BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall

[JebemMajke]

I'll start building krankenstein in a minute. I've been busy debugging bbe sonic stomp.

So, BF 4 fet done, E3 done, Zvex Box Of Metal almost done ( waiting for pots ). Krankenstein and dr boogie are next

[pakrat]

That's a lot of gain coming from your house.

[J0K3RX]

Blacker Forest 4 gain stages

Build doc:
http://db.tt/Sr6COBTg

Pics:
http://i875.photobucket.com/albums/ab315/Cap_87/IMG096.jpg
http://i875.photobucket.com/albums/ab315/Cap_87/IMG095.jpg

There are two different sets of pot values of the tonestack..Jim?? Layout it's the same anyway
Feel free to ask questions or pm me

That looks great Riccardo!!! In looking back at the schematic I have found a mistake... ggedamed created the schematic so you can kick his @ss  Just joking about the butt kicking of course!! I really appreciate him drawing that schematic so maybe some @ss kissing would be in better order since I hate drawing schematics! Anyway, R17 - 22k is not needed so you can leave it out. If you look closely you will see that it is parallel with R16 that is also 22k which will give you around 11k at the source... It will work like this and might not sound bad at 11k but why have 2 resistors if not needed... honest mistake

[JebemMajke]

So that jumper that's connecting voice and 22k in that layout of yours ( talking to Jim ) is not necessary. In fact it shouldn't be there?

Edit

Wire must be there in order for that fet to be connected to voice. Sto the other 22k, from voice to the ground should be lifted?

[J0K3RX]

So that jumper that's connecting voice and 22k in that layout of yours ( talking to Jim ) is not necessary. In fact it shouldn't be there?

Edit

Wire must be there in order for that fet to be connected to voice. Sto the other 22k, from voice to the ground should be lifted?

Miša,

You are correct, good catch! That was a carry over from me using another layout for template to make this one... So, it's my mistake remove the 22k behind the volume pot to ground on my layout... Ok, now you guys can commence in kicking my @ass now  

On Riccardo's layout you can remove either one from what I can see, should be the same..

~ Jim

[J0K3RX]

There are two different sets of pot values of the tonestack..Jim?? Layout it's the same anyway
Feel free to ask questions or pm me

Yes the values differ but they don't make that much of a difference especially with the voice pot installed. Originally the treble pot on the real tube Uberschall is 250k and I thought the treble went way too high for me anyway so I lowered it to 100k and the bass on the original tube preamp is 1M and I noticed that after turning the bass past the half way mark there was no noticeable difference in the bass so I changed it to 500k... This was all before I started using the "sweep/voice pot" which causes the tone stack to change into almost a completely different tone stacks... It's kinda like having a variety of different tone stacks and that coupled with the "Wide switch" gives you a large array of tone combinations... So, you can get really scooped mids or really heavy mids and it effects the treble and bass as well... So, I guess what I am saying is the values are not that critical as with a straight old Marshall type tone stack... I would experiment with different values on the voice pot as it creates huge differences in tone and the way the other pots react...  On the Krank schematic it is called the "Sweep pot" and it's 200k to me that is kinda too much but whatever floats your boat...

The way the voice/sweep pot works is you adjust it then make changes to your treble, mids and bass, it gives them different range. If you turn it by itself and don't adjust the other pots it just scoops or boosts the mids and treble mainly and you will be like that's kinda ok but don't stop there, turn the other knobs to get the idea... Also, the wide switch really opens up the sound and really does give it a wider brighter sound!!

[JebemMajke]

There is always gain xD. Even at gain pot turned to 1 there is gain

[J0K3RX]

There is always gain xD. Even at gain pot turned to 1 there is gain

?? Black Forest

Leave out R23 and add jumper...

[Somicide]

Blacker Forest 4 gain stages

Build doc:
http://db.tt/Sr6COBTg

Pics:
http://i875.photobucket.com/albums/ab315/Cap_87/IMG096.jpg
http://i875.photobucket.com/albums/ab315/Cap_87/IMG095.jpg

There are two different sets of pot values of the tonestack..Jim?? Layout it's the same anyway
Feel free to ask questions or pm me

I was just about to request something like this!  The wife is requesting guitar lessons and is a -huge- metal fan; building her a tiny giant with this as a second channel, she loved your clip with drums, jim  

God, I love this woman!

(why is there no :icon_headbang: emoticon?  lol)

[JebemMajke]

There is always gain xD. Even at gain pot turned to 1 there is gain

?? Black Forest

Leave out R23 and add jumper...

Nah, I'll leave it the for now.
2sk117 didn't work here. I've re biased fets ... and checked the twice and there was no sound. Ps I'm aware that it has way different pinout

[J0K3RX]

There is always gain xD. Even at gain pot turned to 1 there is gain

?? Black Forest

Leave out R23 and add jumper...

Nah, I'll leave it the for now.
2sk117 didn't work here. I've re biased fets ... and checked the twice and there was no sound. Ps I'm aware that it has way different pinout

Um.... I think you uncovered yet another mistake made by yours truly Maybe gain pot should be 100k/A...ya think?  

By the way, J201's are working great for me! Way more than enough gain and very little noise... no hum at all!

Sorry for the stupid mistakes people! Very little sleep does funny things...

[JebemMajke]

Yeah. there is almost no difference between 11 o clock and max . So 100k would suffice.

[jymaze]

Suppressing a stage, then paring down the gain pot... I always told you that thing had too much gain!!!

