J201 having very low gain, been struggling for 3 days now!

[requiem1991]

Hello everyone! First post here... sadly out of desperation

1.What does it do, not do, and sound like?
Well it works! (Finally). But when the GAIN pot is turned all the way up I have but a small amount of gain.

2.Name of the circuit = Black Forest Uberschall Emulation

3.Source of the circuit (URL of schematic or project):
http://tagboardeffects.blogspot.nl/2014/06/black-forest-bogner-uberschall-sim.html

4.Any modifications to the circuit?
- Changed the first 22nf cap from multilayer ceramic to grey box.
- Did not have all the right resistor values so I macguyverd some of them always with a MAX margin of 10% resistance of the original component.

5.Any parts substitutions? If yes, list them.
Nope!

6.Positive ground to negative ground conversion?
Nope!

I'm by no means an expert in this and this is actually my 3th build ever.
So the problem is that my pedal just doesn't have much gain. Even when the gain pot is turned ALL the way up it just doesn't have alot.
I changed the J201 to 2n5457 and they had a substantial amount more gain but I didn't like their tone alot.

Could my batch of J201 just be faulty?

power in   =   8.6V
board in   =   8.6v

Q1   
drain   =   4.86v
source   =   0.78v
gate   =   0.00v

Q2   
drain   =   4.90v
source   =   0.82v
gate   =   0.00v

Q3   
drain   =   4.94v
source   =   0.85v
gate   =   0.02v

Q4   
drain   =   4.96v
source   =   0.57v
gate   =   0.05v

Q5   
drain   =   8.40v
source   =   5.70v
gate   =   5.14v

Measuring forward voltage of a diode without"diode check"
Diodes measured at Cathode
D1   =   A 0.82v | C 0.00v
D2   =   A 0.81v | C 0.02v
D3   =   A 0.57v | C 0.05v


Meter with a "Diode check"
Diodes measured at Cathode
D1   =   0.25v
D2   =   0.25v
D3   =   0.25v

[pinkjimiphoton]

hate to sound like a broken record, but do you have a schematic?
that would really help, thanks

[reddesert]

This circuit is like many FET based "amp simulators." I recommend reading the runoffgroove Fetzer Valve page for an analysis of how the FET gain stages work at http://runoffgroove.com/fetzervalve.html You don't have to master every detail of the details, but there are some important ones.

One is that the gain of each stage is given by 0.5 Rdrain / Rsource. In layouts like the one here, the drain resistor is often a trimpot and the source resistor is somewhere around 1k to 3k.  An issue is that depending on the properties of your FET, turning the trimpot to adjust drain voltage to be near 4.5 V may set Rdrain so that it has some gain lower or higher than the circuit design originally intended.

You can make the extremely simple JFET measuring circuit in Figure 10 on the Fetzer Valve webpage to measure your FETs' Vp and Idss to determine if they are in spec for J201s and to see which ones are likely to behave best in your circuit.

[J0K3RX]

Could my batch of J201 just be faulty?

Don't know about faulty..  counterfeit perhaps? Where did you aquire them from? If all is correct it should produce a massive amount of high gain... If you replaced the J201's with 2N5457's and it "had a substantial amount more gain" as you mentioned then something is definitely whack.. If anything the 5457 should sound a bit less gainy than the J201. Besides the reverse polarity diode you can leave the other diodes out, they don't make a humanly audible difference. Why are you getting only 8.6V source voltage? Might want to drop the drains down to around 4V if you have an 8.6v source..   

Maybe skip through this topic...pretty much the birth place of the Black Forest. You have to wade through allot of mindless word drool but there are occasional useful turd nugets of information. 
http://www.diystompboxes.com/smfforum/index.php?topic=98954.0

[requiem1991]

Thx everyone for the replies! Good to see the original author of the schematic (Joker) responding

I order my J201 from Tayda where I order all my stuff and never really had any problems with their components.

Also I forgot a picture of the board: http://imgur.com/a/MUPdO