BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall

[Somicide]

So... Have you made it final yet?  I'm dying to get started here, but want to wait til it's as final as possible before getting started.

[JebemMajke]

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?

I would go 1M c pot. For gain. Because I like that extra bassiness in gain. And my advice is to lower that 10k resistor that's between gain pot and ground. 2.2k should suffice. Or even 1k. As far as boost resistor goes ... It becomes a little less muddy. And a bit more "overdrivey". Which is cool. But not really a must. Bass pot could go 1M or 500k. Your choice. I like 1M. For mid pot ... well most of the times I just leave it at max . So 20k for me.
Voice is really useful. More useful than sweep in E3.

Vol pot should be 1M a pot.

[J0K3RX]

I would go 1M c pot. For gain. Because I like that extra bassiness in gain. And my advice is to lower that 10k resistor that's between gain pot and ground. 2.2k should suffice. Or even 1k. As far as boost resistor goes ... It becomes a little less muddy. And a bit more "overdrivey". Which is cool. But not really a must. Bass pot could go 1M or 500k. Your choice. I like 1M. For mid pot ... well most of the times I just leave it at max . So 20k for me.
Voice is really useful. More useful than sweep in E3.

Vol pot should be 1M a pot.

ok, mine has plenty of bass and gain either way so don't know bout the 1M/C pot for gain and I don't have one to try..? would like to keep it standardized as much as possible... Everybody is gonna have different guitars with different pickups, some active hot pickups, some hot passive, some not so hot passive, some with a lot of bass or treble etc... so 100k/A is good in my opinion and people can try others if they like..

Agreed on the resistor that's between the gain pot and ground... It should probably be 1k like you said or maybe just a jumper? I only had it there so when you turn the gain all the way down it wouldn't turn the signal completely off... This is optional

Boost is also optional... I like to use one resistor to give it a little less gain (like a crunch channel) and a boost resistor to give it more gain (like a lead channel) but if you really wanted you can find the resistor that gives it the max amount of gain (without getting noisy/muddy) and just use the volume pot on your guitar to get the crunch sound... So, it is optional... don't use it and save yourself a switch  

Voice/Sweep is useful and affects the characteristics of the tone stack making the value of some of the pots like treble and mids not so critical... and the Wide switch does even more... So the treble can be anywhere from 100k to 250k and the mids can be anywhere from 10k to 25k.. just my opinion.. But to keep them somewhat standardized for a wide array of players and different guitars etc I would use 100k for treble and 10k for mids and 500k for bass.

Agreed - Volume should be 1M

Trying to get this to a "standard" setup.. You will see why, shortly! 

[J0K3RX]

[JebemMajke]

I would go 1M c pot. For gain. Because I like that extra bassiness in gain. And my advice is to lower that 10k resistor that's between gain pot and ground. 2.2k should suffice. Or even 1k. As far as boost resistor goes ... It becomes a little less muddy. And a bit more "overdrivey". Which is cool. But not really a must. Bass pot could go 1M or 500k. Your choice. I like 1M. For mid pot ... well most of the times I just leave it at max . So 20k for me.
Voice is really useful. More useful than sweep in E3.

Vol pot should be 1M a pot.

ok, mine has plenty of bass and gain either way so don't know bout the 1M/C pot for gain and I don't have one to try..? would like to keep it standardized as much as possible... Everybody is gonna have different guitars with different pickups, some active hot pickups, some hot passive, some not so hot passive, some with a lot of bass or treble etc... so 100k/A is good in my opinion and people can try others if they like..

Agreed on the resistor that's between the gain pot and ground... It should probably be 1k like you said or maybe just a jumper? I only had it there so when you turn the gain all the way down it wouldn't turn the signal completely off... This is optional

Boost is also optional... I like to use one resistor to give it a little less gain (like a crunch channel) and a boost resistor to give it more gain (like a lead channel) but if you really wanted you can find the resistor that gives it the max amount of gain (without getting noisy/muddy) and just use the volume pot on your guitar to get the crunch sound... So, it is optional... don't use it and save yourself a switch  

Voice/Sweep is useful and affects the characteristics of the tone stack making the value of some of the pots like treble and mids not so critical... and the Wide switch does even more... So the treble can be anywhere from 100k to 250k and the mids can be anywhere from 10k to 25k.. just my opinion.. But to keep them somewhat standardized for a wide array of players and different guitars etc I would use 100k for treble and 10k for mids and 500k for bass.

Agreed - Volume should be 1M

Trying to get this to a "standard" setup.. You will see why, shortly! 

Dont forget that it should be log. With lin you go from awfully quiet to "what the @#$%!!" loud somewhere between 10 and 11 o'clock.


1M C for gain because, most of the gain changes are somewhere between 25k and 100k. And the rest just ads a bit bass to the gain. But that's my opinion. Haven't tried wide sw yet .

[J0K3RX]

Ok, now for the Black Forest - No Return version Sorry... couldn't help myself You should be able to add this to the previous version with very little modification... This is just optional folks... don't feel like the standard version isn't the latest because it is! This just adds a little fire

Ok, Volume is 1M/A... layout spec wrong. deal with it

[pakrat]

50k trimmers eh? I couldn't find A20k right angle pot, will A25k be ok? Mmmmmmm.... variac...........

[jymaze]

What is the point of that "variac" board (weird name for sure)? It looks like just another volume pot with another buffer after it to me. It is a class A buffer okay, but why would we need a class A buffer to transmit some massively distorted sound? Not sure what the point is in all respect.

