Thank You!

So many projects so little time.

I have an amp to build before I start the PCB.

Although, I imagine the PCB for the "flipster" could be converted with minimal trace cutting.

[Johan]

the third stage needs a 1M ground reference on its input ( gate )...that stage in the reall amps also has a cap bypassing the anoderesistor ( the 100k trimmer in this case ) but that might not be needed to get the ( slightly "foggy" ) sound of the originals...

johan

[hank reynolds 3rd]

nice one Nelson!!
wanted to have something like this for a bit (an orange amp in a box!!)
ta
if I've got time at work tomorrow I'll try a layout..does anyone know of any free/trail pcb drawing software for Mac??

Sam

[nelson]

the third stage needs a 1M ground reference on its input ( gate )...that stage in the reall amps also has a cap bypassing the anoderesistor ( the 100k trimmer in this case ) but that might not be needed to get the ( slightly "foggy" ) sound of the originals...

johan

Thanks Johan, schematic updated.
I was toying with the idea of putting the 1000pF cap in there, might aswell keep it as true as possible.

The 1972 version also has an inductor on the wiper of the boost pot.

I worked from the 1974 version.

[evertonberger]

Hey all
I am from Brazil and i not find the schematic for
Orange/Citrus Graphic MKII JFET version
anyone have this schematic... please!!!!
Thanks

[nelson]

Drop me a mail, I will send it to you.

hempathy_@_nospam_hotmail.com

[Arn C.]

Hey Nelson,
     I tried emailing you and bounced back.   Real interested in the schematic!
arn.conklin@ametek.com

Thanks!
Arn C.

[nelson]

[Arn C.]

Thanks a Bunch Nelson!!!!

Peace!
Arn C.

[Marcos - Munky]

Thanks a lot. It looks very interesting.

[nelson]

Your welcome guys.


Making the boost footswitchable would be worthwhile.

The FAC could be simplified. Or left out completely to save the hassle of a rotary switch.

I havent built it. Its on my long to do list.


If you guys decide too please submit a build report.

[Gladmarr]

Any suggestions as to what JFET to use?  I'm interested to see if this thing compares at all to one of my Oranges... 

[nelson]

Any suggestions as to what JFET to use?  I'm interested to see if this thing compares at all to one of my Oranges... 

Experiment.

I would try Q1+2 2N5457 Q3 + 4 J201's.

Just because.

[Branimir]

Hm, i've been lurking at all the schems of the oranges (heh), and i think i spotted an error here...

The capacitor connected to the bass pot has been marked 0,22uF, while i have seen a schem or two with that value, i suspect it should have been 0,022uF (22nF).

I've tried all the variations of the orange tonestack in the duncan TSC and that one with the 220nF next to the bass pot makes bass response unusable...

Other major differences between different orange tonstacks are in that highmid determing capacitor, usually 1500pF or 330pF, the larger valued one lets more highmids...

This is just my logic, i'm not trying to say anything bad about your design, but i have some limited expirience with this type of tonestack and this value really gives some wierd graphs...