BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall

[palobonilla]

recently recorded, only the pedal and the cab https://soundcloud.com/palo-bonilla/ptest2

[J0K3RX]

recently recorded, only the pedal and the cab https://soundcloud.com/palo-bonilla/ptest2

Man yours sounds awesome!!  I wonder wtf I did wrong here?? I even used your board layout. Are you sure all the part values are correct? I am gonna mess with mine tonight and see if I can figure it out... Any voltages might be helpful? Damn-it! Yours sounds great man!!

[palobonilla]

Man yours sounds awesome!!  Huh I wonder wtf I did wrong here?? I even used your board layout. Are you sure all the part values are correct? I am gonna mess with mine tonight and see if I can figure it out... Any voltages might be helpful? Damn-it! Yours sounds great man!!

Hey James, you used it like a pedal? or like a preamp? remember if you gonna use it lik a preamp you need to bypass the twin T, i will post the voltages tomorrow i'm a little busy right now, but what you need just tell me

[palobonilla]

i will verify the layout too 

[palobonilla]

i found a mistake on the value of one resistor, it´s marked on the layout as 100 ohm (green circle on the image) but actually it´s 470k i hope this fix the problem

[palobonilla]

ok, i have checked the entire layout  values an there were a LOT of mistakes

[J0K3RX]

I am using it like a preamp into a cab simulator straight into Reaper. I see the corrections you have found, that's great! I will try those and go over the schematic against the layout just in case there are anymore... I was sure I got it 100% with the layout but the changes should help, I hope!? Thanks man! It just sounds insane in your clips so I gotta get this thing!! And the tone stack sounds very functional in your sound clips as well which is rare with that type of tone stack!

[palobonilla]

I am using it like a preamp into a cab simulator straight into Reaper. I see the corrections you have found, that's great! I will try those and go over the schematic against the layout just in case there are anymore... I was sure I got it 100% with the layout but the changes should help, I hope!? Thanks man! It just sounds insane in your clips so I gotta get this thing!! And the tone stack sounds very functional in your sound clips as well which is rare with that type of tone stack!

You're welcome James, i'm shure that the corrections will fix your pedal but in any case just tellme i will be glad to help you, by the way yes the tone stack works fine it's almost the same used in a old schematic of the dr. boogie

[caspercody]

Anyway to get a recording using it into a amp?

[palobonilla]

Anyway to get a recording using it into a amp?

I don´t have an amp but i´m thinking about borrow one and make a videoclip, just need some time

[J0K3RX]

Is it just my eyes and few remaining brain cells or is source and drain mixed up on this??? I mean according to the standard pinout of a J201...? Please another set of eyes!! I am tired so I could be having hallucinations... This layout is backwards and upside down to what I am used to working with so it's driving me nutso

Oh, and the two caps C2 and C3 are supposed to be 15n not 10n... my bad!

[Roger Martin]

I love it when you guys make a complete project topic like this.
PCB + schematic + mp3 demo.
Many thank yous to generous good guys like JOK3RX Jim, Galego, Slade, Merlin B, DeadAstronauts Rob H and many more i haven't mentioned. 

[J0K3RX]

I love it when you guys make a complete project topic like this.
PCB + schematic + mp3 demo.
Many thank yous to generous good guys like JOK3RX Jim, Galego, Slade, Merlin B, DeadAstronauts Rob H and many more i haven't mentioned. 

Roger, you can thank palobonilla for this one... And if it works then even better!!

Now, what do you think of the J201 orientation in the layout??

[J0K3RX]

c'mon.... too many smart people here not to verify...  I am dyslexic so help a handicapper out here!!   

[palobonilla]

c'mon.... too many smart people here not to verify...  icon_cry I am dyslexic so help a handicapper out here!!   Kiss

Yeah those are reversed, but it doesent matters, i have just mount a probe circuit in the bread board testing the jfets drain a source reversed and not reversed there is no difference

[deadastronaut]

looks weird to me too..

[caspercody]

Just looking at the first JFET, and the Source and Drain are wrong. They need to be swapped with each other.

[J0K3RX]

Tried both ways with the jfets and with the new part values and still doesn't work...  

It passes signal but clips and squeals so badly that it completely kills the signal until the note decays. Pure white noise and one note sends it into a full on clip and kills the signal..? Something ain't right here and I know I have all of the values correct according to the layout, no solder bridges, shorts etc... I also tested all resistors and jfets used and all are correct and working good.  rcustoms created a layout for it going from left/input to right/output using only the schematic as reference. I may try that if I find some time but at this point I have to lay it down.. I have too much going on and I have a couple other great sounding pedals like the tight metal that I am finishing up. Unless somebody comes up with a "verified" ground breaking fix, it's off to the bone pile for this where it will be slowly stripped of all components until there is nothing left but a rotting carcass of a circuit board... ashes to ashes, dust to dust  

[deadastronaut]

@jim:  do you just build without breadboading first?....just curious.

[caspercody]

Not sure if it matters, but after looking over the PCB layout the first stage JFET drain is not connected directly to Vdd. It is connected to R6 (the side not connected to Vdd).

Not sure what type of JFET was used on the PCB, but it looks like the drain and source are reversed. A J201 pin out is:

G
S
D

The pin out on the PCB appears to be:

G
D
S

Thanks
Rob