[JebemMajke]

Someone asked so here is my answer.
This thing eats MT-2 for breakfast. With the amount of gain, dynamics and the overall inability to become a buzzing mosquito, which is the biggest turn of in a MT-2. Seriously build bf 4 fet version and you won't be disappointed. E3 has less gain than bf 4 fet, but has more definition and clarity. But bf4 fet has more bass which is always cool as @#$%  . I swear to much ... 

[J0K3RX]

Suppressing a stage, then paring down the gain pot... I always told you that thing had too much gain!!!

Um.... If I do recall, it was you who came up with the idea to turn the 5th jfet into an additional gain stage It was in "the other forum" of course... let's say around the 2nd page 5 post up from the bottom.  

Now it's actually back where I started on the very first BF, it came full circle. For some reason I don't remember getting this much gain in the beginning using the 4 gain stages... That's why I asked you how to get more gain out of it... remember?

I am just bustin yer chops man... You have been there since the very beginning and have been an invaluable help!!! Would probably not have made it this far without your help... And lately you have been saying to bring it down a notch... I did try it a while back when you first mentioned it but it sounded bad and had very little gain, but that board had been reworked so many times that it was shot to hell! I kept using it but finally gave up, trashed that board and took a break and worked on other stuff. Then I found a board that I etched a long time ago from my very first BF layout that I never used... populated it with the current parts and WOW!

Now we have Riccardo's kick@ass 1590b layout with on-board pots and my surfboard with on-board pots... 

I think this version is finally done pending a few minor value changes/corrections! I have encountered almost zero bugs with mine! Everybody agree?

[jymaze]

Hey Jok3rx,

I was just being annoying don't take me seriously. It is a good circuit and you get to have full credit for that.

I am trying to finish my Petruccifier, but I am lagging and it is just there on my bench 2 solder points from being done... Fear of finishing/failure I think... So I started a 2x12 cab now... I will try to push myself to finish it this week though.

I did a simulation and there is about 15 dB in total gain difference between a 100k pot and a 1 meg pot. Fortunately the frequency response is not too affected, but still the 1 meg pot gets more bass in (potentially a tad less tight in real life?). There is still plenty of gain, about like the Seventheaven if I remember correctly.

[ggedamed]

Ha! My ass is safe (again):



See the two white circled resistors? You also had two capacitors in paralell, so I thought, why not? The man likes things in paralell. Actually, spare time provided, I'll parallel some JFETs to lower the already low noise (of course, I'm talking of my pedal, which is not too different from your BF 4 stages, more like a BF 3 stages).

Miša, 2SK117 is smokin'. Sure, it has a different pinout and you have to rebias, but it has (much) lower noise and (much) higher transconductance. My batch of 2SK117 and 2SK170 have Vp around 0.45-0.55V, so it's not fit for the first stage as is, especially if you have hot/active pickups. But, one can always bias it through a voltage divider instead of self-bias.

[J0K3RX]

Ha! My ass is safe (again):



See the two white circled resistors? You also had two capacitors in paralell, so I thought, why not? The man likes things in paralell. Actually, spare time provided, I'll parallel some JFETs to lower the already low noise (of course, I'm talking of my pedal, which is not too different from your BF 4 stages, more like a BF 3 stages).

Miša, 2SK117 is smokin'. Sure, it has a different pinout and you have to rebias, but it has (much) lower noise and (much) higher transconductance. My batch of 2SK117 and 2SK170 have Vp around 0.45-0.55V, so it's not fit for the first stage as is, especially if you have hot/active pickups. But, one can always bias it through a voltage divider instead of self-bias.

Yup thanks... Miša already pointed the resistors out earlier, that was a mistake I made from using the same layout from another board (E3) and modified for this... It was overlooked, by me. Just leave  one of them out, maybe the one behind the vol pot..but doesn't matter. The parallel caps are just the way the schematics for the Bogner Uberschall had them... of course you could replace with one cap of the combined value if you have any caps of those odd values... I left them in like that cause I didn't want to lose any Bogner MOJO magic

[J0K3RX]

Hey Jok3rx,

I was just being annoying don't take me seriously. It is a good circuit and you get to have full credit for that.

I am trying to finish my Petruccifier, but I am lagging and it is just there on my bench 2 solder points from being done... Fear of finishing/failure I think... So I started a 2x12 cab now... I will try to push myself to finish it this week though.

I did a simulation and there is about 15 dB in total gain difference between a 100k pot and a 1 meg pot. Fortunately the frequency response is not too affected, but still the 1 meg pot gets more bass in (potentially a tad less tight in real life?). There is still plenty of gain, about like the Seventheaven if I remember correctly.

ha ha...  Well, I would give Reinhold Bogner full credit for this circuit! I am a wanna be circuit copying solder monkey, nothing more... 

Now unveil this Petruccifier you have been blowing your wad on, damn-it!!

[J0K3RX]

Ok, so I think this is final for the Black Forest "standard version"...?

One of the 22k resistors in parallel on the 5th jfet from source to ground - remove. Agreed
Gain pot corrected to 100k/A Agreed

These are debatable but I have tested and they work either way.
Treble pot - 100k/B
Bass pot - 500k/B
Mid pot - 10k/A or 20k/A... not much difference that I can tell.
Voice pot - 50k/B but can be as high as 150k/B... I prefer 100k/B

Boost resistor - not sure, find your preference... Recommended - use a trim pot to find "your value" then replace with fixed resistor of same value.

I miss anything?