[pakrat]

Jim said it adds a sort of tube warmth or saturation to it. Worth a try I'd say, it can always be removed.

[jymaze]

Ok, why not. I may recycle the idea to replace the Tillman preamp I have in one of my guitars. Problem is that it may eat batteries much quicker with a current draw equal to IDDS.

[ggedamed]

Post-gain? Maybe a post-volume volume, buffered by a Hi-Fi/Viktor Kempf style buffer.
BTW, this is the article that made me start stalking Viktor Kempf and the other russian JFET sorcerers. Looking at his designs, it seems that he moved on since then.

To decrease the consumption you could add a resistor in the source (look at figure 4B in the above article). Or you can split that resistor in half and put one in each of the sources, like Erno Borbely did. But I'm pretty sure that other than the 2 FET mojo, this addon adds next to nothing to the sound. One can use this kind of follower to have no DC offset at the output or to drive low-impedance loads. But with a 10k load there's no difference whatsoever between this and a basic source follower, in a guitar pedal. If you'd want it to drive headphones, you'd use higher Idss JFETs.

Also R21's value of 1k on the schematic must be a typo. J201's maximum Idss is 1mA, so it cannot work there.

One important thing to understand about this circuit is that it is very much in the spirit of DIY.
I mean, you better use a breadboard, it's not really fit for series production.
Just build the first stage with whatever JFET you have at hand and you adjust it right. Replace the trimmer with an resistor. Listen to the output.
Than build the second gain stage in the same manner and adjust it. Replace the trimmer with an resistor.
Than connect the first stage to the second one through the gain pot and the surrounding circuitry. Listen to the output.
Than build, adjust and connect additional stages until you have enough distortion or noise (depending on which is more important to you). Replace the trimmers with resistors. Listen to the output.
Than add the tone stack and the final gain stage. Listen to the output.
At the end you'll have your very own one-of-a-kind distortion, the way you like it, made with whatever you had at hand and fit like a glove to your rig. And I promise you'll love it.

[JebemMajke]

Krankenstein done ... omg ... this one is a mother@#$%er ... gain is almost limitless . This one is the best so far. E3 and Krankenstein are going in the same box as my preamps and BF 4 fet is going to be tweaked a bit more, but it;s still a great pedal. Good design Jim.

BUT KRANKENSTEIN ROCKS!!!!! xD

[hangingmonkey]

Is r15 820 r or k?

[pakrat]

820r / 820ohm

[J0K3RX]

Here's the latest layout for the Black Forest no add-ons, just the main board.. Only a few very minor corrections and the older board will work perfectly fine if you have already etched it.

https://dl.dropboxusercontent.com/u/11178619/New%20Preamps/BF5.pdf

[J0K3RX]

Krankenstein done ... omg ... this one is a mother@#$%er ... gain is almost limitless . This one is the best so far. E3 and Krankenstein are going in the same box as my preamps and BF 4 fet is going to be tweaked a bit more, but it;s still a great pedal. Good design Jim.

BUT KRANKENSTEIN ROCKS!!!!! xD

So, what you are saying is that you really like the Krank? I guess the layout is "verified" then?

I tell you man these Russians are not to be F#%ked with!!! They are the masters of this stuff... and these designs are 7 or 8 years old!

[J0K3RX]

Also R21's value of 1k on the schematic must be a typo. J201's maximum Idss is 1mA, so it cannot work there.

correct - R21 should be 10k

[J0K3RX]

So... Have you made it final yet?  I'm dying to get started here, but want to wait til it's as final as possible before getting started.

Jeff, the last standard version without the add-on is very good in my opinion... build it!

This...
https://dl.dropboxusercontent.com/u/11178619/New%20Preamps/BF5%20-%20S.png

and this
https://dl.dropboxusercontent.com/u/11178619/New%20Preamps/BF5.pdf

[JebemMajke]

Krankenstein done ... omg ... this one is a mother@#$%er ... gain is almost limitless . This one is the best so far. E3 and Krankenstein are going in the same box as my preamps and BF 4 fet is going to be tweaked a bit more, but it;s still a great pedal. Good design Jim.

BUT KRANKENSTEIN ROCKS!!!!! xD

So, what you are saying is that you really like the Krank? I guess the layout is "verified" then?

I tell you man these Russians are not to be F#%ked with!!! They are the masters of this stuff... and these designs are 7 or 8 years old!

This one is odd ... at certain settings it sounds just like Devin Townsend while he was using 5150. And on the other hand it does Pantera and that kind of sound without breaking a sweat. E3 always sounds the same. And is better for certain extreme metal genre. Black, thrash, speed ... E3 has it. But krankenstein goes from 5150 to krank. It's better for death, sludge, stoner, doom. Even some EVH. It's interaction with guitars vol pot is better than with E3. Ps i think i've broke high and mid pots. It sounds like they are maxed all the time, and have no responce, no matter what i do. And it has this long beeeeeep.
It can be subdued with guitars vol pot. But it;s annoying.

[J0K3RX]

Ps i think i've broke high and mid pots. It sounds like they are maxed all the time, and have no responce, no matter what i do. And it has this long beeeeeep.
It can be subdued with guitars vol pot. But it;s annoying.

Damn-it! You think something is wrong on the layout perhaps??? pakrat is having problems with the krank also but not the same as yours... F$%K!