BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall

[Cap]

@pakrat: did you tried my layout? damn.., I'm still waiting for my new copper boards to arrive ...hope to find time this week to add the gate ...and try to etch myself my layout!!!!

[pakrat]

I didn't use your layout because I had already built this on the original pcb. I definitely plan to build one on your layout too, just to have it be more compact. If you have trouble etching the pcb, I'll make you one and send it to you 

[J0K3RX]

I tested mine today back to back against an AMT P1 pedal (since I don't have an Uberschall) through a TubeWorks MosValve power amp into a 4x12 cab with celestion v30's and also running direct using impulses with myself and two other guitar players and it was a unanimous decision that we all agreed the BF totally stomped the living sh!t outa the P1! All I have to say is WOW and good luck!!!

[pakrat]

With those resistor changes, my build sounds amazing as well. Are you going to update the layout with all of the value changes?

[J0K3RX]

With those resistor changes, my build sounds amazing as well. Are you going to update the layout with all of the value changes?

Yeah, I will do that maybe this weekend...

Now I am doing an ENGL version using the same board and I already have a working version of the ENGL which sounds jaw dropping!!!

Thanks for all your help pakrat!!!

If you get a chance and if you have a tube screamer stick it in front of the BF and set the level on the TS @ about 3 or 4 with the drive all the way down and tell me what you think?

[pakrat]

It's my pleasure brotha

[haveyouseenhim]

Just got back from the music store making the toner transfers. Should be populating tonight

Could you repost the newest version with corrected parts list? Perdy please?

[J0K3RX]

Just got back from the music store making the toner transfers. Should be populating tonight

Could you repost the newest version with corrected parts list? Perdy please?

I updated the layout on page 6 also rather than keep uploading to my dropbox acct... The only difference in this layout is the added jumper which can be removed along with R19 for attaching the optional noise gate and the addition of C25 - 470pF cap by R1 which if you have already etched the board you can easily solder on the back solder side of the board.



Board Transfer
http://dl.dropbox.com/u/11178619/BFUltra%20-%20R3.2.pdf

[haveyouseenhim]

Thanks J

[haveyouseenhim]

*%^*(^$*$(!    I made the wrong pcb!     I cant even get started on this cursed project     ALL OF MY RAGE

I just realized that I can cut a trace and drill two holes it should fix it

[pakrat]

If you are talking about the trace cut at R19, I did exactly the same thing and it's fine.

[J0K3RX]

*%^*(^$*$(!    I made the wrong pcb!     I cant even get started on this cursed project     ALL OF MY RAGE

I just realized that I can cut a trace and drill two holes it should fix it

There are no major changes that you can't modify on the older board layout... I try not to change the layout too much if at all for just that reason. There is also the small 470pF cap by where R2 used to be, you can just drill an extra hole by the ground trace and bend the lead over and solder it to ground for the the other lead of the cap you can use the bottom hole where R2 was along with the jumpers wire that goes in it. The leads on 470pF caps are really small so it will fit in that hole with the jumper no problem. The only other change is the added jumper between C23 and R19 incase you want to attach the noise gate addon. Again you can just drill a couple small holes between C23 and R19 right on the trace and then take an x-acto blade and remove the trace copper in between the two holes... Then solder to the traces.. Easy

BTW -  I would recommend that you get the pedal working first and then mess with the noise gate if you feel the need... If you do it all together at one time and if something doesn't work or sound right it just adds an extra layer of complexity to trouble shooting... If you do it after you have it fully working and then you install the gate and have problems then you know exactly what it is etc..

Here is the board transfer again... It's hard to see at the bottom of the giant layout pic.
http://dl.dropbox.com/u/11178619/BFUltra%20-%20R3.2.pdf

[Cap]

Ok, the updated layout with noise gate instead of presence will be ready this week-end
I have one question for you guys: in the first layout I made, pots are (from "stomp-side" )

Gain--Vol--Pres(Gate)
Tre--Mid--Bass

If I replace the presence pot with gate pot there are a couple of jumperwires to solder but this layout has none!:
Gate--Vol--Gain
Tre---Mid--Bass

Which one you like??

Ciao

[wgc]

Sweet, thx cap!  I usually advocate "less knobs" so if you're taking requests, I'd love to see the gate as a trim pot, and 5 knobs only.  Otherwise the second is good for me...

Actually glad my parts haven't arrived yet... Gonna redo the etches of jok3rs new pcb and this new one when ready!

Thanks gentlemen for your fine work!

[haveyouseenhim]

Here's a video demoing the gain dropout.  Btw, don't let my puberty voice fool you. I'm 23 and I sound 13

[J0K3RX]

Here's a video demoing the gain dropout.  Btw, don't let my puberty voice fool you. I'm 23 and I sound 13

wow man, you really had me freakin out there! So, I ran and checked mine to make sure you had not uncovered yet another bug in the pedal that I had not noticed yet... I am VERY HAPPY to report that mine does NOT do that thank God! BTW - Are you running directly into the front input of the ValveKing? It sounds as if all of the tone and lower ass end has been sucked out of it is the reason why I ask. This really should be used as a stand alone preamp in my opinion... I have ran it direct using impulses, into a power amp, into the fx return power section of a 5150 and straight into the guitar input of a couple guitar amps. Of all that I tested I really do not like the sound through the front input of a guitar amp!!! I don't know about the gain pot, that is strange?? It sounds to me like the pot reaches a certain point and then kicks on to almost full gain and turning it up beyond that point has almost no increase in gain? Anything below that point turns almost completely off? Can you measure the voltages at the drain of Q1 thru Q5 and post your findings here? I'm just curious as to what they are set at?

One thing you can do is solder the tip output jack wire to the bottom side of the board right on the 2nd lug of the gain pot. It's not going to have any gain obviously but it should act as a volume knob from the first stage and you should be able to roll it up and down without it cutting out at any point. Also you can try to solder the output jack to the output side of R4 which is the 68k resistor that leads into the 2nd stage and do the same test...  You can bias these by ear but if you get one stage that is way off range it will only get worse as you go down the line...

My guess is that one of the stages after the first stage is set wildly out of range and the gain pot is opening up the circuit only when it reaches a certain level? Or, Q1 is set wrong and it only delivers enough signal when the gain pot reaches a certain level? This may also account for the massive noise/buzz you are getting if one or two stages are really loud which leads me to believe that the problem is after the first stage somewhere because of all the noise you are getting. Normally if the first stage is set too high or low it does not introduce added noise because you are not really getting high gain at that stage. Really as a "rule" the drain voltage at each stage should be half of the source voltage on the power rail right at that stage! So, Q1, Q2 and Q3 are going to have a different source voltage than Q4, Q5 and Q6 because R6 is resisting some of the voltage going to the first three stages. Whatever voltage you are getting on the positive side of C1 (which should be 8.7v) is the source voltage for the first three stages so, you will bias those stages @ half of that voltage which would be 4.35v. On stages Q4, Q5 and Q6 you should have straight source voltage which will be whatever your power adapter is putting out and should be 9.5v ideally. So, all along the power rail from the right side (power supply side) of R6 you should have 9.5v. So, Q4 and Q5 should be biased @ 4.5v to 4.75v. And by the way, you should be using a regulated power adapter. A crappy power adapter will produce crappy results with high gain pedals...

Do you have the boost switch wired up? The reason I ask is because it sounds like a low gain setting. Even at that setting you are getting a hell of a lot of noise? I know it's not boxed up but geeeesh!? I know you may be getting all of this noise because of the biasing but these high gain preamps really need shielded input/output wires! What kind of cables you use also makes a big difference! I any case, at the gain level you are reaching even unboxed with no shielded input/output cables you should have almost no noise at all...

[haveyouseenhim]

As for the bass, I know why it's not coming through and I thought I mentioned it to you. I don't have any 500k pots so I'm using a 250k till I can get one.


Here's all of my voltages.   I started with your suggested voltages and then biased by ear till it sounded best

Q1
D   4.76
S   .66
G   0

Q2
D   4.05
S   .56
G   0

Q3
D   4.05
S   .68
G   0

Q4
D   3.03
S   .60
G   0

Q5
D   4.20
S   .51
G   0

Q6
D   9.12
S   4.62
G   4.18

[pakrat]

Mike, liked your vid and agree with JOK3RX that it sounds like a bit lower gain than what it should be. My build isn't perfect either but it has monstrous gain and almost no noise at all without the gate installed. I didn't box mine yet either and did not use any shielded wire, and it is biased to the voltages JOK3RX stated. I lost a week here due to hurricane Sandy (I'm on Long Island) but as soon as I clean up around here I'll check my voltages and list them for you if that would help.

[haveyouseenhim]

Whatever the result i'm going to keep this one and call it the orange grove because the guys at the shop say it sounds like a good Orange amp. I'll build a new one with the newest pcb and then try different fets and experiment a lil.


Good to see that you survived  


EDIT   @ Jim   Is that randall emulator any closer to the top of your list?

[pakrat]

Mike, I have a Randall RG100 layout if you're interested. It's not verified as far as I know, but I have all of the parts to build it.